Progress 09/01/01 to 08/31/05
Outputs
Results collected during 4 year duration of project are summarized below. We have investigated the effect of transportation stress on circulating ACTH and cortisol concentrations and subsequent responsiveness of the anterior pituitary (AP) to trophic hormone (CRF or AVP) stimulation in cattle. Transportation resulted in an increase in plasma ACTH and cortisol within 1 h. ACTH and cortisol remained elevated for 6 and 10 h respectively. After cessation of transport (10 h) the magnitude and duration of ACTH secretion in response to CRF or AVP administration was dramatically reduced in transported animals relative to nontransported controls. We also investigated whether increased ACTH secretion during transportation is associated with changes in AP CRF receptor 1 (CRFR1) and AVP receptor V3 (V3) mRNA abundance and effects of central (ICV) administration of a CRF or AVP receptor antagonist on the endocrine, immune and feed intake responses to transportation stress. CRFR1
and V3 mRNAs were increased after 10 h transportation. ICV administration of the CRF receptor antagonist astressin (AST) reduced plasma ACTH at 1, 2, and 4 h relative to start of transportation but had no effect on plasma cortisol. In contrast, ACTH and cortisol were higher in animals treated with dAVP (arginine vasopressin receptor antagonist) at 4 and 6 h relative to start of transportation. Combined AST and dAVP administration reversed inhibitory effects of AST and stimulatory effects of dAVP. Antagonist administration does not appear to have dramatic effects on transportation stress induced changes in feed intake and immune function, but final analysis is ongoing. Given unexpected potentiating effects of dAVP on transportation stress induced elevations in stress hormones, we determined effects of dAVP and AST on ACTH and cortisol concentrations following LPS injection and LPS-induced regulation of AP CRFR1 and V3 mRNAs. ACTH and cortisol were not affected by dAVP or AST treatment
alone. LPS increased plasma ACTH and cortisol and the stimulatory effect of LPS was further enhanced by dAVP treatment, but blunted (ACTH only) in response to AST treatment. LPS decreased abundance of CRFR1 and V3 mRNAs and effects of LPS were blocked by ICV dAVP but not AST administration. However, AST decreased AP CRFR1 and V3 mRNA abundance in control animals not treated with LPS. In summary, results obtained from this project provide the following new mechanistic insight into regulation of the stress response in cattle: 1) Decreased AP responsiveness to CRF and AVP plays a key role in control of duration of the endocrine response to stress in cattle, but reduced responsiveness is not mediated by decreased AP abundance of CRFR1 and V3 mRNAs. 2) Transportation stress-induced secretion of ACTH is in part mediated through AP CRFR1. 3) CRFR1 mediated pathways promote basal expression of CRFR1 and V3 mRNAs in the AP. 4) Central V3 receptor signaling pathways inhibit ACTH and cortisol
secretion in response to transportation and inflammatory stress and promote down regulation of AP CRFR1 and V3 mRNAs in response to inflammatory stress.
Impacts
Under most management systems, livestock are exposed to unavoidable stressors such as handling, restraint and transport. Transportation stress has been linked to economically significant production diseases such as bovine respiratory disease in cattle transported to feedlots. Economic loss from bovine respiratory disease alone has been estimated at over $624 million annually. Despite a large volume of literature describing regulation of the stress response in rodents, very little data exists on mechanisms regulating the response in economically important species such as cattle. Information generated from this project has enhanced understanding of the mechanisms that control the stress response in cattle. Understanding these mechanisms is necessary to develop new approaches to minimize the negative effects of stress on health and well being.
Publications
- Weber, P.S.D., Madsen, S.A., Smith, G.W., Ireland, J.J. and Burton, J.L. 2001. Pre-translational regulation of neutrophil L-selectin in glucocorticoid challenged cattle. Veterinary Immunology and Immunopathology 83:213-240.
- Weber, P.S.D., Toelboell, T., Chang, L.C., Tirrell, J.D., Saama, P.J., Smith, G.W. and Burton, J.L. 2004. Mechanisms of glucocorticoid-induced down regulation of neutrophil L-selectin: Evidence for effects at the genome level and primarily on blood neutrophils. Journal of Leukocyte Biology 75:815-827.
- Dover, H., Kobayashi, Y., Drolet, A., Patel, O.V., Bettegowda, A., Q. Li, Q., Chapin, L., Knights, M., Coussens, P.M. and Smith, G.W. 2005. Stress-induced suppression of anterior pituitary and adrenal gland gene expression profiles in cattle. Proceedings of Plant and Animal Genome XIII. San Diego, CA.
|
Progress 01/01/04 to 12/31/04
Outputs
The stress-induced increase in ACTH and cortisol is regulated by corticotropin releasing factor (CRF) and arginine vasopressin (AVP). Effects of CRF and AVP are mediated via their anterior pituitary (AP) receptors, CRFR1 and V3 respectively. We previously demonstrated that transportation stress-induced ACTH secretion is reduced following administration of the CRF receptor antagonist astressin, but surprisingly, transportation stress-induced ACTH and cortisol secretion is enhanced following administration of the V3 receptor antagonist dAVP. Thus, we examined whether dAVP also potentiates ACTH and cortisol secretion in response to systemic inflammatory stress (LPS injection) and determined the effect of dAVP administration on LPS-induced regulation of AP CRFR1 and V3 mRNAs. In Study 1, Holstein steers received i.v. saline or dAVP (10 microgram per kg), followed 1 h later by i.v. LPS (200 ng per kg) or saline (n = 4 per treatment). Previous studies demonstrated that dose
of dAVP utilized effectively blocks AVP-induced ACTH and cortisol secretion in cattle. Blood samples were collected at time of LPS injection and 2h later for determination of plasma ACTH and cortisol. ACTH and cortisol secretion were not affected by dAVP treatment alone. LPS increased ACTH secretion by 400% (P < 0.001) and the stimulatory effect of LPS was enhanced 200% by dAVP treatment (P < 0.001). A similar effect on cortisol secretion was observed, but the magnitude of increase was less. In Study 2, we determined the effect of dAVP on LPS-induced changes in AP CRFR1 and V3 mRNA abundance. Intracerebroventricular (ICV) cannulated Holstein steers received either saline or ICV dAVP (750 micrograms) followed 1 h later by i.v. saline or LPS. At 4 h post LPS, steers were sacrificed and AP collected for RNA isolation. Relative concentrations of AP CRFR1 and V3 mRNAs (normalized relative to RPL-19 mRNA) were determined using quantitative real-time PCR procedures. LPS decreased (P < 0.05)
abundance of CRFR1 and V3 mRNAs compared to saline (control), but effects of LPS were blocked by ICV dAVP administration. Results lead to the suggestion that AP V3 receptor signaling pathways may inhibit LPS-induced ACTH and cortisol secretion and LPS-induced down regulation of AP CRFR1 and V3 mRNAs in cattle.
Impacts
Under most management systems, livestock are exposed to unavoidable stressors such as handling, restraint and transport. Transportation stress has been linked to economically significant production diseases such as bovine respiratory disease in cattle transported to feedlots. Economic loss from bovine respiratory disease alone has been estimated at over $624 million annually. Despite a large volume of literature describing regulation of the stress response in rodents, very little data exists on mechanisms regulating the response in economically important species such as cattle. Current and future information generated from this dramatically enhance our understanding of the mechanisms that control the stress response in cattle. Understanding these mechanisms is necessary to develop new approaches to minimize the negative effects of stress on health and well being.
Publications
- Knights, M., Ames, N.K., Smith, G.W. 2004. Involvement of anterior pituitary arginine vasopressin receptor V3 in the stress response of cattle. Journal of Animal Science 82 (Supplement 1):459.
- Knights, M., Smith, G.W. 2004. Systemic inflammatory stress decreases the abundance of mRNA for GnRH receptor, LH-beta and FSH-beta in the bovine anterior pituitary. Biology of Reproduction 70 (Special Issue):175.
|
Progress 01/01/03 to 12/31/03
Outputs
To study regulation of the stress response in cattle we have developed and validated a transportation stress model to examine the roles of corticotropin releasing factor (CRF) and arginine vasopressin (AVP) and their respective receptors, CRFR1 and V3. During the previous year, we evaluated whether increased ACTH secretion during transportation was associated with changes in CRFR1, V3 and POMC mRNA abundance in anterior pituitaries (AP) of Holstein steers collected at 0, 4 and 10 h relative to start of transportation. Abundance of CRFR1 and V3 mRNAs were elevated after 10 h transportation (P < 0.05), but POMC mRNA did not change. This suggests that the decline in AP responsiveness to CRF and AVP following transportation observed in year 1 may not be directly associated with reduced receptor mRNA abundance. We then tested the hypothesis that central (ICV) administration of a CRF and (or) AVP receptor antagonist will block the endocrine response to transportation stress
in cattle. Holstein steers (n = 4/treatment) received diluent (saline; Con), astressin (CRF receptor antagonist; AST), deaminoAVP (AVP receptor antagonist; dAVP) or AST and dAVP 30 min prior to start of 6 h transportation. Plasma ACTH and cortisol concentrations were measured 0, 1, 2, 3, 4, 6, 12 and 24 h relative to start of transportation. ACTH and cortisol were elevated within 1 h from start of transportation (P < 0.001), remained elevated during the 6 h transportation period, but returned to pre-transportation levels by 12 h. ICV AST administration reduced plasma ACTH at 1, 2, and 4 h relative to start of transportation (Trt, P = .01; Trt X Time, P < 0.05) but had no effect on cortisol. In contrast, ACTH and cortisol were higher in dAVP treated versus Con steers at 4 and 6 h relative to start of transportation (ACTH: Trt, P = 0.08; Trt X Time, P < 0.05; Cortisol: Trt, P < 0.01, Trt X Time, P < 0.05). Combined AST and dAVP administration reversed the inhibitory effects of AST and
stimulatory effects of dAVP on ACTH. Therefore, transportation stress-induced secretion of ACTH (and cortisol) is in part mediated through AP CRFR1 and can be reduced by ICV antagonist administration. The role of AVP and the V3 receptor is unclear as V3 inhibition potentiates transportation induced ACTH and cortisol secretion.
Impacts
Under most management systems, livestock are exposed to unavoidable stressors such as handling, restraint and transport. Transportation stress has been linked to economically significant production diseases such as bovine respiratory disease in cattle transported to feedlots. Economic loss from bovine respiratory disease alone has been estimated at over $624 million annually. Despite a large volume of literature describing regulation of the stress response in rodents, very little data exists on mechanisms regulating the response in economically important species such as cattle. Current and future information generated from this dramatically enhance our understanding of the mechanisms that control the stress response in cattle. Understanding these mechanisms is necessary to develop new approaches to minimize the negative effects of stress on health and well being.
Publications
- Knights, M., Smith, G.W. 2003. Effect of transportation stress on hypothalamic-pituitary-adrenal axis activation and subsequent responsiveness to trophic hormone stimulation in cattle. Joint Meeting of the American Society for Animal Science/American Dairy Science Association, Phoenix, AZ
- Knights M., Qahwash, I.M., Smith, G.W. 2003. Effect of CRF receptor antagonist administration on pituitary CRFR1 and V3 receptor mRNA and the endocrine response to systemic inflammatory stress in cattle. Proceedings of the 85th Annual Meeting of the Endocrine Society, Philadelphia, PA
|
Progress 01/01/02 to 12/31/02
Outputs
We have developed and validated a transportation stress model to study the roles of corticotropin releasing factor (CRF) and arginine vasopressin (AVP) and their respective receptors, CRFR1 and V3, in regulation of the stress resposne. We first determined if the stress-induced secretion of ACTH in cattle is regulated through the R1 and V3 receptors. Holstein steers with intracerebroventricular (icv) cannulas were given either CRF (0.5 ug/kg) or AVP (1 ug/kg) IV and 0, 250, 500 or 750 ug icv of astressin (AST; CRFR1 antagonist) or deamino AVP (V3 antagonist) respectively (n = 3 per treatment). A dose of 750 ug of AST or deamino AVP given icv was able to significantly (P < 0.05) reduce the CRF and AVP (iv) induced secretion of ACTH, respectively. We then monitored changes in ACTH during transport and measured responsiveness of the anterior pituitary (AP) to CRF and AVP challenge following transport. Steers (n = 6-7 per group) were transported for 10h or were used as
non-transported controls. Plasma concentrations of ACTH were measured from blood samples collected every 2h. Following transport, steers in both groups were randomly assigned to receive CRF or AVP and blood samples collected every 0.5 h for another 3 h. In transported steers, plasma ACTH was elevated (P < 0.05) within first 2 h of transport, remained elevated for 8 h, and returned to pre/non-transported levels by 10 h. There was no change in plasma ACTH in non-transported controls. Prior transportation dramatically decreased (P < 0.001) secretion of ACTH in response to CRF or AVP challenge, primarily through a decrease (P < 0.05) in magnitude of the peak. We also evaluated the effect of systemic administration of AST on basal and LPS-induced ACTH and cortisol secretion, and basal and LPS-induced regulation of CRFR1, V3 and POMC mRNA in the bovine AP. Holstein steers (n = 4 per treatment) were assigned to receive i.v. saline (control), AST (10ug/kg), LPS (200 ng/kg) or AST followed 1 h
later by LPS. Blood samples were collected at time of LPS injection and 2h later for determination of plasma ACTH and cortisol. At 2h after LPS, steers were sacrificed and AP collected for RNA isolation. Concentrations of CRFR1, V3 and POMC mRNA (normalized relative to RPL-19 mRNA) in the AP were determined using quantitative, real-time RT-PCR procedures. Administration of AST alone had no effect on plasma ACTH and cortisol. Plasma ACTH and cortisol increased (P < 0.001) in response to LPS. Pre-treatment with AST blunted (54%; P < 0.05) the LPS-induced increase in ACTH, but not cortisol. Administration of AST alone caused a significant decrease in both CRFR1 and V3 mRNA (P < 0.05) in the AP relative to control. LPS treatment tended (P = 0.07) to decrease AP CRFR1 mRNA and significantly decreased V3 mRNA (P < 0.05) relative to control. Pre-treatment with AST did not alter LPS-induced changes in AP CRFR1 and V3 mRNA. POMC mRNA abundance was not changed in response to any treatments.
Impacts
Our results provide new fundamental information on regulation of pituitary receptors for CRF and AVP and mechanisms regulating the stress response in cattle. Understanding these mechanisms is necessary to develop new approaches to minimize the negative effects of stress on health and well being.
Publications
- Qahwash, I.M., Cassar, C.A., Radcliff, R.P., Smith, G.W. 2002. Bacterial lipopolysaccharide-induced coordinate down regulation of arginine vasopressin receptor V3 and corticotropin releasing factor receptor 1 messenger ribonucleic acids in the anterior pituitary of endotoxemic steers. Endocrine 18:13-20.
|
Progress 01/01/01 to 12/31/01
Outputs
Exposure to stress has a severe negative impact on health and well being of livestock and can predispose animals to disease. Even in the most ideal animal production scenarios, common husbandry stressors cannot be readily avoided. In general, the stress response is attributed to the actions of two hormones, corticotropin releasing factor (CRF) and arginine vasopressin (AVP). Actions of AVP and CRF at the anterior pituitary are mediated by AVP receptor V3 (V3) and CRF receptor 1 (CRFR1). However, the regulation and specific roles of CRF and AVP and their respective receptors in mediating the physiological, neurobiological and immunological components of the response to husbandry stressors are not known. We have determined the effect of systemic inflammatory stress on V3 and CRFR1 mRNAs in the bovine anterior pituitary and determined whether the observed regulation is tissue specific. Holstein steers (n = 20) were injected with 200 ng/kg bacterial lipopolysaccharide
(LPS) and tissues collected 0, 2, 4, 12 and 24 h later. All animals responded to LPS administration with an increase in body temperature, plasma ACTH and cortisol (P < 0.05). Abundance of anterior pituitary V3 mRNA was decreased at 2, 4 and 12 h following LPS administration (P < 0.05) and returned to basal by 24 h. A similar temporal regulation of pituitary CRFR1 mRNA (P < 0.05) but not pituitary POMC mRNA, was observed following LPS administration. Similar down regulation of CRFR1 mRNA was not observed in other brain regions following LPS administration (cerebellum, hypothalamus). Our results indicate that V3 and CRFR1 mRNAs are coordinately down regulated in the anterior pituitary during systemic inflammatory stress. Decreased AVP and CRF receptor expression may help regulate the pituitary-adrenal response to stress.
Impacts
Our studies provide new information on the regulation of CRF and AVP receptors during a stress response. Increased understanding of the mechanisms controlling the physiological, immunological, and neurobiological responses to stress may ultimately form part of the basis for development of new methods to enhance health and well being of livestock.
Publications
- Qahwash, I.Q.., Radcliff, R.P. and Smith, G.W. 2001. Regulation of arginine vasopressin receptor V3 messenger RNA in the anterior pituitary of endotoxemic steers. Proceedings of the 83rd Annual Meeting of the Endocrine Society, June, 2001, Denver, CO, p. 365.
|
|