The Gut-Lung Axis in Systemic Inflammation. Role of Mesenteric Lymph as a Conduit

Immune mRNA Expression and Fecal Microbiome Composition Change Induced by Djulis (Chenopodium formosanum Koidz.) Supplementation in Aged Mice: A Pilot Study

Background and Objectives: The aging process has always been associated with a higher susceptibility to chronic inflammatory lung diseases. Several studies have demonstrated the gut microbiome's influence on the lungs through cross-talk or the gut-lungs axis maintaining nutrient-rich microenvironments. Taiwan djulis (Chenopodium formosanum Koidz.) provides antioxidant and anti-inflammatory characteristics that could modulate the gut microbiome. This could induce the gut-lung axis through microbial cross-talk, thus favoring the modulation of lung inflammation. Materials and Methods: Here, we investigate the immune mRNA expression in the spleen, fecal microbiome composition, and hyperplasia of the bronchial epithelium in aged 2-year-old BALB/c mice after 60 days of supplementation of djulis. Results: The pro-inflammatory cytokines IFN-γ, TNF-α, and IL-1β, T; cells CD4 and CD8; and TLRs TLR3, TLR4, TLR5, TLR7, TLR8, and TLR9 were reduced in their mRNA expression levels, while the anti-inflammatory cytokines IL-2, IL-4, and IL-10 were highly expressed in the C. formosanum-treated group. Interestingly, the fecal microbiome composition analysis indicated higher diversity in the C. formosanum-treated group and the presence of butyrate-producing bacteria that are beneficial in the gut microbiome. The histopathology showed reduced hyperplasia of the bronchial epithelium based on the degree of lesions. Conclusions: Our findings suggest that Taiwan djulis can modulate the gut microbiome, leading to microbial cross-talk; reducing the mRNA expression of pro-inflammatory cytokines, T cells, and TLRs; and increasing anti-inflammatory cytokines in the spleen, as cytokines migrate in the lungs, preventing lung inflammation damage in aged mice or the gut-lung axis. Thus, Taiwan djulis could be considered a beneficial dietary component for the older adult population. The major limitation includes a lack of protein validation of cytokines and TLRs and quantification of the T cell population in the spleen as a marker of the gut-lung axis.

Gut-derived immune cells and the gut-lung axis in ARDS

The gut serves as a vital immunological organ orchestrating immune responses and influencing distant mucosal sites, notably the respiratory mucosa. It is increasingly recognized as a central driver of critical illnesses, with intestinal hyperpermeability facilitating bacterial translocation, systemic inflammation, and organ damage. The "gut-lung" axis emerges as a pivotal pathway, where gut-derived injurious factors trigger acute lung injury (ALI) through the systemic circulation. Direct and indirect effects of gut microbiota significantly impact immune responses. Dysbiosis, particularly intestinal dysbiosis, termed as an imbalance of microbial species and a reduction in microbial diversity within certain bodily microbiomes, influences adaptive immune responses, including differentiating T regulatory cells (Tregs) and T helper 17 (Th17) cells, which are critical in various lung inflammatory conditions. Additionally, gut and bone marrow immune cells impact pulmonary immune activity, underscoring the complex gut-lung interplay. Moreover, lung microbiota alterations are implicated in diverse gut pathologies, affecting local and systemic immune landscapes. Notably, lung dysbiosis can reciprocally influence gut microbiota composition, indicating bidirectional gut-lung communication. In this review, we investigate the pathophysiology of ALI/acute respiratory distress syndrome (ARDS), elucidating the role of immune cells in the gut-lung axis based on recent experimental and clinical research. This exploration aims to enhance understanding of ALI/ARDS pathogenesis and to underscore the significance of gut-lung interactions in respiratory diseases.

Mycoplasma pneumoniae pneumonia-associated thromboembolism with plastic bronchitis: a series of five case reports and literature review

BACKGROUND

Mycoplasma pneumoniae pneumonia is a common respiratory infection among children. However, the occurrence of thromboembolism with plastic bronchitis in association with Mycoplasma pneumoniae pneumonia is extremely rare. This case series presents five cases of children with Mycoplasma pneumoniae pneumonia who developed thromboembolism and plastic bronchitis. The clinical presentation, diagnostic approach, and management strategies are discussed.

METHODS

A retrospective analysis was conducted on medical records from a pediatric hospital. Patient demographics, clinical features, laboratory findings, imaging results, treatment modalities, and outcomes were collected.

RESULTS

The patients in our case series presented with varying degrees of respiratory distress, cough, and fever. Imaging studies revealed evidence of thromboembolism based on pulmonary artery occlusion. Bronchial casts were observed by bronchoscopy. Laboratory tests demonstrated elevated D-dimer levels and fibrinogen degradation products. All patients received a combination of low molecular weight heparin anticoagulation and supportive care.

CONCLUSION

Thromboembolism with plastic bronchitis associated with Mycoplasma pneumoniae pneumonia is a rare but potentially serious complication in children. Prompt recognition and management are crucial for improving patient outcomes. This case series highlights the diverse clinical presentations, diagnostic challenges, and treatment strategies for this unique clinical entity. Further research is needed to better understand the pathogenesis and optimal management of this condition.

Forsythiaside A alleviates acute lung injury by inhibiting inflammation and epithelial barrier damages in lung and colon through PPAR-γ/RXR-α complex

INTRODUCTION

Acute lung injury (ALI) is a lung disease characterized by inflammation and still requires further drug development. Forsythiaside A as the active compound of Forsythiae Fructus has the therapeutic potential for ALI.

OBJECTIVE

To investigate the mechanism of forsythiaside A in treating ALI through PPAR-γ and its conjugate RXR-α based on gut-lung axis.

METHODS

This study constructed in vitro and in vivo injury models using LPS and TNF-α. Forsythiaside A was used for the drug treatment, and RXR-α inhibitor UVI3003 was used to interfere with PPAR-γ/RXR-α complexes in the cells. HE staining was used for histopathological examination. Serum endotoxin contents were determined using limulus lysate kit. IHC staining and Western blot were conducted to assess the protein expressions. ELISA was applied to examine the content of pro-inflammatory cytokines in the cell supernatants. The protein interactions were analyzed via CO-IP.

RESULTS

In vivo results showed that forsythiaside A regulated PPAR-γ/RXR-α and inhibited TLR4/MAPK/NF-κB and MLCK/MLC2 signal pathways, thus inhibiting inflammation and epithelial barrier damages of lung and colon in ALI mice induced by intratracheal LPS. PPAR-γ/RXR-α were promoted by forsythiaside A in lungs, whereas inhibited by forsythiaside A in colons. Additionally, in vitro results showed that forsythiaside A suppressed inflammation and epithelial barrier damages in macrophages and lung/colon epithelial cells, by manipulating PPAR-γ/RXR-α to suppress the LPS- and TNF-α-induced activation of TLR4/MAPK/NF-κB and NF-κB/MLCK/MLC2 signal pathways. Moreover, further mechanism study indicated that forsythiaside A showed a cell-specific regulatory effect on PPAR-γ/RXR-α complex. Specifically, the PPAR-γ/RXR-α protein interactions were promoted by forsythiaside A in LPS-induced macrophages RAW264.7 and TNF-α-induced lung epithelial cells A549, but inhibited by forsythiaside A in TNF-α-induced colon epithelial cells SW620.

CONCLUSION

In the treatment of ALI, Forsythiaside A inhibited inflammation and epithelial barrier damages of lung and colon through its regulation on PPAR-γ/RXR-α complex.

Impact of conjugation to different lipids on the lymphatic uptake and biodistribution of brush PEG polymers

Delivery to peripheral lymphatics can be achieved following interstitial administration of nano-sized delivery systems (nanoparticles, liposomes, dendrimers etc) or molecules that hitchhike on endogenous nano-sized carriers (such as albumin). The published work concerning the hitchhiking approach has mostly focussed on the lymphatic uptake of vaccines conjugated directly to albumin binding moieties (ABMs such as lipids, Evans blue dye derivatives or peptides) and their subsequent trafficking into draining lymph nodes. The mechanisms underpinning access and transport of these constructs into lymph fluid, including potential interaction with other endogenous nanocarriers such as lipoproteins, have largely been ignored. Recently, we described a series of brush polyethylene glycol (PEG) polymers containing end terminal short-chain or medium-chain hydrocarbon tails (1C2 or 1C12, respectively), cholesterol moiety (Cho), or medium-chain or long-chain diacylglycerols (2C12 or 2C18, respectively). We evaluated the association of these materials with albumin and lipoprotein in rat plasma, and their intravenous (IV) and subcutaneous (SC) pharmacokinetic profiles. Here we fully detail the association of this suite of polymers with albumin and lipoproteins in rat lymph, which is expected to facilitate lymph transport of the materials from the SC injection site. Additionally, we characterise the thoracic lymph uptake, tissue and lymph node biodistribution of the lipidated brush PEG polymers following SC administration to thoracic lymph cannulated rats. All polymers had moderate lymphatic uptake in rats following SC dosing with the lymph uptake higher for 1C2-PEG, 2C12-PEG and 2C18-PEG (5.8%, 5.9% and 6.7% dose in lymph, respectively) compared with 1C12-PEG and Cho-PEG (both 1.5% dose in lymph). The enhanced lymph uptake of 1C2-PEG, 2C12-PEG and 2C18-PEG appeared related to their association profile with different lipoproteins. The five polymers displayed different biodistribution patterns in major organs and tissues in mice. All polymers reached immune cells deep within the inguinal lymph nodes of mice following SC dosing. The ability to access these immune cells suggests the potential of the polymers as platforms for the delivery of vaccines and immunotherapies. Future studies will focus on evaluating the lymphatic targeting and therapeutic potential of drug or vaccine-loaded polymers in pre-clinical disease models.

ANALYSIS AND IDENTIFICATION OF FERROPTOSIS-RELATED GENE SIGNATURE FOR ACUTE LUNG INJURY

ABSTRACT

Background: Recent studies have shown that ferroptosis is involved in the evolution of acute lung injury (ALI), a serious respiratory pathological process leading to death. However, the regulatory mechanisms underlying ferroptosis in ALI remain largely unknown. The current study analyzed and identified a ferroptosis-related gene signature for ALI. Methods: Key genes associated with ferroptosis in ALI were identified by bioinformatics analysis. GSE104214, GSE18341, and GSE17355 datasets were downloaded from the Gene Expression Omnibus database. The signature genes were screened by least absolute shrinkage and selection operator regression, and the key genes of ALI were screened by weighted correlation network analysis (WGCNA), followed by immune infiltration analysis and functional enrichment analysis. In addition, mRNA expression of key genes in the lungs of mice with hemorrhagic shock (HS) and sepsis was verified. Results: A total of 2,132 differential genes were identified by various analyses, and 9 characteristic genes were detected using Lasso regression. We intersected nine signature genes with WGCNA module genes and finally determined four key genes ( PROK2 , IL6 , TNF , SLC7A11 ). All four key genes were closely correlated with immune cells and regulatory genes of ALI, and the expression of the four genes was significantly different in the lung tissues of HS and sepsis models. Besides, the ferroptosis-related molecules GPX4 and ACSL4 showed remarkable difference in these models. Conclusion: These results indicate that PROK2 , IL6 , TNF , and SLC7A11 may be key regulatory targets of ferroptosis during ALI. This study proved that ferroptosis is a common pathophysiological process in three ALI models.

Tributyrin Supplementation Rescues Chronic-Binge Ethanol-Induced Oxidative Stress in the Gut-Lung Axis in Mice

Excessive alcohol consumption increases the severity and worsens outcomes of pulmonary infections, often due to oxidative stress and tissue damage. While the mechanism behind this relationship is multifaceted, recent evidence suggests ethanol-induced changes to the gut microbiome impact the gut-lung axis. To assess this, a chronic-binge ethanol feeding mouse model was used to determine how ethanol altered the gut microbiome, small intestinal epithelial barrier, and immune responses, as well as neutrophil abundance and oxidative stress in the lungs, and how supporting gut health with tributyrin supplementation during chronic-binge ethanol exposure affected these responses. We found that ethanol consumption altered gut bacterial taxa and metabolic processes, distorted small intestinal immune responses, and induced both bacteria and endotoxin translocation into the lymphatic and circulatory systems. These changes were associated with increased neutrophil (Ly6G) presence and markers of oxidative stress, lipocalin-2 and myeloperoxidase, in the lungs. Importantly, tributyrin supplementation during ethanol exposure rescued gut bacterial function (p < 0.05), small intestinal barrier integrity, and immune responses, as well as reducing both Ly6G mRNA (p < 0.05) and lipocalin-2 mRNA (p < 0.01) in the lungs. These data suggest ethanol-associated disruption of gut homeostasis influenced the health of the lungs, and that therapeutics supporting gut health may also support lung health.

People are an organic unity: Gut-lung axis and pneumonia

People are an organic unity. Every organ of our body doesn't exist alone. They are a part of our body and have important connections with other tissues or organs. The gut-lung axis is a typical example. Here, we reviewed the current research progress of the gut-lung axis. The main cross-talk between the intestine and lungs was sorted out, i.e. the specific interaction content contained in the gut-lung axis. We determine a relatively clear concept for the gut-lung axis, that is, the gut-lung axis is a cross-talk that the gut and lungs interact with each other through microorganisms and the immune system to achieve bidirectional regulation. The gut and lungs communicate with each other mainly through the immune system and symbiotic microbes, and these two pathways influence each other. The portal vein system and mesenteric lymphatics are the primary communication channels between the intestine and lungs. We also summarized the effects of pneumonia, including Coronavirus disease 2019 (COVID-19) and Community-Acquired Pneumonia (CAP), on intestinal microbes and immune function through the gut-lung axis, and discussed the mechanism of this effect. Finally, we explored the value of intestinal microbes and the gut-lung axis in the treatment of pneumonia through the effect of intestinal microbes on pneumonia.

Impact of hyperoxia on the gut during critical illnesses

Molecular oxygen is typically delivered to patients via oxygen inhalation or extracorporeal membrane oxygenation (ECMO), potentially resulting in systemic hyperoxia from liberal oxygen inhalation or localized hyperoxia in the lower body from peripheral venoarterial (VA) ECMO. Consequently, this exposes the gastrointestinal tract to excessive oxygen levels. Hyperoxia can trigger organ damage due to the overproduction of reactive oxygen species and is associated with increased mortality. The gut and gut microbiome play pivotal roles in critical illnesses and even small variations in oxygen levels can have a dramatic influence on the physiology and ecology of gut microbes. Here, we reviewed the emerging preclinical evidence which highlights how excessive inhaled oxygen can provoke diffuse villous damage, barrier dysfunction in the gut, and gut dysbiosis. The hallmark of this dysbiosis includes the expansion of oxygen-tolerant pathogens (e.g., Enterobacteriaceae) and the depletion of beneficial oxygen-intolerant microbes (e.g., Muribaculaceae). Furthermore, we discussed potential impact of oxygen on the gut in various underlying critical illnesses involving inspiratory oxygen and peripheral VA-ECMO. Currently, the available findings in this area are somewhat controversial, and a consensus has not yet to be reached. It appears that targeting near-physiological oxygenation levels may offer a means to avoid hyperoxia-induced gut injury and hypoxia-induced mesenteric ischemia. However, the optimal oxygenation target may vary depending on special clinical conditions, including acute hypoxia in adults and neonates, as well as particular patients undergoing gastrointestinal surgery or VA-ECMO support. Last, we outlined the current challenges and the need for future studies in this area. Insights into this vital ongoing research can assist clinicians in optimizing oxygenation for critically ill patients.

Dynamic changes in the migratory microbial components of colon tissue during different periods of sepsis in an LPS-induced rat model

Previous studies have shown that bacterial translocation may play an important role in worsening gastrointestinal injury during sepsis. However, the dynamics of specific microbiota components in intestinal tissues at different sepsis stages remain unclear. Rats receiving intraperitoneal lipopolysaccharide (LPS) were sacrificed at 12 h and 48 h post-injection. Routine blood, serum cytokines, and microbiota in colon tissue, colonic contents, and lung tissue at different time points were assessed. Migratory microbial components in colonic tissue at 12 h and 48 h post-LPS were identified using source tracking, characteristic component identification, and abundance difference analyses. Colonic tissue microbiota changed dynamically over time after LPS injection, involving translocation of microbial components from colon contents and lung tissue at different time points. Bacteria migrating to colon tissue at 12 h sepsis were mainly from colonic contents, while those at 48 h were predominantly from the lung tissue. The migratory microbial components in colon tissue were widely associated with blood indicators and colonizing genus abundance and microbiota functionality in colon tissue. In this study, the temporal dynamics of bacterial translocation from various sources into colon tissues at different sepsis progression stages were characterized for the first time, and the species composition of these migrating microbes was delineated. These bacterial migrants may contribute to the pathophysiological processes in sepsis through direct interactions or indirectly by modulating colonic microbiota community structure and function.

Peptoniphilus gorbachii alleviates collagen-induced arthritis in mice by improving intestinal homeostasis and immune regulation

Introduction

The intricate connection between gut microbiota and rheumatoid arthritis (RA) pathogenesis has gained prominence, although the specific microbial species contributing to RA development remain largely unknown. Recent studies have sought to comprehensively explore alterations in the human microbiome, focusing on identifying disease-related microbial species through blood analysis. Consequently, this study aimed to identify RA-associated microbial species using a serum microbial array system and to investigate the efficacy and underlying mechanisms of potential microbial species for RA treatment.

Methods

Serum immunoglobulin M levels against 384 intestinal microbial species were assessed using a microbial microarray in patients with RA and healthy individuals. We investigated the therapeutic potential of the identified microbial candidate regarding arthritis development, immune responses, gut barrier function, and gut microbiome using a collagen-induced arthritis (CIA) mouse model.

Results

Our findings revealed significant alterations in antibody levels against 36 microbial species in patients with RA compared to healthy individuals. Notably, the antibody levels against Peptoniphilus gorbachii (PG) were decreased in patients with RA and exhibited an inverse correlation with RA disease activity. In vitro experiments demonstrated that PG produced acetate and butyrate, while exhibiting anti-inflammatory properties. In CIA mice, PG administration suppressed arthritis symptoms, reduced the accumulation of inflammatory monocytes in the mesenteric lymph nodes, and downregulated gene expression of pro-inflammatory cytokines in the ileum. Additionally, PG supplementation restored intestinal barrier integrity and partially resolved gut microbial dysbiosis in CIA mice. The fecal microbiota in PG-treated mice corresponded to improved intestinal barrier integrity and reduced inflammatory responses.

Conclusion

This study highlights the potential of serum-based detection of anti-microbial antibodies to identify microbial targets at the species level for RA treatment. Moreover, our findings suggest that PG, identified through the microbial microarray analysis, holds therapeutic potential for RA by restoring intestinal barrier integrity and suppressing the immunologic response associated with RA.

Lung protection of Chimonanthus nitens Oliv. essential oil driven by the control of intestinal disorders and dysbiosis through gut-lung crosstalk

This work aimed to investigate whether Chimonanthus nitens Oliv. essential oil (CEO)-mediated lung protection was implicated in gut-lung crosstalk. Results showed that CEO attenuated lung and intestinal impairment by improving histopathological changes and inhibiting TLR4/NF-κB signaling pathway in LPS-stimulated rats, suggesting that there might be a mechanism for its lung protection involved in gut-lung interaction through manipulating the overlap in pathological changes via the similar inflammatory response. Furthermore, CEO-triggered intestinal protection was in parallel with the mitigation of ROS production, apoptosis, Ca2+ transport and mitochondrial membrane potential loss in vivo, and its intestinal protection was confirmed in vitro through IEC-6 cells. Importantly, a combination with CEO and LPS significantly remodeled gut microbiota composition compared with LPS alone in rats, while no significant impact on lung microbiota. Therefore, CEO-exerted lung protection was linked to gut and lung interactions involvement with the control of intestinal disorders and dysbiosis.

A severe case of disseminated cryptococcosis in a young French bulldog living in South-East Queensland caused by Cryptococcus gattii VGII

BACKGROUND

Cryptococcus is one of the most common systemic mycosis worldwide, infecting young adults of the large to giant breed dogs. Infection is commonly acquired from the environment via the sinonasal cavity as the main portal of entry. It either remains there, or spreads to the central nervous system (CNS) and the eye (optic nerve and retina) by penetration of the cribriform plate, or haematogenously to other viscera. Lung involvement is uncommon in cats and dogs in contrast to human and equine patients. Whilst there is a wide genetic diversity amongst Cryptococcus neoformans and Cryptococcus gattii isolates along the West Coast and Northern parts of Australia, the molecular diversity of C. gatti is considered very low on the East Coast of Australia, with a huge preponderance of VGI cases. We report on a young small breed brachycephalic dog that presented with extreme gastrointestinal and respiratory signs, but no CNS involvement. It is the first reported case of C. gattii VGII genotype in a companion animal from Queensland.

CASE REPORT

A 9-month old female entire French Bulldog presented initially for diarrhoea. Clinical progression was accompanied by the development of respiratory signs, so the patient was referred to a 24 h care facility. Following hospitalisation, the patient became hypoxemic requiring mechanical ventilation. A bronchoalveolar lavage performed antemortem confirmed abundant Cryptococcal spp. Further culturing and genotyping identified the species as Cryptococcus gattii VGII. Post-mortem findings indicated gross gastrointestinal and mesenteric involvement, with possible dissemination to the local mesenteric lymph node and lungs.

CONCLUSION

This case describes a rare example of a Cryptococcus spp suspected of disseminating from the gastrointestinal tract to the lungs, without involvement of the CNS. The observation of this finding in a small brachycephalic breed is unusual, and the finding of genotype VGII on the East Coast of Queensland is extremely unusual as there is no prior travel history of the dog or owners. The presence of a miliary lung pattern with primary gastrointestinal disease in a small breed dog warrants adding cryptococcosis to the differential diagnosis.

An underlying mechanism behind interventional pulmonology techniques for refractory asthma treatment: Neuro-immunity crosstalk

Asthma is a common disease that seriously threatens public health. With significant developments in bronchoscopy, different interventional pulmonology techniques for refractory asthma treatment have been developed. These technologies achieve therapeutic purposes by targeting diverse aspects of asthma pathophysiology. However, even though these newer techniques have shown appreciable clinical effects, their differences in mechanisms and mutual commonalities still deserve to be carefully explored. Therefore, in this review, we summarized the potential mechanisms of bronchial thermoplasty, targeted lung denervation, and cryoablation, and analyzed the relationship between these different methods. Based on available evidence, we speculated that the main pathway of chronic airway inflammation and other pathophysiologic processes in asthma is sensory nerve-related neurotransmitter release that forms a "neuro-immunity crosstalk" and amplifies airway neurogenic inflammation. The mechanism of completely blocking neuro-immunity crosstalk through dual-ablation of both efferent and afferent fibers may have a leading role in the clinical efficacy of interventional pulmonology in the treatment of asthma and deserves further investigation.

Causal effects of the gut microbiome on COVID-19 susceptibility and severity: a two-sample Mendelian randomization study

Background

The coronavirus disease 2019 (COVID-19) caused a global pandemic, with potential severity. We aimed to investigate whether genetically predicted gut microbiome is associated with susceptibility and severity of COVID-19 risk.

Methods

Mendelian randomization (MR) analysis of two sets with different significance thresholds was carried out to infer the causal relationship between the gut microbiome and COVID-19. SNPs associated with the composition of the gut microbiome (n = 5,717,754) and with COVID-19 susceptibility (n = 14,328,058), COVID-19 severity (n = 11,707,239), and COVID-19 hospitalization (n = 12,018,444) from publicly available genome-wide association studies (GWAS). The random-effect inverse variance weighted (IVW) method was used to determine causality. Three more MR techniques-MR Egger, weighted median, and weighted mode-and a thorough sensitivity analysis were also used to confirm the findings.

Results

IVW showed that 18 known microbial taxa were causally associated with COVID-19. Among them, six microbial taxa were causally associated with COVID-19 susceptibility; seven microbial taxa were causally associated with COVID-19 severity ; five microbial taxa were causally associated with COVID-19 hospitalization. Sensitivity analyses showed no evidence of pleiotropy or heterogeneity. Then, the predicted 37 species of the gut microbiome deserve further study.

Conclusion

This study found that some microbial taxa were protective factors or risky factors for COVID-19, which may provide helpful biomarkers for asymptomatic diagnosis and potential therapeutic targets for COVID-19.

Imbalance of gut microbiota is involved in the development of chronic obstructive pulmonary disease: A review

Chronic obstructive pulmonary disease (COPD) is a common chronic disease characterized by chronic airway inflammation and remodeling, which seriously endangers human health. Recent developments in genomics and metabolomics have revealed the roles of the gut microbiota and its metabolites in COPD. Dysbiosis of the gut microbiota directly increases gut permeability, thereby promoting the translocation of pathological bacteria. The gut microbiota and associated metabolites may influence the development and progression of COPD by modulating immunity and inflammation. Furthermore, the systemic hypoxia and oxidative stress that occur in COPD may also be involved in intestinal dysfunction. The cross-talk between the gut and lungs is known as the gut-lung axis; however, an overview of its mechanism is lacking. This review highlights the critical and complex interplay of gut microbiota and immune responses in the gut-lung axis, further explores possible links between the gut and lungs, and summarizes new interventions through diet, probiotics, vitamins, and fecal microbiota transplantation, which are critical to COPD.

Podoplanin-positive dilated lymphatic vessels in duodenum associates with three-month mortality in patients with cirrhosis

Dilated and dysfunctional gut lymphatic vessels (LVs) have been reported in experimental cirrhosis. Here, we studied LVs in duodenal (D2)-biopsies of liver cirrhosis patients and investigated the prognostic role of a LV marker, podoplanin (PDPN), in predicting the mortality of patients with cirrhosis. A prospective, single-center cohort study was performed in liver cirrhosis patients (n = 31) and matched healthy controls (n = 9). D2-biopsies were obtained during endoscopy procedure, immunostained with PDPN, and scored based on 1) intensity and 2) density of positively-stained LVs per high power field. Gut and systemic inflammation were estimated by quantifying duodenal CD3⁺ intraepithelial lymphocytes (IELs), CD68⁺ macrophages, and serum TNF-α and IL-6 levels, respectively. Gut permeability and inflammation as assessed by quantifying gene expression of TJP1, OCLN, TNF-α, and IL-6 in D2-biopsies. Gene expression of LV markers, PDPN (8-fold), and LYVE1 (3-fold) was enhanced in D2-biopsies of cirrhosis patients compared to control (p < 0.0001). The mean PDPN score in decompensated cirrhosis patients (6.91 ± 1.26, p < 0.0001) was significantly increased as compared to those with compensated (3.25 ± 1.60). PDPN score positively and significantly correlated with the number of IELs (r = 0.33), serum TNF-α (r = 0.35), and IL-6 (r = 0.48) levels, while inversely correlated with TJP1 expression (r = -0.46, p < 0.05 each). In Cox regression, the PDPN score was a significant and independent 3-month-mortality predictor in patients (HR: 5.61; 1.08-29.109; p = 0.04). The area under the curve for the PDPN score was 84.2, and cutoff value for predicting mortality was ≥6.5 with 100% sensitivity and 75% specificity. Collectively, dilated LVs with high PDPN expression in D2-biopsies is a characteristic feature of patients with decompensated cirrhosis. PDPN score correlates with enhanced gut and systemic inflammation and also associates with 3-month mortality in cirrhosis.

Ablation of CD226 on CD4+ T cells modulates asthma progress associated with altered IL-10 response and gut microbiota

To investigate the role of the costimulatory molecule CD226 in asthma pathogenesis, we produced a CD4⁺ T-cell-specific CD226 knockout mice model (Cd226^ΔCD4) and induced airway allergic inflammation by administering ovalbumin (OVA). Our results revealed alleviated lung inflammation, decreased levels of OVA-specific IgE, and increased levels of IL-10 in the serum of Cd226^ΔCD4 mice (P < 0.05). Moreover, IL-10 levels in CD4⁺ T cells were significantly elevated in the mediastinal lymph node, spleen, and Peyer's patches in the Cd226^ΔCD4 mice compared with those in controls (P < 0.05 to P < 0.01). Notably, there was a significantly higher IL-10 mRNA levels in the large intestine of the mice (P < 0.05). The protective effect of CD226 deficiency is also associated with the accumulation of gut TCRγδ⁺ intraepithelial lymphocytes and reversion of the gut microbiome dysbiosis. The Bacteroidetes-to-Firmicutes ratio and the abundance of Akkermansia increased in the absence of CD226 after OVA treatment. Our data reveal the synchronous changes in the lung and intestine in OVA-treated CD226-knockout mice, supporting the gut-lung axis concept and providing evidence for novel therapeutic approaches for asthma.

Omega-3 polyunsaturated fatty acids alleviates lung injury mediated by post-hemorrhagic shock mesenteric lymph

Severe hemorrhage-induced acute lung injury (ALI) remains the major contributor to critical patient mortality and is associated with posthemorrhagic shock mesenteric lymph (PHSML) return. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) play overall protection on acute hemorrhage, but a reliable mechanism needs to be identified. The aims of this study were to investigate the role of ω-3 PUFAs in alleviating ALI and whether is related to the endotoxin contained in PHSML. Mesenteric lymph was harvested from rats subjected to hemorrhagic shock (hemorrhage-induced hypotension of 40 ± 2 mmHg for 90 min plus by resuscitation) or sham shock. The effect of ω-3 PUFAs on pulmonary function, water content, morphology, and LBP, CD14, TNF-α, and IL-6 levels were observed in rats subjected to hemorrhagic shock, while the effect of PHSML intravenous infusion on the beneficial effect of ω-3 PUFAs also was investigated. In addition, the effect of ω-3 PUFAs on the endotoxin contents in mesenteric lymph were detected. Hemorrhagic shock-induced ALI was characterized by increased functional residual capacity (FRC), lung resistance (RI), inspiratory capacity (IC), respiratory frequency, water contents and structural damage, along with increases in LBP, IL-6, and TNF-α. ω-3 PUFAs treatment reduced FRC, RI, IC, frequency, water contents, LBP, IL-6, TNF-α, and alleviated morphological damage. In contrast, PHSML infusion abolished the advantageous effects of ω-3 PUFAs on the above indices and CD14. Furthermore, the endotoxin level of PHSML was significantly enhanced, but declined following ω-3 PUFAs administration. These findings together suggested that treatment with ω-3 PUFAs ameliorates hemorrhagic shock-induced ALI, which is associated with reduced endotoxin contained in PHSML.

Gut-lung crosstalk during critical illness

PURPOSE OF REVIEW

Study of organ crosstalk in critical illness has uncovered complex biological communication between different organ systems, but the role of microbiota in organ crosstalk has received limited attention. We highlight the emerging understanding of the gut-lung axis, and how the largest biomass of the human body in the gut may affect lung physiology in critical illness.

RECENT FINDINGS

Disruption of healthy gut microbial communities and replacement by disease-promoting pathogens (pathobiome) generates a maladaptive transmitter of messages from the gut to the lungs, connected via the portal venous and the mesenteric lymphatic systems. Gut barrier impairment allows for microbial translocation (living organisms or cellular fragments) to the lungs. Host-microbiota interactions in the gut mucosa can also impact lung physiology through microbial metabolite secretion or host-derived messengers (hormones, cytokines or immune cells). Clinical examples like the prevention of ventilator-associated pneumonia by selective decontamination of the digestive tract show that the gut-lung axis can be manipulated therapeutically.

SUMMARY

A growing body of evidence supports the pathophysiological relevance of the gut-lung axis, yet we are only at the brink of understanding the therapeutic and prognostic relevance of the gut microbiome, metabolites and host-microbe interactions in critical illness.

Medical and Surgical Implications of Mesenteric Adipose Tissue in Crohn's Disease: A Review of the Literature

Mesenteric adipose tissue (MAT) has gained substantial attention as an active player in Crohn's disease (CD), but its clinical significance is poorly understood and likely reflects, in part, difficulties assessing MAT noninvasively. Recent radiologic studies have identified candidate surrogate markers that may reflect inflammatory alterations of MAT in CD and have found that certain features including visceral adipose tissue may inform risk of complicated disease behavior, risk for surgery, and postoperative outcomes. Additionally, emerging surgical data have suggested MAT may even be a therapeutic target to mitigate postoperative recurrence of CD. However, the current studies have variable results, reduced sample sizes, and methodological limitations that preclude incorporating the radiologic and surgical findings into clinical practice. Nonetheless, the results are promising and potentially have important implications for the medical and surgical management of CD, which merits that additional studies are warranted. Thus, we have reviewed the available literature on the medical and surgical implications of MAT in CD to summarize our current understanding and identify gaps in knowledge to inform future investigations.

Systematic identification of the interventional mechanism of Qingfei Xiaoyan Wan (QFXYW) in treatment of the cytokine storm in acute lung injury using transcriptomics-based system pharmacological analyses

CONTEXT

Acute lung injury (ALI) is a complex, severe inflammation disease with high mortality, and there is no specific and effective treatment for ALI. Qingfei Xiaoyan Wan (QFXYW) has been widely used to treat lung-related diseases for centuries.

OBJECTIVE

This study evaluates the potential effects and elucidates the therapeutic mechanism of QFXYW against LPS induced ALI in mice.

MATERIALS AND METHODS

BALB/c Mice in each group were first orally administered medicines (0.9% saline solution for the control group, 0.5 mg/kg Dexamethasone, or 1.3, 2.6, 5.2 g/kg QFXYW), after 4 h, the groups were injected LPS (1.0 mg/kg) to induce ALI, then the same medicines were administered repeatedly. The transcriptomics-based system pharmacological analyses were applied to screen the hub genes, RT-PCR, ELISA, and protein array assay was applied to verify the predicted hub genes and key pathways.

RESULTS

QFXYW significantly decreased the number of leukocytes from (6.34 ± 0.51) × 10⁵/mL to (4.01 ± 0.11) × 10⁵/mL, accompanied by the neutrophil from (1.41 ± 0.19) × 10⁵/mL to (0.77 ± 0.10) × 10⁵/mL in bronchoalveolar lavage fluid (BALF). Based on Degree of node connection (Degree) and BottleNeck (BN), important parameters of network topology, the protein-protein interaction (PPI) network screened hub genes, including IL-6, TNF-α, CCL2, TLR2, CXCL1, and MMP-9. The results of RT-PCR, ELISA, and protein chip assay revealed that QFXYW could effectively inhibit ALI via multiple key targets and the cytokine-cytokine signalling pathway.

CONCLUSIONS

This study showed that QFXYW decreased the number of leukocytes and neutrophils by attenuating inflammatory response, which provides an important basis for the use of QFXYW in the treatment of ALI.

Simvastatin protects against intestinal ischemia/reperfusion-induced pulmonary artery dysfunction

AIMS

The lung is an important target organ damage in intestinal ischemia/reperfusion (II/R), but mechanisms involved in II/R-induced pulmonary artery (PA) dysfunction, as well as its treatment, are not clear. The present study aimed to investigate the mechanisms involved in the II/R-induced PA dysfunction and a possible protective role of acute simvastatin pretreatment.

MAIN METHODS

Male Wistar rats were subjected to occlusion of the superior mesenteric artery for 45 min followed by 2 h reperfusion (II/R) or sham-operated surgery (sham). In some rats, simvastatin (20 mg/kg, oral gavage) was administrated 1 h before II/R.

KEY FINDINGS

II/R reduced acetylcholine-induced relaxation and phenylephrine-induced contraction of PA segments, which were prevented by acute simvastatin pretreatment in vivo or restored by inducible nitric oxide synthase (iNOS) inhibition in situ with 1400 W. Elevated reactive oxygen species (ROS) levels and higher nuclear translocation of nuclear factor kappa B (NFκB) subunit p65 were observed in PA of II/R rats and prevented by simvastatin. Moreover, simvastatin increased superoxide dismutase (SOD) activity and endothelial nitric oxide synthase (eNOS) expression in PA of the II/R group as well as prevented the increased levels of interleukin (IL)-1β and IL-6 in lung explants following II/R.

SIGNIFICANCE

The study suggests that pretreatment with a single dose of simvastatin prevents the II/R-induced increase of inflammatory factors and oxidative stress, as well as PA endothelial dysfunction and adrenergic hyporreactivity. Therefore, acute simvastatin administration could be therapeutic for pulmonary vascular disease in patients suffering from intestinal ischemic events.

The gut-lung axis: Gut microbiota changes associated with pulmonary fibrosis in mouse models induced by bleomycin

The main objective of this study was to investigate the alterations in the gut microbiota (GM) of pulmonary fibrosis (PF) mice induced by bleomycin (BLM) with its underlying mechanisms. BLM was docked with the targets of TGF-β/SMAD and caspase-3 pathways using the molecular docking technique. HE staining and Masson staining were applied to observe the histopathological changes in the pulmonary tissues. Detection of the apoptotic signals was conducted by flow cytometry and TUNEL staining. The mRNA expression of targets involved in the TGF-β/SMAD and caspase-3 signaling pathways in lungs was determined by qPCR. Immunohistochemistry (IHC) assay was used to detect the expression levels of cleaved caspase-3 and BAX proteins in mice lung tissues. 16S rDNA sequencing analysis was used to investigate the changes of GM in the fecal samples of mice in each group. The results showed that the apoptosis rate of pulmonary cells in the BLM group distinctly increased, with the expression levels of crucial target pro-apoptotic gene caspase-3, BAX with the corresponding protein, cleaved caspase-3, BAX were apparently elevated. This was accompanied by a significant increase in pro-fibrotic targets level such as TGF-β, fibronectin, collagen I, and collagen III. The mechanisms of PF induced by BLM were related to apoptosis of lung tissue cells such as alveolar epithelial cells and destroyed alveolar structure and excessive production of extracellular matrix (ECM), which may be bound up with activating TGF-β/SMAD and caspase-3 pathways. As for the GM, it was found that, after BLM induced PF in mice, the micro ecological balance of the GM was destroyed; the distance of PCo1 and Pco2 was significantly elongated, and the relative abundance of some intestinal probiotics like Catenibacterium and Lactobacillus (L. johnsonii and L. gasseri) dramatically lowered while the relative abundance of Verrucomicrobiales and Enterobacteriales substantially increased. Therefore, GM changes associated with PF in mouse models induced by BLM and the concept of "gut-lung axis" might provide an optional therapeutic strategy for PF.

Friendly fungi: symbiosis with commensal Candida albicans

Mucosal tissues are constitutively colonized by a wide assortment of host-adapted microbes. This includes the polymorphic fungus Candida albicans which is a primary target of human adaptive responses. Immunogenicity is replicated after intestinal colonization in preclinical models with a surprising array of protective benefits for most hosts, but harmful consequences for a few. The interaction between fungus and host is complex, and traditionally, the masking of antigenic fungal ligands has been viewed as a tactic for fungal immune evasion during invasive infection. However, we propose that dynamic expression of cell wall moieties, host cell lysins, and other antigenic C. albicans determinants is necessary during the more ubiquitous context of intestinal colonization to prime immunogenicity and optimize mammalian host symbiosis.

Potential roles of gut microbial tryptophan metabolites in the complex pathogenesis of acne vulgaris

Acne vulgaris is a chronic inflammatory skin disease in which the influence of gut microbiota has been implicated but without clarification of mechanisms. Gut microbiota may exert such an influence via metabolites, particularly those of tryptophan. End metabolites of tryptophan activate receptors, including aryl hydrocarbon, G protein-coupled, and pregnane X receptors to stabilize the immune microenvironment and intestinal mucosal homeostasis. Any impact on the pathogenesis of acne vulgaris remains unclear. The current review collates recent advances concerning potential roles of tryptophan metabolism in mediating skin inflammation, follicular sebaceous gland function and intestinal permeability, all of which influence the pathogenesis of acne vulgaris. The aim was to improve understanding of the pathogenesis of acne vulgaris and to expose therapeutic opportunities.

Probiotics: Protecting Our Health from the Gut

The gut microbiota (GM) comprises billions of microorganisms in the human gastrointestinal tract. This microbial community exerts numerous physiological functions. Prominent among these functions is the effect on host immunity through the uptake of nutrients that strengthen intestinal cells and cells involved in the immune response. The physiological functions of the GM are not limited to the gut, but bidirectional interactions between the gut microbiota and various extraintestinal organs have been identified. These interactions have been termed interorganic axes by several authors, among which the gut-brain, gut-skin, gut-lung, gut-heart, and gut-metabolism axes stand out. It has been shown that an organism is healthy or in homeostasis when the GM is in balance. However, altered GM or dysbiosis represents a critical factor in the pathogenesis of many local and systemic diseases. Therefore, probiotics intervene in this context, which, according to various published studies, allows balance to be maintained in the GM, leading to an individual's good health.

Murine in utero exposure to simulated complex urban air pollution disturbs offspring gut maturation and microbiota during intestinal suckling-to-weaning transition in a sex-dependent manner

Background

Emerging data indicate that prenatal exposure to air pollution may lead to higher susceptibility to several non-communicable diseases. Limited research has been conducted due to difficulties in modelling realistic air pollution exposure. In this study, pregnant mice were exposed from gestational day 10–17 to an atmosphere representative of a 2017 pollution event in Beijing, China. Intestinal homeostasis and microbiota were assessed in both male and female offspring during the suckling-to-weaning transition.

Results

Sex-specific differences were observed in progeny of gestationally-exposed mice. In utero exposed males exhibited decreased villus and crypt length, vacuolation abnormalities, and lower levels of tight junction protein ZO-1 in ileum. They showed an upregulation of absorptive cell markers and a downregulation of neonatal markers in colon. Cecum of in utero exposed male mice also presented a deeply unbalanced inflammatory pattern. By contrast, in utero exposed female mice displayed less severe intestinal alterations, but included dysregulated expression of Lgr5 in colon, Tjp1 in cecum, and Epcam, Car2 and Sis in ileum. Moreover, exposed female mice showed dysbiosis characterized by a decreased weighted UniFrac β-diversity index, a higher abundance of Bacteroidales and Coriobacteriales orders, and a reduced Firmicutes/Bacteroidetes ratio.

Conclusion

Prenatal realistic modelling of an urban air pollution event induced sex-specific precocious alterations of structural and immune intestinal development in mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00481-y.

Revisiting the gut-liver axis: gut lymphatic system in liver cirrhosis and portal hypertension

The lymphatic vascular system runs parallel to the blood vascular system, comprising a network of lymphatic vessels and secondary lymphoid organs. The intestinal lymphatic capillaries (lacteals) and the associated collecting vessels in the mesentery form the gut lymphatic system. The gut lymphatic vasculature comprises the longest-studied lymphatic vessel bed and plays a significant role in the uptake and transport of dietary fat, abdominal fluid balance, and gut immunosurveillance. Gut is closely connected to liver through the portal circulation. In several experimental and clinical studies, the "gut-liver-axis" has been demonstrated to contribute to the pathogenesis of portal hypertension, liver cirrhosis, and its complications. Given a significant impact of gut health on the liver, in the current review, we highlight "gut-liver axis" in context to the circulatory physiology of gut lymphatic vessels. Despite their paramount importance in maintaining fluid and immune homeostasis in the gut, gut lymphatic vessels remain one of the most understudied physiological systems in liver disease pathology. In the current review, we delineate the connections of gut lymphatics with abdominal fluid homeostasis and bacterial translocation in the pathogenesis of liver cirrhosis and portal hypertension. We describe mechanisms and factors that drive gut lymphangiogenesis and lymphatic vessel dysfunction during inflammation. The review also underscores the role of gut lymphatic endothelial cells in regulating gut and liver immunity. We finally discuss the prognostic and therapeutic prospects of studying gut lymphatic vessels in advanced liver cirrhosis.

Mesenteric Lymph Duct Ligation Alleviates Acute Lung Injury Caused by Severe Acute Pancreatitis Through Inhibition of High Mobility Group Box 1-Induced Inflammation in Rats

BACKGROUND

Acute lung injury (ALI) is the most common complication and one of the leading causes of mortality of severe acute pancreatitis (SAP). Nevertheless, no effective therapeutic schemes are presently available.

AIMS

To investigate the effect and potential mechanism of mesenteric lymph duct ligation (MLDL) on experimental SAP-induced ALI.

METHODS

Immediately following MLDL, rats were subjected to SAP by retrograde injection of 5% sodium taurocholate into the biliopancreatic duct. At 24 h after modeling, tissues were collected for morphological examination. The levels of TNF-α, IL-6, intercellular adhesion molecule-1 (ICAM1), diamine oxidase (DAO), and D-lactic acid (D-LA) in serum, and the myeloperoxidase (MPO) activity in lung tissues were determined. Moreover, the expressions of high mobility group box 1 (HMGB1), receptor of advanced glycation endproducts (RAGE), and NF-κB p65 at the mRNA and protein levels in lung tissues, and the expressions of HMGB1, RAGE, and TNF-α at the mRNA level in intestinal lymphoid tissues were evaluated.

RESULTS

MLDL significantly attenuated the histological injury of the pancreas and lung and reduced the production of TNF-α, IL-6, and ICAM1. Besides, MLDL repressed the activity of MPO in the lung. However, the levels of serum DAO and D-LA were decreased without obvious morphological improvement in intestinal injury. Moreover, MLDL apparently reduced the up-regulation of HMGB1, RAGE, and NF-κB p65 in lung tissues, as well as the expressions of HMGB1, RAGE, and TNF-α in intestinal lymphoid tissues.

CONCLUSIONS

Mesenteric lymph was a source of harmful factors leading to SAP-ALI. MLDL could alleviate SAP-ALI probably by inhibiting HMGB1-induced production of inflammation factors.

Peripheral blood microbial signatures in current and former smokers

The human microbiome has a role in the development of multiple diseases. Individual microbiome profiles are highly personalized, though many species are shared. Understanding the relationship between the human microbiome and disease may inform future individualized treatments. We hypothesize the blood microbiome signature may be a surrogate for some lung microbial characteristics. We sought associations between the blood microbiome signature and lung-relevant host factors. Based on reads not mapped to the human genome, we detected microbial nucleic acids through secondary use of peripheral blood RNA-sequencing from 2,590 current and former smokers with and without chronic obstructive pulmonary disease (COPD) from the COPDGene study. We used the Genome Analysis Toolkit (GATK) microbial pipeline PathSeq to infer microbial profiles. We tested associations between the inferred profiles and lung disease relevant phenotypes and examined links to host gene expression pathways. We replicated our analyses using a second independent set of blood RNA-seq data from 1,065 COPDGene study subjects and performed a meta-analysis across the two studies. The four phyla with highest abundance across all subjects were Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. In our meta-analysis, we observed associations (q-value < 0.05) between Acinetobacter, Serratia, Streptococcus and Bacillus inferred abundances and Modified Medical Research Council (mMRC) dyspnea score. Current smoking status was associated (q < 0.05) with Acinetobacter, Serratia and Cutibacterium abundance. All 12 taxa investigated were associated with at least one white blood cell distribution variable. Abundance for nine of the 12 taxa was associated with sex, and seven of the 12 taxa were associated with race. Host-microbiome interaction analysis revealed clustering of genera associated with mMRC dyspnea score and smoking status, through shared links to several host pathways. This study is the first to identify a bacterial microbiome signature in the peripheral blood of current and former smokers. Understanding the relationships between systemic microbial signatures and lung-related phenotypes may inform novel interventions and aid understanding of the systemic effects of smoking.

Prediction of exacerbation frequency of AECOPD based on next-generation sequencing and its relationship with imbalance of lung and gut microbiota: a protocol of a prospective cohort study

INTRODUCTION

Patients with frequent acute exacerbation phenotype chronic obstructive pulmonary disease (AECOPD) have a higher hospitalisation rate than infrequent exacerbation, the disease progresses quickly and treatment is more difficult. At present, it is impossible to predict patients with COPD with frequent acute exacerbation phenotypes. The composition of the lower respiratory tract flora and the intestinal flora is closely related to AECOPD, but the specific association mechanism between them is not very clear. This study used metagenomic next-generation sequencing (mNGS) technology to explore the microbial characteristics of the intestinal tract and airways of patients with COPD, and analyse the correlation between the sequencing results and inflammatory factors, immune factors and nutritional factors.

METHODS AND ANALYSIS

This will be a prospective cohort study. We intend to recruit 152 patients with stable COPD. In the baseline, we will detect the participants' induced sputum and faecal flora through mNGS, and changes in blood immune levels, and the patient's condition is evaluated. Every 2 months, we will check the number of acute exacerbation through the phone range. After 12 months, we will check again the changes in the blood immune level, evaluate the patient's condition and count the number of episodes.

ETHICS AND DISSEMINATION

This study has been approved by the ethics committee of Guangdong Provincial Hospital of Traditional Chinese Medicine (approval number ZF2019-219-03). The results of the study will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (ChiCTR2000032870).

New insights into lipopolysaccharide inactivation mechanisms in sepsis

The complex pathophysiology of sepsis makes it a syndrome with limited therapeutic options and a high mortality rate. Gram-negative bacteria containing lipopolysaccharides (LPS) in their outer membrane correspond to the most common cause of sepsis. Since the gut is considered an important source of LPS, intestinal damage has been considered a cause and a consequence of sepsis. Although important in the maintenance of the intestinal epithelial cell homeostasis, the microbiota has been considered a source of LPS. Recent studies have started to shed light on how sepsis is triggered by dysbiosis, and an increased inflammatory state of the intestinal epithelial cells, expanding the understanding of the gut-liver axis in sepsis. Here, we review the gut-liver interaction in Gram-negative sepsis, exploring the mechanisms of LPS inactivation, including the recently described contribution of an isoform of the cholesteryl-ester transfer protein (CETPI). Although several key questions remain to be answered when the pathophysiology of sepsis is reviewed, new contributions coming to light exploring the way LPS might be inactivated in vivo, suggest that new applications might soon reach the clinical setting.

Aspiration of conjugated bile acids predicts adverse lung transplant outcomes and correlates with airway lipid and cytokine dysregulation

INTRODUCTION

Duodeno-gastroesophageal reflux aspiration is associated with chronic lung allograft dysfunction (CLAD). Reflux aspirate can contain bile acids (BA), functional molecules in the gastro-intestinal tract with emulsifying properties. We sought to determine and quantify the various BA species in airways of the lung transplant recipients to better understand the various effects of aspirated BA that contribute to post-transplantation outcomes.

METHODS

Bronchial washings (BW) were prospectively collected from lung transplant recipients and subsequently assayed by liquid chromatography-mass spectrometry for 13 BA and 25 lipid families. Patients were monitored for CLAD, rejection, inflammation and airway infections.

RESULTS

Detectable BA were present in 45/50 patients (90%) at 3 months after transplant. Elevated BA and predominance of conjugated species were independent predictors of CLAD (hazard ratio 7.9; 95% confidence interval 2.7-23.6; p < 0.001 and 7.3; 2.4-22; p < 0.001, respectively) and mortality (hazard ratio 4.4; 1.5-12.7; p = 0.007 and 4.8; 1.4-15.8; p = 0.01, respectively). High BA associated with increased positive bacterial cultures (60% vs 25%, p = 0.02). Primary conjugated species independently correlated with the rate of bacterial cultures during the first-year post-transplant (Beta coefficient: 0.77; 0.28-1.26; p = 0.003) and changes in airway lipidome and cytokines.

CONCLUSIONS

Higher BA levels and predominance of conjugated BA are independent predictors of chronic lung allograft dysfunction, mortality and bacterial infections. Primary conjugated BA are related to distinct changes in airway lipidome and inflammatory cytokines. This elucidates novel evidence into the mechanism following BA aspiration and proposes novel markers for prediction of adverse post-transplant outcomes.