Inhibitory effects of antihypertensive drugs on human cytochrome P450 2J2 activity: Potent inhibition by azelnidipine and manidipine.

The inhibitory effects of antihypertensive drugs (dihydropyridine calcium channel blockers, angiotensin II receptor blockers, and angiotensin-converting enzyme inhibitors) on cytochrome P450 2J2 (CYP2J2) activity were examined. Amlodipine, azelnidipine, barnidipine, benidipine, cilnidipine, efonidipine, felodipine, manidipine, nicardipine, nifedipine, nilvadipine, nisoldipine, nitrendipine, telmisartan, delapril, and quinapril inhibited luciferin-2J2/4F12 O-dealkylase activity of recombinant human CYP2J2 in a concentration-dependent manner (IC50 = 0.116-9.19 µM). Kinetic analyses of the inhibition indicated that azelnidipine, barnidipine, benidipine, cilnidipine, efonidipine, manidipine, nicardipine, telmisartan, delapril, and quinapril competitively inhibited CYP2J2 activity, while amlodipine, felodipine, nifedipine, nilvadipine, nisoldipine, and nitrendipine showed mixed inhibition. Among these drugs, manidipine showed the strongest reversible inhibition with Ki value of 0.0294 µM. The docking simulation data supported the potent inhibition of CYP2J2 by these drugs. Next, the effect of preincubation on CYP2J2 inhibition was investigated to determine whether these antihypertensive drugs inhibited CYP2J2 activity in a metabolism-dependent manner. A 20-min preincubation of azelnidipine and felodipine in the presence of NADPH potentiated the inhibition of CYP2J2. Furthermore, kinetic analysis of the inactivation showed that azelnidipine caused a preincubation time- and concentration-dependent decrease in CYP2J2 activity yielding kinact/KI value of 105 l/mmol/min, although felodipine showed no preincubation time-dependent inhibition. The azelnidipine-mediated inactivation required NADPH. These results indicated that manidipine is a potent competitive reversible inhibitor while azelnidipine is a potent mechanism-based inactivator of human CYP2J2.

Influence of azole antifungal drugs on blood tacrolimus levels after switching from intravenous tacrolimus to once-daily modified release tacrolimus in patients receiving allogeneic hematopoietic stem cell transplantation.

WHAT IS KNOWN AND OBJECTIVE: Azole antifungal drugs are often co-administered with tacrolimus after allogeneic hematopoietic stem cell transplantation (HSCT). However, the influence of azole antifungal drugs on variation in tacrolimus pharmacokinetics when switching from intravenous tacrolimus (Tac-iv) to once-daily modified release tacrolimus (Tac-MR) remains to be elucidated. This study was performed to evaluate the effects of oral azole antifungal drugs on variation in tacrolimus pharmacokinetics after conversion to Tac-MR in HSCT patients. METHODS: Patients concomitantly receiving fluconazole (FLCZ) or voriconazole (VRCZ) along with tacrolimus were evaluated retrospectively. Blood tacrolimus concentrations before and after changing to oral administration were compared between FLCZ and VRCZ groups. RESULTS AND DISCUSSION: A total of 52 patients (34 FLCZ and 18 VRCZ) were included in the analysis. There were no significant differences in the most recent daily dose (Div ) and blood level (Civ ) of Tac-iv, Civ /Div , and ratio of daily dose of tacrolimus on the first to second day after changing to Tac-MR (Dpo1-2 ) to Div between FLCZ and VRCZ groups (P > 0.2). The trough levels of tacrolimus on the first to second day after switching to Tac-MR (Cpo1-2 ) and on the third to fifth day after the switch (Cpo3-5 ) were significantly higher in the VRCZ group than the FLCZ group (P < 0.05). The values of (Civ /Div )/(Cpo1-2 /Dpo1-2 ) and (Civ /Div )/(Cpo3-5 /Dpo3-5 ) in the VRCZ group were significantly lower compared with those in the FLCZ group (P < 0.05). Furthermore, individual values of (Civ /Div )/(Cpo3-5 /Dpo3-5 ) in the FLCZ group varied widely. WHAT IS NEW AND CONCLUSION: Voriconazole increased blood tacrolimus level more markedly than FLCZ after switching to Tac-MR, whereas FLCZ caused a large variation in tacrolimus blood level. These results suggest that therapeutic monitoring of tacrolimus after the switch may need to be performed carefully considering that orally co-administered VRCZ and FLCZ exhibit different change in blood tacrolimus level just after the switch.

Elevated levels of plasma Big endothelin-1 and its relation to hypertension and skin lesions in individuals exposed to arsenic.

Chronic arsenic (As) exposure affects the endothelial system causing several diseases. Big endothelin-1 (Big ET-1), the biological precursor of endothelin-1 (ET-1) is a more accurate indicator of the degree of activation of the endothelial system. Effect of As exposure on the plasma Big ET-1 levels and its physiological implications have not yet been documented. We evaluated plasma Big ET-1 levels and their relation to hypertension and skin lesions in As exposed individuals in Bangladesh. A total of 304 study subjects from the As-endemic and non-endemic areas in Bangladesh were recruited for this study. As concentrations in water, hair and nails were measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The plasma Big ET-1 levels were measured using a one-step sandwich enzyme immunoassay kit. Significant increase in Big ET-1 levels were observed with the increasing concentrations of As in drinking water, hair and nails. Further, before and after adjusting with different covariates, plasma Big ET-1 levels were found to be significantly associated with the water, hair and nail As concentrations of the study subjects. Big ET-1 levels were also higher in the higher exposure groups compared to the lowest (reference) group. Interestingly, we observed that Big ET-1 levels were significantly higher in the hypertensive and skin lesion groups compared to the normotensive and without skin lesion counterpart, respectively of the study subjects in As-endemic areas. Thus, this study demonstrated a novel dose-response relationship between As exposure and plasma Big ET-1 levels indicating the possible involvement of plasma Big ET-1 levels in As-induced hypertension and skin lesions.