Bacterial Evasion of Host Defense Mechanisms Immunological Aspects of Microbial Host Interaction Connective Tissue Alterations:Tissue Destruction in Periodontitis BONE RESORPTION

1. HOST MICROBIAL
INTERACTION IN
PERIODONTAL DISEASE
PRESENTED BY:
ANUSHRI GUPTA
PG 2ND YEAR

2. INTRODUCTION
• The mouth, like all external surfaces of the body and the gut, has a
substantial microflora living in symbiosis with a healthy host.
• The microflora of the mouth contains hundreds of species of aerobic
and anaerobic bacteria.
• Cultural studies indicate that more than 500 distinct microbial
species can be found in dental plaque.
•Although bacteria are necessary for periodontal disease to take
place, a susceptible host is also needed.
• The immune-inflammatory response that develops in the gingival and
periodontal tissues in response to the chronic presence of plaque
bacteria results in destruction of structural components of the
periodontium leading, ultimately, to clinical signs of periodontitis.

3. •The host response is essentially protective, but both
hyporesponsiveness
and hyper-responsiveness of certain pathways can
result in enhanced tissue destruction.
• Closer investigations of the destructive pathway of periodontal
disease began to focus on the relation-ship between bacteria and
the
host response in the initiation and progression of periodontal
disease..
• This shift in etiological theory produced a paradigm that called
attention to the fact that although microorganisms are the cause of
periodontitis, the clinical expression of the disease depends on how
the host responds to the extent and virulence of the microbial
burden.
• It was found that degradation of host tissue results from this
bacterial-host interaction.

4. • A dynamic equilibrium exists between dental plaque bacterium and
innate host defense system.
• Dental plaque bacteria have adapted survival strategies favoring
growth, while the host limits growth by combination of
innate and adaptive immune responses.
• This interaction represents a highly evolved interaction between
bacteria and host.

5. WHAT IS HOST ?
•An organism which harbors the parasite
WHAT IS BACTERIA?
• Extremely small—usually 0.3 to 2.0
micrometers in diameter—and relatively
simple microorganisms possessing the
prokaryotic type of cell construction.
INTERACTION
• The combined effect of two or more
independent variables acting
simultaneously on a dependent variable.

6. DIFFERENT TYPES OF INTERACTIONS
• Symbiosis: It is an association in which both host and parasite are
so
dependent upon each other that cannot live without the help of other
and none of them suffers any harm from the association.
• Commensal: Is a non disease forming organism; which is a part of
the resident flora.
• Commensalisms: is an association in which parasite is deriving
benefits
without causing injury to its host.
• Parasitism: is an association where parasites gets benefits and the
host gets harmful effects.
• Mutualism: is an association where parasite and host both are
benefited.

7. PATHOGEN
• Pathogen is an organism that causes disease.
• Opportunistic pathogens: are normally not
pathogenic , but are able to become so if their
local environment is changed
• They can overgrow and the microbial load can cause disease.
• Virulence : ability of a microorganisms to cause the disease.
To function as pathogen, bacteria must:
1. Colonize at appropriate host tissue site.
2. Cause destruction of the host tissues.
• Toxins : Anything that is injurious, destructive, or fatal
or
A poisonous substance, especially a protein, that is produced
by living
cells or organisms and is capable of causing disease when
introduced
into the body tissues but is often also capable of inducing
neutralizing

8. Bacterial Adherence in Periodontal Environment
• Attachment to Acquired pellicle or onto the saliva coated tooth
surfaces.
Gingival
Crevice
First site for
contact &
attachment of
bacteria
Mechanical
cleansing by
saliva and GCF
Inhibits
bacterial
growth by
antibody and
phagocytic
secretion.
Gingival
Epithelium
Bacterial
Invasion
Antimicrobial
peptides (AMPs)
that kill bacteria.
IL8 attracts
PMNs and
Macrophages to
reduce microbial
IL-1b to enhance
local
inflammatory
action.
Barrier Function

9. Host Tissue Invasion
Mode of entry of bacteria:
• Through the ulceration in the epithelium
• Through gingival sulcus
• Through periodontal pockets
• Direct penetration of microorganisms
Organisms capable of invading tissues directly:
• Actinibacillus actinomycetum comitans
• P. gingivilis
• Fusobacterium nucleatum
• Trepanoma denticola
• This ability of the bacteria to invade the host tissue is one of the key
characteristic in distinguishing pathogenic from non pathogenic
strains.
• Localization of bacteria in the tissues provides an ideal position from
which the bacteria can deliver toxic molecules and enzymes to the host
tissue cells and this may be the significance of invasion as a virulence
factor.

10. •The bursts of disease activity in periodontal diseases may be
related to active phases of bacterial invasion of the tissues.
• Bacteria in the tissue may enable persistence of the species in the
pocket by providing a reservoir for colonization.
Advantages of tissue invasion:
• Tissues can provide reservoir for colonization
• Can not be eliminated easily by mechanical methods.
• Systemic antibodies are required to eliminate bacteria
• The presence of bacteria within the tissue makes periodontitis
more resistance to the treatment

11. Bacterial Evasion of Host Defense Mechanisms
Periodontal diseases provide a unique situation for the study of
microbial-host interactions. More than 500 different microbial species
can be found in the oral biofilm; however, only a few of those are
associated with periodontal disease.
Direct damage to polymorph nuclear leucocytes and
macrophages
Reduced PMN chemotaxis
Degradation of immunoglobulins
Degradation of fibrin
Altered lymphocyte function
Damage to crevicular epithelium
Production of volatile sulphur compounds
Degradation of periodontal tissues by bacterial enzyme .

12. Bacterial Enzymes Capable of Degrading
Host Tissues

13. Immunological Aspects of
Microbial Host Interaction
• Well characterized interactions involve release of:
1. IL-1,6,8
2. TNF
3. Prostaglandins
From monocytes,
macrophages and PMNs
exposed to bacterial
endotoxin (LPS)

15. Innate Responses (Non-specific)
• Innate reactions include the inflammatory response and do not
involve immunological mechanisms.
Adaptive Responses (Specific)
• Adaptive reactions that include immunological responses tend to
be very effective as the host response is specifically “tailored” to the
offending
pathogen(s).
Host Defense Processes

16. •Although adaptive and innate immune responses are traditionally
distinguished, in vivo they are integral parts of the host defenses
against infections (i.e., innate immunity is not inactivated after the
adaptive response is initiated).
• Innate immunity is required for the activation of a more specific
adaptive immune response, but it also plays an important role in the
management of host-microbial interactions.
• The innate immune system is rapidly activated (within minutes),
and it is responsible for the defense during the initial hours and
days of the infection.
• Alternatively, adaptive immunity requires at least 7 to 10 days
before an adequate cellular or humoral response occurs.
Innate Immunity in Periodontal Disease

17. •The host may respond through inflammation to a range of challenges, from bacteria to cholesterol.
• However, the nature of the response differs and its character depends on the microbial triggering of
specific receptors, the signal transduction pathways, and the way cells and tissues respond to these signals
in terms of cytokine and defensive protein production.
• Innate immunity represents the inherited resistance to microbial infection, which is detected by Pattern
Recognition Receptors (PRRs).
• PRRs are strategically located at the interface between the mammalian host and the microbes, and have
evolved to recognize conserved microbial motifs, known as Microbe Associated Molecular Patterns
(MAMPs) OR Pathogen Associated Molecular Patterns (PAMPs)
• Toll Like Receptors (TLRs) constitute an evolutionarily ancient PRR family, which plays a central role in the
induction of innate immune and inflammatory responses and act as bridge b/w the innate and acquired
immune systems.

18. •TLRs are single-pass transmembrane proteins with N-terminals that
present leucine-rich repeats that are responsible for the recognition of
their ligands and with C-terminal cytoplasmic domains that are very
similar to the cytoplasmic region of the interleukin-1 receptor, which
are called Toll/IL-1 receptor domains (TIR domains).
• Thus, subsequent to the recognition of a ligand by TLRs, the signal
generated makes use of pathways similar to those used by the IL-1
receptor
STRUCTURE OF TLR

19. Types of TLRs

20. • Within periodontal tissues, TLR2 and TLR4 expression appears to
be severely increased in diseased states.
• TLR-4 is expressed in equal levels by gingival and periodontal
fibroblasts.
• TLR-2 is expressed in higher levels by PDL fibroblasts.
• Human gingival and periodontal fibroblasts are known to produce
various inflammatory cytokines such as IL-1,6,8 when stimulated by
bacterial LPS.
• CD-14 is responsible for pattern recognition of common bacterial cell
surface components such LPS and PGN (peptidoglycan).
• Cementoblasts also express TLR-2,4 as well as CD-14
• It has been suggested that TLR4 mediates the response to LPS
while TLR2 is involved in response to other bacterial cell wall
components.
TLR Expression and Microbial Recognition in Periodontal Tissues

21. • TLRs are expressed predominantly in cells which mediate first-line
defense,
such as neutrophils, monocytes/ macrophages, and dendritic cells, as
well as
epithelial cells.
• Distinct members of the TLR family respond to different types of
MAMPs, endowing the innate response with a relative specificity.
Nucleotide-binding
oligomerization
domain-containing
protein 1

22. Host responses to Bacterial
Infection
• Epithelial Cells
• Dendritic Cells or Langerhans Cells
• Macrophages
• Cementoblasts
• PMNs
• Fibroblast
• Endothelial Cells
• Osteoblasts

23. Epithelial Cells
• Epithelial cell express TLR-2, 9.
• LPS from Aac increases expression of ICAM-1 (Intercellular
Adhesion Molecule 1) and LFA-1 (Lymphocyte function-associated
antigen 1) due to bacterial LPS.
• However, P.gingivalis LPS down regulates ICAM1 and LFA1
secretion.
• There is increased PMN migration towards the pocket.
• Increased IL-8 production in response to LPS production by
various pathogens.
• It also activate endothelial cells, macrophages, dendritic cells
and PMNs to produce MMPs.

24. Dendritic Cells or Langerhans Cells
• DCs express TLR-9.
• Recognize MAMPs and initiate maturation process.
• Mature DCs present antigens to (major histocompatibility complex)
MHC Class-II.
• Produce cytokines and co-stimulatory molecules (CD- 36,40,54,80,86)
that induce activation of T-lymphocytes
• DCs + P.gingivalis fimbriae + T lymphocytes = Th1 type response.
• DCs + P.gingivalis LPS = Th2 type response.

25. Macrophages
• Act as professional phagocytes with the primary function of engulfing
and destroying microbes.
• Produce cytokines and MMP-1, NO when stimulated by LPS by
periodontal pathogens.
Cementoblasts
• Stimulated by LPS exhibit decreased levels of expression of RANKL
(Receptor Activator Of Nuclear Factor-kappa Beta ligand) and similar
to gingival fibroblasts, increase expression of both OPG
(osteoprotegrin) and OPN (Osteopontin).

26. Fibroblast
• Gingival fibroblast:
• Produces proinflammatory cytokines and also express adhesion
molecules in
response to PAMPs such as LPS, PGN and DNA of various pathogens.
• PDL fibroblast :
• Produces Alkaline Phosphatase activity similar to osteoblasts.
• These cells can also liberate proteinases causing tissue destruction.
• The capsular polysaccharide from Aac can inhibit expression of IL-6
and IL-8 induction in gingival fibroblasts by LPS from the same micro-
organism
and modulate an immune response in blocking bone resorption which
is supported by an increase in OPG expression by LPS stimulated
Gingival
fibroblasts.
• On stimulation with PGN, PDL fibroblasts express higher levels of IL-
8 than gingival fibroblasts, perhaps because of more TLR-2
expression.

27. • May be stimulated by IL-8 secreted by other cells and also directly by
LPS through TLR-4 ultimately leading to activation and increased
adhesion of monocytes.
• This is due to the induction of cytokine production and increased
expression of adhesion molecules like ICAMs (Intercellular Adhesion
Molecule) and VCAM-1 (Vascular Cell Adhesion Molecule 1) by MAMPs.
• Also function as APCs (Antigen-presenting cells ).
Endothelial cells

28. Osteoblasts
• P. intermedia LPS inhibits osteoblast differentiation and mineralization.
• Capsular polysaccharide from Aac promote osteoclast differentiation of
bone marrow cells.
• In absence of stromal cells and osteoblasts, LPS inhibits RANKL
(Receptor Activator Of Nuclear Factor-kappa Beta ligand) induced
differentiation of osteoclast precursors as a result of decreased M-CSF
(macrophage colony-stimulating factor) and RANK receptor.
• If osteoclast precursors are primed with RANKL, LPS synergistically
increases differentiation influenced by autocrine stimulation with LPS,
induced TNFa and
PGE2.

29. Monocytes
• Stimulated by MAMPs produce inflammatory cytokines and also
increase proliferation and adhesion to endothelial cells.
• LPS induced differentiation of monocytes into osteoclasts even in
absence of osteoblasts and the induction of RANKL expression is the key
mechanism in it.
• In the presence of IL-12, P.gingivalis LPS significantly increases
Interferon gamma production by T cells and also augments production of
IL-12 by monocytes.
• Without co-stimulatory factors, P.g LPS fails to induce proinflammatory
cytokines on monocytes ; on the contrary, it induces expression of anti-
inflammatory IL-10 that can down regulate IL-12 levels.

30. B Lymphocytes
• They are Directly stimulated by MAMPs specifically CpG (Cytosine
phosphate Guanine) DNA because they lack TLR-2 while simultaneously
expressing TLR-9.
• This leads to proliferation, antibody production and production of
proinflammatory cytokines.

31. T Lymphocytes
• It play role in cell-mediated immunity.
• It gets activation by LPS is species specific.
• LPS from E.coli was shown to induce both CD4+ and CD8+ T cells to
produce interferon gamma.
• P.gingivalis LPS was shown to induce Th2 cells to produce Th2 type
cytokines.
• CpG DNA induces differentiation and activation of T cells
• Also inhibits CD4+ apoptosis.

32. ROLE OF GINGIPAIN
• Pick et al. (1994) separated the trypsin-like activity in P. Gingivalis
culture supernatants called 'gingipain' and found that there were two
separate cysteine proteinase activities, one with arginine and one with
lysine specificity
• Arg-gingipain have been found potently to enhance vascular
permeability.
• These enzymes increase gingival crevicular fluid production and thus
provide
a continuous supply of nutrients for the bacterium, enhancing its growth
and
virulence.
• Arg-gingipain has also been found to be a very efficient enzyme for the
production of the potent chemotactic factor C5a by directly cleaving the
C5
component of complement.
• These enzyme also degrades C3,and in this way eliminates the
creation of
C3-derived opsonins.
• This render sp. Gingivalis more resistant to phagocytosis by

33. ROLE OF GINGIPAIN
• Fibrinogen is a major target for lys-gingipain and it thus increases the
local clotting time, leading to gingival bleeding.
• The bleeding of periodontal sites is of primary importance for the
growth
of P. Gingivalis, since it ensures the rich source of haem and iron that it
requires for survival.
• Gingipains act as adhesins and have a strong binding affinity for
fibrinogen , fibronectin and laminin.
• It inhibits haemagglutination.
• Since these complexes are present on the surfaces of both the vesicles
and membranes of P. Gingivalis , they may play an important role in the
attachment of this bacterium to host cells.

35. Connective Tissue Alterations:
Tissue Destruction in Periodontitis
• Remodeling of connective tissues that leads to a net loss of
local soft tissues, bone and periodontal attachment apparatus.
• The fundamental event in the transition from gingivitis to
periodontitis is the loss of soft tissue attachment to the tooth and
subsequent
loss of alveolar bone.
• Mediators produced as part of host response contribute to tissue
destruction include Proteinase,Cytokines, Prostaglandins

36. FACTORS CAUSING TISSUE DESTRUCTION
Bacterial products
PMNs
Proteinases
Cytokines
Prostaglandins
Reactive oxygen sp.

37. BACTERIAL PRODUCTS
• Degrade basement membrane and extracellular
matrix proteins including collagen, proteoglycans, and
glycoproteins. This would destroy periodontal
connective tissue and facilitates bacterial invasion.
• Interferes with tissue repair by inhibiting clot
formation or lysing the fibrin matrix in periodontal
lesions.
• Activates latent host tissue collagenase which would
enhance host tissue enzyme mediated tissue
destruction.
• Inactivates proteins important in host defense.

38. Neutrophils / Polymorphonuclear
Leukocytes
• Elastase, a serine protease, is contained in the primary granules of
the PMN; may cause tissue breakdown and is present with increased
activity
at sites of gingival inflammation.
• Lactoferrin is contained in the secondary granules of the PMN, and
is released during PMN migration and is associated with PMN
activation.
• A greater proportion of lactoferrin to elastase was found in advanced
periodontitis lesions than in gingivitis sites.
• TNF – Alpha plays a major role in development of inflammation by
stimulating the release of cytokines, including IL-1B from neutrophils.
• Lipoxin A4 is a cytokine regulating lipid mediator that can reduce the
inflammation induced by TNF – A.
• P.gingivalis impedes transendothelial migration of neutrophils and
prevents epithelial cells from secreting IL-8 in response to bacterial
challenge.

39. PROTEINASES
•Proteinases (collagenase, elastase - like and trypsinlike, as well as
serine and cysteine proteinases) cleave proteins by hydrolyzing
peptide bonds.
• Depending on the location of activity of the enzyme on its substrate:
1. Endopeptidases
2. Exopeptidases,
Proteinase Inhibitors:
Alpha-2
macroglobulin(A2-
M)
• Inhibits gingival
collagenase
Alpha1 antitrypsin
(A1-AT)
• Inhibits PMN
collagenase

40. • Matrix metalloproteinases (MMPs) are considered to be primary
proteinases involved in periodontal tissue destruction by degradation of
extracellualr matrix molecules.
• MMPs are a family of proteolytic enzymes found in neutrophils,
macrophages, fibroblasts, epithelial cells, osteoblasts and osteoclasts
that degrade matrix molecules such collagen, elastin and gelatin.
• MMP1 and MMP8, both are collagenases and are elevated in tissues
and GCF
associated with periodontitis.
• MMP 8 is released by infiltrating neutrophils whereas MMP1 is
expressed by resident cells including fibroblasts,
monocytes/macrophages and epithelial cells.
• Neutrophil (PMN) Collagenase is found in higher concentrations in
inflamed gingival specimens than in clinically healthy gingiva.
• Their increase during experimental gingivitis and decrease after
periodontal treatment suggest that MMPs from PMNs are involved in
periodontal tissue breakdown.

41. • MMPs are also produced by Aac and Pg which is not considered
a major factor in disease progression.
• MMPs are secreted in the inactive/latent form.
• Activation by proteolytic cleavage of a portion of the latent
enzyme.
• Proteases capable of MMP activation:
1. Chymotrypsin like protease by T. denticola
2. Neutrophil Cathepsin G by Host cell enzyme
• MMPs are inactivated by:
1. Alpha-macroglobulins found in serum and GCF.
2. Tissue Inhibitors of MMPs produced by cells of host tissue and
fluid.
3. Tetracycline appears to inactivate neutrophil MMP
Other Proteinases
1. Elastase degrades elastin, collagen, fibronectin.
2. Cathepsin – G: MMP – 8 activation.

42. Cytokines
• Cytokines are soluble proteins, secreted by cells involved in both the
innate and adaptive host response, and act as messenger molecules
that transmit signals to other cells.
• Actions:
1. Initiation and maintenance of immune and inflammatory responses.
2. Regulation of growth and differentiation of cells.
• Interleukins are important members of the cytokine group and are
primarily involved in communication between leukocytes and other
cells, such as epithelial cells, endothelial cells, and fibroblasts engaged
in the inflammatory process.
• Interleukin (IL)-1a, IL-1b, and tumor necrosis factor (TNF)-alpha
stimulate bone resorption and inhibit bone formation.

43. • IL-1, IL-6 and TNF-alpha have the central role in periodontal
destruction.
• IL1a and IL1b are the 2 active forms.
• Main factor of IL-1 : Osteoclast Activating Factor.
• IL-1 is produced by activated macrophages or lymphocytes but may
also be produced by mast cells, fibroblasts, keratinocytes and
endothelial cells.
• Bacterial LPS is a potent activator of macrophage IL-1 and TNF-a
secretion.
• TNF-a and IL-1 can upregulate their own production.
• IL-6 also results in Bone remodeling.
• TNF-a and TNF-b are active forms.
• TNFa shares similar biologic activity of IL-1a including stimulation of
bone resorption.
• TNF-β is primarily produced by Th1 subset of CD4+ T cells that have
been activated by antigen or mitogen

44. • IL-1 is a potent stimulant of osteoclast proliferation,
differentiation, and activation
• TNF-ά have same effects on osteoclasts but less potent.
Proinflammatory effects of IL-1 and TNF-a:
1. Stimulation of endothelial cells to express selectins that
facilitate recruitment of leukocytes.
2. Activation of macrophage IL-1production.
3. Induction of PGE2 by macrophages and gingival fibroblasts.

45. Prostaglandins
• Prostaglandins are arachidonic acid metabolites generated by
cyclooxygenases (COX-I, COX-2).
• Arachidonic acid is a 20-carbon polyunsaturated fatty acid found in plasma
membrane of most cells.
• COX-2 is upregulated by IL-1β, TNF-β and bacterial LPS leading to
formation of
PGE2 associated with inflammation
• PGE2 is increased in periodontal sites demonstrating inflammation and
attachment loss.
• PGE2 also induces MMPs and osteoclastic Bone Resorption.
• PGE2 is elevated in gingivitis and Periodontitis in active disease.
• PGE2 is partly responsible for bone loss associated with periodontitis

46. Elevated prostaglandin E2 levels are detected in the gingiva and
gingival crevicular fluid of patients with periodontal diseases,
compared to periodontally healthy subjects in 1974, Goodson Et
Al. reported a 10-fold increase of prostaglandin E2 levels in
inflamed gingival tissue, compared with healthy gingival tissue.
Macrophages produce prostaglandin E (PGE) and (IL-1)
and
lymphocytes produce Interleukin-1 (IL-1) which activate
Osteoclasts.

47. REACTIVE OXYGEN SPECIES
• Any species capable of independent existence that contain one or more
unpaired electrons.
• Inflammatory cells and in particular PMN once stimulated produce
reactive oxygen species via metabolic pathway of the respiratory burst,
which occurs in the process of phagocytosis.
• These includes superoxide anion, hydrogen peroxide, hydroxyl
radicle and hyperchlorus acid.
ROS can
cause
Protein
damage
Lipid
Peroxidation
DNA
damage

48. COLLAGEN DEGRADATION IN HOST BACTERIAL
INTERACTION
• Tissue remodeling is usually tightly regulated by a complex interplay of
cell-cell and cell-matrix interactions involving the production of
enzymes, activators, inhibitors and regulatory molecules such as
cytokines and growth factors.
• The accelerated breakdown of connective tissues occurring in
pathological situations, such as periodontal diseases.
• The endopeptidases (or proteinases) are key enzymes in tissue
degradative processes, since the protein components of most matrices
are the predominant determinants of tissue structure and function.

49. • Collagenase :
• Collagenase 1 or MMP 1 or fibroblast collagenase can hydrolyses
collagen type 1,2,3,6,8,and 10
• Collagenase 11 or MMP 8 or PMN’s collagenase can hydrolyze
collagen
type 1 and 3
• Elastase :
• MMP 2 and MMP 9 can degrade collagen type 4, 7, 10 and 11 and
Elastin.
• Stromeolysin :
• Stromeolysin 1
• Stromeolysin 2
• Stromeolysin 3
Degrade proteoglycans, basement membrane , laminin and
fibronectin.

50. • Higher levels of antibodies to collagen type I were found in the
peripheral blood of patients with periodontitis than in healthy controls.
• In addition to antibodies to collagen type-1 there are several other
types of auto reactive components.
• Increased reactions of IgG auto antibodies to desmosomal
proteins were observed in sera from individuals with periodontitis in
comparison to sera from healthy individuals.
• Two regulators of MMP expression are IL-1 AND TGF-β. These
substance are present in inflamed tissue
• In macrophages MMP production is stimulated by LPS and inhibited
by
INF-γ, IL-4 and IL-10.

51. MEDIATORS AFFECTING COLLAGEN
Increase in collagen synthesis:
• PDGF
• TGFβ
• FGF
• IGF
Decrease In Collagen Synthesis:
• Cytokines
• IL-1α, β
• INF γ
• TNF α
• Hormones like Glucocorticoids
• Others like PGE2

52. BONE RESORPTION
• Bone resorption is mediated by osteoclasts.
• Concomitant with the breakdown of the connective tissue
attachment during disease progression.
• The mechanisms involved in bone resorption respond to
signals from inflammatory cells in the lesion and initiate
degradation of bone in order to maintain a “safety” distance to
the periphery of the inflammatory cell infiltrate.

53. Mediators of Bone Resorption
BACTERIAL
COMPONENT
• Capsular and surface
associated material
• LPS
• Lipoteichoic acid
• Peptodoglycans
• Muramyl dipeptide
• Lipoprotein
HOST
MEDIATORS
• Inflammatory mediators
• PGE2
• Leukotrienes
• 12- HETE
(Hydroxyeicosatetraenoic
acid)
• Heparin
• Thrombin
• Bradykinin
• Cytokines
• IL-1,6
• TNF
• TGF β
• PDGF

54. Mediators of Bone Resorption
Stimulators
• IL-1
• IL-6
• TNF
• PGE2
• M-CSF (Macrophage colony-
stimulating factor)
• RANK (Receptor Activator Of
Nuclear Factor-kappa Beta)
• RANKL (RANK ligand )
• Vitamin-D
• PTH hormone
Inhibitors
• Interferon gamma
• OPG (Osteoprotegrin)
• Estrogens
• Androgens
• Calcitonin
• Cyclosporin

55. •Bone loss in periodontal disease are listed by Haussmann in
1974
• Direct action of plaque products on bone progenitor cells induce
their differentiation into osteoclasts.
• Plaque products acts directly on bone destroying it through a
noncellular mechanism.
• Plaque products stimulate gingival cells, causing them to release
mediators which in turn trigger bone progenitor cells to
differentiate
into osteoclasts.
• Plaque products cause gingival cells to release agents that can
act as
co-factor in bone resorption.
• Plaque products can cause gingival cells to release agents that
destroy
bone by direct chemical action without osteoclasts.

56. Osteoclasts:
• Osteoclasts are multinucleated cells that develop from osteoclast
progenitor
cells/macrophages.
• Mediators such as IL-1 beta, PGE2 and TNF alpha, IL-6, IL-11 and IL-
17 may act as activators of osteoclasts.

57. MECHANISM OF BONE RESORPTION
Osteoblast
induced
Osteoclast
induced

58. OSTEOBLAST INDUCED
• All systemic and local bone resorbing factors exert their influence
by stimulating osteoblasts.
• Osteoblasts are involved in the regulation of osteoclasts function
because they have receptors for systemic factors such as
parathromone and 125-OH2 (Vitamin D) and locally produced
factors such as prostaglandins, leukotrienes and cytokines which
effects local changes and exert their influence by stimulating
osteoblasts.
• Stimulated osteoblasts stimulate osteoclast formation by secretion
of cytokines, growth factors in particular granulocyte macrophage
colony stimulating factors (GM-CSF) and macrophage colony
stimulating factor (M-CSF) and interleukin-6.

59. • IL-6 secretion is stimulated by IL-1 attachment to osteoblasts
receptor.
• All these secreted cytokine in presence of IL-3 can stimulate the
development of precursors cells in marrow , these precursors cells
are stimulated by IL-6 to become osteoclasts
• Bone resorbing agent such as PTH hormone stimulates osteoblast
to synthesize and collagenase and plasminogen activator which
digests the osteoid exposing the mineralizing matrix which may be
chemotactic to osteoclast
• Osteoblasts release short range soluble activators for osteoclasts

60. OSTEOCLAST MEDIATED
• The resorption area is defined beneath the ruffled border of osteoclast.
• This is highly specialized region of cytoplasmic infolding of plasma
membrane, t containing podosomes which are specialized protrusion of
the ventral surface of osteoclasts which adhere directly to the bone
surface on being broken down.
• Osteoclasts also produce ROS which may play a role in pathological
demineralization of bone during disease
• RANK (Receptor Activator Of Nuclear Factor-kappa Beta) is a receptor
expressed by osteoclast progenitor cells.
• RANKL and OPG are cytokines that belong to the TNF family and are
produced by osteoblasts and bone marrow stromal cells.
• While RANKL promotes activation of osteoclasts, OPG has the
opposite effect.
• Thus, the binding of RANKL to the RANK will result in the
differentiation of osteoclast progenitor cells into active osteoclasts,
while OPG that binds to RANKL will inhibit the differentiation process.

61. Pathobiology of Periodontal Diseases
Stimuli and factors regulating Osteoclastognesis

62. Schematic illustration presents hypothetical mechanisms
of immune intervention in the periodontal bone resorption
induced by RANKL-mediated osteoclastogenesis.
• In the presence of periodontopathic organisms CD4+ T cells
presents
increased expression of RANKL, triggering the activation of
osteoclasts and causing bone loss.

63. • A characteristic cytokine profile has been associated with each type
of periodontal disease (i.e., inflammation of marginal soft tissues
without active
bone resorption [gingivitis] or with active bone resorption
[periodontitis]).
• Thus expression of Th1-type cytokines has been associated with
gingivitis, whereas Th2-type cytokines were found in higher levels in
periodontitis-affected tissues.
• Even though this distinction was not clear because both Th1 and
Th2 cytokines were produced in gingivitis and periodontitis-affected
tissues; and the predominant profile may actually represent the
current activity of
tissue destruction.

64. ROLE OF NO IN BONE RESORPTION
• There is good evidence to suggest that NO (nitric oxide) has biphasic
effects on osteoclastic bone resorption.
• Low concentrations of no have been shown to potentiate IL-1 induced
bone resorption, based on the observation that NO inhibitors inhibit IL-1
induced bone resorption in vitro.
• Constitutive production of NO within osteoclasts has been suggested
to be essential for normal osteoclast function.

65. • The chronic immune system plays an important role in healing
process, which consists regeneration and repair:
Regeneration involves the replacement of tissue with new, identical
tissues that function same as the orignal tissue
Repair involves replacement of one tissue with another tissue, such
as fibrous connective tissue
• Under normal conditions, a platelet rich clot forms at the site of injury
which facilitates in healing.
• In periodontal infections, the platelet rich clot does not form.
• The periodontal healing cycle during the pathogenesis of periodontal
diseases is primarily post inflammatory and cellular elements other
than platelets provide important signals in this process.
• Periodontal repair occurs in overlapping phases of
1. Inflammation shutdown,
2. Angiogenesis
3. Fibrogenesis.
Healing Process in Periodontitis

66. Inflammation Shutdown
• In post inflammatory healing process, shut down of inflammatory
processes and initiation of post healing is orchestrated by leukocytes
• Anti inflammatory signals generated by leukocyte are:
IL-1 receptor antagonist (IL- 1ra)
Transforming growth factor-β (TGF-β)
• IL-4, IL-10, IL-11 also depress inflammatory response
• In the inflamed periodontal tissues:
• IL-1ra
Macrophages
• TGF-b
Mast cells
lymphocytes
Neutrophils
Macrophages

67. Potential therapeutic strategies to treat bone
resorption

68. Angiogenesis and Fibrogenesis
• IL-1β and TNF-β participate both in inflammation and healing
• IL-1β are indirectly involved in inducing fibroblast proliferation and
collagen synthesis by stimulating the production of PGE2 or release of
secondary cytokines such as Platelet derived growth factor (PDGF)
• PDGF is a protein complex formed by different combinations of A,B, C
and D chains (PDGFAA, AB,BB,CC,DD)
• PDGF is structurally and functionally related to vascular endothelial
growth factor(VEGF), an important factor in endothelial proliferation
• PDGF activates fibroblasts and osteoblasts resulting induction of
protein synthesis.

69. • Also TGF-β promotes the elaboration of fibroblast extracellular
matrix adhesion
• TGF-β is potent inhibitor of osteoclast formation
• Osteoclast differentiation and activation are inhibited by interferon-
γ (INF- γ ) which is secreted by natural killer cells, Th1 cells and
macrophages
• The main effect of INF-γ appears to be inhibition IL-1 and TNF-ά
induced osteoclast activation.
• IL-1ra also effective in blocking IL-1 and TNF-ά induced osteoclast
activation

70. CONCLUSION
• The host-bacterial interaction theory may explain why otherwise healthy
individuals with moderate levels of plaque do not exhibit loss of periodontal
support.
• In these individuals, PMNS are effective in blocking invading pathogens without
destroying the collagen content
of the periodontium in the process.
• If these same pathogens attempted to invade the periodontium of people
predisposed to periodontal disease, it appears that impaired chemotaxis and
phagocytosis of defense cells may put these individuals at significantly greater risk
for progressive periodontal destruction.

71. REFERENCES
•Text book of periodontology: Carranza 12 edn
•Text book of microbiology: Ananthnarayana 7 edn
• Oringer rj. American academy of periodontology, research, science,
and therapy committee. Modulation of the host response in periodontal
therapy. J periodontol. 2002;73(4): 460-470.
• The role of reactive oxygen and antioxidant species in periodontal
tissue destruction periodontology 2000;2007;vol43
• Toll-like receptors and their role in periodontal health and disease.
Periodontology 2000;2007;vol43;41-50
• Robbinson's basic pathology 10 edition
• Harsh Mohan - Textbook of Pathology 6th Edition