Protective effects of PX478 on gut barrier in a mouse model of ethanol and burn injury

A review of gut failure as a cause and consequence of critical illness

In critical illness, all elements of gut function are perturbed. Dysbiosis develops as the gut microbial community loses taxonomic diversity and new virulence factors appear. Intestinal permeability increases, allowing for translocation of bacteria and/or bacterial products. Epithelial function is altered at a cellular level and homeostasis of the epithelial monolayer is compromised by increased intestinal epithelial cell death and decreased proliferation. Gut immunity is impaired with simultaneous activation of maladaptive pro- and anti-inflammatory signals leading to both tissue damage and susceptibility to infections. Additionally, splanchnic vasoconstriction leads to decreased blood flow with local ischemic changes. Together, these interrelated elements of gastrointestinal dysfunction drive and then perpetuate multi-organ dysfunction syndrome. Despite the clear importance of maintaining gut homeostasis, there are very few reliable measures of gut function in critical illness. Further, while multiple therapeutic strategies have been proposed, most have not been shown to conclusively demonstrate benefit, and care is still largely supportive. The key role of the gut in critical illness was the subject of the tenth Perioperative Quality Initiative meeting, a conference to summarize the current state of the literature and identify key knowledge gaps for future study. This review is the product of that conference.

Golgi condensation causes intestinal lipid accumulation through HIF-1α-mediated GM130 ubiquitination by NEDD4

The breakdown of Golgi proteins disrupts lipid trafficking, leading to lipid accumulation in the small intestine. However, the causal mechanism of the effects of Golgi protein degradation on the Golgi structure related to lipid trafficking in the small intestine remains unknown. Here we find that Golgi protein degradation occurs under hypoxic conditions in high-fat-diet-fed mice. Hypoxia-induced degradation promotes structural changes in the Golgi apparatus, termed 'Golgi condensation'. In addition, hypoxia-inducible factor 1α (HIF-1α) activation enhances Golgi condensation through the ubiquitination and degradation of Golgi matrix protein 130 (GM130), which is facilitated by neural precursor cell expressed developmentally downregulated protein 4 (NEDD4). Golgi condensation upon exposure to hypoxia promotes lipid accumulation, apolipoprotein A1 retention and decreased chylomicron secretion in the intestinal epithelium. Golgi condensation and lipid accumulation induced by GM130 depletion are reversed by exogenous GM130 induction in the intestinal epithelium. Inhibition of either HIF-1α or NEDD4 protects against GM130 degradation and, thereby, rescues cells from Golgi condensation, which further increases apolipoprotein A1 secretion and lipid accumulation both in vivo and in vitro. Furthermore, the HIF-1α inhibitor PX-478 prevents Golgi condensation, which decreases lipid accumulation and promotes high-density lipoprotein secretion in high-fat-diet-fed mice. Overall, our results suggest that Golgi condensation plays a key role in lipid trafficking in the small intestine through the HIF-1α- and NEDD4-mediated degradation of GM130, and these findings highlight the possibility that the prevention of structural modifications in the Golgi apparatus can ameliorate intestinal lipid accumulation in obese individuals.

Dexmedetomidine against intestinal ischemia/reperfusion injury: A systematic review and meta-analysis of preclinical studies

BACKGROUND

Intestinal ischemia/reperfusion injury (IRI) is a multifactorial, complex pathophysiological process in clinical settings. In recent years, intestinal IRI has received increasing attention due to increased morbidity and mortality. To date, there are no effective treatments. Dexmedetomidine (DEX), a highly selective α2-adrenergic receptor agonist, has been demonstrated to be effective against intestinal IRI. In this systematic review and meta-analysis, we evaluated the efficacy and potential mechanisms of DEX as a treatment for intestinal IRI in animal models.

METHODS

Five databases (PubMed, Embase, Web of Science, Cochrane Library, and Scopus) were searched until March 15, 2023. Using the SYRCLE risk bias tool, we assessed methodological quality. Statistical analysis was conducted using STATA 12 and R 4.2.2. We analyzed the related outcomes (mucosa damage-related indicators; inflammation-relevant markers, oxidative stress markers) relied on the fixed or random-effects models.

RESULTS

There were 15 articles including 18 studies included, and 309 animals were involved in the studies. Compared to the model groups, DEX improved intestinal IRI. DEX decreased Chiu's score and serum diamine oxidase (DAO) level. DEX reduced the level of inflammation-relevant markers (interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α). DEX also improved oxidative stress (decreased malondialdehyde (MDA), increased superoxide dismutase (SOD)).

CONCLUSIONS

DEX's effectiveness in ameliorating intestinal IRI has been demonstrated in animal models. Antioxidation, anti-inflammation, anti-apoptotic, anti-pyroptosis, anti-ferroptosis, enhancing mitophagy, reshaping the gut microbiota, and gut barrier protection are possible mechanisms. However, in light of the heterogeneity and methodological quality of these studies, further well-designed preclinical studies are warranted before clinical implication.

Infrared Raman spectroscopy enables noninvasive biochemical assessment of skin tissue and the thermal stability

Raman-active modes of human skin and pork belly have been studied systematically by a near-infrared Raman spectrometer with an exciting laser of 1064 nm. The main components and quantitative determination of pork belly are extracted by fitting the Raman spectra with the normalized Raman spectra of biochemical reagents such as collagen, elastin, triolein, fibronectin, fibrin, and hyaluronic acid. It demonstrates that the main components and quantity are various at different locations of pork belly, while the main components of human skin are similar to those of pig skin. In a further step, the evolution of the heating time-dependent Raman modes of isolated pig skin has been investigated for the mechanism of burnt skin. One can find that the spatial structure and main components of skin have an excellent thermal stability in the temperature range from -120 to 200 ∘C, which is confirmed by the temperature dependent Raman spectra of isolated pig skin, microporous acellular dermal matrix (MADM) as well as their corresponding biochemical reagents (collagen, elastin, triolein, etc.). These results help understand the mechanism of the living skin burnt by fire or hot water, and supplies an alternative technology for surgeons to diagnose the depth of a burn injury in time.

CHRONIC ETHANOL USE WORSENS GUT PERMEABILITY AND ALTERS TIGHT JUNCTION EXPRESSION IN A MURINE SEPSIS MODEL

ABSTRACT

Alcohol use disorder is associated with increased mortality in septic patients. Murine studies demonstrate that ethanol/sepsis is associated with changes in gut integrity. This study examined intestinal permeability after ethanol/sepsis and investigated mechanisms responsible for alterations in barrier function. Mice were randomized to drink either 20% ethanol or water for 12 weeks and then were subjected to either sham laparotomy or cecal ligation and puncture (CLP). Intestinal permeability was disproportionately increased in ethanol/septic mice via the pore, leak, and unrestricted pathways. Consistent with increased permeability in the leak pathway, jejunal myosin light chain (MLC) kinase (MLCK) expression and the ratio of phospho-MLC to total MLC were both increased in ethanol/CLP. Gut permeability was altered in MLCK -/- mice in water/CLP; however, permeability was not different between WT and MLCK -/- mice in ethanol/CLP. Similarly, jejunal IL-1β levels were decreased while systemic IL-6 levels were increased in MLCK -/- mice in water/CLP but no differences were identified in ethanol/CLP. While we have previously shown that mortality is improved in MLCK -/- mice after water/CLP, mortality was significantly worse in MLCK -/- mice after ethanol/CLP. Consistent with an increase in the pore pathway, claudin 4 levels were also selectively decreased in ethanol/CLP WT mice. Furthermore, mRNA expression of jejunal TNF and IFN-γ were both significantly increased in ethanol/CLP. The frequency of CD4 + cells expressing TNF and IL-17A and the frequency of CD8 + cells expressing IFN-γ in Peyer's Patches were also increased in ethanol/CLP. Thus, there is an ethanol-specific worsening of gut barrier function after CLP that impacts all pathways of intestinal permeability, mediated, in part, via changes to the tight junction. Differences in the host response in the setting of chronic alcohol use may play a role in future precision medicine approaches toward the treatment of sepsis.

Role of Mesenchymal Stem/Stromal Cells in Modulating Ischemia/Reperfusion Injury: Current State of the Art and Future Perspectives

Ischemia/reperfusion injury (IRI) is a multistep damage that occurs in several tissues when a blood flow interruption is inevitable, such as during organ surgery or transplantation. It is responsible for cell death and tissue dysfunction, thus leading, in the case of transplantation, to organ rejection. IRI takes place during reperfusion, i.e., when blood flow is restored, by activating inflammation and reactive oxygen species (ROS) production, causing mitochondrial damage and apoptosis of parenchymal cells. Unfortunately, none of the therapies currently in use are definitive, prompting the need for new therapeutic approaches. Scientific evidence has proven that mesenchymal stem/stromal cells (MSCs) can reduce inflammation and ROS, prompting this cellular therapy to also be investigated for treatment of IRI. Moreover, it has been shown that MSC therapeutic effects were mediated in part by their secretome, which appears to be involved in immune regulation and tissue repair. For these reasons, mediated MSC paracrine function might be key for injury amelioration upon IRI damage. In this review, we highlight the scientific literature on the potential beneficial use of MSCs and their products for improving IRI outcomes in different tissues/organs, focusing in particular on the paracrine effects mediated by MSCs, and on the molecular mechanisms behind these effects.

Mesenchymal stem cells against intestinal ischemia-reperfusion injury: a systematic review and meta-analysis of preclinical studies

Background

Intestinal ischemia–reperfusion injury (IRI) causes localized and distant tissue lesions. Multiple organ failure is a common complication of severe intestinal IRI, leading to its high rates of morbidity and mortality. Thus far, this is poorly treated, and there is an urgent need for new more efficacious treatments. This study evaluated the beneficial effects of mesenchymal stem cells (MSCs) therapy on intestinal IRI using many animal experiments.

Methods

We conducted a comprehensive literature search from 4 databases: Pubmed, Embase, Cochrane library, and Web of science. Primary outcomes included the survival rate, Chiu’s score, intestinal levels of IL-6, TNF-α and MDA, as well as serum levels of DAO, D-Lactate, and TNF-α. Statistical analysis was carried out using Review Manager 5.3.

Results

It included Eighteen eligible researches in the final analysis. We demonstrated that survival rates in animals following intestinal IRI were higher with MSCs treatment compared to vehicle treatment. Besides, MSCs treatment attenuated intestinal injury caused by IRI, characterized by lower Chiu’s score (− 1.96, 95% CI − 2.72 to − 1.19, P < 0.00001), less intestinal inflammation (IL-6 (− 2.73, 95% CI − 4.19 to − 1.27, P = 0.0002), TNF-α (− 3.00, 95% CI − 4.74 to − 1.26, P = 0.0007)) and oxidative stress (MDA (− 2.18, 95% CI − 3.17 to − 1.19, P < 0.0001)), and decreased serum levels of DAO (− 1.39, 95% CI − 2.07 to − 0.72, P < 0.0001), D-Lactate (− 1.54, 95% CI − 2.18 to − 0.90, P < 0.00001) and TNF-α (− 2.42, 95% CI − 3.45 to − 1.40, P < 0.00001). The possible mechanism for MSCs to treat intestinal IRI might be through reducing inflammation, alleviating oxidative stress, as well as inhibiting the apoptosis and pyroptosis of the intestinal epithelial cells.

Conclusions

Taken together, these studies revealed that MSCs as a promising new treatment for intestinal IRI, and the mechanism of which may be associated with inflammation, oxidative stress, apoptosis, and pyroptosis. However, further studies will be required to confirm these findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02896-y.

Maintenance of gut barrier integrity after injury: Trust your gut microRNAs

The gastrointestinal (GI) tract is a highly dynamic structure essential for digestion, nutrient absorption, and providing an interface to prevent gut bacterial translocation. In order to maintain the barrier function, the gut utilizes many defense mechanisms including proliferation, apoptosis, and apical junctional complexes. Disruption of any of these parameters due to injury or disease could negatively impact the intestinal barrier function and homeostasis resulting in increased intestine inflammation, permeability, bacterial dysbiosis, and tissue damage. MicroRNAs are small noncoding RNA sequences that are master regulators of normal cellular homeostasis. These regulatory molecules affect cellular signaling pathways and potentially serve as candidates for providing a mechanism of impaired gut barrier integrity following GI-related pathologic conditions, ethanol exposure, or trauma such as burn injury. MicroRNAs influence cellular apoptosis, proliferation, apical junction complex expression, inflammation, and the microbiome. Due to their widespread functional affiliations, altered expression of microRNAs are associated with many pathologic conditions. This review explores the role of microRNAs in regulation of intestinal barrier integrity. The studies reviewed demonstrate that microRNAs largely impact intestine barrier function and provide insight behind the observed adverse effects following ethanol and burn injury. Furthermore, these studies suggest that microRNAs are excellent candidates for therapeutic intervention or for biomarkers to manage gut barrier integrity following trauma such as burn injury and other GI-related pathologic conditions.