Ablation of Toll-like receptor 4 mitigates central blood pressure response during hyperhomocysteinemia

Association of homocysteine level with risk of stroke: A dose-response meta-analysis of prospective cohort studies

BACKGROUND AND AIMS

Homocysteine (Hcy) level has been increasingly linked with stroke and ischemic stroke (IS). However, a dose-response meta-analysis of prospective cohort studies of the association is lacking. We aimed to explore the quantitative dose-response association of Hcy level with stroke and IS in a meta-analysis of prospective cohort studies.

METHODS AND RESULTS

We performed a systematic search of PubMed, Embase and Web of Science databases up to April 25, 2019 for prospective cohort studies assessing the association of Hcy level with stroke and IS. We used random-effect models to estimate the pooled relative risk (RRs) (with 95% confidence intervals [CIs]) for the association of Hcy with risk of stroke and IS. Restricted cubic splines were used to evaluate possible linear or nonlinear association of Hcy level with stroke and IS. We included 10 prospective cohort studies (7 articles) with 11,061 participants in the meta-analysis. Hcy level was associated with increased risk of stroke (RR = 1.58, 95% CI 1.25-2.00, I² = 39.5%) and IS (RR = 1.54, 95% CI 1.21-1.97, I² = 36.4%) for the highest versus the lowest categories. We found a linear association between Hcy level and stroke (P_nonlinearity = 0.660) and IS (P_nonlinearity = 0.981). For each 1-μmol/L increase in Hcy, the pooled RR was 1.06 (95% CI 1.01-1.12, I² = 59.0%) for stroke and 1.05 (95% CI 1.00-1.11, I² = 58.6%) for IS.

CONCLUSION

This meta-analysis indicated that elevated Hcy level was associated with increased risk of stroke and IS.

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.

Homocysteine and homocysteine-related compounds: an overview of the roles in the pathology of the cardiovascular and nervous systems

Homocysteine, an amino acid containing a sulfhydryl group, is an intermediate product during metabolism of the amino acids methionine and cysteine. Hyperhomocysteinemia is used as a predictive risk factor for cardiovascular disorders, the stroke progression, screening for inborn errors of methionine metabolism, and as a supplementary test for vitamin B₁₂ deficiency. Two organic systems in which homocysteine has the most harmful effects are the cardiovascular and nervous system. The adverse effects of homocysteine are achieved by the action of several different mechanisms, such as overactivation of N-methyl-d-aspartate receptors, activation of Toll-like receptor 4, disturbance in Ca²⁺ handling, increased activity of nicotinamide adenine dinucleotide phosphate-oxidase and subsequent increase of production of reactive oxygen species, increased activity of nitric oxide synthase and nitric oxide synthase uncoupling and consequent impairment in nitric oxide and reactive oxygen species synthesis. Increased production of reactive species during hyperhomocysteinemia is related with increased expression of several proinflammatory cytokines, including IL-1β, IL-6, TNF-α, MCP-1, and intracellular adhesion molecule-1. All these mechanisms contribute to the emergence of diseases like atherosclerosis and related complications such as myocardial infarction, stroke, aortic aneurysm, as well as Alzheimer disease and epilepsy. This review provides evidence that supports the causal role for hyperhomocysteinemia in the development of cardiovascular disease and nervous system disorders.