Intestinal Epithelial AMPK Deficiency Causes Delayed Colonic Epithelial Repair in DSS-Induced Colitis

Abstract

Dysfunctions in the intestinal barrier, associated with an altered paracellular pathway, are commonly observed in inflammatory bowel disease (IBD). The AMP-activated protein kinase (AMPK), principally known as a cellular energy sensor, has also been shown to play a key role in the stabilization and assembly of tight junctions. Here, we aimed to investigate the contribution of intestinal epithelial AMPK to the initiation, progression and resolution of acute colitis. We also tested the hypothesis that protection mediated by metformin administration on intestinal epithelium damage required AMPK activation. A dextran sodium sulfate (DSS)-induced colitis model was used to assess disease progression in WT and intestinal epithelial cell (IEC)-specific AMPK KO mice. Barrier integrity was analyzed by measuring paracellular permeability following dextran-4kDa gavage and pro-inflammatory cytokines and tight junction protein expression. The deletion of intestinal epithelial AMPK delayed intestinal injury repair after DSS exposure and was associated with a slower re-epithelization of the intestinal mucosa coupled with severe ulceration and inflammation, and altered barrier function. Following intestinal injury, IEC AMPK KO mice displayed a lower goblet cell counts with concomitant decreased Muc2 gene expression, unveiling an impaired restitution of goblet cells and contribution to wound healing process. Metformin administration during the recovery phase attenuated the severity of DSS-induced colitis through improvement in intestinal repair capacity in both WT and IEC AMPK KO mice. Taken together, these findings demonstrate a critical role for IEC-expressed AMPK in regulating mucosal repair and epithelial regenerative capacity following acute colonic injury. Our studies further underscore the therapeutic potential of metformin to support repair of the injured intestinal epithelium, but this effect is conferred independently of intestinal epithelial AMPK.

Allopurinol Disrupts Purine Metabolism to Increase Damage in Experimental Colitis

“…Likewise, AMPK-P is elevated in response to energy depletion, and, as such, should be appropriately elevated to support energetically taxing wound healing [ 34 , 35 ]. Taken with a recent study, which used a transgenic AMPK KO mouse model to show delayed epithelial repair during DSS colitis and attributed the changes to decreased IEC proliferation, epithelial barrier maturation, and differentiation during the recovery phase of DSS colitis, these data further support our observations [ 36 ]. Indeed, through comparison of immunofluorescence at peak colitis and during recovery, it was observed that the control group showed slightly increased AMPK-P:DAPI and Ki67:DAPI at peak disease but displayed an increase in expression during recovery, while colon tissue in mice receiving allopurinol showed no initiation of these wound healing responses ( Figure 4 C,D).…”

Picroside III, an Active Ingredient of Picrorhiza scrophulariiflora, Ameliorates Experimental Colitis by Protecting Intestinal Barrier Integrity

“…Olivier et al. also reported that the loss of AMPK in Caco‐2 monolayers leads to a delay in tight junction reorganization and repositioning during calcium conversion, resulting in impaired paracellular permeability [32] . The activation of AMPK with AMPK activator 991 accelerated the reassembly and reorganization of tight junction in Caco‐2 monolayers after calcium conversion and improved paracellular permeability [33] .…”

“…[31] Olivier et al also reported that the loss of AMPK in Caco-2 monolayers leads to a delay in tight junction reorganization and repositioning during calcium conversion, resulting in impaired paracellular permeability. [32] The activation of AMPK with AMPK activator 991 accelerated the reassembly and reorganization of tight junction in Caco-2 monolayers after calcium conversion and improved paracellular permeability. [33] In this study, we demonstrated that Picroside III treatment significantly mitigated the inactivation of AMPK in TNF-α-induced Caco-2 cells, and that the silence of AMPK with siRNA could significantly attenuate the upregulation of Picroside III in ZO-1 and occludin expressions and the downregulation of claudin-2 expression.…”

Lactobacillus salivarius WZ1 Inhibits the Inflammatory Injury of Mouse Jejunum Caused by Enterotoxigenic Escherichia coli K88 by Regulating the TLR4/NF-κB/MyD88 Inflammatory Pathway and Gut Microbiota

“…Lactobacillus salivarius can inhibit the adhesion of ETEC K88 to IPEC-J2 cells and, at the same time, has the ability to reduce the pro-inflammatory cytokines IL-1β, TNF-α, IL-8 and TLR4 and significantly reduce the phosphorylation of p38 MAPK and p65 NF-κB, which indicates that Lactobacillus salivarius may reduce inflammation-related cytokines by inhibiting the phosphorylation of p38 MAPK and blocking the NF-κB signaling pathway [ 35 ]. IL-6 has been reported to play a key role in the amplification of inflammatory signals in the gut, and it can inhibit the NF-κB pathway and pro-inflammatory cytokine IL-6 production to reduce intestinal inflammation [ 36 ]. This is consistent with the test results showing that the protein expression of TLR4, NF-κB and MyD88 and the mRNA expression of TNF-α , IL-1β and IL-6 in the L.S + E. coli group were lower than those of the E. coli group ( p < 0.01).…”