Different antioxidative potencies of dihydropyridine calcium channel modulators in various models

Macrophage Lxrα reduces atherosclerosis in Ldlr-/- mice independent of Arl7 transactivation

BACKGROUND

Liver X receptor alpha (Lxrα) is a sterol-regulated transcription factor that limits atherogenesis by regulating cholesterol homeostasis and inflammation in macrophages. Transcriptional profiling identified the reverse cholesterol transport protein Arf-like 7 (Arl7, Arl4c) as a Lxrα target gene. We hypothesized that the LXR response element (LXRE) sequence on the murine macrophage Arl7 promoter may play a critical role in Lxrα's atherosuppressive effects.

METHODS

Employing low density lipoprotein receptor-deficient mice with macrophage-specific Lxrα overexpression (Ldlr^-/- MΦ-Lxrα), we constructed a novel in vivo Ldlr^-/- MΦ-Lxrα Arl7^MutLXRE model possessing macrophage-specific mutations within the Arl7 promoter LXRE sequences (Arl7^MutLXRE) using the CRISPR/spCas9 genome editing technique. In vitro and in vivo transplantation studies were conducted using bone marrow-derived macrophages (BMDMs) and peritoneal macrophages (PMs).

RESULTS

Ldlr^-/-, Ldlr^-/- MΦ-Lxrα, and Ldlr^-/- MΦ-Lxrα Arl7^MutLXRE mice on a 60% high-fat diet displayed no significant differences in body weight, fat mass, glucose homeostasis, or lipid metabolism. Macrophage Lxrα promoted Arl7 expression, enhanced cholesterol efflux, and reduced foam cell formation in an Arl7 LXRE-dependent manner. In contrast, Lxrα reduced macrophage activation, inflammatory cytokine expression, and efferocytosis independent of Arl7 LXRE. Western diet-fed Ldlr^-/- mice reconstituted with transgenic BMDMs revealed that macrophage Lxrα reduced atherosclerotic plaque formation independent of Arl7 LXRE.

CONCLUSION

Lxrα's anti-atherosclerotic effects in Ldlr^-/- mice are not primarily attributable to Lxrα's influence on Arl7 expression. This evidence suggests that Lxrα's effects on plaque inflammation may be more critical to in vivo atherogenesis than its effects on macrophage cholesterol efflux and foam cell development.

1,4-Dihydropyridine Derivatives: Dihydronicotinamide Analogues-Model Compounds Targeting Oxidative Stress

Many 1,4-dihydropyridines (DHPs) possess redox properties. In this review DHPs are surveyed as protectors against oxidative stress (OS) and related disorders, considering the DHPs as specific group of potential antioxidants with bioprotective capacities. They have several peculiarities related to antioxidant activity (AOA). Several commercially available calcium antagonist, 1,4-DHP drugs, their metabolites, and calcium agonists were shown to express AOA. Synthesis, hydrogen donor properties, AOA, and methods and approaches used to reveal biological activities of various groups of 1,4-DHPs are presented. Examples of DHPs antioxidant activities and protective effects of DHPs against OS induced damage in low density lipoproteins (LDL), mitochondria, microsomes, isolated cells, and cell cultures are highlighted. Comparison of the AOA of different DHPs and other antioxidants is also given. According to the data presented, the DHPs might be considered as bellwether among synthetic compounds targeting OS and potential pharmacological model compounds targeting oxidative stress important for medicinal chemistry.

Effect of amlodipine, lisinopril and allopurinol on acetaminophen-induced hepatotoxicity in rats

Background

Exposure to chemotherapeutic agents such as acetaminophen may lead to serious liver injury. Calcium deregulation, angiotensin II production and xanthine oxidase activity are suggested to play mechanistic roles in such injury.

Objective

This study evaluates the possible protective effects of the calcium channel blocker amlodipine, the angiotensin converting enzyme inhibitor lisinopril, and the xanthine oxidase inhibitor allopurinol against experimental acetaminophen-induced hepatotoxicity, aiming to understand its underlying hepatotoxic mechanisms.

Material and methods

Animals were allocated into a normal control group, a acetaminophen hepatotoxicity control group (receiving a single oral dose of acetaminophen; 750 mg/kg/day), and four treatment groups receive N-acetylcysteine (300 mg/kg/day; a reference standard), amlodipine (10 mg/kg/day), lisinopril (20 mg/kg/day) and allopurinol (50 mg/kg/day) orally for 14 consecutive days prior to acetaminophen administration. Evaluation of hepatotoxicity was performed by the assessment of hepatocyte integrity markers (serum transaminases), oxidative stress markers (hepatic malondialdehyde, glutathione and catalase), and inflammatory markers (hepatic myeloperoxidase and nitrate/nitrite), in addition to a histopathological study.

Results

Rats pre-treated with amlodipine, lisinopril or allopurinol showed significantly lower serum transaminases, significantly lower hepatic malondialdehyde, myeloperoxidase and nitrate/nitrite, as well as significantly higher hepatic glutathione and catalase levels, compared with acetaminophen control rats. Serum transaminases were normalized in the lisinopril treatment group, while hepatic myeloperoxidase was normalized in the all treatment groups. Histopathological evaluation strongly supported the results of biochemical estimations.

Conclusion

Amlodipine, lisinopril or allopurinol can protect against acetaminophen-induced hepatotoxicity, showing mechanistic roles of calcium channels, angiotensin converting enzyme and xanthine oxidase enzyme in the pathogenesis of hepatotoxicity induced by acetaminophen.

Substituent Effect on the Photolability of 4-Aryl-1,4-Dihydropyridines

The electronic nature of substituents attached to the 4-aryl moiety of 1,4-dihydropyridines strongly affects the photophysical and photochemical behavior of these family of compounds. The presence of an electron donor substituent on the 4-aryl moiety (or the absence of electron-withdrawing ones) modifies the luminescence lifetimes (τ < 100 ps) and diminishes the photodecomposition quantum yields. For electron-withdrawing substituents, the photodegradation quantum yield is affected by the media, changing more than two orders of magnitude as the polarity is increased. Studies in micellar media allow us to conclude that 4-aryl-1,4-dihydropyridines are located near to the interface; however, the surface charge of micelles has no effect on the photodegradation rate constant or the photoproducts profile. The main conclusion of this work is that the photolability of 4-aryl-1,4-dihydropyridines can be significantly reduced by the incorporation of antioxidant moieties.

Disruption of intracellular calcium regulation is integral to aminoglycoside-induced hair cell death

Intracellular Ca(2+) is a key regulator of life or death decisions in cultured neurons and sensory cells. The role of Ca(2+) in these processes is less clear in vivo, as the location of these cells often impedes visualization of intracellular Ca(2+) dynamics. We generated transgenic zebrafish lines that express the genetically encoded Ca(2+) indicator GCaMP in mechanosensory hair cells of the lateral line. These lines allow us to monitor intracellular Ca(2+) dynamics in real time during aminoglycoside-induced hair cell death. After exposure of live larvae to aminoglycosides, dying hair cells undergo a transient increase in intracellular Ca(2+) that occurs shortly after mitochondrial membrane potential collapse. Inhibition of intracellular Ca(2+) elevation through either caged chelators or pharmacological inhibitors of Ca(2+) effectors mitigates toxic effects of aminoglycoside exposure. Conversely, artificial elevation of intracellular Ca(2+) by caged Ca(2+) release agents sensitizes hair cells to the toxic effects of aminoglycosides. These data suggest that alterations in intracellular Ca(2+) homeostasis play an essential role in aminoglycoside-induced hair cell death, and indicate several potential therapeutic targets to stem ototoxicity.

Regulatory volume decrease in cardiomyocytes is modulated by calcium influx and reactive oxygen species

We investigated the role of Ca(2+) in generating reactive oxygen species (ROS) induced by hyposmotic stress (Hypo) and its relationship to regulatory volume decrease (RVD) in cardiomyocytes. Hypo-induced increases in cytoplasmic and mitochondrial Ca(2+). Nifedipine (Nife) inhibited both Hypo-induced Ca(2+) and ROS increases. Overexpression of catalase (CAT) induced RVD and a decrease in Hypo-induced blebs. Nife prevented CAT-dependent RVD activation. These results show a dual role of Hypo-induced Ca(2+) influx in the control of cardiomyocyte viability. Hypo-induced an intracellular Ca(2+) increase which activated RVD and inhibited necrotic blebbing thus favoring cell survival, while simultaneously increasing ROS generation, which in turn inhibited RVD and induced necrosis.

Differential roles of dihydropyridine calcium antagonist nifedipine, nitrendipine and amlodipine on gentamicin-induced renal tubular toxicity in rats

In the present study, we investigated the antioxidative potencies of dihydropyridine calcium antagonists prototype nifedipine, the second generation drug nitrendipine, and the long acting, third generation drug amlodipine on gentamicin-induced renal tubular toxicity in Sprague-Dawley rats. In addition, we analyzed the relationship between renal tubular cell apoptosis and the antioxidative properties of these dihydropyridine calcium antagonists. Results showed that treatment with gentamicin alone caused significant changes in the levels of urinary protein, urinary N-acetyl-beta-d-glucosaminidase, serum creatinine, and blood urea nitrogen. Nifedipine and amlodipine effectively reversed the effect of gentamicin on these parameters. In contrast, nitrendipine either had no effect or worsened gentamicin-induced changes in the levels of urinary protein, urinary N-acetyl-beta-d-glucosaminidase, serum creatinine, and blood urea nitrogen. Furthermore, gentamicin treatment caused significant increases in the levels of malondialdehyde, nitric oxide, nitric oxide synthase and significant decreases in the levels of reduced glutathione, glutathione-S-transferase, and superoxide dismutase in kidney tissues. These effects were dramatically reduced by nifedipine and amlodipine but not affected by nitrendipine. In addition to the biochemical changes, histopathological studies showed that gentamicin caused structural damages in the kidneys; renal tubular cell apoptosis, a decrease in Bcl-2 expression and an increase in Bax expression were observed in all rats treated with gentamicin, nifedipine and amlodipine effectively reversed the effect of gentamicin while nitrendipine worsened them. In conclusion, this study clearly indicated that nifedipine and amlodipine protected against gentamicin-induced nephrotoxicity while nitrendipine had little effect, or even worsened.

Influence of atenolol and nifedipine on nitric-oxide deficient cardiomyocyte hypertrophy and expression of the cardio-endocrine peptide intermedin and its receptor components

BACKGROUND/AIMS

Chronic inhibition of nitric oxide (NO) synthesis is associated with hypertension, myocardial ischemia, oxidative stress and hypertrophy; expression of adrenomedullin (AM) and intermedin (IMD) and their receptor activity modifying proteins (RAMPs 1-3) is augmented in cardiomyocytes, indicating that the myocardial AM/ IMD system may be activated in response to pressure loading and ischemic insult. The aim was to examine effects on (i) parameters of cardiomyocyte hypertrophy and on (ii) expression of AM and IMD and their receptor components in NO-deficient cardiomyocytes of an intervention chosen specifically for ability to alleviate pressure loading and ischemic injury concurrently.

METHODS

The NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 35 mg.kg(-1).day(-1)) was given to rats for 8 weeks, with/ without concurrent administration of beta-adrenoceptor antagonist, atenolol (25 mg.kg(-1).day(-1)) / calcium channel blocker, nifedipine (20mg.kg(-1).day(-1)).

RESULTS

In L-NAME treated rats, atenolol / nifedipine abolished increases in systolic blood pressure and plasma AM and IMD levels and in left ventricular cardiomyocytes: (i) normalized increased cell width and mRNA expression of hypertrophic (sk-alpha-actin) and cardio-endocrine (ANP, BNP, ET) genes; (ii) normalized augmented membrane protein oxidation; (iii) normalized mRNA expression of AM, IMD, RAMP1, RAMP2 and RAMP3.

CONCLUSIONS

normalization of blood pressure and membrane oxidant status together with prevention of hypertrophy and normalization of the augmented expression of AM, IMD and their receptor components in NO-deficient cardiomyocytes by atenolol / nifedipine supports involvement of both pressure loading and ischemic insult in stimulating cardiomyocyte hypertrophy and induction of these counter-regulatory peptides and their receptor components. Attenuation of augmented expression of IMD in this model cannot however be explained simply by prevention of cardiomyocyte hypertrophy.

Oxidation of C4-hydroxyphenyl 1,4-dihydropyridines in dimethylsulfoxide and its reactivity towards alkylperoxyl radicals in aqueous medium

This work reports the electrochemical oxidation of three newly synthesized C4-hydroxyphenyl-substituted 1,4-dihydropyridine derivatives in dimethylsulfoxide. The reactivity of the compounds with ABAP-derived alkylperoxyl radicals in aqueous buffer pH 7.4, was also studied. The oxidation mechanism involves the formation of the unstable dihydropyridyl radical, which was confirmed by controlled-potential electrolysis (CPE) and ESR experiments. The final product of the CPE, that is, pyridine derivative, was identified by GC-MS technique for the three derivatives. A direct reactivity of the synthesized compounds toward ABAP-derived alkylperoxyl radicals was found. The pyridine derivative was identified by GC-MS as the final product of the reaction. Results reveal that this type of 1,4-DHPs significantly reacts with the radicals, even compared with commercial 1,4-DHP drugs with a well-known antioxidant ability.

Endothelial antioxidant actions of dihydropyridines and angiotensin converting enzyme inhibitors

Dihydropyridines and angiotensin converting enzyme inhibitor effects on superoxide and nitric oxide (NO) were compared in high glucose (20 mM, 24 h)-treated human Ea.hy 926 endothelial cells. High glucose stimulated superoxide both extracellularly (lucigenin chemiluminescence, cytochrome c reduction) and intracellularly (dihydrorhodamine 123 fluorescence). The dihydropyridines amlodipine, nisoldipine, BayK 8644 or the angiotensin converting enzyme inhibitors captopril and enalaprilat attenuated extra- and intracellular superoxide formation; nifedipine blocked extracellular increases only, ramiprilat was without antioxidant effect. Dihydropyridines and captopril also prevented NADPH-driven superoxide release. Antioxidant actions were blunted by a bradykinin B(2) receptor antagonist or an inhibitor of p38 mitogen activated protein kinase (MAPK), and were accompanied by improved NO release (amperometric sensor). p38MAPK inhibition prevented the NO-sparing actions of dihydropyridines but not angiotensin converting enzyme inhibitors. Thus, dihydropyridines and angiotensin converting enzyme inhibitors limit high glucose-induced superoxide formation and improve NO bioavailability in human endothelial cells, in part via bradykinin and p38MAPK.