Antihypertensive and Antihyperlipidemic Effects of Thymoquinone in L-NAME-Induced Hypertensive Rats

Thymoquinone (TQ) is gaining increasing considerations in medical research due to its broad spectrum of biological activities against diseases such as neurodegeneration and hypertension. The objective of this study was to evaluate the antihypertensive and lipid-lowering potential of TQ on L-NAME-induced hypertensive rats. Hypertension was induced in 36 Sprague Dawley rats by administration of L-Nitro-Arginine Methyl Ester (L-NAME) in drinking water for 4 weeks. Then rats were divided into 6 groups (n=6): L-NAME?alone, L-NAME+TQ2.5, L-NAME+TQ5, L-NAME+TQ10, L-NAME+captopril, and control. Mean Arterial Pressure (MAP) and heart rate was recorded by the non-invasive tail-cuff technique weekly for 28 days. TQ reversed established hypertension in TQ5 and TQ10 groups and prevented further increase in MAP in the TQ2.5 group. Unlike the captopril treated group, TQ antihypertensive activity was associated with an increase in serum aldosterone concentration and ACE activity. TQ treatment at the high dose significantly lowered total cholesterol and LDL levels in comparison with the healthy control group at the end of the 4th week of treatment. This study confirms the antihypertensive action of TQ. Furthermore, it can be concluded that inhibition of ACE did not play a role in the underlying antihypertensive mechanism. However, blocking angiotensin II receptors is a likely mechanism for lowering the MAP.