Autophagy can alleviate severe burn-induced damage to the intestinal tract in mice

Kinetics of Inflammatory Mediators in the Immune Response to Burn Injury: Systematic Review and Meta-Analysis of Animal Studies

Burns are often accompanied by a dysfunctional immune response, which can lead to systemic inflammation, shock, and excessive scarring. The objective of this study was to provide insight into inflammatory pathways associated with burn-related complications. Because detailed information on the various inflammatory mediators is scattered over individual studies, we systematically reviewed animal experimental data for all reported inflammatory mediators. Meta-analyses of 352 studies revealed a strong increase in cytokines, chemokines, and growth factors, particularly 19 mediators in blood and 12 in burn tissue. Temporal kinetics showed long-lasting surges of proinflammatory cytokines in blood and burn tissue. Significant time-dependent effects were seen for IL-1β, IL-6, TGF-β1, and CCL2. The response of anti-inflammatory mediators was limited. Burn technique had a profound impact on systemic response levels. Large burn size and scalds further increased systemic, but not local inflammation. Animal characteristics greatly affected inflammation, for example, IL-1β, IL-6, and TNF-α levels were highest in young, male rats. Time-dependent effects and dissimilarities in response demonstrate the importance of appropriate study design. Collectively, this review presents a general overview of the burn-induced immune response exposing inflammatory pathways that could be targeted through immunotherapy for burn patients and provides guidance for experimental set-ups to advance burn research.

Long noncoding RNA H19 act as a competing endogenous RNA of Let-7g to facilitate IEC-6 cell migration and proliferation via regulating EGF

Intestinal mucosal injury is one of the most significant complications of burns. In our previous study, it was found that autophagy could alleviate burn-induced intestinal injury, but the underlying mechanisms are still unclear. Irregular expression of long noncoding RNAs (lncRNAs) is present in many diseases, including burns. However, the relationship between lncRNAs and intestinal mucosal injury requires further elucidation. In this study, we established a burn mice model and detected the expression level of autophagy-related proteins. Then, H19 content after autophagy intervention was tested in vitro and in vivo. The interaction of H19 with Let-7g and that of Let-7g with epidermal growth factor (EGF) were verified by dual-luciferase reporter assays. We found that the expression of the autophagy-associated proteins LC3-II and Beclin-1 was raised in the intestinal tract of the burn mice model. Similarly, the transfection of H19 raised autophagy levels. H19 was elevated after autophagy intervention in vitro and in vivo. H19 overexpression was able to promote IEC-6 cell migration and proliferation. Let-7g was suppressed by the overexpression of H19 and the combination of Let-7g mimic was able to abolish the physiological effect of H19. Moreover, the suppression of Let-7g increased the expression of EGF protein, which heightened IEC-6 cell migration and proliferation. Besides this, dual-luciferase assays revealed that Let-7g was a direct target of H19 as well as the EGF gene. Taken together, autophagy-mediated H19 increases in mouse intestinal tract after severe burn and functions as a sponge to Let-7g to regulate EGF, which suggests that H19 serves as a potential therapeutic target and biomarker for intestinal mucosal injury after burns.

Identification of differentially expressed long non-coding RNAs in mice intestines after severe burns and a preliminary study into the key gene H19

BACKGROUND

The intestine is considered the key organ in stress response to severe burns and injury to intestine after severe burns can be fatal. However, the injury and subsequent repair of intestinal tissues after severe burns at the genetic level are poorly understood. Long non-coding RNAs (lncRNAs) have important functions in regulating many biological processes, including gene transcription and translation. Autophagy is a process of intracellular degradation and reutilization of cytoplasmic proteins and organelles.

METHODS

We herein analyzed the genome-wide expression profile of lncRNAs and mRNAs after severe burns in the intestines of mice by lncRNA microarray. qRT-PCR was performed to verify the reliability of microarray analysis results, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used for bioinformatics analysis of differentially expressed mRNAs. The common regulatory network between the top ten differentially expressed lncRNAs and trans-related mRNAs was visualized by Cytoscape (v3.7.2). Next, we hypothesized that H19 is the key gene for intestinal mucosal repair. After H19 was overexpressed, the changes in downstream autophagy protein expression levels were observed.

RESULTS

GO and KEGG analysis indicated that the differentially expressed mRNAs were mainly enriched in a cell cycle- and mitosis-related genes.Overexpression of lncRNA-H19 showed that the autophagy-related gene Trim21 was up-regulated, while HIF1α was down-regulated.

CONCLUSION

LncRNA-H19 played a key role in repairing the intestinal mucosa, and overexpression of lncRNA-H19 activated autophagy and migration of intestinal epithelial cells (IEC-6).

Expression profile and bioinformatics analysis of circular RNA in intestinal mucosal injury and repair after severe burns

Circular RNA (circRNA) is a novel noncoding RNA that is mostly found in humans and animals. Although the flux of circRNA research has increased in recent years, its precise function is still unclear. Some studies demonstrate that circRNAs can function as microRNA (miRNA) sponges involved in the regulation of competitive endogenous RNAs networks and play a crucial role in many biological processes. Other studies show that circRNAs play multiple biological roles in gastrointestinal diseases. However, the expression characteristics and function of circRNA in intestinal mucosal injury and repair after severe burn have not been reported. This study aims to screen differentially expressed circRNAs in intestinal mucosal injury and repair after severe burns and understand their underlying mechanisms. To test our hypothesis that circRNA may play a role in promoting repair in intestinal mucosa injury after severe burns, we collected the intestinal tissues of three severely burned mice and three pseudo-scalded mice and evaluated the expression of circRNAs via microarray analysis. Quantitative real-time polymerase chain reaction was also used to validate the circRNA microarray data by selecting six based on different multiples, original values, and p values. The host genes of all differentially expressed circRNAs and the downstream target genes of six selected DEcircRNAs were identified by Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes pathway analysis. Meanwhile, we also created a circRNA-miRNA-mRNA network to predict the role and function of circRNAs in intestinal mucosal injury and repair after severe burns.

Epidermal growth factor regulation by autophagy-mediated lncRNA H19 in murine intestinal tract after severe burn

To investigate the regulation of epidermal growth factor (EGF) by autophagy‐mediated long non‐coding RNA (lncRNA) H19 in the intestinal tracts of severely burned mice. C57BL/6J mice received third‐degree burns to 30% of the total body surface area. Rapamycin and 3‐methyladenine (3‐MA) were used to activate and inhibit autophagy, and the changes in LC3 and Beclin1 levels were assessed by Western blotting. The effect of autophagy on lncRNA H19 was detected by qRT‐PCR. Adenovirus‐mediated overexpression of lncRNA H19 in IEC‐6 cells was used to assess the effects of lncRNA H19 on EGF and let‐7g via bioinformatics analysis, Western blotting and qRT‐PCR. let‐7g mimic/inhibitor was used to overexpress/inhibit let‐7g, and qRT‐PCR and Western blotting were used to detect the effects of let‐7g on EGF. The expression levels of LC3‐II, Beclin1 and lncRNA H19 were increased in intestinal tissues and IEC‐6 cells after rapamycin treatment but were reversed after 3‐MA treatment. LC3‐II, Beclin1 and lncRNA H19 levels increased in intestinal tissues after the burn, and these increases were more significant after rapamycin treatment but decreased after 3‐MA treatment. The lncRNA H19 overexpression in IEC‐6 cells resulted in increased and decreased expression levels of EGF and let‐7g, respectively. Furthermore, overexpression and inhibition of let‐7g resulted in decreased and increased expression of EGF, respectively. Taken together, intestinal autophagy is activated after a serious burn, which can increase the transcription level of lncRNA H19. lncRNA H19 may regulate the repair of EGF via let‐7g following intestinal mucosa injury after a burn.

Inhibition of Autophagy Signaling via 3-methyladenine Rescued Nicotine-Mediated Cardiac Pathological Effects and Heart Dysfunctions

Rationale: Cigarette smoking is a well-established risk factor for myocardial infarction and sudden cardiac death. The deleterious effects are mainly due to nicotine, but the mechanisms involved and theranostics remain unclear. Thus, we tested the hypothesis that nicotine exposure increases the heart sensitivity to ischemia/reperfusion injury and dysfunction, which can be rescued by autophagy inhibitor.

Methods: Nicotine or saline was administered to adult rats via subcutaneous osmotic minipumps in the absence or presence of an autophagy inhibitor, 3-methyladenine (3-MA). After 30 days of nicotine treatment, the rats underwent the cardiac ischemia/reperfusion (I/R) procedure and echocardiography analysis, and the heart tissues were isolated for molecular biological studies.

Results: Nicotine exposure increased I/R-induced cardiac injury and cardiac dysfunction as compared to the control. The levels of autophagy-related proteins including LC3 II, P62, Beclin1, and Atg5 were upregulated in the reperfused hearts isolated from nicotine-treated group. In addition, nicotine enhanced cardiac and plasma ROS production, and increased the phosphorylation of GSK3β (ser9) in the left ventricle tissues. Treatment with 3-MA abolished nicotine-mediated increase in the levels of autophagy-related proteins and phosphorylation of GSK3β, but had no effect on ROS production. Of importance, 3-MA ameliorated the augmented I/R-induced cardiac injury and dysfunction in the nicotine-treated group as compared to the control.

Conclusion: Our results demonstrate that nicotine exposure enhances autophagy signaling pathway, resulting in development of ischemic-sensitive phenotype of heart. It suggests a potentially novel therapeutic strategy of autophagy inhibition for the treatment of ischemic heart disease.

Edaravone reduces oxidative stress and intestinal cell apoptosis after burn through up-regulating miR-320 expression

BACKGROUND

Intestinal mucosa barrier dysfunction after burn injury is an important factor for causing mortality of burn patients. The current study established a burn model in rats and used a free radical scavenger edaravone (ED) to treat the rats, so as to investigate the effect of edaravone on intestinal mucosa barrier after burn injury.

METHODS

Anesthetized rats were subjected to 40% total body surface area water burn immediately, followed by treatment with ED, scrambled antagomir, or antagomiR-320. Intestinal mucosa damage was observed by hematoxylin-eosin staining and graded by colon mucosal damage index (CMDI) score. The contents of total sulfhydryl (TSH), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were determined by spectrophotometry. Cell apoptosis, protein relative expression,and the in situ expressions of p-Akt and p-Bad were detected by flow cytometry, Western blotting and immunohistochemistry, respectively. The miR-320 expression was determined by quantitative real-time polymerase chain reaction.

RESULTS

ED alleviated intestinal mucosal damage caused by burn injury, down-regulated the levels of MDA, cytochrome C, cleaved caspase-9 and cleaved caspase-3, but up-regulated the levels of TSH, SOD, CAT and Bcl-2. We also found that ED could reduce oxidative stress, inhibit cell apoptosis, increase the expressions of p-Akt, p-Bad and miR-320, and decrease PTEN expression. PTEN was predicted to be the target gene for miR-320, and cell apoptosis could be promoted by inhibiting miR-320 expression.

CONCLUSION

ED regulates Akt/Bad/Caspase signaling cascade to reduce apoptosis and oxidative stress through up-regulating miR-320 expression and down-regulating PTEN expression, thus protecting the intestinal mucosal barrier of rats from burn injury.

Role of Endoplasmic Reticulum Stress-Autophagy Axis in Severe Burn-Induced Intestinal Tight Junction Barrier Dysfunction in Mice

Severe burn injury induces intestinal barrier dysfunction; however, the underlying mechanisms remain elusive. Our previous studies have shown that the intestinal epithelial tight junction (TJ) barrier dysfunction is associated with both endoplasmic reticulum (ER) stress and autophagy in severely burned mice, but the precise role of ER stress and autophagy in the burn-induced intestinal TJ barrier dysfunction needs to be determined. In this study, female C57/BL6 mice were assigned randomly to either sham burn or 30% total body surface area (TBSA) full-thickness burn. The effects of ER stress and autophagy on the intestinal epithelial TJ barrier were validated by inducing or inhibiting both ER stress and autophagy in mice treated with sham burn or burn injury. The intestinal permeability, expression, and localization of TJ proteins, ER stress, and autophagy were assessed by physiological, morphological, and biochemical analyses. The results showed that inducing ER stress with tunicamycin or thapsigargin caused the activation of autophagy, the increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins in the sham-burned mice, and aggravated the burn-induced activation of autophagy, increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins. In contrast, inhibiting ER stress with 4-phenylbutyrate alleviated the burn-induced activation of autophagy, increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins. In addition, inducing autophagy with rapamycin resulted in the increase of intestinal permeability, as well as the reduction and reorganization of TJ proteins in the sham-burned mice, and aggravated the burn-induced increase of intestinal permeability as well as the reduction and reorganization of TJ proteins. However, inhibiting autophagy with 3-methyladenine attenuated the burn-induced increase of intestinal permeability, as well as the reduction and reorganization TJ proteins. It is suggested that the ER stress-autophagy axis contributes to the intestinal epithelial TJ barrier dysfunction after severe burn injury.

Over-expression of CNTF in bone marrow mesenchymal stem cells protects RPE cells from short-wavelength, blue-light injury

Increasing evidence has demonstrated that excessive blue-light (BL) with high photochemical energy and phototoxicity could induce apoptosis in retinal pigment epithelium (RPE) cells. RPE apoptosis leads to retina damage and further aggravate age-related macular degeneration (ARMD). Because of their neuroprotective, plasticity, and immunomodulatory ability, bone marrow mesenchymal stem cells (BMSCs) are recognized for retinal neuroprotection. RPE cells possess ciliary neurotrophic factor (CNTF) receptor complexes and can respond to CNTF; hence, we investigated the effects of BMSCs over-expressing CNTF on BL-injured RPE cells. BL-injured RPE cells were co-cultured with CNTF-BMSCs and GFP-BMSCs for 24 and 48 h. Superoxide dismutase and malondialdehyde assays were conducted to examine the effects of CNTF-BMSCs on the oxidative stress of RPE cells. VEGF protein secretion by RPE was determined by ELISA, and western blotting analysis was used to determine apoptotic protein expression and autophagic flux. Immunofluorescence was used to demonstrate the relationship between autophagy and apoptosis. We found that CNTF-BMSCs enhanced antioxidant capacity, decreased VEGF secretion, promoted autophagic flux, and inhibited apoptosis in BL-injured RPE cells, compared to GFP-BMSCs. Our findings suggest that CNTF over-expression enhances the protective effects of BMSCs on RPE cells, thus indicating subretinal-transplantation of CNTF-BMSCs may be a promising therapy for BL-injured retina.