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Undurti N. Das

Abstract

Abdominal aortic aneurysm (AAA) is a chronic inflammatory condition, triggered by the local accumulation of macrophages, oxidative stress and damage to the aortic wall. Pro-inflammatory eicosanoids seem to play a significant role in AAA. The pro-inflammatory events seen in AAA could be due to a deficiency of anti-inflammatory eicosanoids such as lipoxin A4 (LXA4), resolvins, protectins and maresins as a result of reduced tissue concentrations of their precursors: arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Thus, an imbalance between pro- and anti-inflammatory eicosanoids may underlie AAA. Angiotensin-II (Ang-II), a pro-inflammatory molecule, seems to have a role in AAA. I propose that AAA is due to the local (abdominal aortic wall) deficiency of AA and other PUFAs and their anti-inflammatory metabolites especially LXA4. The beneficial action of EPA and DHA reported in the animal experimental models of AAA induced by Ang-II infusion can be attributed to their (EPA and DHA) ability to enhance the formation of not only resolvins, protectins and maresins but also LXA4. It is likely that abdominal aortic tissue (endothelial cells, smooth muscle cells and other cells) may be deficient in AA, EPA and DHA, and have defective activity of 5-, 12-, and 15-lipoxygenases and cyclooxygenase, especially COX-2 resulting in decreased formation of LXA4, resolvins, protectins and maresins. Thus, methods designed to enhance the formation of LXA4 and other anti-inflammatory eicosanoids may form a new approach to prevent and manage AAA.

Open access

Undurti N. Das

Abstract

Obesity and its consequent complications such as hypertension and metabolic syndrome are increasing in incidence in almost all countries. Insulin resistance is common in obesity. Renin– angiotensin system (RAS) is an important target in the treatment of hypertension and drugs that act on RAS improve insulin resistance and decrease the incidence of type 2 diabetes mellitus, explaining the close association between hypertension and type 2 diabetes mellitus. RAS influences food intake by modulating the hypothalamic expression of neuropeptide Y and orexins via AMPK dephosphorylation. Estrogen reduces appetite by its action on the brain in a way similar to leptin, an anorexigenic action that seems to be mediated via hypothalamic pro-opiomelanocortin (POMC) neurons in the arcuate nucleus and synaptic plasticity in the arcuate nucleus similar to leptin. Estrogen stimulates lipoxin A4, a potent vasodilator and platelet anti-aggregator. Since both RAS and estrogen act on the hypothalamic neuropeptides and regulate food intake and obesity, it is likely that RAS modulates LXA4 synthesis. Thus, it is proposed that Angiotensin-II receptor blockers and angiotensin-converting enzymes and angiotensin-II antagonists may have the ability to augment LXA4 synthesis and thus bring about their beneficial actions.