STIM1/Orai1-mediated store-operated Ca2+ entry: the tip of the iceberg

Highly efficient mechanisms regulate intracellular calcium (Ca2+) levels. The recent discovery of new components linking intracellular Ca2+ stores to plasma membrane Ca2+ entry channels has brought new insight into the understanding of Ca2+ homeostasis. Stromal interaction molecule 1 (STIM1) was identified as a Ca2+ sensor essential for Ca2+ store depletion-triggered Ca2+ influx. Orai1 was recognized as being an essential component for the Ca2+ release-activated Ca2+ (CRAC) channel. Together, these proteins participate in store-operated Ca2+ channel function. Defective regulation of intracellular Ca2+ is a hallmark of several diseases. In this review, we focus on Ca2+ regulation by the STIM1/Orai1 pathway and review evidence that implicates STIM1/Orai1 in several pathological conditions including cardiovascular and pulmonary diseases, among others

Cigarette Smoking and Erectile Dysfunction: Focus on NO Bioavailability and ROS Generation

Introduction.  Thirty million men in the United States suffer from erectile dysfunction (ED) and this number is expected to double by 2025. Considered a major public health problem, which seriously affects the quality of life of patients and their partners, ED becomes increasingly prevalent with age and chronic smoking is a major risk factor in the development of ED. Aim.  To review available evidence concerning the effects of cigarette smoking on vascular changes associated with decreased nitric oxide (NO) bioavailability and increased reactive oxygen species (ROS) generation. Methods.  We examined epidemiological and clinical data linking cigarette smoking and ED, and the effects of smoking on vascular NO bioavailability and ROS generation. Main Outcome Measures.  There are strong parallels between smoking and ED and considerable evidence supporting the concept that smoking-related ED is associated with reduced bioavailability of NO because of increased ROS. Results.  Cigarette smoking-induced ED in human and animal models is associated with impaired arterial flow to the penis or acute vasospasm of the penile arteries. Long-term smoking produces detrimental effects on the vascular endothelium and peripheral nerves and also causes ultrastructural damage to the corporal tissue, all considered to play a role in chronic smoking-induced ED. Clinical and basic science studies provide strong indirect evidence that smoking may affect penile erection by the impairment of endothelium-dependent smooth muscle relaxation or more specifically by affecting NO production via increased ROS generation. Whether nicotine or other products of cigarette smoke mediate all effects related to vascular damage is still unknown. Conclusions.  Smoking prevention represents an important approach for reducing the risk of ED. The characterization of the components of cigarette smoke leading to ED and the mechanisms by which these components alter signaling pathways activated in erectile responses are necessary for a complete comprehension of cigarette smoking-associated ED. Tostes RS, Carneiro FS, Lee AJ, Giachini FRC, Leite R, Osawa Y, and Clinton Webb R. Cigarette smoking and erectile dysfunction: Focus on NO bioavailability and ROS generation. J Sex Med 2008;5:1284–1295.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75024/1/j.1743-6109.2008.00804.x.pd

Vascular O-GlcNAcylation augments reactivity to constrictor stimuli by prolonging phosphorylated levels of the myosin light chain

O-GlcNAcylation is a modification that alters the function of numerous proteins. We hypothesized that augmented O-GlcNAcylation levels enhance myosin light chain kinase (MLCK) and reduce myosin light chain phosphatase (MLCP) activity, leading to increased vascular contractile responsiveness. The vascular responses were measured by isometric force displacement. Thoracic aorta and vascular smooth muscle cells (VSMCs) from rats were incubated with vehicle or with PugNAc, which increases O-GlcNAcylation. In addition, we determined whether proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation. PugNAc enhanced phenylephrine (PE) responses in rat aortas (maximal effect, 14.2±2 vs 7.9±1 mN for vehicle, n=7). Treatment with an MLCP inhibitor (calyculin A) augmented vascular responses to PE (13.4±2 mN) and abolished the differences in PE-response between the groups. The effect of PugNAc was not observed when vessels were preincubated with ML-9, an MLCK inhibitor (7.3±2 vs 7.5±2 mN for vehicle, n=5). Furthermore, our data showed that differences in the PE-induced contractile response between the groups were abolished by the activator of AMP-activated protein kinase (AICAR; 6.1±2 vs 7.4±2 mN for vehicle, n=5). PugNAc increased phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and protein kinase C-potentiated inhibitor protein of 17 kDa (CPI-17), which are involved in RhoA/Rho-kinase-mediated inhibition of myosin phosphatase activity. PugNAc incubation produced a time-dependent increase in vascular phosphorylation of myosin light chain and decreased phosphorylation levels of AMP-activated protein kinase, which decreased the affinity of MLCK for Ca2+/calmodulin. Our data suggest that proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation, favoring vascular contraction

Vascular biology of magnesium and its transporters in hypertension

Magnesium may influence blood pressure by modulating vascular tone and structure through its effects on myriad biochemical reactions that control vascular contraction/dilation, growth/apoptosis, differentiation and inflammation. Magnesium acts as a calcium channel antagonist, it stimulates production of vasodilator prostacyclins and nitric oxide and it alters vascular responses to vasoconstrictor agents. Mammalian cells regulate Mg2+ concentration through special transport systems that have only recently been characterized. Magnesium efflux occurs via Na2+-dependent and Na2+-independent pathways. Mg2+ influx is controlled by recently cloned transporters including Mrs2p, SLC41A1, SLC41A2, ACDP2, MagT1, TRPM6 and TRPM7. Alterations in some of these systems may contribute to hypomagnesemia and intracellular Mg2+ deficiency in hypertension and other cardiovascular pathologies. In particular, increased Mg2+ efflux through dysregulation of the vascular Na+/Mg2+ exchanger and decreased Mg2+ influx due to defective vascular and renal TRPM6/7 expression/activity may be important in altered vasomotor tone and consequently in blood pressure regulation. The present review discusses the role of Mg2+ in vascular biology and implications in hypertension and focuses on the putative transport systems that control magnesium homeostasis in the vascular system. Much research is still needed to clarify the exact mechanisms of cardiovascular Mg2+ regulation and the implications of aberrant cellular Mg2+ transport and altered cation status in the pathogenesis of hypertension and other cardiovascular diseases

Inhibitory effects of PPAR-γ on endothelin-1-induced inflammatory pathways in vascular smooth muscle cells from normotensive and hypertensive rats

The present study evaluated the effects of endothelin (ET)-1 and the peroxisome proliferator activated receptor γ (PPAR-γ) agonist, rosiglitazone, on inflammatory markers in vascular smooth muscle cells (VSMCs) from normotensive (WKY) and hypertensive (SHRSP) rats. Rat VSMC-derived mesenteric arteries from WKY and SHRSP were treated with ET-1 (100 mmol/L) and rosiglitazone (1μmol/L) or ET type A (ETA) or type B (ETB) receptor antagonists. Nuclear factor kappa-B (NFκB) binding activity was assessed by electrophoretic mobility shift assay and phospho-inhibitory κB (IκB); vascular cell adhesion molecule (VCAM)-1, intercellular adhesion molecule (ICAM)-1, and cyclooxygenase (COX)-2 expression was determined using Western blotting. ET-1 significantly increased NFκB binding, and VCAM-1, ICAM, and COX-2 expression to a greater degree in SHRSP than in WKY VSMC. These changes were associated with increased phosphorylation of IκB, thus resulting in decreased NFκB inhibition. Co-incubation with PPAR-γ activator rosiglitazone, or ETA or ETB receptor antagonism prevented ET-1-stimulated vascular proinflammatory effects in both WKY and SHRSP VSMC. Proinflammatory effects of ET-1 in VSMCs are mediated via both ETA and ETB receptor subtypes. These effects may be abrogated by the PPAR-γ activator rosiglitazone. PPAR-γ activators may thus prevent deleterious ET-1-dependent proinflammatory vascular effects in VSMC in hypertension

Transient receptor potential melastatin 7 (TRPM7) cation channels, magnesium and the vascular system in hypertension

Decreased Mg(2+) concentration has been implicated in altered vascular reactivity, endothelial dysfunction and structural remodeling, processes important in vascular changes and target organ damage associated with hypertension. Unlike our knowledge of other major cations, mechanisms regulating cellular Mg(2+) handling are poorly understood. Until recently little was known about protein transporters controlling transmembrane Mg(2+) influx. However, new research has uncovered a number of genes and proteins identified as transmembrane Mg(2+) transporters, particularly transient receptor potential melastatin (TRPM) cation channels, TRPM6 and TRPM7. Whereas TRPM6 is found primarily in epithelial cells, TRPM7 is ubiquitously expressed. Vascular TRPM7 has been implicated as a signaling kinase involved in vascular smooth muscle cell growth, apoptosis, adhesion, contraction, cytoskeletal organization and migration, and is modulated by vasoactive agents, pressure, stretch and osmotic changes. Emerging evidence suggests that vascular TRPM7 function might be altered in hypertension. The present review discusses the importance of Mg(2+) in vascular biology in hypertension and focuses on transport systems, mainly TRPM7, that might play a role in the control of vascular Mg(2+) homeostasis. Elucidation of the relationship between the complex systems responsible for regulation of Mg(2+) homeostasis, the role of TRPM7 in vascular signaling, and the cardiovascular impact will be important for understanding the clinical implications of hypomagnesemia in cardiovascular disease

Receptor and nonreceptor tyrosine kinases in vascular biology of hypertension

Purpose of review: Extensive evidence indicates that receptor tyrosine kinases and nonreceptor tyrosine kinases underlie vascular damage in hypertension. However, recent clinical studies using vascular endothelial growth factor (VEGF) receptor inhibitors (bevacizumab, axitinib) revealed the unexpected finding of increased blood pressure. Whether this is a generalized receptor tyrosine kinase phenomenon or a VEGF receptor-specific effect is unclear. The present review focuses on current findings regarding the role of tyrosine kinases and signaling in vascular pathobiology of hypertension. Recent findings: Multiple complex and interacting signaling pathways activated by receptor and nonreceptor tyrosine kinases are upregulated and have been implicated in vascular alterations associated with high blood pressure. Experimental evidence suggests that receptor tyrosine kinase activation by direct ligand binding as well as by ligand-independent mechanisms through transactivation by G protein-coupled receptors plays a role in vascular signaling and cardiovascular diseases. Summary: Cellular mechanisms and signaling pathways mediated by tyrosine kinases involved in hypertensive vascular damage are currently the subject of intensive investigation. The unexpected finding of hypertension as a side effect in patients treated with VEGF receptor inhibitors suggests that some tyrosine kinases negatively regulate vascular function. Further characterization of these processes will provide greater understanding of the role of tyrosine kinases in vascular pathobiology in hypertension and should provide new insights on novel therapeutic targets.</p