Store-independent Orai1-mediated Ca2+ entry and cancer.

Ca2+ channels play an important role in the development of different types of cancer, and considerable progress has been made to understand the pathophysiological mechanisms underlying the role of Ca2+ influx in the development of different cancer hallmarks. Orai1 is among the most ubiquitous and multifunctional Ca2+ channels. Orai1 mediates the highly Ca2+-selective Ca2+ release-activated current (ICRAC) and participates in the less Ca2+-selective store-operated current (ISOC), along with STIM1 or STIM1 and TRPC1, respectively. Furthermore, Orai1 contributes to a variety of store-independent Ca2+ influx mechanisms, including the arachidonate-regulated Ca2+ current, together with Orai3 and the plasma membrane resident pool of STIM1, as well as the constitutive Ca2+ influx processes activated by the secretory pathway Ca2+-ATPase-2 (SPCA2) or supported by physical and functional interaction with the small conductance Ca2+-activated K+ channel 3 (SK3) or the voltage-dependent Kv10.1 channel. This review summarizes the current knowledge concerning the store-independent mechanisms of Ca2+ influx activation through Orai1 channels and their role in the development of different cancer features.

(-)­Oleocanthal inhibits proliferation and migration by modulating Ca2+ entry through TRPC6 in breast cancer cells.

Triple negative breast cancer is an aggressive type of cancer that does not respond to hormonal therapy and current therapeutic strategies are accompanied by side effects due to cytotoxic actions on normal tissues. Therefore, there is a need for the identification of anti-cancer compounds with negligible effects on non-tumoral cells. Here we show that (-)­oleocanthal (OLCT), a phenolic compound isolated from olive oil, selectively impairs MDA-MB-231 cell proliferation and viability without affecting the ability of non-tumoral MCF10A cells to proliferate or their viability. Similarly, OLCT selectively impairs the ability of MDA-MB-231 cells to migrate while the ability of MCF10A to migrate was unaffected. The effect of OLCT was not exclusive for triple negative breast cancer cells as we found that OLCT also attenuate cell viability and proliferation of MCF7 cells. Our results indicate that OLCT is unable to induce Ca2+ mobilization in non-tumoral cells. By contrast, OLCT induces Ca2+ entry in MCF7 and MDA-MB-231 cells, which is impaired by TRPC6 expression silencing. We have found that MDA-MB-231 and MCF7 cells overexpress the channel TRPC6 as compared to non-tumoral MCF10A and treatment with OLCT for 24-72 h downregulates TRPC6 expression in MDA-MB-231 cells. These findings indicate that OLCT impairs the ability of breast cancer cells to proliferate and migrate via downregulation of TRPC6 channel expression while having no effect on the biology of non-tumoral breast cells.

[CO2 LASER for the treatment of vaginal symptoms of genitourinary syndrome of menopause]. / Place du LASER au CO2 pour le traitement des symptômes vaginaux du syndrome génito-urinaire de la ménopause.

Genitourinary syndrome of menopause (GSM) brings together a collection of signs including vaginal dryness, burning sensation and itching discomfort as well as deterioration of sexual health, dysuria, urgenturia and repeated urinary infections and may be responsible for a significant impairment of quality of life in symptomatic postmenopausal women. The management of GSM therefore represents a public health issue. Systemic or local hormonal treatments are frequently offered, as well as non-hormonal treatments. The existence of contraindications to hormonal treatments and the constraints of using local treatments lead us to propose other therapeutic options. CO2 LASER is now part of the therapeutic arsenal for the treatment of vaginal dryness in the context of GSM. There is a growing interest in this technique, especially for women who have a contraindication to hormonal therapy, as it is a globally effective, long-acting alternative with very little adverse effect. Current evidence suggests that this tool could provide a quality of life benefit to many patients with minimal side effect exposure, if used in the respect of its indications and implementation protocols. However, clinical data based on high-level therapeutic trials remain absolutely essential for this treatment to be validated and recommended by health professionals.

Orai1 and Orai2 mediate store-operated calcium entry that regulates HL60 cell migration and FAK phosphorylation.

Store-operated Ca2+ entry (SOCE) is a major mechanism for the regulation of intracellular Ca2+ homeostasis and cellular function. Emerging evidence has revealed that altered expression and function of the molecular determinants of SOCE play a critical role in the development or maintenance of several cancer hallmarks, including enhanced proliferation and migration. Here we show that, in the acute myeloid leukemia cell line HL60, Orai2 is highly expressed at the transcript level, followed by the expression of Orai1. Using fluorescence Ca2+ imaging we found that Orai2 silencing significantly attenuated thapsigargin-induced SOCE, as well as knockdown of Orai1, while silencing the expression of both channels almost completely reduced SOCE, thus suggesting that SOCE in these cells is strongly dependent on Orai1 and Orai2. On the other hand, the expression of TRPC1, TRPC3 and TRPC6 is almost absent at the transcript and protein level. Bromodeoxyuridine cell proliferation assay revealed that Orai1 and Orai2 expression silencing significantly reduced HL60 cell proliferation. Furthermore, knockdown of Orai1 and Orai2 significantly attenuated the ability of HL60 to migrate in vitro as determined by transwell migration assay, probably due to the impairment of FAK tyrosine phosphorylation. These findings provide evidence for a role for Orai1 and Orai2, in SOCE and migration in the human HL60 promyeloblastic cell line. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Transient receptor potential channels in human platelets: expression and functional role.

Recent studies have demonstrated that mammalian homologues of Drosophila transient receptor potential (TRP) channels are widely expressed in human platelets. Occupation of G protein-coupled receptors by agonists results in activation of these channels, which results in Na+ and Ca2+ entry. Canonical or classic TRP (TRPC) family members have been reported to associate with different Ca2+-handling proteins, including the type II inositol 1,4,5-trisphosphate receptor, the endoplasmic reticulum Ca2+ sensor STIM1 (STromal Interaction Molecule-1) or the Ca2+ permeable channel Orai1. The dynamic interaction of TRPC channels with the above mentioned proteins has been found to be important for both store-operated and capacitative Ca2+ entry, as well as for non-capacitative Ca2+ influx. The former is a major mechanism for Ca2+ entry in human platelets. This mechanism, activated by a reduction in the concentration of free Ca2+ in the intracellular stores, results in the formation of signaling complexes involving STIM proteins, Orai1, Orai2, TRPC1 and TRPC6. There is a growing body of evidence supporting that Ca2+ signaling dysfunction plays an important role in the pathogenesis of several platelet-linked disorders, including those associated to type 2 diabetes mellitus. Abnormal Ca2+ signals in response to physiological agonists have been associated to platelet hyperactivity. The expression of several TRPCs, STIM1 and Orai1, as well as their interaction, has been reported to be altered in platelets from type 2 diabetic patients, which results in attenuated capacitative Ca2+ entry but enhanced non-capacitative Ca2+ influx; thus suggesting a role for Ca2+ handling proteins, including TRPs, in the pathomechanism of diabetic complications.

Homocysteine, intracellular signaling and thrombotic disorders.

Homocysteine, a sulphur-containing amino acid derived from methionine, has been presented as an independent risk factor for cardiovascular disorders, including atherosclerosis and thrombogenesis. The mechanisms underlying homocysteine-induced effects have been intensively investigated over the last two decades. Homocysteine can induce oxidative stress promoting oxidant injury to vascular and blood cells. Hyperhomocysteinemia often results in intracellular Ca2+ mobilization, endoplasmic reticulum (ER) stress, with the subsequent development of apoptotic events, chronic inflammation leading to endothelial dysfunction and remodeling of the extracellular matrix. Homocysteine has also been reported to induce modulation of gene expression through alteration of the methylation status. The effects of elevated concentrations of circulating homocysteine on the vascular wall, platelet function and coagulation factors promote the development of a pro-coagulant state. The pathophysiological significance of homocysteine in the development of vascular disorders through the induction of endothelial dysfunction and abnormal platelet activity and blood coagulation is discussed in this review.

Effect of homocysteine on calcium mobilization and platelet function in type 2 diabetes mellitus.

Type 2 diabetes mellitus induces a characteristic platelet hyperactivity that might be due to several factors including oxidative stress and abnormal intracellular Ca(2+) homeostasis. Hyperhomocysteinaemia is considered a risk factor in the development of thrombosis although its effect on platelet function and the mechanisms involved are still poorly understood. Here we show that homocysteine induce a concentration-dependent increase in endogenous production of reactive oxygen species (ROS), which was significantly greater in platelets from diabetic patients than in controls. Platelet treatment with homocysteine resulted in Ca2+ release from the dense tubular system and the acidic stores. Ca2+ mobilization-induced by homocysteine consisted in two components, an initial slow increase in intracellular free Ca (+) concentration ([Ca2+]i) and a rapid and marked increase in [Ca2+]i, th second leading to the activation of platelet aggregation. As well as ROS generation, Ca2+ mobilization and platelet aggregation were significantly greater in platelets from diabetic donors than in controls, which indicate that platelets from diabetic donors are more sensitive to homocysteine. These findings, together with the hyperhomocysteinaemia reported in diabetic patients, strongly suggest that homocysteine might be considered a risk factor in the development of cardiovascular complications associated to type 2 diabetes mellitus.

Effect of homocysteine on calcium mobilization and platelet function in type 2 diabetes mellitus.

Type 2 diabetes mellitus induces a characteristic platelet hyperactivity that might be due to several factors including oxidative stress and abnormal intracellular Ca2+ homeostasis. Hyperhomocysteinaemia is considered a risk factor in the development of thrombosis although its effect on platelet function and the mechanisms involved are still poorly understood. Here we show that homocysteine (Hcy) induce a concentration-dependent increase in endogenous production of reactive oxygen species (ROS), which was significantly greater in platelets from diabetic patients than in controls. Platelet treatment with Hcy resulted in Ca2+ release from the dense tubular system and the acidic stores. Ca2+ mobilisation-induced by Hcy consisted in two components, an initial slow increase in intracellular free Ca2+ concentration ([Ca2+]i) and a rapid and marked increase in [Ca2+]i, the second leading to the activation of platelet aggregation. As well as ROS generation, Ca2+ mobilization and platelet aggregation were significantly greater in platelets from diabetic donors than in controls, which indicate that platelets from diabetic donors are more sensitive to Hcy. These findings, together with the hyperhomocysteinaemia reported in diabetic patients, strongly suggest that Hcy might be considered a risk factor in the development of cardiovascular complications associated to type 2 diabetes mellitus.