MyD88 deficiency ameliorates weight loss caused by intestinal oxidative injury in an autophagy‐dependent mechanism

Abstract

Background Gut health plays a vital role in the overall health and disease control of human and animals. Intestinal oxidative stress is a critical player in the induction and progression of cachexia which is conventionally diagnosed and classified by weight loss. Therefore, reduction of intestinal oxidative injury is a common and highly effective strategy for the maintenance of human and animal health. Here we identify intestinal myeloid differentiation primary response gene 88 (MyD88) as a novel target for intestinal oxidative stress using canonical oxidative stress model induced by paraquat (PQ) in vitro and in vivo. Methods Intestinal oxidative stress was induced by administration of PQ in intestinal epithelial cells (IECs) and mouse model. Cell proliferation, apoptosis, DNA damage, mitochondrial function, oxidative status, and autophagy process were measured in wild-type and MyD88-deficient IECs during PQ exposure. Autophagy inhibitor (3-methyladenine) and activator (rapamycin) were employed to assess the role of autophagy in MyD88-deficient IECs during PQ exposure. MyD88 specific inhibitor, ST2825, was used to verify function of MyD88 during PQ exposure in mouse model. ResultsMyD88 protein levels and apoptotic rate of IECs are increased in response to PQ exposure (P < 0.001). Intestinal deletion of MyD88 blocks PQ-induced apoptosis (~42% reduction) and DNA damage (~86% reduction), and improves mitochondrial fission (~37% reduction) and function including mitochondrial membrane potential (~23% increment) and respiratory metabolism capacity (~26% increment) (P < 0.01). Notably, there is a marked decrease in reactive oxygen species in MyD88-deficient IECs during PQ exposure (~70% reduction), which are consistent with high activity of antioxidative enzymes (~83% increment) (P < 0.001). Intestinal ablation of MyD88 inhibits mTOR signalling, and further phosphorylates p53 proteins during PQ exposure, which eventually promotes intestinal autophagy (~74% increment) (P < 0.01). Activation of autophagy (rapamycin) promotes IECs growth as compared with 3-methyladenine-treatment during PQ exposure (~173% increment), while inhibition of autophagy (3methyladenine) exacerbates oxidative stress in MyD88-deficient IECs (P < 0.001). In mouse model, inhibition of MyD88 using specific inhibitor ST2825 followed by PQ treatment effectively ameliorates weight loss (~4% increment), decreased food intake (~92% increment), gastrocnemius and soleus loss (~24% and ~20% increment, respectively), and intestinal oxidative stress in an autophagy dependent manner (P < 0.01). Conclusions MyD88 modulates intestinal oxidative stress in an autophagy-dependent mechanism, which suggests that reducing MyD88 level may constitute a putative therapeutic target for intestinal oxidative injury-induced weight loss.

Dietary supplementation with a microencapsulated complex of thymol, carvacrol, and cinnamaldehyde improves intestinal barrier function in weaning piglets

“…Myeloid differentiation primary response protein 88 (MyD88) plays an important role in regulating innate immune responses and host defense against pathogens by controlling the Toll‐like receptor family 33 . The downregulation of TLR4 , MyD88 , and NF‐κB were found to be associated with a release of less pro‐inflammatory cytokines and the alleviation of intestinal oxidative injury in weaning piglets 34 . The inhibition of XBP1 would also suppress the NF‐ κ B signaling pathway by the inhibition of X‐linked inhibitor of apoptosis protein, resulting less cell apoptosis and increased viability 35 .…”

“…33 The downregulation of TLR4, MyD88, and NF-κB were found to be associated with a release of less pro-inflammatory cytokines and the alleviation of intestinal oxidative injury in weaning piglets. 34 The inhibition of XBP1 would also suppress the NF-κB signaling pathway by the inhibition of X-linked inhibitor of apoptosis protein, resulting less cell apoptosis and increased viability. 35 In the present study, MEEO significantly downregulated the mRNA expression of NF-κB, MYD88, XBP1and TLR4 in intestinal mucosa, and MEEO works better than CTC, suggesting that piglets in the MEEO group had a less intestinal inflammatory response and further implying that the MEEO consumption reinforced the intestinal barrier function.…”

MyD88 deficiency aggravates the severity of acute pancreatitis by promoting MyD88-independent TRIF pathway-mediated necrosis

“…In addition, autophagy and oxidative stress play important roles in the pathogenesis of AP. MyD88 deficiency ameliorates oxidative injury in an autophagy-dependent mechanism ( 30 ). However, its role in AP remains unclear.…”

Development of Intestinal Injury and Restoration of Weaned Piglets under Chronic Immune Stress

“…Subsequently, the sections were added, with BSA incubating for 30 min and then the primary antibody was added overnight at 4°C. Next, the sections were incubated with Alexa Fluor ® 488-conjugated or Alexa Fluor ® 594-conjugated second antibody (1:400) for 1 h at 37 °C [ 30 ]. After the sections were slightly dried, the nuclei were stained with DAPI and incubated at room temperature for 10 min.…”