Background and purpose: Inhibition of cholesteryl ester transfer protein (CETP) with torcetrapib in humans increases plasma high density lipoprotein (HDL) cholesterol levels but is associated with increased blood pressure. In a phase 3 clinical study, evaluating the effects of torcetrapib in atherosclerosis, there was an excess of deaths and adverse cardiovascular events in patients taking torcetrapib. The studies reported herein sought to evaluate off-target effects of torcetrapib. Experimental approach: Cardiovascular effects of the CETP inhibitors torcetrapib and anacetrapib were evaluated in animal models. Key results: Torcetrapib evoked an acute increase in blood pressure in all species evaluated whereas no increase was observed with anacetrapib. The pressor effect of torcetrapib was not diminished in the presence of adrenoceptor, angiotensin II or endothelin receptor antagonists. Torcetrapib did not have a contractile effect on vascular smooth muscle suggesting its effects in vivo are via the release of a secondary mediator. Treatment with torcetrapib was associated with an increase in plasma levels of aldosterone and corticosterone and, in vitro, was shown to release aldosterone from adrenocortical cells. Increased adrenal steroid levels were not observed with anacetrapib. Inhibition of adrenal steroid synthesis did not inhibit the pressor response to torcetrapib whereas adrenalectomy prevented the ability of torcetrapib to increase blood pressure in rats. Conclusions and implications: Torcetrapib evoked an acute increase in blood pressure and an acute increase in plasma adrenal steroids. The acute pressor response to torcetrapib was not mediated by adrenal steroids but was dependent on intact adrenal glands.

Functional interleuin-8 (IL-8) receptors (IL-8RA and IL-8RB:CXCR1 and CXCR2, respectively) have been described in human, monkey, dog, rabbit, and guinea pig. Although three IL-8R homologues have been found in rat, only one of these, rat CXCR2, appears to be functional based on responsiveness to ligands. Similarly, CXC chemokines induce biological responses through the murine homolog of CXCR2, but the identification of functional rodent CXCR1 homologues has remained elusive. We have identified and characterized the mouse CXCR1 homologue (mCXCR1). Murine CXCR1 shares 68 and 88% amino acid identity with its human and rat counterparts, respectively. Similar to the tissue distribution pattern of rat CXCR1, we found murine CXCR1 mRNA expression predominantly in lung, stomach, bone marrow, and leukocyte-rich tissues. In contrast to previous reports, we determined that mCXCR1 is a functional receptor. We show predominant engagement of this receptor by mouse GCP-2/CXCL6, human GCP-2, and IL-8/CXCL8 by binding, stimulation of GTP␥S exchange, and chemotaxis of mCXCR1-transfected cells. Furthermore, murine CXCR1 is not responsive to the human CXCR2 ligands ENA-78/CXCL5, NAP-2/CXCL7, GRO-␣, -␤, -␥/CXCL1-3, or rat CINC-1-3. In addition, we show concomitant elevation of mCXCR1 and its proposed major ligand, GCP-2, positively correlated with paw swelling in murine collagen-induced arthritis. This report represents the first description of a functional CXCR1-like receptor in rodents.

H ypertension is one of the most common chronic diseases with complex pathogenesis. It is likely that hypertension is a consequence of an interaction between genetic and environmental factors. Although genome-wide association studies have identified multiple genes that are associated with hypertension, a great deal of our current understanding of the molecular mechanisms involved in blood pressure (BP) regulation 1 has come from analysis of the genes responsible for monogenetic syndromes of hypertension and hypotension. For example, loss-of-function mutations in the Na + /Cl − cotransporter (NCC; SLC12A3) causes Gitelman syndrome: patients are either normotensive or hypotensive with hypochloremic metabolic alkalosis and hypokalemia. [2][3][4][5] Increased NCC membrane expression resulting from either gain-of-function mutations with-no-lysine kinase 1 or loss-offunction mutations with-no-lysine kinase 4 leads to Gordon syndrome, characterized by salt-sensitive (SS) hypertension, hyperkalemia, and metabolic acidosis. 6,7 Loss-of-function mutations in Na− cotransporter (NKCC2, SLC12A1) or renal outer medullary potassium channel (ROMK, KCNJ1) are responsible for Bartter syndrome type I and type II, respectively. [8][9][10][11] These disorders are characterized by polyuria, salt wasting, hypokalemia, metabolic alkalosis, hypercalciuria, and hypotension. Furthermore, Ji et al 12 demonstrated that heterozygous mutations in all 3 of these genes, SLC12A3, SLC12A1, and KCNJ1, are associated with clinically significant BP reduction and protection from development of hypertension. Thus, these syndromes further underscore a key role of renal Abstract-The renal outer medullary potassium channel (ROMK, KCNJ1) mediates potassium recycling and facilitates sodium reabsorption through the Na + /K + /2Cl − cotransporter in the loop of Henle and potassium secretion at the cortical collecting duct. Human genetic studies indicate that ROMK homozygous loss-of-function mutations cause type II Bartter syndrome, featuring polyuria, renal salt wasting, and hypotension; humans heterozygous for ROMK mutations identified in the Framingham Heart Study have reduced blood pressure. ROMK null mice recapitulate many of the features of type II Bartter syndrome. We have generated an ROMK knockout rat model in Dahl salt-sensitive background by using zinc finger nuclease technology and investigated the effects of knocking out ROMK on systemic and renal hemodynamics and kidney histology in the Dahl salt-sensitive rats. The ROMK −/− pups recapitulated features identified in the ROMK null mice. The ROMK +/− rats, when challenged with a 4% salt diet, exhibited a reduced blood pressure compared with their ROMK +/+ littermates. More importantly, when challenged with an 8% salt diet, the Dahl salt-sensitive rats with 50% less ROMK expression showed increased protection from salt-induced blood pressure elevation and signs of protection from renal injury. Our findings in ROMK knockout Dahl salt-sensitive rats, together with the previous reports in humans and m...

R enal outer medullary potassium channel (ROMK) is encoded by the KCNJ1 (potassium inwardly-rectifying channel, subfamily J, member 1) gene and expressed in the apical membranes of thick ascending limb of Henle and cortical collecting duct cells; ROMK mediates potassium recycling and facilitates sodium reabsorption through Na− cotransporter in the thick ascending limb of Henle and potassium secretion in cortical collecting duct.1-3 Thus, ROMK plays a critical role in the regulation of renal sodium reabsorption and the body's potassium homeostasis. Human genetic studies indicated that loss-of-function mutations in ROMK cause type II Bartter syndrome, 4-6 featuring polyuria, polydipsia, salt wasting, hypokalemia, alkalosis, hypercalciuria, low blood pressures, elevated plasma renin and aldosterone, and excess production of renal prostaglandins. ROMK heterozygous mutations in humans protect from the development of hypertension.7 ROMK-deficient mice exhibit a Bartter syndrome type II-like phenotype. 8,9 Heterozygous disruption of ROMK in rats is associated with reduced blood pressure and less severe renal injury.10 Furthermore, acute pharmacological intervention with a small molecule ROMK inhibitor (ROMKi) compound A evoked diuresis and natriuresis in rats and dogs, 11 which establishes the concept that ROMK inhibition represents a novel diuretic mechanism. We, therefore, hypothesize that chronic ROMK inhibition by selective small molecules would induce natriuresis and diuresis and, thereby, lower blood pressure and protect from end-organ damage in hypertensive subjects. To this end, we examined the effects of a selective and potent ROMKi B, recently synthesized by Merck & Co, Inc, 12 on systemic hemodynamics, renal function and structure, vascular function, and cardiac structure and compared the effects with those of hydrochlorothiazide (HCTZ) in 2 separate Abstract-The renal outer medullary potassium (ROMK) channel mediates potassium recycling and facilitates sodium reabsorption through the Na + /K + /2Cl − cotransporter in the loop of Henle and potassium secretion at the cortical collecting duct. Evidence from the phenotype of humans and rodents with functional ROMK deficiency supports the contention that selective ROMK inhibitors (ROMKi) will represent a novel diuretic with potential of therapeutic benefit for hypertension. ROMKi have recently been synthesized by Merck & Co, Inc. The present studies were designed to examine the effects of ROMKi B on systemic hemodynamics, renal function and structure, and vascular function in Dahl salt-sensitive rats. Four experimental groups-control, high-salt diet alone; ROMKi B 3 mg·kg −1 ·d −1 ; ROMKi B 10 mg·kg −1 ·d −1 ; and hydrochlorothiazide 25 mg·kg −1 ·d −1 -were included in prophylactic (from week 1 to week 9 on high-salt diet) and therapeutic studies (from week 5 to week 9 on high-salt diet), respectively. ROMKi B produced sustained blood pressure reduction and improved renal and vascular function and histological alterations induced by a high-salt diet. ROMKi B was...

We investigated the effects of chronic mineralocorticoid receptor blockade with eplerenone on the development and progression of hypertension and end organ damage in Dahl salt-sensitive rats. Eplerenone significantly attenuated the progressive rise in systolic blood pressure (SBP) (204 ± 3 vs. 179±3 mmHg, p < 0.05), reduced proteinuria (605.5 ± 29.6 vs. 479.7 ± 26.1 mg/24h, p < 0.05), improved injury scores of glomeruli, tubules, renal interstitium, and vasculature in Dahl salt-sensitive rats fed a high-salt diet. These results demonstrate that mineralocorticoid receptor antagonism provides target organ protection and attenuates the development of elevated blood pressure (BP) in a model of salt-sensitive hypertension.