Abstract-Calcium channel blockers are widely used antihypertensives. Mineralocorticoid receptor antagonists are also used to treat hypertension and heart failure. We report here that a number of widely used dihydropyridine class calcium channel blockers are able to inhibit aldosterone-induced activation of mineralocorticoid receptor. These dihydropyridines varied in the extent of their effect on mineralocorticoid receptor, with nimodipine and felodipine the most potent and amlodipine the least. In contrast, both diltiazem and verapamil, nondihydropyridine calcium channel blockers, had no effect on mineralocorticoid receptor. These dihydropyridines compete with aldosterone for binding and block aldosterone-induced coactivator recruitment to mineralocorticoid receptor. The mineralocorticoid receptor S810L mutant, which is activated by steroidal mineralocorticoid receptor antagonist such as eplerenone, is inhibited by these drugs. Furthermore, nimodipine decreased aldosterone-induced expression of the mineralocorticoid receptor target gene epithelial sodium channel gamma subunit in adrenalectomized rats, demonstrating that dihydropyridine calcium channel blockers can function as mineralocorticoid receptor antagonists in vivo. Molecular modeling indicates that dihydropyridines dock into the ligand binding domain of mineralocorticoid receptor in a consensus pose that partially overlaps with steroidal mineralocorticoid receptor antagonists. Together, our data suggest that, in addition to their calcium channel blocking activity, a number of dihydropyridine calcium channel blockers also have mineralocorticoid receptor antagonist activity at high doses, a finding which may thus prove useful for the design of novel antihypertensive drugs in the future. Key Words: calcium channel blockers Ⅲ aldosterone Ⅲ mineralocorticoid receptor antagonist Ⅲ dihydropyridine H ypertension is a widespread public health problem and a major risk factor for cardiovascular and renal disease. Numerous antihypertensive drugs have been developed to lower blood pressure (BP); these drugs target a number of mechanisms and are often used in combination. 1,2 Calcium channel blockers (CCBs) are among the most frequently used antihypertensives and are grouped into 2 classes based on the chemical structures: the dihydropyridines such as amlodipine and nifedipine, and nondihydropyridines (diltiazem and verapamil). 3 Another heavily targeted mechanism for treatment of hypertension is the renin-angiotensin-aldosterone system. Angiotensin converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARBs) are among the standard therapies for BP control. 4 Mineralocorticoid receptor (MR) antagonists, such as eplerenone, block MR activation and show similar BP lowering efficacy as ACEi or ARB. 5,6 Targeting multiple mechanisms provides an advantage in control of hypertension, as most hypertensive patients require 2 or more medications to achieve their BP goal. 7Here we report a surprising finding, that the dihydropyridine CCBs have MR antagonist acti...

Insulin sensitizing thiazolidinediones (TZDs) are generally considered to work as agonists for the nuclear receptor peroxisome proliferative activated receptor-gamma (PPARγ). However, TZDs also have acute, non-genomic metabolic effects and it is unclear which actions are responsible for the benefi cial pharmacology of these compounds. We have taken advantage of an analog, based on the metabolism of pioglitazone, which has much reduced ability to activate PPARγ. This analog (PNU-91325) was compared to rosiglitazone, the most potent PPARγ activator approved for human use, in a variety of studies both in vitro and in vivo. The data demonstrate that PNU-91325 is indeed much less effective than rosiglitazone at activating PPARγ both in vitro and in vivo. In contrast, both compounds bound similarly to a mitochondrial binding site and acutely activated PI-3 kinase-directed phosphorylation of AKT, an action that was not affected by elimination of PPARγ activation. The two compounds were then compared in vivo in both normal C57 mice and diabetic KKAy mice to determine whether their pharmacology correlated with biomarkers of PPARγ activation or with the expression of other gene transcripts. As expected from previous studies, both compounds improved insulin sensitivity in the diabetic mice, and this occurred in spite of the fact that there was little increase in expression of the classic PPARγ target biomarker adipocyte binding protein-2 (aP2) with PNU-91325 under these conditions. An examination of transcriptional profi ling of key target tissues from mice treated for one week with both compounds demonstrated that the relative pharmacology of the two thiazolidinediones correlated best with an increased expression of an array of mitochondrial proteins and with expression of PPARγ coactivator 1-alpha (PGC1α), the master regulator of mitochondrial biogenesis. Thus, important pharmacology of the insulin sensitizing TZDs may involve acute actions, perhaps on the mitochondria, that are independent of direct activation of the nuclear receptor PPARγ. These fi ndings suggest a potential alternative route to the discovery of novel insulin sensitizing drugs.

The nuclear hormone receptor retinoic acid receptor-related orphan C2 (RORC2, also known as RORγt) is a promising target for the treatment of autoimmune diseases. A small molecule, inverse agonist of the receptor is anticipated to reduce production of IL-17, a key proinflammatory cytokine. Through a high-throughput screening approach, we identified a molecule displaying promising binding affinity for RORC2, inhibition of IL-17 production in Th17 cells, and selectivity against the related RORA and RORB receptor isoforms. Lead optimization to improve the potency and metabolic stability of this hit focused on two key design strategies, namely, iterative optimization driven by increasing lipophilic efficiency and structure-guided conformational restriction to achieve optimal ground state energetics and maximize receptor residence time. This approach successfully identified 3-cyano- N-(3-(1-isobutyrylpiperidin-4-yl)-1-methyl-4-(trifluoromethyl)-1 H-pyrrolo[2,3- b]pyridin-5-yl)benzamide as a potent and selective RORC2 inverse agonist, demonstrating good metabolic stability, oral bioavailability, and the ability to reduce IL-17 levels and skin inflammation in a preclinical in vivo animal model upon oral administration.

The liver X receptors (LXRs), members of the nuclear receptor superfamily, play an important role in controlling lipid homeostasis by activating several genes involved in reverse cholesterol transport. These include members of the ATP binding cassette (ABC) superfamily of transporter proteins ABCA1 and ABCG1, surface constituents of plasma lipoproteins like apolipoprotein E, and cholesterol ester transport protein. They also play an important role in fatty acid metabolism by activating the sterol regulatory element-binding protein 1c gene. Here, we identify human LXRalpha (hLXRalpha) as an autoinducible gene. Induction in response to LXR ligands is observed in multiple human cell types including macrophages and occurs within 2--4 h. Analysis of the hLXRalpha promoter revealed three LXR response elements (LXREs); one exhibits strong affinity for both LXRalpha:RXR and LXRbeta:RXR (a type I LXRE), and deletion and mutational studies indicate it plays a critical role in LXR-mediated induction. The other two LXREs are identical to each other, exist within highly conserved Alu repeats, and exhibit selective binding to LXRalpha:RXR (type II LXREs). In transfections, the type I LXRE acts as a strong mediator of both LXRalpha and LXRbeta activity, whereas the type II LXRE acts as a weaker and selective mediator of LXRalpha activity. Our data suggest a model in which LXR ligands trigger an autoregulatory loop leading to selective induction of hLXRalpha gene expression. This would lead to increased hLXRalpha levels and transcription of its downstream target genes such as ABCA1, providing a simple yet exquisite mechanism for cells to respond to LXR ligands and cholesterol loading.

We evaluated the effects of two thiazolidinediones (TZDs), the potent PPARgamma agonist rosiglitazone currently being used to treat diabetes, and a structurally similar experimental compound that is a poor PPARgamma agonist, in a non-diabetic, established hypertension model with continuous measurement of blood pressure by telemetry. Hypertension was induced in male Dahl salt-sensitive rats by a three-week pre-treatment with 4% salt before initiation of treatment. Fasting blood samples were taken for analysis of a biomarker panel to assess metabolic, anti-inflammatory and antioxidant activity of the treatments. Both TZDs significantly reduced both systolic and diastolic blood pressure. When used at the maximally effective doses established for metabolic improvement, both compounds produced equivalent reduction in lipids and elevation of adiponectin, yet the poorer PPARgamma agonist produced significantly greater reductions in blood pressure. Neither compound had a significant effect on circulating glucose or insulin in this animal model. The data demonstrate that these TZDs lower blood pressure significantly in Dahl rats and that this cardiovascular pharmacology is not directly correlated with the metabolic actions or with the magnitude of PPARgamma activation. These data suggest that it may be possible to find insulin-sensitising agents that have beneficial cardiovascular pharmacology with broad applications for disease prevention.