Despite recent rapid advances in understanding the molecular mechanisms of the HIF pathways in response to hypoxia, many important questions remain to be answered? Unraveling such questions should provide new insights into cellular adaptation to hypoxia and aid to discover new therapeutic approaches to reduce animal diseases. Genetic selection for breeds of animals resistant to the extreme climatic conditions. Optimisation of gradual shift of animals from one altitude to another.

1. By: Dr Wani Ahad
M.V.Sc Scholar
Animal Biotechnology

2. 
 The term “stress” was borrowed from the field of
physics by Hans Selye
(Hans Selye, 1926)
 And has been widely used in biology to describe a
set of physiological and behavioural changes
elicited by adverse stimuli
He proposed that “stress is a non-specific response of the
body to any change”
Stress

3.  In 1929, Cannon described stress as the
sympatho-adreno medullary (SAM) system
attempt to regulate homeostasis when
threatened by a variety of adverse stressors
(Walter Cannon, 1929)
 Is the condition “where the environmental demand exceeds
the natural regulatory capacity of an organism’’
(Bruce McEwen and Jaap Koolhaas, 2011)
Stress

4. 
HISTORY
 Bernard recognized that the stability
of the milieu interieur depended on
ensembles of compensating mechanisms
(Bernard, 1878)
 Fifty years later, Walter Cannon (1929) introduced the
term “homeostasis” to describe the dynamic, interactive
nature of these mechanisms in maintaining the stability of
the internal environment

5. 
 Endocrine and neuroendocrine events proceed in an
interdependent manner to regulate multiple, variable stress
responses, each unique, but influenced by previous events
Summers (2001)
 Thermal stress on livestock particularly cattle and buffaloes
decreases oestrus expression and conception rate
Upadhya et al., (2007)
HISTORY

6. 
 ABIOTIC
 Environmental
 Changes in temperature (Heat or Cold)
and relative humidity
 Ventilation
 High altitude(Hypoxia)
 Managemental
 Fear
STRESS FACTORS

7. 
 Social
 Isolation
 High population density
 Mixing
Pathology
 Pain
 Feeding
 Hunger
 Thirst
STRESS FACTORS

8. 
BIOTIC
 Diseases:
 Bacterial
 Viral
 Fungal
 Parasitic
STRESS FACTORS

9. 
 Stressful events can activate the Hypothalamo-Pituitary-Adrenal
(HPA) axis or sympatho-adrenomedullary (SAM) system
 The short term responses are produced by The Fight or Flight
Response via SAM pathway and long term responses via HPA
pathway
 HPA axis increases the release of Corticotrophin Releasing
Hormone (CRH) from the hypothalamic paraventricular nucleus
(Campagne, 2006)
General pathways involved
in stress

10. 
Stress pathways (HPA)
Hypothalamus
(PVN)
CRH
Ant.pituitary
ACTH
Cortisol
Release of
Neurotransmitters
(i.e. NE,
cholecystokinin,
serotonin)
-
Adrenal
Gland
Catecholamines
Stress
event
+
Energy Metabolism

11. 
High Altitude
Hypoxia

12. 
 Is the reduction of oxygen supply to a tissue below
physiological levels despite adequate blood perfusion to the
tissue
(Illingworth et al., 2014)
 Is a condition in which the body or a region of the body is
deprived of adequate oxygen supply
(Woorons & Xavier, 2014)
Hypoxia
(Hypoxiation or Anoxemia)

13. 
 Low partial pressure of oxygen in the blood
a) Low oxygen inspired air e.g high altitude
b) Inadequate ventilation due to lung disease or depression of
breathing by drugs
c) Defective transfer of oxygen from lung alveoli to blood
Causes

14. 
 Low content of oxygen in the blood due to inadequate or
abnormal haemoglobin e.g anemia
 Failure of the heart and circulation to deliver an
adequate oxygen supply to the tissues, even though the
content in the blood may be normal
 Poisoning of cells so that they cannot use the oxygen
delivered to them
Causes

15. 
 Generalized hypoxia affecting the whole body
 Local hypoxia affecting a particular region of the body
 Acute hypoxia a sudden or rapid depletion in the
availability of oxygen at the tissue level
 Chronic hypoxia a usually slow, insidious reduction in
tissue oxygenation
Classification

16. 
 Anemic hypoxia is due to reduction of the oxygen-carrying
capacity of the blood due to decreased total hemoglobin or
altered hemoglobin constituents
 Histotoxic hypoxia is due to impaired use of oxygen by
tissues
 Ischemic hypoxia is the local deficiency of arterial blood in
an organ
Types

17. 
 Hypoxic hypoxia is due to insufficient oxygen reaching
to the blood
 Stagnant hypoxia due to the failure to transport sufficient
oxygen because of inadequate blood flow e.g Hypo-
volumic shock
 Embolic hypoxia due to an emboli in the blood vessels
e,g air,blood clot etc
Types

18. 
 Hypoxia Inducible Factors (HIFs) are important
transcription factors in the cellular adaptation to hypoxia
by regulating different sets of genes involved in
angiogenesis, metabolism and cell homeostasis
(Semenza and Wang, 2011)
 They are heterodimeric transcription factors consisting of
two structurally related subunits, one is an oxygen
sensitive HIFα subunit (HIF-1α , HIF-2α or EPAS1 and
HIF3α)
Counter Mechanism

19. 
 and the other is the stable subunit, HIF-1β/ARNT-subunit
(Aryl hydrocarbon Receptor Nuclear Translocator)
(Wang et al., 1995)
 HIF-1α is expressed in all cells
 HIF2α and HIF3α are selectively expressed in certain tissues,
including vascular endothelial cells, type II pneumocytes,
renal interstitial cells & liver parenchymal cells
(Bertout et al., 2008)
Hypoxia Inducible Factor

20. 
HIF1α and HIF1β structures
774/789 aa
HIF-1β
/ARNT
b
HLH
A PAS B
826 aaHIF-1α
b
HLH
A PAS B
TAD
C
ID
TAD
N
NLS-N NLS-C

21. 
Protein Expression as a Function of [O2]
Oxygen Concentration
HIF-1 expression
increases exponentially
when O2 concentration
decreases. The curve
shows a point of
inflection around 4-5%
O2, which is the O2
concentration in normal
human tissues
(Semenza GL. 1997)

22.  Conserved proline residue in HIF-1α are hydroxylated by
prolyl hydroxylase/PHD (oxygen dependent)
(Ivan et al., 2001)
 In normal conditions hydroxylation of proline causes the
binding of von Hippel-Lindau tumor suppressor (VHL) protein
by an E3 ubiquitin ligase
(Kaelin and Ratcliffe, 2008)
 The binding leads to the ubiquitination of HIF-1α &
degradation by proteasome
(Giaccia A J et al., 2004)
Mechanism

23. 
 Under hypoxic conditions prolyl hydroxylase is not
activated
 HIF-1α accumulates and translocates into nucleus
 In the nucleus, it binds to HIF-1β through their HLH
and PAS domains forming HIF-1 and binds to HRE
present in target genes
(Mole et al., 2009; Xia et al., 2009)
Mechanism

24. 
HIF-1 is a heterodimer
HIF-1
hypoxia
HIF-1
HREHIF-1
Pol II
complex
CBP/p300
Angiogenesis
(VEGF)
Glucose
metabolism
Cell
proliferation

25. 
 Helps normal tissues as well as tumors to survive
under hypoxic conditions
 Stimulates lipid storage and inhibits lipid catabolism
through β-oxidation
(Bostrom et al., 2006)
 HIF1α and HIF2α can modulate the expression of
cytochrome c oxidase isoforms so as to maximize
efficiency of the ETC
(Gordan et al., 2007)
Role of HIF-1

26. 
 Regulate angiogenic genes such as vascular endothelial
growth factor (VEGF)
(Manalo et al., 2005)
 HIF activation has been observed in the tissue from patients with
inflammatory conditions such as arthritis, artherosclerosis, and
autoimmune diseases
(Nizet and Johnson, 2009)
 So far, more than 40 target genes have been found to be
regulated by HIF-1
 These genes can be classified into 3 main groups:
Role of HIF-1

27. HIF-1
HYPOXIA
Vascular Permeability
VEGF
VEGFR-1
Vasodilation
Nitric oxide synthases
Endothelial Sprouting
Angiopoietin-1
Proliferation & migration of
endothelial cells
VEGF PGF
Inhibitory Factors
Angiopoietin-2
Extra Cellular
Matrix
Matrix
Metalloproteinases

28. 
 Erythropoeitin (EPO)
 Nitric oxide synthase (NOS)
 Transferrin
 Transferrin receptor
 Vascular endothelial
growth factor (VEGF)
 VEGF receptor -1
(Skuli et al., 2009)
HIF-1 Target Genes
Group 1:
O2 Delivery

29. 
 Hexokinase
 Phosphofructokinase
 Aldolase
 3-Phospho Glyceraldehyde
dehydrogenase
 Phosphoglycerate kinase
 Enolase (ENO)
 Pyruvate kinase
 Glucose transporter 1
 Lactate dehydrogenase (Gordan et al., 2007)
Group 2:
Glucose
/Energy
Metabolism
HIF-1 Target Genes

30. 
 Insulin-like growth
factor 2 (IGF-2)
 IGF binding protein 1
 IGF binding protein 3
 P21/WAF1/CIP1
 p35srj
Group 3:
Cell Proliferation
/Viability
HIF-1 Target Genes

31. 
Symptoms Signs
 Dyspnea
 Restlessness
 Anorexia
 Confusion
 Agitation
 Headache
 Tremor
 Nausea
 Fatigue
 Respiratory distress
 Cyanosis
 Tachypnea
 Tachycardia
 Cardiac arrhythmias
 Hypertension
 Hypotension
 Lethargy
 Coma

32. 
Impacts of Hypoxia
 Brisket disease: Subcutaneous
accumulation of fluid under the
abdomen,brisket,neck and jowl
(John H Newman et al., 2011)
 Hypertrophy of myocardium
 Valvular incompetency
 Polycythemia
 Polypnoea

33. 
 Hypoxia induced oxidative stress
for short or long time periods
affects corpus luteum
development and function, leading
to the decreased sheep fertility at
high altitude
(Parraguez VH et al., 2013)
 Respiratory alkalosis
Impacts of Hypoxia

34. 
 Cyanosis bluish tinge to the
skin, lips, and nails
 Acute mountain sickness
accompanied by loss of
appetite, nausea, vomiting,
fatigue, weakness, irritability
or trouble sleeping
(Hall D.P et al., 2014)
Impacts of Hypoxia

35. 
 High-altitude pulmonary
edema (HAPE) usually
develops with in 24 to 96
hours
(Kleinsasser et al., 2003)
 High-altitude cerebral
edema (HACE) is a rare but
potentially fatal condition
(Patir H et al., 2012)
Impacts of Hypoxia

36. 
 Pregnant animals are at high risk
 Premature labor
 Small birth weights
 The average survivability of these breed has been
reported to be 60%
 Inverse correlation between hypoxic zone & sperm
concentration
 Decrease sperm motility
(Sokol, 2006)
Impacts of Hypoxia

37. 
 Early embryonic loss in livestock
(Reynolds, 2005)
 Cortisol alters oxytocin receptor expression
(Champagne, 2006)
 Reduced oocyte quality in cattle
(Rocha, 2003)
 Heat stress reduces the developmental ability of embryos
(Rutledge, 2001 )
Impacts of Stress

38. 
 To limit the impact of extreme climatic events
 Genetic selection for breeds resistant to the extreme
climatic conditions
 Optimisation of gradual shift of flock from one altitude to
another
 Careful management and well designed housing at the
level of the farming system for different altitudes are
important in achieving the optimum animal performance
Conclusion