Activation of Myofibroblast TRPA1 by Steroids and Pirfenidone Ameliorates Fibrosis in Experimental Crohn's Disease

BACKGROUND & AIMS

The transient receptor potential ankyrin 1 (TRPA1) channel is highly expressed in the intestinal lamina propria, but its contribution to gut physiology/pathophysiology is unclear. Here, we evaluated the function of myofibroblast TRPA1 channels in intestinal remodeling.

METHODS

An intestinal myofibroblast cell line (InMyoFibs) was stimulated by transforming growth factor-β1 to induce in vitro fibrosis. Trpa1 knockout mice were generated using the Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) system. A murine chronic colitis model was established by weekly intrarectal trinitrobenzene sulfonic acid (TNBS) administration. Samples from the intestines of Crohn's disease (CD) patients were used for pathologic staining and quantitative analyses.

RESULTS

In InMyoFibs, TRPA1 showed the highest expression among TRP family members. In TNBS chronic colitis model mice, the extents of inflammation and fibrotic changes were more prominent in TRPA1^-/- knockout than in wild-type mice. One-week enema administration of prednisolone suppressed fibrotic lesions in wild-type mice, but not in TRPA1 knockout mice. Steroids and pirfenidone induced Ca²⁺ influx in InMyoFibs, which was antagonized by the selective TRPA1 channel blocker HC-030031. Steroids and pirfenidone counteracted transforming growth factor-β1-induced expression of heat shock protein 47, type 1 collagen, and α-smooth muscle actin, and reduced Smad-2 phosphorylation and myocardin expression in InMyoFibs. In stenotic intestinal regions of CD patients, TRPA1 expression was increased significantly. TRPA1/heat shock protein 47 double-positive cells accumulated in the stenotic intestinal regions of both CD patients and TNBS-treated mice.

CONCLUSIONS

TRPA1, in addition to its anti-inflammatory actions, may protect against intestinal fibrosis, thus being a novel therapeutic target for highly incurable inflammatory/fibrotic disorders.

P2X7 Receptor Mediates Spinal Microglia Activation of Visceral Hyperalgesia in a Rat Model of Chronic Pancreatitis

BACKGROUND & AIMS

Molecular mechanisms underlying the activated spinal microglia in association with the pain in chronic pancreatitis (CP) remain unknown. We tested whether P2X7R on spinal microglia mediates the pathogenesis of visceral pain using a CP rat model.

METHODS

The CP model was induced via intraductal injection of 2% trinitrobenzene sulfonic acid into male Sprague-Dawley rats. Hyperalgesia was assessed based on the mechanical sensitivity to Von-Frey filaments (VFFs), and nocifensive behaviors were measured in response to electrical stimulation of the pancreas. Three weeks after CP induction, spinal cord samples were harvested for immunostaining, immunoblot, and real-time polymerase chain reaction analyses of the P2X7R. Changes in nocifensive behaviors and associated molecular effectors were assessed by blocking spinal cord P2X7R pharmacologically using the selective P2X7R antagonist brilliant blue G (BBG) or genetically using short interfering RNA (siRNA).

RESULTS

CP induced a significant up-regulation of spinal P2X7R expression, which colocalized with a microglial marker (OX-42). Intrathecal administration of BBG significantly attenuated CP-related visceral hyperalgesia in response to VFF-mediated or electrical stimulation of the pancreas, which was associated with suppressed spinal expression of P2X7R and inhibited activation of spinal microglia. Intrathecal injection of siRNA to knock down P2X7R expression in the spinal cord would suppress the nociceptive behaviors in CP rats.

CONCLUSIONS

Spinal microglia P2X7R mediates central sensitization of chronic visceral pain in CP. BBG may represent an effective drug for the treatment of chronic pain in CP patients.