Facilitative interaction between angiotensin II and oxidised LDL in cultured human coronary artery endothelial cells

Nigella sativa and Its Protective Role in Oxidative Stress and Hypertension

Hypertension increases the risk for a variety of cardiovascular diseases, including stroke, coronary artery disease, heart failure, and peripheral vascular disease. The increase in oxidative stress has been associated with the pathogenesis of hypertension. Increase of blood pressure is due to an imbalance between antioxidants defence mechanisms and free radical productions. Excessive production of reactive oxygen species reduces nitric oxide bioavailability leading to an endothelial dysfunction and a subsequent increase in total peripheral resistance. Hypertension can cause few symptoms until it reaches the advanced stage and poses serious health problems with lifelong consequences. Hypertensive patients are required to take drugs for life to control the hypertension and prevent complications. Some of these drugs are expensive and may have adverse reactions. Hence, it is timely to examine scientifically, complimentary therapies that are more effective and with minimal undesirable effects. Nigella sativa (NS) and its active constituents have been documented to exhibit antioxidant, hypotensive, calcium channel blockade and diuretic properties which may contribute to reduce blood pressure. This suggests a potential role of NS in the management of hypertension, and thus more studies should be conducted to evaluate its effectiveness.

The secretory phospholipase A2 group IIA: a missing link between inflammation, activated renin-angiotensin system, and atherogenesis?

Inflammation, lipid peroxidation and chronic activation of the rennin – angiotensin system (RAS) are hallmarks of the development of atherosclerosis. Recent studies have suggested the involvement of the pro-inflammatory secretory phospholipase A₂ (sPLA₂)-IIA in atherogenesis. This enzyme is produced by different cell types through stimulation by pro-inflammatory cytokines. It is detectable in the intima and in media smooth muscle cells, not only in atherosclerotic lesions but also in the very early stages of atherogenesis. sPLA₂-IIA can hydrolyse the phospholipid monolayers of low density lipoproteins (LDL). Such modified LDL show increased affinity to proteoglycans. The modified particles have a greater tendency to aggregate and an enhanced ability to insert cholesterol into cells. This modification may promote macrophage LDL uptake leading to the formation of foam cells. Furthermore, sPLA₂-IIA is not only a mediator for localized inflammation but may be also used as an independent predictor of adverse outcomes in patients with stable coronary artery disease or acute coronary syndromes. An interaction between activated RAS and phospholipases has been indicated by observations showing that inhibitors of sPLA₂ decrease angiotensin (Ang) II-induced macrophage lipid peroxidation. Meanwhile, various interactions between Ang II and oxLDL have been demonstrated suggesting a central role of sPLA₂-IIA in these processes and offering a possible target for treatment. The role of sPLA₂-IIA in the perpetuation of atherosclerosis appears to be the missing link between inflammation, activated RAS and lipidperoxidation.