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1. SREE VIDYANIKETHAN COLLEGE OF PHARMACY
PathoPhysiology Assignment on
1.Chemical mediators on Inflammation
2.Drug Hypersensitivity
Submitted to: Submitted By:
Dr.Ramya.K
Assistant Professor
Department of Pharmacy
Practice
A Sowjanya
II Pharm D
20P91T0003

2. CHEMICAL MEDIATORS OF INFLAMMATION
Also called as permeability factors or endogenous mediators of increased vascular
permeability, these are a large and increasing number of endogenous compounds which can
enhance vascular permeability. However, currently many chemical mediators have been
identified which partake in other processes of acute inflammation as well e.g. vasodilatation,
chemotaxis, fever, pain and cause tissue damage.
The substances acting as chemical mediators of inflammation may be released from the cells,
the plasma, or damaged tissue itself. They are broadly classified into 2 groups:
i) mediators released by cells,
ii) mediators originating from plasma.
Chemical mediators derived from various sources and their contribution in acute inflammation
are shown in Fig
CHEMICAL MEDIATORS OFACUTE INFLAMMATION
1.CELL-DERIVED MEDIATORS
1. Vasoactive amines (Histamine, 5-hydroxytryptamine, neuropeptides)
2. Arachidonic acid metabolites (Eicosanoids)
i. Metabolites via cyclo-oxygenase pathway (prostaglandins, thromboxane A2,
prostacyclin, resolvins).
ii. Metabolites via lipo-oxygenase pathway (5-HETE, leukotrienes, lipoxins)
3. Lysosomal components (from PMNs, macrophages)
4. Platelet activating factor

3. 5. Cytokines (IL-1, TNF-a, TNF-B, IFN-y, chemokines)
6. Free radicals (Oxygen metabolites, nitric oxide)
11. PLASMA-DERIVED MEDIATORS (PLASMA PROTEASES)
Products of:
1. The kinin system
2. The clotting system
3. The fibrinolytic system
4. The complement system
I.CELL-DERIVED MEDIATORS
1.VASOACTIVE AMINES
Two important pharmacologically active amines that have role in the early inflammatory
response (first one hour) are histamine and 5 hydroxytryptamine (5-HT) or serotonin; another
recently added group is of neuropeptides.
i) Histamine
It is stored in the granules of mast cells, basophils and platelets. Histamine is released from
these cells by various agents as under:
a) Stimuli or substances inducing acute inflammation e.g. heat, cold, irradiation, trauma,
irritant chemicals, immunologic reactions etc.
b) Anaphylatoxins like fragments of complement C3a, and C5a, which increase vascular
permeability and cause oedema in tissues.
c) Histamine-releasing factors from neutrophils, monocytes and platelets.
d) Interleukins.
The main actions of histamine are: vasodilatation, increased vascular (venular) permeability,
itching and pain. Stimulation of mast cells and basophils also releases products of arachidonic
acid metabolism including the release of slow reacting substances of anaphylaxis (SRS-As).
The SRS-As consist of various leukotrienes (LTC,, LTD, and LTE).
ii) 5-Hydroxytryptamine (5-HT or serotonin).
It is present in tissues like chromaffin cells of GIT, spleen, nervous tissue, mast cells and
platelets. The actions of 5-HT are similar to histamine but it is a less potent mediator of
increased vascular permeability and vasodilatation than histamine. It may be mentioned here
that carcinoid tumour is a serotonin-secreting tumour (Chapter 20).

4. iii) Neuropeptides.
Another class of vasoactive amines is tachykinin neuropeptides, such as substance P,
neurokinin A, vasoactive intestinal polypeptide (VIP) and somatostatin. These small peptides
are produced in the central and peripheral nervous systems.
The major proinflammatory actions of these neuropeptides is as follows:
a) Increased vascular permeability.
b) Transmission of pain stimuli.
c) Mast cell degranulation.
2. ARACHIDONIC ACID METABOLITES (EICO SANOIDS).
Arachidonic acid metabolites or eicosanoids are the most potent mediators of inflammation,
much more than oxygen free radicals.
Arachidonic acid is a fatty acid, eicosatetraenoic acid; Greek word 'eikosa' means 'twenty'
because of 20 carbon atom composition of this fatty acid. Arachidonic acid is a constituent of
the phospholipid cell membrane, besides its presence in some constituents of diet. Arachidonic
acid is released from the cell membrane by phospholipases. It is then activated to form
arachidonic acid metabolites or eicosanoids by one of the following 2 pathways: via cyclo-
oxygenase pathway and via lipo-oxygenase pathway.
i) Metabolites via cyclo-oxygenase pathway:
Prostaglan dins, thromboxane A2, prostacyclin. The name 'prosta glandin' was first given to a
substance found in human seminal fluid but now the same substance has been isolated from a
number of other body cells. Prostaglandins and related compounds are also called autocoids
because these substances are mainly auto- and paracrine agents. The terminology used for
prostaglandins is abbreviation as PG followed by suffix of an alphabet and a serial number e.g.
PGG2, PGE2 etc.
Cyclo-oxygenase (COX), a fatty acid enzyme present as COX-1 and COX-2, acts on activated
arachidonic acid to form prostaglandin endoperoxide (PGG₂). PGG, is enzymatically
transformed into PGH, with generation of free radical of oxygen. PGH, is further acted upon
by enzymes and results in formation of the following 3 metabolites .

5. a) Prostaglandins (PGD2, PGE, and PGF2-0). PGD, and PGE2 act on blood vessels to cause
increased venular permeability, vasodilatation and bronchodilatation and inhibit inflammatory
cell function. PGF2-a induces vasodilatation and bronchoconstriction.
b) Thromboxane A, (TXA,). Platelets contain the enzyme thromboxane synthetase and hence
the metabolite, thromboxane A2, formed is active in platelet aggregation, besides its role as a
vasoconstrictor and broncho-constrictor.
c) Prostacyclin (PGI). PGI, induces vasodilatation, broncho dilatation and inhibits platelet
aggregation.
d) Resolvins are a newly described derivative of COX pathway. These mediators act by
inhibiting production of pro-inflammatory cytokines. Thus, resolvins are actually helpful-drugs
such as aspirin act by inhibiting COX activity and stimulating production of resolvins.
It may be mentioned here that some of the major anti inflammatory drugs act by inhibiting
activity of the enzyme COX; e.g. non-steroidal anti-inflammatory drugs (NSAIDs), COX-2
inhibitors.
ii) Metabolites via lipo-oxygenase pathway:
5-HETE, leukotrienes, lipoxins. The enzyme, lipo-oxygenase, a predominant enzyme in
neutrophils, acts on activated arachidonic acid to form hydroperoxy eicosatetraenoic acid (5-
HPETE) which on further peroxidation forms following 2 metabolites.
a) 5-HETE (hydroxy compound), an intermediate product, is a potent chemotactic agent for
neutrophils.

6. b) Leukotrienes (LT) are so named as they were first isolated from leucocytes. Firstly, unstable
leukotriene A, (LTA) is formed which is acted upon by enzymes to form LTB (chemotactic for
phagocytic cells and stimulates phagocytic cell adherence) while LTC,, LTD, and LTE, have
common actions by causing smooth muscle contraction and thereby induce vasoconstriction,
bronchoconstriction and increased vascular permeability; hence they are also called as slow
reacting substances of anaphylaxis (SRS-As).
c) Lipoxins (LX) are a recently described product of lipooxygenase pathway. Lipooxygenase-
12 present in platelets acts on LTA, derived from neutrophils and forms LXA, and LXB,.
Lipoxins act to regulate and counterbalance actions of leukotrienes.
3. LYSOSOMAL COMPONENTS.
The inflammatory cells-neutrophils and monocytes, contain lysosomal granules which on
release elaborate a variety of mediators of inflammation. These are as under:
i) Granules of neutrophils
Neutrophils have 3 types of granules: primary or azurophil, secondary or specific, and tertiary.
a) Primary or azurophil granules are large azurophil granules which contain functionally active
enzymes. These are myeloperoxidase, acid hydrolases, acid phosphatase, lysozyme, defensin
(cationic protein), phospholipase, cathepsin G, elastase, and protease.
b) Secondary or specific granules contain alkaline phosphatase, lactoferrin, gelatinase,
collagenase, lysozyme, vitamin-B12 binding proteins, plasminogen activator. c) Tertiary
granules or C particles contain gelatinase and acid hydrolases. Myeloperoxidase causes
oxidative lysis by generation of oxygen free radicals, acid hydrolases act within the cell to
cause destruction of bacteria in phagolysosome while prote ases attack on the extracellular
constituents such as basement membrane, collagen, elastin, cartilage etc.
However, degradation of extracellular components like collagen, basement membrane, fibrin
and cartilage by proteases results in harmful tissue destruction which is kept in check by
presence of antiproteases like a-antitrypsin and a-macroglobulin.
ii) Granules of monocytes and tissue macrophages.
These cells on degranulation also release mediators of inflammation like acid proteases,
collagenase, elastase and plasminogen activator. However, they are more active in chronic
inflammation than acting as mediators of acute inflammation.
4. PLATELET ACTIVATING FACTOR (PAF).
It is released from IgE-sensitised basophils or mast cells, other leucocytes, endothelium and
platelets. Apart from its action on platelet aggregation and release reaction, the actions of PAF
as mediator of inflammation are:
• increased vascular permeability;
• vasodilatation in low concentration and vasoconstriction otherwise;
• bronchoconstriction;
• adhesion of leucocytes to endothelium;
• chemotaxis.

7. 5. CYTOKINES.
Cytokines are polypeptide substances pro duced by activated lymphocytes (lymphokines) and
activated monocytes (monokines). These agents may act on 'self' cells producing them or on
other cells. Although over 200 cytokines have been described, major cytokines acting as
mediators of inflammation are: interleukin-1 (IL-1), tumour necrosis factor (TNF)-a and ẞ,
interferon (IFN)-y, and chemokines (IL-8, PF-4).
IL-1 and TNF-a are formed by activated macrophages while TNF-ẞ and IFN-y are produced
by activated T cells. The chemokines include interleukin 8 (released from activated
macrophages) and platelet factor-4 from activated platelets, both of which are potent
chemoattractant for inflammatory cells and hence their name.
The actions of various cytokines as mediator of inflammation are as under:
i) IL-1 and TNF-a, TNF-ẞ induce endothelial effects in the form of increased leucocyte
adherence, thrombogenicity, elaboration of other cytokines, fibroblastic proliferation and acute
phase reactions.
ii) IFN-y causes activation of macrophages and neutrophils and is associated with synthesis of
nitric acid synthase. iii) Chemokines are a family of chemoattractants for inflammatory cells
(as discussed above) and include:
• IL-8 chemotactic for neutrophils;
• platelet factor-4 chemotactic for neutrophils, monocytes and eosinophils;
• MCP-1 chemotactic for monocytes;
• And eotaxin chemotactic for eosinophils.
6. FREE RADICALS: OXYGEN METABOLITES AND NITRIC OXIDE.
Free radicals act as potent mediator of inflammation:
i) Oxygen-derived metabolites are released from activated neutrophils and macrophages and
include superoxide oxygen (O2), H2O, OH' and toxic NO products. These oxygen-derived free
radicals have the following action in inflammation:
• Endothelial cell damage and thereby increased vascular permeability.
• Activation of protease and inactivation of antiprotease causing tissue matrix damage.
• Damage to other cells.
The actions of free radicals are counteracted by antioxidants present in tissues and serum which
play a protective role .
ii) Nitric oxide (NO) was originally described as vascular relaxation factor produced by
endothelial cells. Now it is known that NO is formed by activated macrophages during the
oxidation of arginine by the action of enzyme, NO synthase. NO plays the following role in
mediating inflammation:
• Vasodilatation
• Anti-platelet activating agent
• Possibly microbicidal action.

8. II. PLASMA-DERIVED MEDIATORS(Plasma Proteases)
These include the various products derived from activation and interaction of 4 interlinked
systems: kinin, clotting, fibrinolytic and complement. Each of these systems has its inhibitors
and accelerators in plasma with negative and positive feedback mechanisms respectively.
Hageman factor (factor XII) of clotting system plays a key role in interactions of the four
systems. Activation of factor XII in vivo by contact with basement membrane and bacterial
endotoxins, and in vitro with glass or kaolin, leads to activation of clotting, fibrinolytic and
kinin systems. In inflammation, activation of factor XII is brought about by contact of the factor
leaking through the endothelial gaps. The end-products of the activated clotting, fibrinolytic
and kinin systems activate the complement system that generate permeability factors. These
permeability factors, in turn, further activate clotting system.
The inter-relationship among 4 systems is summarised in Fig.
1. THE KININ SYSTEM.
This system on activation by factor Xlla generates bradykinin, so named because of the slow
contraction of smooth muscle induced by it. First, kallikrein is formed from plasma
prekallikrein by the action of prekallikrein activator which is a fragment of factor Xlla.
Kallikrein then acts on high molecular weight kininogen to form bradykinin .

9. Bradykinin acts in the early stage of inflammation and its effects include:
• smooth muscle contraction;
• vasodilatation;
• increased vascular permeability;
• pain.
2. THE CLOTTING SYSTEM.
Factor Xlla initiates the cascade of the clotting system resulting in formation of fibrinogen
which is acted upon by thrombin to form fibrin and fibrinopeptides (Fig. 6.12). The actions of
fibrinopeptides in inflammation are:
• increased vascular permeability;
• chemotaxis for leucocyte;
• anticoagulant activity.
3. THE FIBRINOLYTIC SYSTEM.
This system is activated by plasminogen activator, the sources of which include kallikrein of
the kinin system, endothelial cells and leucocytes. Plasminogen activator acts on plasminogen
present as component of plasma proteins to form plasmin. Further breakdown of fibrin by
plasmin forms fibrino peptides or fibrin split products (Fig. 6.13).
The actions of plasmin in inflammation are as follows:
• activation of factor XII to form prekallikrein activator that stimulates the kinin system
to generate bradykinin; splits off complement C, to form C3 which is a permeability
factor;

10. • degrades fibrin to form fibrin split products which increase vascular permeability and
are chemotactic to leucocytes.
4. THE COMPLEMENT SYSTEM.
The activation of complement system can occur either:
i) by classic pathway through antigen-antibody complexes; or
ii) by alternate pathway via non-immunologic agents such as bacterial toxins, cobra venoms
and IgA.
Complement system on activation by either of these two pathways yields activated products
which include anaphylatoxins (C3a, C4a and C5a), and membrane attack complex (MAC) i.e.
C5b,C6,7,8,9.
The actions of activated complement system in inflammation are as under:
• C3a, C5a, C4a (anaphylatoxins) activate mast cells and basophils to release of
histamine, cause increased vascular permeability causing oedema in tissues, augments
phagocytosis.
• C3b is an opsonin.
• C5a is chemotactic for leucocytes.
• Membrane attack complex (MAC) (C5b-C9) is a lipid dissolving agent and causes holes
in the phospholipid membrane of the cell.
Reference:
1.Textbook of Pathology. Harsh Mohan,
Inflammation & Healing: Chemical mediations of Inflammation. Seventh Edition. New Delhi:
Jaypee Brothers Medical Publishers(p) Ltd,2015.

11. DRUG HYPERSENSITIVITY
HYPERSENSITIVITY:
It is defined as an immune response, where the reaction is out of proportion to the damage
caused by the antigen or pathogen does more harm than good .There are three types of hyper
sensitivity ,they are ;
• Food hypersensitivity
• Drug hypersensitivity
• Chemical hypersensitivity
INTRODUCTION :
Drug hypersensitivity reactions are adverse effects of pharmaceutical formulations (including
active drugs and excipients) that clinically resemble allergy. Iatrogenic by nature, drug
allergy does against the ultimate purpose of prescribing a drug which is to alleviate, and not to
induce the disease.
1. Immediate type in which on administration of antigen,
the reaction occurs immediately (within seconds to minutes). Immune response in this type is
mediated largely by humoral antibodies (B cell mediated). Immediate type of hyper
sensitivity reactions include type I, II and III.
2. Delayed type in which the reaction is slower in onset and develops within 24-48 hours and
the effect is prolonged. It is mediated by cellular response (T cell mediated) and it includes
Type IV reaction.
The etiopathogenesis and examples of immunologic tissue injury by the 4 types of
hypersensitivity reactions are discussed below and are summarised in the Table.

12. Drug hypersensitivity:
Drug hypersensitivity is an immune mediated reaction to a drug. Symptoms
range from mild to severe and include rash, anaphylaxis, and serum sickness. Diagnosis is
clinical; skin testing is occasionally useful. Treatment is drug discontinuation, supportive
treatment and sometimes desensitization.
Examples of drug hypersensitivity:
o Penicillin
o Ampicillin
o Sulpha drugs
o Amiodarone
o Bleomycin
o Nitrofurantoin

13. Small molecules/drugs can interact with the immune system and inflammatory cells through
different modes of action. The drug or drug metabolite might be able to bind covalently to
proteins or peptides and might form a new antigen, which could stimulate drug-specific B and
T cells if the innate immune system is also activated. If the subject is exposed to the drug again,
urticaria/angioedema/ anaphylaxis can occur if drug-specific IgE is formed. More common is
the stimulation of T cells, which cause various forms of exanthems depending on the type of
T-cell stimulation. The piperacillin model of Sullivan et al might belong to this "classical"
immune stimulation by drugs: these authors showed that IL-22 seems to be an important
cytokine involved in maculopapular exanthema and that the activated CD4 cells are cyto toxic.
Drugs can bind directly to the highly polymorphic immune receptors aß T-cell receptor (TCR)
or HLA class II molecules. Such off-target activities are termed p-i and represent an important
cause of T cell mediated DHRs, including DRESS syndrome and Stevens-Johnson syndrome
or toxic epidermal necrolysis (SJS/TEN). Some drugs bind to a particular HLA molecule only
(pi-HLA; eg, abacavir to HLA-B*57:01), which explains the HLA restriction, and others bind
to the TCR (pi-TCR). In all T cell-mediated DHRs from patients with mild maculopapular
exanthema to those with SJS/TEN, cytotoxic T cells (CD4 and CD8) are involved, and in some
cases natural killer (NK) cells might play a role. For details of p-i stimulation and their
functional consequence, see Pichler et al. The third possibility of DHRs refers to drug binding
and interference with receptors or enzymes of inflammatory cells. Many possibilities exist.
This might result in mast cell activa tion by drug binding to MRGPRX2 (with subsequent
urticaria and anaphylaxis) or in enhanced inflamma tion, if, for example, COX of activated
eosinophils, basophils, or neutrophils are blocked (nonsteroidal anti-inflammatory drug
(NSAID) intolerance). In all 3 forms of drug hypersensitivity, the predominant reac tion to a
drug is nonreactivity/"tolerance," whereby tolerance comprises different mechanism, including
lack of costimulation, ignorance, and active tolerance. The underlying mechanism of
tolerance/nonreactiv ity in all 3 modes of drug-induced immune/inflammatory cell stimulations
is unknown. Fas L, Fas ligand.

14. Signs and Symptoms of Drug Hypersensitivity:
Symptoms and signs of drug allergies vary by patient and drug, and a single drug may cause
different reactions in different patients. The most serious is anaphylaxis (type I
hypersensitivity reaction). exanthema (eq, morbilliform eruption), urticaria, and fever ore
common. Fixed drug reactions reactions that recur at the same body site each time a patient is
exposed to the some drug-are uncommon.
➢ Some distinct clinical syndromes can involve other types of hypersensitivity reactions.
• Serum Sickness. This reaction typically occurs 7 to 10 days after exposure and causes
fever, arthralgias, and rash. Mechanism is a type III hypersensitivity reaction due to
drug-antibody complexes and complement activation. Some patients have frank
arthritis, edema, or gastrointestinal symptoms. Symptoms are self-limited, lasting 1 to
2 weeks. Beta-lactam and sulfonamide antibiotics, iron-dextron, and carbamazepine are
most commonly implicated.
• Drug-induced immune hemolytic anemia. This disorder may develop when an
antibody-drug-red blood cell (KBC) interaction occurs (eg, with cephalosporins and
with cefotetan) or when a drug(eq, fludarabine, methyldopa) alters the KBL membrane
in a way that induce autoantibody production. I hese reactions are type II
hypersensitivity reactions.
• DRESS (drug rash with eosinophilia and systemic symptoms). This condition, also
called drug induced hypersensitivity syndrome (VHS), is a type hypersensitivity
reaction that can start up to 12 weeks after initiation of drug treatment and can occur
after a dose increase. Symptoms may persist or recur for several weeks after stopping
drug treatment. Patients have prominent eosinophilia and often develop hepatitis,
exanthema, facial swelling, generalized edema, and lymphadenopathy. Drugs include
Carbamazepine, phenytoin, allopurinol, and lamotrigine are frequently implicated.
• Pulmonary effects: Some drugs induce respiratory symptoms deterioration in
pulmonary function, and other pulmonary changes (colled drug-induced pulmonary
disease, most commonly interstitial lung disease). I hese effects are thought to be
primarily type III and type IV hypersensitivity reactions. Drugs that may have these
effects include bleomycin, amiodarone, nitrofurantoin, amphotericin B,
sulphonamides, and sulfasalazine.
• Renal effects: Tubulointerstitial nephritis is the most common allergic renal reaction
methicillin, antimicrobials, and cimetidine are commonly implicated. I upes I, II, and/
or IV hypersensitivity reactions can be involved.
• Other autoimmune phenomena: Hydralazine, propylthiouracil, and procainamide con
couse a systemic lupus erythematosus (SLE)-like syndrome, which is a type III
hypersensitivity reaction.
Diagnosis of Drug Hypersensitivity:
• Patient's report of a reaction soon after taking a drug.
• Skin testing.
• Sometimes drug provocation testing.
• Sometimes direct and indirect antiglobulin assays
The following can help differentiate drug hypersensitivity from toxic and adverse drug effects
and from problems due to drug interactions.

15. • Time of onset.
• Known effects of a drug.
• Results of a repent drug challenge
For example, a dose-related reaction is often drug toxicity, not drug hypersensitivity.
Treatment:
When a hypersensitivity reaction arises, the immediate discontinuation of the triggering drug
is the safest option. The reaction itself can only be managed with supportive care, e.g., with
glucocorticoids.
Treatment of drug allergies is stopping the implicated drug: most symptoms and signs clear
within a few days after the drug is stopped.
➢ Symptomatic and supportive treatment for acute reactions may include:
• Antihistamines for pruritus.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) for arthralgias.
• Corticosteroids for severe reactions (eg, exfoliative dermatitis, bronchospasm).
• Epinephrine for anaphylaxis
Conditions such as drug fever, a nonpruritic rash, or mild organ system reactions require no
treatment other than discontinuation of a drug.
Reference:
1. Textbook of pathology, Harsh Mohan, Immunopathology including Amyloidosis:
Hypersensitivity, seventh edition, New Delhi: Jaypee Brothers medical publishers (p)
Ltd.,2015.
2. www.ncbi.nlm.nih.gov
3. www.jacionline.org