ORAI3 is dispensable for store-operated Ca2+ entry and immune responses by lymphocytes and macrophages

Reduced store operated calcium entry contributes to autophagy mediated escape of prostate cancer to oxaliplatin treatment

Oxaliplatin, a third-generation platinum-based chemotherapeutic drug, induces cell cycle arrest and apoptosis in prostate cancer treatment. However, both intrinsic and acquired resistance mechanisms limit its therapeutic efficacy. Notably, chemotherapeutic agents often induce autophagy-a cellular recycling process-that can contribute to drug resistance. Calcium (Ca2+) signalling plays a pivotal role in regulating cell fate. However, the involvement of Ca2+ and Ca2+ channels in oxaliplatin resistance within prostate cancer cells remains controversial and poorly understood. In this study, we demonstrate that oxaliplatin treatment enhances autophagy in prostate cancer cells. Concurrently, oxaliplatin modulates the expression of key proteins involved in store-operated calcium entry (SOCE): it upregulates Orai3 channels while downregulating Orai1 and Stim1. These alterations result in diminished SOCE activity, contributing to an apoptosis-resistant phenotype. Importantly, we found that targeting Orai3 expression and inhibiting autophagy sensitizes prostate cancer cells to oxaliplatin-induced apoptosis. Our findings suggest that combining Orai3 downregulation with autophagy inhibition may enhance the efficacy of oxaliplatin in treating prostate cancer. This combinatorial approach could hold potential for overcoming resistance and improving therapeutic outcomes.

2-Hydroxy-4-n-octyloxybenzophenone induces developmental neurotoxicity and multiple sclerosis-like symptoms through cacna1a regulated Ca2 + inward flow and microglial activation

2-Hydroxy-4-n-octyloxybenzophenone (UV-531) is a UV absorber widely used in infrastructure, cosmetics, and rubber products. The previous study found that UV-531 exposure irritate the skin and interfere with androgen secretion. However, the developmental toxicity and neurotoxic effects of UV-531 are still at an exploratory stage, and the effects of UV-531 on the environment and living organisms need to be further explored. Here, we exposed zebrafish to environmental relevant doses of UV-531 (0.1, 0.2, 0.4, 0.8 and 1.6 μg/L) and observed no significant developmental toxicity, but significant neurotoxicity. We assessed locomotor ability and responsiveness of zebrafish by general locomotion and light/dark challenge. Changes in dopaminergic (DA) neurons were observed using transgenic zebrafish slc18a2:GFP. Changes in cerebral vessels and blood-brain barrier (BBB) were observed using transgenic zebrafish fli1:GFP. Gene expression was detected by transcriptome and real-time qPCR. The effect of UV-531 on calcium homeostasis was determined by measuring Ca2+ levels. Microglia status was assessed by in situ hybridization. It was observed that UV-531 treatment resulted in a reduced locomotor activity, DA neurons injury, cerebral vessels damage, BBB leakage, calcium homeostasis imbalance, and abnormal expression of genes related to neurodevelopment and function. RNA-seq results indicated that Ca2+ import across plasma membrane was highly associated with UV-531-induced developmental neurotoxicity and cacna1aa and cacna1ab were key regulators. These findings suggest that UV-531 induced calcium homeostasis imbalance caused by upregulating cacna1aa and cacna1ab may contribute to multiple sclerosis (MS). Accordingly, UV-531 exposure triggered neuroinflammation, injured myelin, ultimately leading to the development of MS-like symptoms, including decreased responsiveness to external stimuli, microglia activation, dysregulation of mbp and MS-related genes ahsg1, btg1, and grna. In summary, exposure to environmental relevant doses of UV-531 caused neurological damage and led to MS-like symptoms. Given the effects of UV-531 on the organisms, a safe dose range should be established.

Calcium signaling at the interface between astrocytes and brain inflammation

Astrocytes are the most prevalent glial cells of the brain and mediate vital roles in the development and function of the nervous system. Astrocytes, along with microglia, also play key roles in initiating inflammatory immune responses following brain injury, stress, or disease-related triggers. While these glial immune responses help contain and resolve cellular damage to the brain, dysregulation of astrocyte activity can in some cases amplify inflammation and worsen impact on neural tissue. As nonexcitable cells, astrocytes excitability is regulated primarily by Ca2+ signals that control key functions such as gene expression, release of inflammatory mediators, and cell metabolism. In this review, we examine the molecular and functional architecture of Ca2+ signaling networks in astrocytes and their impact on astrocyte effector functions involved in inflammation and immunity.

Blocking Orai1 constitutive activity inhibits B-cell cancer migration and synergistically acts with drugs to reduce B-CLL cell survival

Orai1 channel capacity to control store-operated Ca2+ entry (SOCE) and B-cell functions is poorly understood and more specifically in B-cell cancers, including human lymphoma and leukemia. As compared to normal B-cells, Orai1 is overexpressed in B-chronic lymphocytic leukemia (B-CLL) and contributes in resting B-CLL to mediate an elevated basal Ca2+ level through a constitutive Ca2+ entry, and in BCR-activated B-cell to regulate the Ca2+ signaling response. Such observations were confirmed in human B-cell lymphoma and leukemia lines, including RAMOS, JOK-1, MEC-1 and JVM-3 cells. Next, the use of pharmacological Orai1 inhibitors (GSK-7975 A and Synta66) blocks constitutive Ca2+ entry and in turn affects B-cell cancer (primary and cell lines) survival and migration, controls cell cycle, and induces apoptosis through a mitochondrial and caspase-3 independent pathway. Finally, the added value of Orai1 inhibitors in combination with B-CLL drugs (ibrutinib, idelalisib, rituximab, and venetoclax) on B-CLL survival was tested, showing an additive/synergistic effect including in the B-cell cancer lines. To conclude, this study highlights the pathophysiological role of the Ca2+ channel Orai1 in B-cell cancers, and pave the way for the use of ORAI1 modulators as a plausible therapeutic strategy.

ALOX5 drives the pyroptosis of CD4+ T cells and tissue inflammation in rheumatoid arthritis

Pyroptosis, an inflammatory form of programmed cell death, is linked to the pathology of rheumatoid arthritis (RA). Here, we investigated the molecular mechanism underlying pyroptosis in T cells isolated from patients with RA. Compared with healthy individuals, patients with RA had more pyroptotic CD4+ T cells in blood and synovia, which correlated with clinical measures of disease activity. Moreover, the mRNA expression and protein abundance of arachidonate 5-lipoxygenase (ALOX5), which converts arachidonic acid to leukotriene A4 (LTA4), were increased in CD4+ T cells from patients with RA and, among patients with RA, were lowest in those in clinical remission. Knockdown or pharmacological inhibition of ALOX5 suppressed CD4+ T cell pyroptosis and improved symptoms in two rodent models of RA. Mechanistically, the increase in ALOX5 activity in RA CD4+ T cells enhanced the production of the LTA4 derivative LTB4, which stimulated Ca2+ influx through ORAI3 channels, leading to the activation of NLRP3 inflammasomes and pyroptosis. Our findings reveal a role for ALOX5 in RA and provide a molecular basis for further exploring the clinical utility of ALOX5 inhibition in RA and for using ALOX5 as a biomarker to distinguish active disease and remission in RA.

Orai3 and Orai1 mediate CRAC channel function and metabolic reprogramming in B cells

The essential role of store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ (CRAC) channels in T cells is well established. In contrast, the contribution of individual Orai isoforms to SOCE and their downstream signaling functions in B cells are poorly understood. Here, we demonstrate changes in the expression of Orai isoforms in response to B cell activation. We show that both Orai3 and Orai1 mediate native CRAC channels in B cells. The combined loss of Orai1 and Orai3, but not Orai3 alone, impairs SOCE, proliferation and survival, nuclear factor of activated T cells (NFAT) activation, mitochondrial respiration, glycolysis, and the metabolic reprogramming of primary B cells in response to antigenic stimulation. Nevertheless, the combined deletion of Orai1 and Orai3 in B cells did not compromise humoral immunity to influenza A virus infection in mice, suggesting that other in vivo co-stimulatory signals can overcome the requirement of BCR-mediated CRAC channel function in B cells. Our results shed important new light on the physiological roles of Orai1 and Orai3 proteins in SOCE and the effector functions of B lymphocytes.