Alpha-Lipoic Acid Improves Antioxidant Capacity but Has No Blood Pressure Lowering Effect in Rats Administered Nicotine

Abstract

Background: Nicotine has been implicated as a major player in smoking-induced cardiac toxicity. Alpha-lipoic acid (ALA) is a unique and potent antioxidant that scavenges reactive oxygen species with the ability to regenerate other antioxidants.

Objective: Oxidative stress is thought to play a fundamental role in nicotine toxicity; this study therefore, investigated the effect of dietary supplementation with ALA on nicotine-induced cardiac toxicity.

Methods: Twenty-eight (28) male Sprague-Dawley rats (150-200 g) were divided into 4 groups of 7 rats each of control, nicotine only, nicotine + ALA, and ALA only. Nicotine (0.5 mg/kg i.p.) and ALA (200 mg/kg) were administered for four weeks and the animals were fed with rat chow ad libitum. Rats were then anaesthetized with urethane and α-chloralose (5 ml/kg/b.w. i.p.); blood pressure recordings were obtained by the cannulation of left carotid artery connected to a pressure transducer and a Power-lab system. Blood samples were withdrawn for biochemical analysis.

Results: The study showed increased systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressures (MAP), and rate pressure product (RPP) in nicotine administered rats and nicotine + ALA group compared to control. Increased levels of C-reactive protein (CRP), malondialdehyde (MDA) and reduced levels of antioxidant enzymes (glutathione peroxidase [GPx] and superoxide dismutase [SOD]) were observed in the nicotine group. No significant change was found in the lipid profile across the groups. Supplementation with ALA (Group 3) reduced the elevated MDA levels and increased SOD and GPx levels in the nicotine treated rats but did not affect blood pressure.

Conclusion: This study showed that ALA suppressed oxidative stress but not blood pressure in rats administered nicotine.