Analysis of AVP functions via V1a and V1b receptors with knockout mice. Akito Tanoue

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1 Analysis of AVP functions via V1a and V1b receptors with knockout mice Akito Tanoue Department of Pharmacology, National Research Institute for Child Health and Development

2 Arginine-Vasopressin (AVP) is involved in regulating diverse functions -pituitary- ACTH secretion -uterus- Muscle contraction -liver- Glycogenolysis -kidney- Anti-diuresis -platelet- Aggregation -Cardiovascular-ascular Vasoconstriction -pancreas- Insulin secretion -adrenal- Hormone secretion These physiological effects of AVP are mediated via the AVP receptor subfamily. Subtype V1a V1b V2 Expression site Vessels Anterior pituitary Renal tubules action vasoconstriction ACTH secretion antidiuresis

3 SBP (mmhg) 12 1 WT (18) V1aR-KO (15) V1bR-KO (14) Reduced Blood Pressure (BP) in V1aR-KO MAP (mmhg) Catecholamine 12 1 ng/ml pg/ml AVP Koshimizu et al., Proc Natl Acad Sci U S A. 26 Pressor Response in Perfused Mesenteric Arterial Beds Increase in pressure (mmhg) 4 2 AVP (5 mm) 1. The decreased BP in V1aR-KO mice could result from the decreased vascular tonus.

4 SBP (mmhg) BP change in the hypertension model Control (WT) (12) V1aR-KO (11) 9. 1% NaCl days after subtotal nephrectomy Rt. K Lt. K Lt. K Bladder Bladder Subtotal nephrectomy MAP (mmhg) Effect of the V1aR antagonist (1μg/kg, i.v.) on BP in the hypertensive mice control (WT) (6) V1aR-KO (11) (min) The V1a receptor is involved in developing and/or maintaining hypertension, and blockade of the V1a receptor results in decreasing BP in the hypertensive mice.

5 BP and HR response to the AVP stimulation 2. AVP stimulates vasoconstriction via V1aR and also stimulates vasodilatation via V2R, and the decreased pressor response to the AVP stimulation in KO mice could result in the decreased BP.

6 Decreased sypatethic nerve activity in CNS of V1aR-KO BP and HR change after the AVP injection into the intra-cereberoventricle (icv) Catecolamines after the AVP injection (icv) MAP (mmhg) 4 2 MAP Control (WT) ng/ml 15 1 Control (WT) Epinephrine(EP) pg/ml Decreased EP and NE in KO V1aR-KO 5 1 Control (WT) V1aR KO HR (bpm) 1 5 HR (min) AVP 1 ng (icv) was injected into icv. Oikawa et al., Eur J Pharmacol Norepinephrine(NE) 2 1 Vehicle AVP (ng) 5 Epi NE AVP(1ng) 3. Decreased sympathetic nerve activity in response to AVP could cause the decreased BP in KO mice.

7 Reduced Blood Volume and Plasma aldosterone level in V1aR-KO Blood volume (ml) Aldosterone (ng/ml) WT (5) V1aR-KO (5) AVP stimulates aldosterone release from adrenal gland cells via V1aR Aoyagi et al., Endocrinology. 27 Impaired aldosterone release in V1aR-KO adrenal cells Birumachi et al. Eur J Pharmacol AVP-stimulated aldosterone release was impaired in V1aR-KO mice, and impaired aldosterone release could result in the lower plasma aldosterone level and consequent lower blood volume and BP.

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9 Decreased plasma renin activity and angiotension II in V1aR-KO Aoyagi et al., Amer J Physiol 28

10 Decreased renin expression in the kidney of V1aR-KO Number of renin positive cells in the kidney Renin RNA expressions in the kidney Immunohistochemistry with renin antibody in V1aR-KO Renin expressions in the kidney Aoyagi et al., Amer J Physiol 28

11 Decreased expression of nnos and COX-2 in the kidney of V1aR-KO Regulation of renin secretion by NO and PGE2 in MD cells Decreased expression of nnos and COX-2 in the kidney of V1aR-KO (Macradensa cell) Urinary Cl - concentration nnos, COX2 NO, PGE 2 Immunohistochemistry w ith COX2 and nnos antibody PGE2 lev els in V1aR-KO renin より No. of nnos positive cells in the kidney COX2 expressions in the kidney V1aR is involved in regulating NOS and COX2, and decreased expressions cause the reduced renin production

12 Co-localization of nnos with V1aR in Macradensa (MD) cell Expression of V1a receptor in the MD cell. The co-localization of the V1aR mrna and nnos were determined by in situ hybridization and immunostaining in kidney mirror sections. Arrowheads indicate MD cells, where the V1aR mrna was co-localized with nnos.

13 Co-localization of COX-2 with V1aR in MD cell Co-localization of COX-2 with V1aR in TAL Expression of V1a receptor in the MD cell. The co-localization of the V1aR mrna and COX-2 were determined by in situ hybridization and immunostaining in kidney mirror sections. Arrowheads indicate MD cells, or renal tubule cells where the V1aR mrna was colocalized with COX-2.

14 Co-localization of renin with V1aR in granule cells Co-localization of renin with V1aR in renal tubles Expression of V1a receptor in the MD cell. The co-localization of the V1aR mrna and renin were determined by in situ hybridization and immunostaining in kidney mirror sections. Arrowheads indicate MD cells, or renal tubule cells where the V1aR mrna was colocalized with renin.

15 Summary of AVP function on regulating RAS and blood volume 1 V1aR mediates the renin production by regulating the nnos and COX-2 in MD cells. 2 AVP-aldosterone system Which are impaired in V1aR-KO, leading to Renin-angiotensin-aldosterone system decreased aldosterone and blood volume AVP regulates RAS via V1aR in the kidney Physiological role of AVP on regulating blood volume V1aR AVP V1aR AVP Angiotensinogen MD cell nnos/no COX-2/PGE2 Distal tubule COX-2/PGE2 V1aR nnos COX2 Renin granule cell renin Proximal tubule renin Angiotensin I ACE Aldosterone Angiotensin II Renin-angiotensin-aldosterone system Na reabsorption Water retension AVP not only stimulates aldosterone release directly from adrenal cortex via the V1a receptor, but also regulates nnos, COX2 and renin via the V1a receptor in the kidney.

16 Impaired glucose tolerance in V1aR-KO mice Blood glucose (mg/dl) Blood glucose (mg/dl) Glucose Tolerance Test (GTT) Fasting 18 h, Glucose 1.5 g/kg i.p WT, male (12) V1aR-KO, male (1) Insulin (pg/ml) Time (min Time (min) Hyperinsulinemic-euglycemic clamp test Decreased phsophorylation of Akt in V1aR-KO Hiroyama et al., J Physiol 27 Glucose tolerance was impaired due to increased hepatic glucose production, and suppressed insulin signal in V1aR-KO.

17 BW, fat weight and glucose tolerance after feeding with the high fat diet Body weight adipose tissue weight (% of body weight) Epididymal -WAT WT KO Retroperitoneal -WAT Normal chow HFD WT KO Fat weight Visceral -WAT WT KO Subcutaneous -WAT & BAT WT KO Total-WAT WT KO WT on HF V1aR-KO on HF WT on NC V1aR-KO on NC Histology of fat and liver after loading with HF diet GTT after HF diet Aoyagi et al. Endocrinology 27 Glucose intolerance was accelerated by the HF diet, leading to hyperglycemia, excessive obesity, and fatty liver in V1aR-KO.

18 Impaired insulin release from cultured islets in V1bR-KO AVP mediates the insulin secretion via the V1b receptors and AVPstimulated insulin secretion was impaired in V1bR-KO.

19 Blood glucose (mg/dl) WT (16) V1aR-KO (2) V1bR-KO (25) Increased insulin sensitivity in V1bR-KO mice GTT ITT V1bR+/+ V1bR-/- V1bR+/+ V1bR-/- GTT under the HF diet condition Fujiwara et al., J Physiol. 27 Insulin sensitivity was enhanced in V1bR-KO due to the enhanced insulin signal in adipocytes.

20 Decreased insulin sensitivity in V1abR-KO GTT on NC diet GTT on high fat diet V1abR-KO WT V1abR-KO WT ITT on NC diet ITT on high fat diet WT V1abR-KO V1abR-KO WT Insulin sensitivity was decreased in V1abR-KO, similar to V1aR-KO.

21 Decreased phosphorylation of Akt by the insulin stimulation in V1abR KO Hiroyama et al., 27 Fujiwara et al., 27 Insulin sensitivity was decreased in V1abR-KO due to the suppressed insulin signal similar to V1aR-KO.

22 Classification of glucose intolerance in V1aR-KO or V1abR KO mice V1aR-KO and V1abR-KO are pre-diabetic on NC diet and diabetic on HF diet

23 Possible mechanism for regulating the glucose tolerance by AVP AVP V1b receptor V1a receptor renin insulin release Hepatic glucose production aldosteron release Insulin signal (Akt Phosphorylation) Water recruitment Glucose tolerance AVP regulates the insulin secretion from the pancreas and insulin signal in fat via the V1b receptor, and AVP regulates hepatic glucose production, insulin signal and aldosteron secretion via the V1a receptor, which consequently affect the glucose tolerance in vivo. Aoyagi et al., Endocrinology 27 modified

24 Acknowledgement Kyoto University Prof. Tsujimoto Dr. Koshimizu Tokyo University of Pharmacy and Life Science Prof. Takeo Dr.Nasa Dr. Oikawa Kitasato University Prof. Kawahara Dr. Yasuoka Kumamoto University Dr. Nonoguchi Dr. Izumi