TRPV4-induced inflammatory response is involved in neuronal death in pilocarpine model of temporal lobe epilepsy in mice

Zhouqing Wang,Sha Sha,Lei Chen,Chunfeng Wu,Yichao Zhu,Dong An,Weixing Xu,Aidong Chen,Ling Chen,Yimei Du,Yingchun Li,Li Zhou

doi:10.1038/s41419-019-1612-3

Abstract

Activation of transient receptor potential vanilloid 4 (TRPV4) induces neuronal injury. TRPV4 activation enhances inflammatory response and promotes the proinflammatory cytokine release in various types of tissue and cells. Hyperneuroinflammation contributes to neuronal damage in epilepsy. Herein, we examined the contribution of neuroinflammation to TRPV4-induced neurotoxicity and its involvement in the inflammation and neuronal damage in pilocarpine model of temporal lobe epilepsy in mice. Icv. injection of TRPV4 agonist GSK1016790A (GSK1016790A-injected mice) increased ionized calcium binding adapter molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) protein levels and Iba-1-positive (Iba-1+) and GFAP-positive (GFAP+) cells in hippocampi, which indicated TRPV4-induced microglial cell and astrocyte activation. The protein levels of nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3 (NLRP3) inflammasome components NLRP3, apoptosis-related spotted protein (ASC) and cysteinyl aspartate-specific protease-1 (caspase-1) were increased in GSK1016790A-injected mice, which indicated NLRP3 inflammasome activation. GSK1016790A also increased proinflammatory cytokine IL-1β, TNF-α and IL-6 protein levels, which were blocked by caspase-1 inhibitor Ac-YVAD-cmk. GSK1016790A-induced neuronal death was attenuated by Ac-YVAD-cmk. Icv. injection of TRPV4-specific antagonist HC-067047 markedly increased the number of surviving cells 3 d post status epilepticus in pilocarpine model of temporal lobe epilepsy in mice (pilocarpine-induced status epilepticus, PISE). HC-067047 also markedly blocked the increase in Iba-1 and GFAP protein levels, as well as Iba-1+ and GFAP+ cells 3 d post-PISE. Finally, the increased protein levels of NLRP3, ASC and caspase-1 as well as IL-1β, TNF-α and IL-6 were markedly blocked by HC-067047. We conclude that TRPV4-induced neuronal death is mediated at least partially by enhancing the neuroinflammatory response, and this action is involved in neuronal injury following status epilepticus.

Highlights

Transient receptor potential vanilloid 4 (TRPV4), a member of the vanilloid transient receptor potential (TRPV) channel family, is selectively permeable to calcium (Ca2+)
For glial fibrillary acidic protein (GFAP) and ionized calcium binding adapter molecule-1 (Iba-1) staining, the brains were coronally sectioned at 40 μm, and free-floating sections were incubated with primary antibodies against GFAP (Cat: MAB360, 1:1000, Millipore, Billerica, MA, USA) or Iba-1 (Cat: ab5076, 1:1000, Abcam, Cambridge, UK) overnight at 4 °C, followed by biotin-conjugated goat anti-mouse IgG (Cat: ab6788, 1:2000, Abcam, Cambridge, UK) and biotin-conjugated rabbit anti-goat IgG antibody (Cat: ab6740, 1:100, Abcam, Cambridge, UK)
TRPV4 has been detected in microglia and astrocytes

Summary

Introduction

Transient receptor potential vanilloid 4 (TRPV4), a member of the vanilloid transient receptor potential (TRPV) channel family, is selectively permeable to calcium (Ca2+). Recent studies have reported the involvement of TRPV4 in the inflammatory response, and activation of TRPV4 can increase the production of proinflammatory cytokines. Wang et al Cell Death and Disease (2019)10:386 leads to the release of interleukin (IL)-1α, IL-1β, IL-6 and IL-8 in lung epithelial cells[5]. TRPV4 deficiency prevents neutrophil responses to inflammatory stimuli in acute lung injury[6]. Increased TRPV4 expression and activation promote IL-1β and IL-6 gene expression in intervertebral disc cells[7]. Microglia cells and astrocytes are major innate immunity cells that produce proinflammatory cytokines[9]. Inhibition of TRPV4 exerts a neuroprotective effect on infrasound-induced injury by decreasing glial cell-released proinflammatory cytokines IL-1β and TNF-α10. The contribution of the increased inflammatory response to TRPV4-related cytotoxicity has attracted increasing attention from researchers

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