The CaSR/TRPV4 coupling mediates pro‐inflammatory macrophage function

Abstract

Aim: Although calcium-sensing receptor (CaSR) and transient receptor potential vanilloid 4 (TRPV4) channels are functionally expressed on macrophages, it is unclear if they work coordinately to mediate macrophage function. The present study investigates whether CaSR couples to TRPV4 channels and mediates macrophage polarization via Ca 2+ signaling. Methods: The role of CaSR/TRPV4/Ca 2+ signaling was assessed in lipopolysaccharide (LPS)-treated peritoneal macrophages (PMs) from wild-type (WT) and TRPV4 knockout (TRPV4 KO) mice. The expression and function of CaSR and TRPV4 in PMs were analyzed by immunofluorescence and digital Ca 2+ imaging. The correlation factors of M1 polarization, CCR7, IL-1β, and TNFα were detected using q-PCR, western blot, and ELISA. Results: We found that PMs expressed CaSR and TRPV4, and CaSR activationinduced marked Ca 2+ signaling predominately through extracellular Ca 2+ entry, which was inhibited by selective pharmacological blockers of CaSR and TRPV4 channels. The CaSR activation-induced Ca 2+ signaling was significantly attenuated in PMs from TRPV4 KO mice compared to those from WT mice. Moreover, the CaSR activation-induced Ca 2+ entry via TRPV4 channels was inhibited by blocking phospholipases A2 (PLA2)/cytochromeP450 (CYP450) and phospholipase C (PLC)/Protein kinase C (PKC) pathways. Finally, CaSR activation promoted the expression and release of M1-associated cytokines IL-1β and TNFɑ, which were attenuated in PMs from TRPV4 KO mice. Conclusion: We reveal a novel coupling of the CaSR and TRPV4 channels via PLA2/CYP450 and PLC/PKC pathways, promoting a Ca 2+ -dependent M1 macrophage polarization. Modulation of this coupling and downstream pathways may become a potential strategy for the prevention/treatment of immune-related disease.

Plasticity

“…14 Another example of cellular plasticity is the "taskrelated" phenotypic switch macrophages typically undergo in the tissue, which is prompted by changes in their bio/mechanical environment and happens during different phases of acute and chronic inflammation. 15,16 And last, Clifford et al have recently come up with a novel model of Na+ uptake in the zebrafish gill, one of the model organs to study ion movements across epithelia which is characterized by "unparalleled plasticity". 17,18 In biomedicine, as stated above, plasticity no longer refers to plasticity of whole organisms only, but the cellular and even subcellular mechanisms which enable organisms to dynamically respond and successfully adjust.…”

“…Another example of cellular plasticity is the “task‐related” phenotypic switch macrophages typically undergo in the tissue, which is prompted by changes in their bio/mechanical environment and happens during different phases of acute and chronic inflammation 15,16 …”

Macrophage plasticity—A matter of timing and mechanical load

“…In this issue of the Journal, Chen and colleagues provide evidence for a functional coupling of the Ca 2+ ‐sensing receptor (CaSR) and the transient receptor potential vanilloid‐type 4 (TRPV4) cation channel that governs the plasticity of peritoneal macrophages (PMs) and promotes their differentiation into a pro‐inflammatory M1 phenotype 1 …”

“…In this issue of the Journal, Chen and colleagues provide evidence for a functional coupling of the Ca 2+ -sensing receptor (CaSR) and the transient receptor potential vanilloid-type 4 (TRPV4) cation channel that governs the plasticity of peritoneal macrophages (PMs) and promotes their differentiation into a pro-inflammatory M1 phenotype. 1 The cation channel TRPV4 is widely expressed in all tissues, including immune cells, and has a highly conserved role as mechanosensitive Ca 2+ channel. In macrophages, its function has been linked to the regulation of macrophage plasticity and their ability to switch phenotype.…”

Modulating TRPV4 Channel Activity in Pro-Inflammatory Macrophages within the 3D Tissue Analog

“…For example, Henry et al [16] showed that TRPV4 agonist increased Ca 2+ influx in human respiratory epithelial cells which further enhanced PGE2 production and IL-8 secretion [16]. Conversely, blocking the TRPV4 channel reduced Ca 2+ entry and lowered the level of the proinflammatory cytokine [17][18][19]. Similarly, H. Shannon et al [20] showed that mice receiving a daily intraperitoneal injection of GSK2193874 demonstrated reduced inflammatory cytokine IL-1β and inflammatory chemokine MIP2 [20].…”