The Role of Activating Transcription Factor 3 in Metformin’s Alleviation of Gastrointestinal Injury Induced by Restraint Stress in Mice

Abstract

Metformin is one of the most commonly used drugs for type 2 diabetes mellitus. In addition to its anti-diabetic property, evidence suggests more potential applications for metformin, such as antiaging, cellular protection, and anti-inflammation. Studies have reported that metformin activates pathways with anti-inflammatory effects, enhances the integrity of gut epithelial tight junctions, and promotes a healthy gut microbiome. These actions contribute to the protective effect of metformin against gastrointestinal (GI) tract injury. However, whether metformin plays a protective role in psychological-stress-associated GI tract injury remains elusive. We aim to elucidate the potential protective effect of metformin on the GI system and develop an effective intervention strategy to counteract GI injury induced by acute psychological stress. By monitoring the levels of GI-nonabsorbable Evans blue dye in the bloodstream, we assessed the progression of GI injury in live mice. Our findings demonstrate that the administration of metformin effectively mitigated GI leakage caused by psychological stress. The GI protective effect of metformin is more potent when used on wild-type mice than on activating-transcription-factor 3 (ATF3)-deficient (ATF3−/−) mice. As such, metformin-mediated rescue was conducted in an ATF3-dependent manner. In addition, metformin-mediated protection is associated with the induction of stress-induced GI mRNA expressions of the stress-induced genes ATF3 and AMP-activated protein kinase. Furthermore, metformin treatment-mediated protection of CD326+ GI epithelial cells against stress-induced apoptotic cell death was observed in wild-type but not in ATF3−/− mice. These results suggest that metformin plays a protective role in stress-induced GI injury and that ATF3 is an essential regulator for metformin-mediated rescue of stress-induced GI tract injury.

Restraint Stress-Induced Immunosuppression Is Associated with Concurrent Macrophage Pyroptosis Cell Death in Mice

“…Here we utilized a previously established mouse model that involved administering Evan blue dye to measure GI leakage levels at various time courses during restraint stress [ 14 , 15 , 16 , 17 ]. By employing this Evans-blue-fed mouse model, we made several noteworthy observations.…”

“…The reasons behind the significant level of immunosuppression induced by restraint stress and the different pathways through which various stressors, such as ambient cold exposure and restraint stress, induce immunosuppression remain unclear. Through the use of an experimental model involving the administration of Evans blue dye to restrained mice [ 14 , 15 , 16 , 17 ], we have demonstrated that restraint stress causes gut leakage in mice ( Figure 4 A, experiment outline, Figure 4 B). Since the spleen serves as a key lymphoid organ responsible for filtering blood, including blood from the GI system, to remove pathogens and foreign substances, it is reasonable to observe leukocyte infiltration into the spleen of mice following restraint stress ( Figure 4 C and Figure 7 D).…”

“…Male wild-type C57BL/6J mice aged 8–12 weeks were purchased from the National Laboratory Animal Center (Taipei, Taiwan) [ 14 , 15 , 16 , 17 ]. Genetically deficient Selp −/− (B6; 129S2- Selp tm1Hyn /J; P-selectin KO) [ 47 , 77 , 78 , 79 ] with a C57BL/6J background were obtained from the Jackson Laboratory (Bar Harbor, ME, USA).…”

“…However, the impact of psychological alterations linked to acute restraint stress on the induction of an immunosuppressive response remains unclear. We have previously used a modified acute restraint stress mouse model by administering the non-absorbable dye Evans blue via gavage, which does not normally appear in the circulation when orally fed [ 14 , 15 , 16 , 17 ]. Through the analysis of plasma levels of Evans blue, a substance that leaks from the gastrointestinal (GI) tract, we can assess the extent of stress-induced GI leakage.…”

Outcome of stress on G protein-coupled receptors and hypoxia inducible factor-1α

“…Additionally, increased levels of HIF-1α protein were detected in the oral cavity of rats with periodontitis exposed to chronic psychological stress [ 3 ], and in the gastric mucosa of rats subjected to acute water-immersion restraint stress [ 4 ]. Conversely, decreased HIF-1α mRNA levels were noted in the duodenum of mice under acute restraint stress [ 11 ]. To gain insights into the mechanisms through which stress modulates intestinal inflammation, this study aimed to assess the effect of acute and chronic stress on the expression of GRP41, GPR43 and HIF-1α.…”