Acute high-fat diet impairs macrophage-supported intestinal damage resolution

Comprehensive proteomic analysis of HCoV-OC43 virions and virus-modulated extracellular vesicles

Viruses are obligate parasites that depend on the cellular machinery for their propagation. Several viruses also incorporate cellular proteins that facilitate viral spread. Defining these cellular proteins is critical to decipher viral life cycles and delineate novel therapeutic strategies. While numerous studies have explored the importance of host proteins in coronavirus spread, information about their presence in mature virions is limited. In this study, we developed a protocol to highly enrich mature HCoV-OC43 virions and characterize them by proteomics. Recognizing that cells release extracellular vesicles whose content is modulated by viruses, and given our ability to separate virions from these vesicles, we also analyzed their protein content in both uninfected and infected cells. We uncovered 69 unique cellular proteins associated with virions including 31 high-confidence hits. These proteins primarily regulate RNA metabolism, enzymatic activities, vesicular transport, cell adhesion, metabolite interconversion, and translation. We further discovered that the virus had a profound impact on exosome composition, incorporating 47 novel cellular proteins (11 high confidence) and excluding 92 others (61 high confidence) in virus-associated extracellular vesicles compared to uninfected cells. Moreover, a dsiRNA screen revealed that 11 of 18 select targets significantly impacted viral yields, including proteins found in virions or extracellular vesicles. Overall, this study provides new and important insights into the incorporation of numerous host proteins into HCoV-OC43 virions, their biological significance, and the ability of the virus to modulate extracellular vesicles.

IMPORTANCE

In recent years, coronaviruses have dominated global attention, making it crucial to develop methods to control them and prevent future pandemics. Besides viral proteins, host proteins play a significant role in viral propagation and offer potential therapeutic targets. Targeting host proteins is advantageous because they are less likely to mutate and develop resistance compared to viral proteins, a common issue with many antiviral treatments. In this study, we examined the protein content of the less virulent biosafety level 2 HCoV-OC43 virus as a stand-in for the more virulent SARS-CoV-2. Our findings reveal that several cellular proteins incorporated into the virion regulate viral spread. In addition, we report that the virus extensively modulates the content of extracellular vesicles, enhancing viral dissemination. This underscores the critical interplay between the virus, host proteins, and extracellular vesicles.

Modulation of cardiac resident macrophages immunometabolism upon high-fat-diet feeding in mice

Background

A high-fat diet (HFD) contributes to various metabolic disorders and obesity, which are major contributors to cardiovascular disease. As an essential regulator for heart homeostasis, cardiac resident macrophages may go awry and contribute to cardiac pathophysiology upon HFD. Thus, to better understand how HFD induced cardiac dysfunction, this study intends to explore the transcriptional and functional changes in cardiac resident macrophages of HFD mice.

Methods

C57BL/6J female mice that were 6 weeks old were fed with HFD or normal chow diet (NCD) for 16 weeks. After an evaluation of cardiac functions by echocardiography, mouse hearts were harvested and cardiac resident CCR2- macrophages were sorted, followed by Smart sequencing. Bioinformatics analysis including GO, KEGG, and GSEA analyses were employed to elucidate transcriptional and functional changes.

Results

Hyperlipidemia and obesity were observed easily upon HFD. The mouse hearts also displayed more severe fibrosis and diastolic dysfunction in HFD mice. Smart sequencing and functional analysis revealed metabolic dysfunctions, especially lipid-related genes and pathways. Besides this, antigen-presentation-related gene such as Ctsf and inflammation, particularly for NF-κB signaling and complement cascades, underwent drastic changes in cardiac resident macrophages. GO cellular compartment analysis was also performed and showed specific organelle enrichment trends of the involved genes.

Conclusion

Dysregulated metabolism intertwines with inflammation in cardiac resident macrophages upon HFD feeding in mice, and further research on crosstalk among organelles could shed more light on potential mechanisms.

TNF compromises intestinal bile-acid tolerance dictating colitis progression and limited infliximab response

The intestine constantly encounters and adapts to the external environment shaped by diverse dietary nutrients. However, whether and how gut adaptability to dietary challenges is compromised in ulcerative colitis is incompletely understood. Here, we show that a transient high-fat diet exacerbates colitis owing to inflammation-compromised bile acid tolerance. Mechanistically, excessive tumor necrosis factor (TNF) produced at the onset of colitis interferes with bile-acid detoxification through the receptor-interacting serine/threonine-protein kinase 1/extracellular signal-regulated kinase pathway in intestinal epithelial cells, leading to bile acid overload in the endoplasmic reticulum and consequent apoptosis. In line with the synergy of bile acids and TNF in promoting gut epithelial damage, high intestinal bile acids correlate with poor infliximab response, and bile acid clearance improves infliximab efficacy in experimental colitis. This study identifies bile acids as an "opportunistic pathogenic factor" in the gut that would represent a promising target and stratification criterion for ulcerative colitis prevention/therapy.

Intestinal macrophages in pathogenesis and treatment of gut leakage: current strategies and future perspectives

Macrophages play key roles in tissue homeostasis, defense, disease, and repair. Macrophages are highly plastic and exhibit distinct functional phenotypes based on micro-environmental stimuli. In spite of several advancements in understanding macrophage biology and their different functional phenotypes in various physiological and pathological conditions, currently available treatment strategies targeting macrophages are limited. Macrophages' high plasticity and diverse functional roles-including tissue injury and wound healing mechanisms-mark them as potential targets to mine for efficient therapeutics to treat diseases. Despite mounting evidence on association of gut leakage with several extraintestinal diseases, there is no targeted standard therapy to treat gut leakage. Therefore, there is an urgent need to develop therapeutic strategies to treat this condition. Macrophages are the cells that play the largest role in interacting with the gut microbiota in the intestinal compartment and exert their intended functions in injury and repair mechanisms. In this review, we have summarized the current knowledge on the origins and phenotypes of macrophages. The specific role of macrophages in intestinal barrier function, their role in tissue repair mechanisms, and their association with gut microbiota are discussed. In addition, currently available therapies and the putative tissue repair mediators of macrophages for treating microbiota dysbiosis induced gut leakage are also discussed. The overall aim of this review is to convey the intense need to screen for microbiota induced macrophage-released prorepair mediators, which could lead to the identification of potential candidates that could be developed for treating the leaky gut and associated diseases.

Dietary long-chain fatty acids promote colitis by regulating palmitoylation of STAT3 through CD36-mediated endocytosis

The Western diet, characterized by its high content of long-chain fatty acids (LCFAs), is widely recognized as a significant triggering factor for inflammatory bowel disease (IBD). While the link between a high-fat diet and colitis has been observed, the specific effects and mechanisms remain incompletely understood. Our study provides evidence that the diet rich in LCFAs can disrupt the integrity of the intestinal barrier and exacerbate experimental colitis in mice. Mechanistically, LCFAs upregulate the signal transducer and activator of transcription-3 (STAT3) pathway in the inflammatory model, and STAT3 knockout effectively counters the pro-inflammatory effects of LCFAs on colitis. Specifically, palmitic acid (PA), a representative LCFA, enters intestinal epithelial cells via the cluster of differentiation 36 (CD36) pathway and participates in the palmitoylation cycle of STAT3. Inhibiting this cycle using pharmacological inhibitors like 2-Bromopalmitate (2-BP) and ML349, as well as DHHC7 knockdown, has the ability to alleviate inflammation induced by PA. These findings highlight the significant role of dietary LCFAs, especially PA, in the development and progression of IBD. Diet adjustments and targeted modulation offer potential therapeutic strategies for managing this condition. Model of LCFAs involvement in the palmitoylation cycle of STAT3 upon internalization into cells. Following cellular uptake through CD36, LCFAs are converted to palmitoyl-CoA. In the presence of DHHC7, palmitoyl-CoA binds to STAT3 at the C108 site, forming palmitoylated STAT3. Palmitoylation further promotes phosphorylation at the Y705 site of STAT3. Subsequently, palmitoylated STAT3 undergoes depalmitoylation by APT2 and translocates to the nucleus to exert its biological functions.

Activation of GPBAR1 attenuates vascular inflammation and atherosclerosis in a mouse model of NAFLD-related cardiovascular disease

While patients with nonalcoholic fatty liver disease (NAFLD) are at increased risk to develop clinically meaningful cardiovascular diseases (CVD), there are no approved drug designed to target the liver and CVD component of NAFLD. GPBAR1, also known as TGR5, is a G protein coupled receptor for secondary bile acids. In this study we have investigated the effect of GPBAR1 activation by BAR501, a selective GPBAR1 agonist, in Apolipoprotein E deficient (ApoE-/-) mice fed a high fat diet and fructose (Western diet), a validated model of NAFLD-associated atherosclerosis. Using aortic samples from patients who underwent surgery for abdominal aneurism, and ex vivo experiments with endothelial cells and human macrophages, we were able to co-localize the expression of GPBAR1 in CD14+ and PECAM1+ cells. Similar findings were observed in the aortic plaques from ApoE-/- mice. Treating ApoE-/- mice with BAR501, 30 mg/kg for 14 weeks, attenuated the body weight gain while ameliorated the insulin sensitivity by increasing the plasma concentrations of GLP-1 and FGF15. Activation of GPBAR1 reduced the aorta thickness and severity of atherosclerotic lesions and decreased the amount of plaques macrophages. Treating ApoE-/- mice reshaped the aortic transcriptome promoting the expression of anti-inflammatory genes, including IL-10, as also confirmed by tSNE analysis of spleen-derived macrophages. Feeding ApoE-/- mice with BAR501 redirected the bile acid synthesis and the composition of the intestinal microbiota. In conclusion, GPBAR1 agonism attenuates systemic inflammation and improve metabolic profile in a genetic/dietetic model of atherosclerosis. BAR501 might be of utility in the treatment for NAFLD-related CVD.