Effect of HIF1α on the TRPC6 channel of glomerular podocytes under chronic hypoxia

Chronic hypoxia promotes pulmonary venous smooth muscle cell proliferation through the CaSR-TRPC6/ROCE pathway

The mechanism underlying chronic hypoxia (CH)-induced pulmonary venous remodeling remains unclear. Cell proliferation is key in vascular remodeling, and the calcium-sensing receptor (CaSR) protein contributes to CH-induced pulmonary venous smooth muscle cell (PVSMC) proliferation. In pulmonary arterial smooth muscle cells, CaSR and transient receptor potential canonical (TRPC) proteins interact, contributing to CH-induced cell proliferation via CaSR-TRPC1/6 signaling. We investigated whether a similar pathway exists in PVSMCs. Rat PVSMCs were isolated and subjected to CH. Cell proliferation was assessed by cell counting, CCK-8, and BrdU incorporation assays. Expression of CaSR and TRPC was analyzed by qPCR and western blotting, while interactions between CaSR and TRPC were detected by co-immunoprecipitation assay. Extracellular Ca2+ restoration was evaluated, to assess store- and receptor-operated Ca2+ entry (SOCE and ROCE, respectively). CH enhanced PVSMC numbers, viability, and DNA synthesis, and upregulated CaSR and TRPC6 expression. Further, CaSR and TRPC6 interacted with one another. CaSR inhibitors (NPS2143, NPS2390) reduced, whereas activators (spermine, R568) enhanced, CH-induced increases in PVSMC numbers, viability, DNA synthesis, and TRPC6 expression. CaSR knockdown using siRNA inhibited CH-induced TRPC6 upregulation and attenuated CH-induced increases in PVSMC numbers, viability, and DNA synthesis. TRPC6 knockdown had no significant effect on CH-induced CaSR upregulation, but significantly attenuated CH-induced increases in PVSMC number, viability, and DNA synthesis. CaSR knockdown reduced ROCE, but not SOCE, enhancement. Overall, CH promotes PVSMC proliferation through the CaSR-TRPC6/ROCE pathway.

Targeting of Hypoxia for Therapeutic Strategy in the Varied Physiological States

Hypoxia-inducible factors (HIFs) are transcription factors that initiate the expression of cellular processes to cope with hypoxic conditions. HIFs are principal regulators of hypoxic adaptation, regulating gene expression involved in glycolysis, erythropoiesis, angiogenesis, proliferation, and stem cell function under low O2. HIFs may play a pivotal role in tumor survival and metastasis in cancer formation and growth. Likewise, HIFs play a key role in microbial pathogenesis, particularly in host-pathogen interaction. Because of the role that HIF-1alpha plays in the biology of cancer and infections, it is a potential therapeutic target not only for malignant growth but also for parasitic infection. Several reports have demonstrated the up-regulation of host cellular HIFs due to infection-induced hypoxia. Hypoxia-inducible pathways have attracted great interest in the down-regulation of prolyl hydroxylase for treating inflammatory diseases and infections by viruses, protozoa, or bacteria, among other pathogens. Interestingly, increasing evidence suggests that HIFs play an important regulatory role in inflammation. For example, in macrophages, HIFs regulate glycolytic energy generation and optimize innate immunity, control pro-inflammatory gene expression, mediate the killing of pathogens and influence cell migration. Therefore, a good understanding of the biochemical mechanism of hypoxia signaling pathways will shed more light on how it could help identify and develop new treatment strategies for cancer and parasitic diseases, including viral, bacterial, fungal and protozoa infections.