Protein Kinase D2 Protects against Acute Colitis Induced by Dextran Sulfate Sodium in Mice

The novel mechanism of human norovirus induced diarrhea: Activation of PKD2 caused by HuNoVs destroyed AQP3 expression through AP2γ in intestinal epithelial cells

Our previous work has demonstrated protein kinase D2 (PKD2) played a critical influence in experimental colitis in animal. However, the role of PKD2 in human norovirus (HuNoVs)-induced diarrhea remained unknown. Aquaporin 3 (AQP3) expression, a critical protein mediating diarrhea, was assessed by western blot, qRT-PCR in intestinal epithelial cells (IECs). Luciferase, IF, IP and ChIP assay were used to explore the mechanism through which HuNoVs regulated AQP3. Herein, we found that AQP3 expression was drastically decreased in IECs in response to VP1 transfection, the major capsid protein of HuNoVs, or HuNoVs infection. Mechanistically, HuNoVs triggered phosphorylation of PKD2 through TLR2/MyD88/IRAK4, which further inhibited AP2γ activation and nuclear translocation, leading to suppress AQP3 transactivation in IECs. Most importantly, PKD2 interacted with MyD88/IRAK4, and VP1 overexpression enhanced this complex form, which, in turn, to increase PKD2 phosphorylation. In addition, endogenous PKD2 interacted with AP2γ, and this interaction was enhanced in response to HuNoVs treatment, and subsequently resulting in AP2γ phosphorylation inhibition. Moreover, inhibition of PKD2 activation could reverse the inhibitory effect of HuNoVs on AQP3 expression. In summary, we established a novel mechanism that HuNoV inhibited AQP3 expression through TLR2/MyD88/IRAK4/PKD2 signaling pathway, targeting PKD2 activity could be a promising strategy for prevention of HuNoVs-induced gastroenteritis.

Alkaline Phosphatase Relieves Colitis in Obese Mice Subjected to Forced Exercise via Its Anti-Inflammatory and Intestinal Microbiota-Shaping Properties

Intestinal alkaline phosphatase (IAP) is an enzyme that plays a protective role in the gut. This study investigated the effect of IAP treatment on experimental colitis in mice subjected to forced exercise on a high-fat diet. C57BL/6 mice with TNBS colitis were fed a high-fat diet and subjected to forced treadmill exercise with or without IAP treatment. Disease activity, oxidative stress, inflammatory cytokines, and gut microbiota were assessed. Forced exercise exacerbated colitis in obese mice, as evidenced by increased disease activity index (DAI), oxidative stress markers, and proinflammatory adipokines and cytokines. IAP treatment significantly reduced these effects and promoted the expression of barrier proteins in the colonic mucosa. Additionally, IAP treatment altered the gut microbiota composition, favoring beneficial Verrucomicrobiota and reducing pathogenic Clostridia and Odoribacter. IAP treatment ameliorates the worsening effect of forced exercise on murine colitis by attenuating oxidative stress, downregulating proinflammatory biomarkers, and modulating the gut microbiota. IAP warrants further investigation as a potential therapeutic strategy for ulcerative colitis.

Small molecule inhibitor CRT0066101 inhibits cytokine storm syndrome in a mouse model of lung injury

Pneumonia is an acute inflammation of the lungs induced by pathogenic microorganisms, immune damage, physical and chemical factors, and other factors, and the latest outbreak of novel coronavirus pneumonia is also an acute lung injury (ALI) induced by viral infection. However, there are currently no effective treatments for inflammatory cytokine storms in patients with ALI/acute respiratory distress syndrome (ARDS). Protein kinase D (PKD) is a highly active kinase that has been shown to be associated with the production of inflammatory cytokines. Therefore, small-molecule compounds that inhibit PKD may be potential drugs for the treatment of ALI/ARDS. In the present study, we evaluated the ability of the small-molecule inhibitor CRT0066101 to attenuate lipopolysaccharide (LPS)-induced inflammatory cytokine production through in vitro cell experiments and a mouse pneumonia model. We found that CRT0066101 significantly reduced the protein and mRNA levels of LPS-induced cytokines (e.g., IL-6, TNF-α, and IL-1β). CRT0066101 inhibited MyD88 and TLR4 expression and reduced NF-κB, ERK, and JNK phosphorylation. CRT0066101 also reduced NLRP3 activation, inhibited the assembly of the inflammasome complex, and attenuated inflammatory cell infiltration and lung tissue damage. Taken together, our data indicate that CRT0066101 exerts anti-inflammatory effects on LPS-induced inflammation through the TLR4/MyD88 signaling pathway, suggesting that CRT0066101 may have therapeutic value in acute lung injury and other MyD88-dependent inflammatory diseases.

Loss of Protein Kinase D2 Activity Protects Against Bleomycin-Induced Dermal Fibrosis in Mice

Protein kinase D (PKD) has been linked to inflammatory responses in various pathologic conditions; however, its role in inflammation-induced dermal fibrosis has not been evaluated. In this study, we aimed to investigate the roles and mechanisms of protein kinase D2 (PKD2) in inflammation-induced dermal fibrosis and evaluate the therapeutic potential of PKD inhibitors in this disease. Using homozygous kinase-dead PKD2 knock-in (KI) mice, we examined whether genetic ablation or pharmacologic inhibition of PKD2 activity affected dermal inflammation and fibrosis in a bleomycin (BLM)-induced skin fibrosis model. Our data showed that dermal thickness and collagen fibers were significantly reduced in BLM-treated PKD2 KI mice compared with that in wild-type mice, and so was the expression of α-smooth muscle actin and collagens and the mRNA levels of transforming growth factor-β1 and interleukin-6 in the KI mice. Corroboratively, pharmacologic inhibition of PKD by CRT0066101 also significantly blocked BLM-induced dermal fibrosis and reduced α-smooth muscle actin, collagen, and interleukin-6 expression. Further analyses indicated that loss of PKD2 activity significantly blocked BLM-induced infiltration of monocytes/macrophages and neutrophils in the dermis. Moreover, using bone marrow-derived macrophages, we demonstrated that PKD activity was required for cytokine production and migration of macrophages. We have further identified Akt as a major downstream target of PKD2 in the early inflammatory phase of the fibrotic process. Taken together, our findings indicate that PKD2 promotes dermal fibrosis via regulating immune cell infiltration, cytokine production, and downstream activation of Akt in lesional skin, and targeted inhibition of PKD2 may benefit the treatment of this condition.

Dietary Alaska Pollock Protein Attenuates the Experimental Colitis Induced by Dextran Sulfate Sodium via Regulation of Gut Microbiota and Its Metabolites in Mice

Protein derived from fish has not only nutritional properties but also health-promoting properties. Few studies have examined the effect of dietary Alaska pollock protein (APP) on the anticolitis effect reported to be associated with metabolic syndrome (MetS). This study investigated the effect of APP intake on colitis symptoms, gut microbiota, and its metabolites in the experimental colitis mouse model induced by dextran sulfate sodium (DSS). Male C57BL/6J mice were divided into three groups: (1) DSS-untreated mice fed an American Institute of Nutrition (AIN) 93G diet (protein source is casein), (2) DSS-treated mice fed an AIN93G diet, and (3) DSS-treated mice fed an APP diet. After the mice were fed the diets for 21 days, experimental colitis was induced by three cycles of 2% DSS administration for 5 days followed by washouts over the course of 5 days. APP-reduced body weight loss increased the disease activity index, and elevated spleen weight and alleviated colon length shortening and colonic tissue damage. Furthermore, APP altered the structure and composition of the microbiota and short-chain fatty acids in feces. Since APP intake alleviates experimental colitis induced by DSS administration through alterations in the gut microbiota and its metabolites, we deduced that APP would inhibit MetS progression via colitis suppression.

Protein Kinase D2 drives chylomicron-mediated lipid transport in the intestine and promotes obesity

Lipids are the most energy-dense components of the diet, and their overconsumption promotes obesity and diabetes. Dietary fat content has been linked to the lipid processing activity by the intestine and its overall capacity to absorb triglycerides (TG). However, the signaling cascades driving intestinal lipid absorption in response to elevated dietary fat are largely unknown. Here, we describe an unexpected role of the protein kinase D2 (PKD2) in lipid homeostasis. We demonstrate that PKD2 activity promotes chylomicron-mediated TG transfer in enterocytes. PKD2 increases chylomicron size to enhance the TG secretion on the basolateral side of the mouse and human enterocytes, which is associated with decreased abundance of APOA4. PKD2 activation in intestine also correlates positively with circulating TG in obese human patients. Importantly, deletion, inactivation, or inhibition of PKD2 ameliorates high-fat diet-induced obesity and diabetes and improves gut microbiota profile in mice. Taken together, our findings suggest that PKD2 represents a key signaling node promoting dietary fat absorption and may serve as an attractive target for the treatment of obesity.

PIK3R3 regulates ZO-1 expression through the NF-kB pathway in inflammatory bowel disease

BACKGROUND AND AIMS

Inflammatory bowel disease (IBD) are the major risk factor for developing colitis associated cancer (CAC). Previously, we have reported that Phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3) was overexpressed in colorectal cancer (CRC), but we don't know the role of PIK3R3 in IBD.

METHODS

We investigated the differential expression of PIK3R3 and ZO-1 in IBD patients by using Immunohistochemical (IHC) and Gene Expression Omnibus (GEO) database analysis. Caco-2 cells were exposed to different conditions to assess protein level changes of PIK3R3 and ZO-1. Caco-2 cell monolayers were transfected with PIK3R3/siPIK3R3 to assess transepithelial electrical resistance. Tight junction protein integrity was assessed by immunoblot and immunofluorescence. For further, intestinal permeability and tight junction protein integrity were assessed in animal study to assess the treatment role of PIK3R3 specific inhibitor TAT-N 15 (N15).

RESULTS

PIK3R3 was increased in IBD patients, and negatively controlled the expression of ZO-1. In vitro, PIK3R3 regulates ZO-1 by activating NF-kB pathway. Overexpression of PIK3R3 in Caco-2 cells decreased transepithelial electrical resistance (TEER), an opposite result was observed in siPIK3R3 cells. In animal study, inhibition of PIK3R3 by N15 contributed to amelioration of DSS-induced intestinal permeability. Mice treated with N15 exhibited less disruption of TJs in colon tissues.

CONCLUSIONS

PIK3R3 was increased in clinical IBD patients with accompanying disruption of ZO-1 expression. Inhibition of PIK3R3 attenuated DSS-induced IBD symptoms in a mouse model. These findings indicated that PIK3R3 could be a therapeutic target for IBD.

A Novel Postbiotic From Lactobacillus rhamnosus GG With a Beneficial Effect on Intestinal Barrier Function

It has long been known that probiotics can be used to maintain intestinal homeostasis and treat a number of gastrointestinal disorders, but the underlying mechanism has remained obscure. Recently, increasing evidence supports the notion that certain probiotic-derived components, such as bacteriocins, lipoteichoic acids, surface layer protein and secreted protein, have a similar protective role on intestinal barrier function as that of live probiotics. These bioactive components have been named 'postbiotics' in the most recent publications. We previously found that the Lactobacillus rhamnosus GG (LGG) culture supernatant is able to accelerate the maturation of neonatal intestinal defense and prevent neonatal rats from oral Escherichia coli K1 infection. However, the identity of the bioactive constituents has not yet been determined. In this study, using liquid chromatography-tandem mass spectrometry analysis, we identified a novel secreted protein (named HM0539 here) involved in the beneficial effect of LGG culture supernatant. HM0539 was recombinated, purified, and applied for exploring its potential bioactivity in vitro and in vivo. Our results showed that HM0539 exhibits a potent protective effect on the intestinal barrier, as reflected by enhancing intestinal mucin expression and preventing against lipopolysaccharide (LPS)- or tumor necrosis factor α (TNF-α)-induced intestinal barrier injury, including downregulation of intestinal mucin (MUC2), zonula occludens-1 (ZO-1) and disruption of the intestinal integrity. Using a neonatal rat model of E. coli K1 infection via the oral route, we verified that HM0539 is sufficient to promote development of neonatal intestinal defense and prevent against E. coli K1 pathogenesis. Moreover, we further extended the role of HM0539 and found it has potential to prevent dextran sulfate sodium (DSS)-induced colitis as well as LPS/D-galactosamine-induced bacterial translocation and liver injury. In conclusion, we identified a novel LGG postbiotic HM0539 which exerts a protective effect on intestinal barrier function. Our findings indicated that HM0539 has potential to become a useful agent for prevention and treatment of intestinal barrier dysfunction- related diseases.

A far-red-emissive AIE active fluorescent probe with large stokes shift for detection of inflammatory bowel disease in vivo

Inflammatory bowel disease (IBD) is a group of chronic remittent or progressive inflammatory gastrointestinal tract diseases, accompanying impaired barrier function.