Novel Crosstalk Between Mechanosensitive TRPV4 and NF-κB Inhibits Pulmonary Inflammation

The NF-κB signaling pathway plays a critical role in activating macrophages in the pathogenesis of many pro-inflammatory diseases. Mounting evidence has pointed to the importance of tissue mechanical properties in modulating key cellular pro-inflammatory responses. Previous studies have highlighted the role of the mechanosensitive membrane cation channel transient receptor potential vanilloid 4 (TRPV4) in limiting macrophage pro-inflammatory responses and attenuating lung injury in bacterial pneumonia. Our current study demonstrates that alveolar macrophage TRPV4 suppresses pro-inflammatory gene expression following activation of multiple Toll-like receptors (e.g., TLR 1, 2, 4, and 9) in response to P. aeruginosa pneumonia in vivo and TLR agonists in vitro, highlighting the broad regulatory role of TRPV4 in modulating the inflammatory response. TRPV4 suppresses pro-inflammatory cytokines by dampening p65-dependent cytokine transcriptional activity, thereby implicating TRPV4 as a negative regulator of the NF-κB pathway. Upon stimulation with lipopolysaccharide (LPS), TRPV4 translocates to the plasma membrane, in part releasing p65 for nuclear translocation. In addition, TRPV4 was found to have sequence homology with IκBα largely within the TRPV4 ankyrin repeat domain (ANKRD), suggesting that TRPV4 may be acting as a mechanosensitive inhibitor of NF-κB. Further, TRPV4 ANKRD was proven to be critical for TRPV4 binding to the NF-κB pathway subunit, p65, in live cells. Given the diverse roles of TRPV4 and NF-κB/p65 in different cell types, we provide a specific example of novel mechanosensitive crosstalk in macrophages that have general consequences to a broad array of NF-κB dependent inflammatory and malignant diseases.