Exposure to microgravity conditions causes cardiovascular deconditioning in astronauts during spaceflight. Until now, no specific drugs are available for countermeasure, since the underlying mechanism is largely unknown. Endothelial cells (ECs) and smooth muscle cells (SMCs) play key roles in various vascular functions, many of which are regulated by purinergic 2 (P2) receptors. However, their function in ECs and SMCs under microgravity conditions is still unclear. In this study, primary ECs and SMCs were isolated from bovine aorta and verified with specific markers. We show for the first time that the P2 receptor expression pattern is altered in ECs and SMCs after 24 h exposure to simulated microgravity using a clinostat. However, conditioned medium compensates this change in specific P2 receptors, for example, P2X7. Notably, P2 receptors such as P2X7 might be the important players during the paracrine interaction. Additionally, ECs and SMCs secreted different cytokines under simulated microgravity, leading into a pathogenic proliferation and migration. In conclusion, our data indicate P2 receptors might be important players responding to gravity changes in ECs and SMCs. Since some artificial P2 receptor ligands are applied as drugs, it is reasonable to assume that they might be promising candidates against cardiovascular deconditioning in the future.

Intracellular calcium concentration in peripheral blood mononuclear cells (PBMCs) of patients with chronic kidney disease (CKD) is significantly increased, and the regulatory mechanisms maintaining cellular calcium homeostasis are impaired. The purpose of this study was to examine the effect of vitamin D3 on predominant regulatory mechanisms of cell calcium homeostasis. The study involved 16 CKD stages 2-3 patients with vitamin D deficiency treated with cholecalciferol 7000-14000 IU/week for 6 months. The regulatory mechanisms of calcium signaling were studied in PBMCs and red blood cells. After vitamin D3 supplementation, serum concentration of 25(OH)D3 increased (P < 0.001) and [Ca(2+)]i decreased (P < 0.001). The differences in [Ca(2+)]i were inversely related to differences in 25(OH)D3 concentration (P < 0.01). Vitamin D3 supplementation decreased the calcium entry through calcium release activated calcium (CRAC) channels and purinergic P2X7 channels. The function of P2X7 receptors was changed in comparison with their baseline status, and the expression of these receptors was reduced. There was no effect of vitamin D3 on P2X7 pores and activity of plasma membrane Ca(2+)-ATPases. Vitamin D3 supplementation had a beneficial effect on [Ca(2+)]i decreasing calcium entry via CRAC and P2X7 channels and reducing P2X7 receptors expression.

The proteasome inhibitor bortezomib (BTZ) is a potent first-line anticancer drug for multiple myeloma; nonetheless, it induced peripheral neuropathy. It has been suggested that many cytokines may play a role in mediating neuropathic pain, but the underlying molecular mechanism is not fully understood. Recent studies have shown that neuropathic pain is closely related to the purinergic ligand-gated ion channel 7 receptor (P2X7R), one of the P2X receptors, which is richly expressed in glial cells. P2X7-p38 pathway is correlated with microglia- and satellite glial cell- (SGC-) mediated neuropathic pain. However, the association of P2X7R and p38MAPK in mediating BTZ-induced neuropathic pain remains unclear. In this study, the relationship between P2X7R activation and p38 phosphorylation in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) in the development and maintenance of BTZ-induced neuropathic pain was elucidated. The results showed that BTZ increased mechanical thresholds in rats, accompanied with upregulation of P2X7R expression and p38MAPK phosphorylation, indicating that P2X7R and p38MAPK are key molecules in the development and maintenance of BTZ-induced neuropathic pain. Inhibiting p38MAPK phosphorylation with SB203580 resulted in downregulation of P2X7R expression levels. Inhibition of P2X7R with Brilliant Blue G (BBG) reversed neuropathic pain might decrease through the expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 via inhibiting p38MAPK phosphorylation. The P2X7R/p38MAPK signaling pathway in SGCs of DRG and microglia of SDH might be a potential pharmacological target behind this mechanism as an opportunity to relieve BTZ-induced neuropathic pain.