Intestinal TLR9 deficiency exacerbates hepatic IR injury via altered intestinal inflammation and short-chain fatty acid synthesis

Multifaceted involvements of Paneth cells in various diseases within intestine and systemically

Serving as the guardians of small intestine, Paneth cells (PCs) play an important role in intestinal homeostasis maintenance. Although PCs uniquely exist in intestine under homeostasis, the dysfunction of PCs is involved in various diseases not only in intestine but also in extraintestinal organs, suggesting the systemic importance of PCs. The mechanisms under the participation of PCs in these diseases are multiple as well. The involvements of PCs are mostly characterized by limiting intestinal bacterial translocation in necrotizing enterocolitis, liver disease, acute pancreatitis and graft-vs-host disease. Risk genes in PCs render intestine susceptible to Crohn’s disease. In intestinal infection, different pathogens induce varied responses in PCs, and toll-like receptor ligands on bacterial surface trigger the degranulation of PCs. The increased level of bile acid dramatically impairs PCs in obesity. PCs can inhibit virus entry and promote intestinal regeneration to alleviate COVID-19. On the contrary, abundant IL-17A in PCs aggravates multi-organ injury in ischemia/reperfusion. The pro-angiogenic effect of PCs aggravates the severity of portal hypertension. Therapeutic strategies targeting PCs mainly include PC protection, PC-derived inflammatory cytokine elimination, and substituting AMP treatment. In this review, we discuss the influence and importance of Paneth cells in both intestinal and extraintestinal diseases as reported so far, as well as the potential therapeutic strategies targeting PCs.

Molecular Mechanisms of Ischaemia-Reperfusion Injury and Regeneration in the Liver-Shock and Surgery-Associated Changes

Hepatic ischemia-reperfusion injury (IRI) represents a major challenge during liver surgery, liver preservation for transplantation, and can cause hemorrhagic shock with severe hypoxemia and trauma. The reduction of blood supply with a concomitant deficit in oxygen delivery initiates various molecular mechanisms involving the innate and adaptive immune response, alterations in gene transcription, induction of cell death programs, and changes in metabolic state and vascular function. Hepatic IRI is a major cause of morbidity and mortality, and is associated with an increased risk for tumor growth and recurrence after oncologic surgery for primary and secondary hepatobiliary malignancies. Therapeutic strategies to prevent or treat hepatic IRI have been investigated in animal models but, for the most part, have failed to provide a protective effect in a clinical setting. This review focuses on the molecular mechanisms underlying hepatic IRI and regeneration, as well as its clinical implications. A better understanding of this complex and highly dynamic process may allow for the development of innovative therapeutic approaches and optimize patient outcomes.

Effect of Houpo-Mahuang Decoction on aggravated asthma induced by cigarette smoke and the expression of TRPA1 and tight junctions in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cigarette smoke (CS) is a common environmental irritant and a risk factor for asthma, as it induces as well as aggravates asthmatic attacks. The injured airway epithelial tight junctions (TJs) aggravate asthma. CS can aggravate asthma by activating the transient receptor potential ankyrin A1 (TRPA1) channel and enhancing TJs destruction. Houpo Mahuang decoction (HPMHD) is a classic traditional Chinese prescription for the treatment of asthma. However, its underlying action mechanism is unclear.

AIM OF THE STUDY

The present study aimed to evaluate the effect of HPMHD on the asthma phenotype and the regulation of TRPA1 and TJs in a CS-induced mouse model of aggravated asthma.

MATERIALS AND METHODS

Under optimized chromatographic and mass spectrometry conditions, the ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) technique was used to detect and analyze the major chemical components of HPMHD. C57BL/6 female mice were randomly divided into seven groups, viz, normal saline (NS) group, ovalbumin (OVA) + CS group, dexamethasone group, HPMHD high-dose group and low-dose groups, n-butanol extract group, and ethyl acetate extract group, with 10 mice in each group. OVA sensitization and challenge, and CS exposure were used to establish the aggravated asthma model. As the main indices to evaluate the protective effect of HPMHD, the eosinophils count in peripheral blood, percentages of inflammatory cells classified and the levels of interleukin (IL)-4, IL-5, IL-13 in the bronchoalveolar lavage fluid (BALF), airway responsiveness enhanced pause (Penh), and changes in lung histopathology were determined and compared among the groups. The mRNA and protein expression of TRPA1 and TJs in lung tissue was also examined.

RESULTS

Using UPLC-QTOF-MS, the chemical components of HPMHD, including ephedrine, pseudoephedrine, laetrile, and amygdalin amide, were identified by 51 signal peaks. Compared with those in the NS group, the eosinophil number in the peripheral blood and the eosinophils and neutrophils percentages in BALF of the OVA + CS group were remarkably increased. Following the inhalation of 50 μl of acetylcholine chloride (ACH) at doses of 25 and 50 mg/mL, the Penh increased significantly (p < 0.01). Moreover, in the OVA + CS group, hematoxylin and eosin (H&E) staining of lung tissue showed a significant number of infiltrated inflammatory cells, increased mucus secretion in the lumen, damaged bronchial mucosa, increased thickness of tracheal wall, and increased score of lung damage (p < 0.01). The IL-4/5/13 levels were also remarkably increased (p < 0.01). The protein as well as gene expression of both ZO-1 and occludin decreased markedly in the lung tissue, while the expression of TRPA1 and claudin-2 was increased (p < 0.05, p < 0.01). Next, the OVA + CS group and the treatment groups were compared. The inflammatory cells, Penh value, and levels of IL-4/5/13 were significantly reduced, and less lung injury was observed in the treatment groups. The gene and protein levels of TRPA1 and TJs were corrected (p < 0.05, p < 0.01); the effects on the HPMHD high-dose and ethyl acetate extract groups were particularly remarkable.

CONCLUSIONS

HPMHD reduced airway hyperresponsiveness, inflammatory cell recruitment and Th2 cytokine secretion in CS-induced aggravated asthma mice, in a manner potentially dependent on regulation of the expression of TRPA1 and TJ proteins. Both the n-butanol and ethyl acetate extracts contained the active ingredients, especially the ethyl acetate extract.

Toll-like receptor 9 deficiency induces osteoclastic bone loss via gut microbiota-associated systemic chronic inflammation

Toll-like receptors (TLRs) play pivotal roles in inflammation and provide important links between the immune and skeletal systems. Although the activation of TLRs may affect osteoclast differentiation and bone metabolism, whether and how TLRs are required for normal bone remodeling remains to be fully explored. In the current study, we show for the first time that TLR9^-/- mice exhibit a low bone mass and low-grade systemic chronic inflammation, which is characterized by the expansion of CD4⁺ T cells and increased levels of inflammatory cytokines, including TNFα, RANKL, and IL1β. The increased levels of these cytokines significantly promote osteoclastogenesis and induce bone loss. Importantly, TLR9 deletion alters the gut microbiota, and this dysbiosis is the basis of the systemic inflammation and bone loss observed in TLR9^-/- mice. Furthermore, through single-cell RNA sequencing, we identified myeloid-biased hematopoiesis in the bone marrow of TLR9^-/- mice and determined that the increase in myelopoiesis, likely caused by the adaptation of hematopoietic stem cells to systemic inflammation, also contributes to inflammation-induced osteoclastogenesis and subsequent bone loss in TLR9^-/- mice. Thus, our study provides novel evidence that TLR9 signaling connects the gut microbiota, immune system, and bone and is critical in maintaining the homeostasis of inflammation, hematopoiesis, and bone metabolism under normal conditions.

New Insights in Mechanisms and Therapeutics for Short- and Long-Term Impacts of Hepatic Ischemia Reperfusion Injury Post Liver Transplantation

Liver transplantation has been identified as the most effective treatment for patients with end-stage liver diseases. However, hepatic ischemia reperfusion injury (IRI) is associated with poor graft function and poses a risk of adverse clinical outcomes post transplantation. Cell death, including apoptosis, necrosis, ferroptosis and pyroptosis, is induced during the acute phase of liver IRI. The release of danger-associated molecular patterns (DAPMs) and mitochondrial dysfunction resulting from the disturbance of metabolic homeostasis initiates graft inflammation. The inflammation in the short term exacerbates hepatic damage, leading to graft dysfunction and a higher incidence of acute rejection. The subsequent changes in the graft immune environment due to hepatic IRI may result in chronic rejection, cancer recurrence and fibrogenesis in the long term. In this review, we mainly focus on new mechanisms of inflammation initiated by immune activation related to metabolic alteration in the short term during liver IRI. The latest mechanisms of cancer recurrence and fibrogenesis due to the long-term impact of inflammation in hepatic IRI is also discussed. Furthermore, the development of therapeutic strategies, including ischemia preconditioning, pharmacological inhibitors and machine perfusion, for both attenuating acute inflammatory injury and preventing late-phase disease recurrence, will be summarized in the context of clinical, translational and basic research.

Effects of cigarette smoke on the aggravation of ovalbumin-induced asthma and the expressions of TRPA1 and tight junctions in mice

The occurrence of asthma is closely related to environmental factors such as cigarette smoke (CS), one of the common risk factors. Environmental stimuli have the potential to activate transient receptor potential ankyrin 1 (TRPA1) and cause or aggravate asthma. The destruction of tight junctions (TJs) between airway epithelial cells by environmental stimuli in asthma has been researched. It is worth exploring whether CS can injury TJs and aggravate asthma by activating TRPA1. The objective of this study was to investigate the aggravation of CS on ovalbumin (OVA)-induced asthma related phenotypes and TJs expression in mice, and to explore the relationship between TRPA1 and the expression of TJs protein. Female wild type (WT) C57BL/6 mice, induced by OVA, CS and OVA plus CS (OVA + CS) respectively, were used to establish a 42-day asthma model, and mice with TRPA1 knockout (TRPA1-/-) were treated in the same way. This study detected the number of inflammatory cells in peripheral blood and bronchoalveolar lavage fluid (BALF), the levels of IL-4, IL-5, IL-13 in BALF, enhanced pause (Penh) of lung function, pathological changes and the gene and protein expressions of TRPA1 and TJs (including ZO-1, Occludin and Claudin-2) in lung tissues. Compared with normal saline (NS) group, WT mice in the OVA group and OVA + CS group were significantly higher in asthma related phenotypes. The WT-OVA + CS group also showed higher Penh value, levels of IL-5 and IL-13 in BALF and lung tissue injury scores when compared with the WT-OVA group and WT-CS group. However, WT-OVA + CS group mice had significantly larger number of neutrophils in BALF than the WT-OVA group, and had larger number of eosinophils in peripheral blood and higher levels of IL-4 in BALF than the WT-CS group. Meanwhile, compared with the WT-NS group, the expressions of TRPA1 and Claudin-2 in lung tissues increased in other three groups while their expressions of ZO-1 and Occludin decreased, among which, the WT-OVA + CS group showed more remarkable changes. Compared with the WT-OVA + CS group, mice in the TRPA1-/--OVA + CS showed a significant decrease in the number of inflammatory cells, levels of IL-4, IL-5 and IL-13 in BALF, Penh value and lung tissue injury score, and a downregulation of Claudin-2 expression while an upregulation of ZO-1 and Occludin expressions. In addition, the airway inflammation and injury, and the expressions of ZO-1, Occluding and Claudin-2 expressions were found with no statistic differences between TRPA1-/--OVA group and TRPA1-/--OVA + CS group. These results suggest that CS has aggravated the airway inflammation, pathological damage and destruction of TJs in airway epithelium of OVA-induced asthmatic mice, the processes of which are related to the increase of TRPA1 expression.