Intravascular adhesion and recruitment of neutrophils in response to CXCL1 depends on their TRPC6 channels

Abstract

Here we report a novel role for TRPC6, a member of the transient receptor potential (TRPC) channel family, in the CXCL1-dependent recruitment of murine neutrophil granulocytes. Representing a central element of the innate immune system, neutrophils are recruited from the blood stream to a site of inflammation. The recruitment process follows a well-defined sequence of events including adhesion to the blood vessel walls, migration, and chemotaxis to reach the inflammatory focus. A common feature of the underlying signaling pathways is the utilization of Ca 2+ ions as intracellular second messengers. However, the required Ca 2+ influx channels are not yet fully characterized. We used WT and TRPC6 −/− neutrophils for in vitro and TRPC6 −/− chimeric mice (WT mice with WT or TRPC6 −/− bone marrow cells) for in vivo studies. After renal ischemia and reperfusion injury, TRPC6 −/− chimeric mice had an attenuated TRPC6 −/− neutrophil recruitment and a better outcome as judged from the reduced increase in the plasma creatinine concentration. In the cremaster model CXCL1-induced neutrophil adhesion, arrest and transmigration were also decreased in chimeric mice with TRPC6 −/− neutrophils. Using atomic force microscopy and microfluidics, we could attribute the recruitment defect of TRPC6 −/− neutrophils to the impact of the channel on adhesion to endothelial cells. Mechanistically, TRPC6 −/− neutrophils exhibited lower Ca 2+ transients during the initial adhesion leading to diminished Rap1 and β 2 integrin activation and thereby reduced ICAM-1 binding. In summary, our study reveals that TRPC6 channels in neutrophils are crucial signaling modules in their recruitment from the blood stream in response to CXCL1. Key point Neutrophil TRPC6 channels are crucial for CXCL1-triggered activation of integrins during the initial steps of neutrophil recruitment.

β2 Integrin Signaling Cascade in Neutrophils: More Than a Single Function

“…For instance, in murine neutrophils, CXCL1 induces a strong calcium influx, which is an important signaling mediator ( Figure 1A ) for β 2 integrin activation ( 123 ). This differential signaling effect is substantiated by the knockout of TRPC6 encoding a plasma membrane calcium channel, resulting in lower calcium transient increases, thus leading to reduced Rap1 and β 2 integrin activation by CXCL1 ( 124 ). Other chemokines remain to be tested for this pathway.…”

Ion Channels Orchestrate Pancreatic Ductal Adenocarcinoma Progression and Therapy

“…Indeed, inhibition of CXCR2 signaling in PDAC shows beneficial results ( Ijichi et al, 2011 ; Steele et al, 2016 ). Recruitment of neutrophils upon CXCR2 activation is mediated by Na + and Ca 2+ -permeable, classical/canonical transient receptor potential 6 (TRPC6) channel ( Lindemann et al, 2013 , 2020 ). TRPC6 is also expressed in PSCs, where it mediates hypoxia-induced migration and production of cytokines ( Nielsen et al, 2017 ).…”

Pharmacological TRPC6 inhibition improves survival and muscle function in mice with Duchenne muscular dystrophy

“…Both dystrophin and TRPC6 are also expressed in vascular smooth muscle, and in mdx mice TRPC6 contributes to greater Ca 2+ i in vessels exposed to cyclic stretch, leading to cell damage ( 23 ). Finally, TRPC6 is also present in immune cells, including neutrophils, where TRPC6 regulates activation by CXCL1 ( 41 ) and lymphocytes to promote apoptosis ( 42 ). TRPC6 upregulation contributes to endothelial permeability and cell diapedesis of immune cells by loosening cell-cell junctions ( 43 ).…”