Porcine epidemic diarrhea virus (PEDV) is an enteric coronavirus that causes high mortality in piglets, thus posing a serious threat to the world pig industry. Porcine epidemic diarrhea (PED) is related to the imbalance of sodium absorption by small intestinal epithelial cells; however, the etiology of sodium imbalanced diarrhea caused by PEDV remains unclear. Herein, we first proved that PEDV can cause a significant decrease in Na+/H+ exchanger 3 (NHE3) expression on the cell membrane, in a viral dose-dependent manner. Further study showed that the PEDV nucleocapsid (N) protein participates in the regulation of NHE3 activity through interacting with Ezrin. Flame atomic absorption spectroscopy results indicated a serious imbalance in Na+ concentration inside and outside cells following overexpression of PEDV N. Meanwhile, molecular docking technology identified that the small molecule drug Pemetrexed acts on the PEDV N-Ezrin interaction region. It was confirmed that Pemetrexed can alleviate the imbalanced Na+ concentration in IPEC-J2 cells and the diarrhea symptoms of Rongchang pigs caused by PEDV infection. Overall, our data suggest that the interaction between PEDV N and Ezrin reduces the level of phosphorylated Ezrin, resulting in a decrease in the amount of NHE3 protein on the cell membrane. This leads to an imbalance of intracellular and extracellular Na+, which causes diarrhea symptoms in piglets. Pemetrexed is effective in relieving diarrhea caused by PEDV. Our results provide a reference to screen for anti-PEDV targets and to develop drugs to prevent PED.IMPORTANCEPorcine epidemic diarrhea (PED) has caused significant economic losses to the pig industry since its initial outbreak, and the pathogenic mechanism of porcine epidemic diarrhea virus (PEDV) is still under investigation. Herein, we found that the PEDV nucleocapsid protein interacts with Ezrin to regulate Na+/H+ exchanger 3 activity. In addition, we screened out Pemetrexed, a small molecule drug, which can effectively alleviate pig diarrhea caused by PEDV. These results provide support for further exploration of the pathogenesis of PEDV and the development of drugs to prevent PED.

Sodium-proton exchanger 3 (NHE3/SLC9A3) located in the apical membrane of renal and gastrointestinal epithelia mediates salt and fluid absorption and regulates pH homeostasis. As an auxiliary regulatory factor of NHE proteins, calcineurin B homologous protein 1 (CHP1) facilitates NHE3 maturation, plasmalemmal expression, and pH sensitivity. Dysfunctions of NHE3 are associated with renal and digestive system disorders. Here, we report the cryo-electron microscopy structure of the human NHE3-CHP1 complex in its inward-facing conformation. We found that a cytosolic helix-loop-helix motif in NHE3 blocks the intracellular cavity formed between the core and dimerization domains, functioning as an autoinhibitory element and hindering substrate transport. Furthermore, two phosphatidylinositol molecules are found to bind to the peripheric juxtamembrane sides of the complex, function as anchors to stabilize the complex, and may thus enhance its transport activity.

Cholelithiasis is a common and frequent condition all over the world with a high prevalence rate in western countries. Individuals with cholesterol gallstone disease experience intense gastrointestinal symptoms and have a high risk of developing comorbidities like cholecystitis, Gall bladder (GB) cancer and pancreatitis. Multiple risk factors associated with cholesterol gallstones include but not limited to genetics, dietary habits, lifestyle changes, comorbid conditions and various drugs. These factors may lead to alteration in bile, cholesterol & phospholipids homeostasis in the GB, intestine and hepatocytes culminating in cholesterol gallstones formation. Surgical (cholecystectomy) and non-surgical (oral dissolution therapy) treatments are available for the disease, albeit with certain complications and high treatment cost. Thus, there is a need for interventions, complementary or alternative therapies for the treatment and prevention of cholesterol gallstones. Currently available drug therapies used for cholesterol gallstones include statins and ezetimibe. Many patients consider traditional herbal practitioners due to their promise of non-invasive and pain free management of gall stones. This present a positive shift towards generally acceptable safety and cost effectiveness of herbal treatment warranting extensive research for alternative or complementary choice such as herbal plants as an emerging area for their potential therapeutic effects. This review discusses current strategies, latest trends available in the disease pathogenesis, drug development for novel targets, risk management, newer anti-lithogenic drugs and herbal plants that target the different aspects of the disease.