Involvement of claudin-5 in H2S-induced acute lung injury

Veronica linariifolia subsp. dilatata ameliorates LPS-induced acute lung injury by attenuating endothelial cell barrier dysfunction via EGFR/Akt/ZO-1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The dried aerial parts of Veronica linariifolia subsp. dilatata (Nakai & Kitag.) D.Y.Hong named Shui Man Jing (SMJ) is a traditional Chinese medicine with a long history of clinical use in the treatment of chronic bronchitis and coughing up blood, however, its role on acute lung injury (ALI) has not been revealed yet.

AIM OF THE STUDY

To assess the efficiency of SMJ on ALI and to investigate whether it inhibited endothelial barrier dysfunction by regulating the EGFR/Akt/ZO-1 pathway to alleviate ALI in vivo and in vitro based on the result of network pharmacology.

MATERIALS AND METHODS

An in vivo model of ALI was established using inhalation of atomized lipopolysaccharide (LPS), and the effects of SMJ on ALI were evaluated through histopathological examination and inflammatory cytokines, lung histology and edema, vascular and alveolar barrier disruption. Network pharmacology was applied to predict the mechanism of SMJ in the treatment of ALI. The crucial targets were validated by RT-PCR, Western Blotting, molecular docking, immunohistochemistry and immunofluorescence methods in vivo and in virto.

RESULTS

Administration of SMJ protected mice against LPS-induced ALI, including ameliorating the histological alterations in the lung tissues, and decreasing lung edema, protein content of bronchoalveolar lavage fluid, infiltration of inflammatory cell and secretion of cytokines. SMJ exerted protective effects in ALI by inhibiting endothelial barrier dysfunction in mice and bEnd.3 cell. SMJ relieved endothelial barrier dysfunction induced by LPS through upregulating the EGFR expression. SMJ also increased the phosphorylation of Akt, and ZO-1 expression both in vivo and in vitro.

CONCLUSION

SMJ attenuates vascular endothelial barrier dysfunction for LPS-induced ALI via EGFR/Akt/ZO-1 pathway, and is a promising novel therapeutic candidate for ALI.

CLDN5: From structure and regulation to roles in tumors and other diseases beyond CNS disorders

Claudin-5 (CLDN5) is an essential component of tight junctions (TJs) and is critical for the integrity of the blood-brain barrier (BBB), ensuring homeostasis and protection from damage to the central nervous system (CNS). Currently, many researchers have summarized the role and mechanisms of CLDN5 in CNS diseases. However, it is noteworthy that CLDN5 also plays a significant role in tumor growth and metastasis. In addition, abnormal CLDN5 expression is involved in the development of respiratory diseases, intestinal diseases, cardiac diseases, and diabetic ocular complications. This paper aims to review the structure, expression, and regulation of CLDN5, focusing on its role in tumors, including its expression and regulation, effects on malignant phenotypes, and clinical significance. Furthermore, this paper will provide an overview of the role and mechanisms of CLDN5 in respiratory diseases, intestinal diseases, cardiac diseases, and diabetic ocular complications.

Countermeasures against Pulmonary Threat Agents

Inhaled toxicants are used for diverse purposes, ranging from industrial applications such as agriculture, sanitation, and fumigation to crowd control and chemical warfare, and acute exposure can induce lasting respiratory complications. The intentional release of chemical warfare agents (CWAs) during World War I caused life-long damage for survivors, and CWA use is outlawed by international treaties. However, in the past two decades, chemical warfare use has surged in the Middle East and Eastern Europe, with a shift toward lung toxicants. The potential use of industrial and agricultural chemicals in rogue activities is a major concern as they are often stored and transported near populated areas, where intentional or accidental release can cause severe injuries and fatalities. Despite laws and regulatory agencies that regulate use, storage, transport, emissions, and disposal, inhalational exposures continue to cause lasting lung injury. Industrial irritants (e.g., ammonia) aggravate the upper respiratory tract, causing pneumonitis, bronchoconstriction, and dyspnea. Irritant gases (e.g., acrolein, chloropicrin) affect epithelial barrier integrity and cause tissue damage through reactive intermediates or by direct adduction of cysteine-rich proteins. Symptoms of CWAs (e.g., chlorine gas, phosgene, sulfur mustard) progress from airway obstruction and pulmonary edema to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which results in respiratory depression days later. Emergency treatment is limited to supportive care using bronchodilators to control airway constriction and rescue with mechanical ventilation to improve gas exchange. Complications from acute exposure can promote obstructive lung disease and/or pulmonary fibrosis, which require long-term clinical care. SIGNIFICANCE STATEMENT: Inhaled chemical threats are of growing concern in both civilian and military settings, and there is an increased need to reduce acute lung injury and delayed clinical complications from exposures. This minireview highlights our current understanding of acute toxicity and pathophysiology of a select number of chemicals of concern. It discusses potential early-stage therapeutic development as well as challenges in developing countermeasures applicable for administration in mass casualty situations.

A comprehensive review of treatments for hydrogen sulfide poisoning: past, present, and future

Hydrogen sulfide (H₂S) poisoning remains a significant source of occupational fatalities and is the second most common cause of toxic gas-induced deaths. It is a rapidly metabolized systemic toxicant targeting the mitochondria, among other organelles. Intoxication is mostly acute, but chronic or in-between exposure scenarios also occur. Some genetic defects in H₂S metabolism lead to lethal chronic H₂S poisoning. In acute exposures, the neural, respiratory, and cardiovascular systems are the primary target organs resulting in respiratory distress, convulsions, hypotension, and cardiac irregularities. Some survivors of acute poisoning develop long-term sequelae, particularly in the central nervous system. Currently, treatment for H₂S poisoning is primarily supportive care as there are no FDA-approved drugs. Besides hyperbaric oxygen treatment, drugs in current use for the management of H₂S poisoning are controversial. Novel potential drugs are under pre-clinical research development, most of which target binding the H₂S. However, there is an acute need to discover new drugs to prevent and treat H₂S poisoning, including reducing mortality and morbidity, preventing sequalae from acute exposures, and for treating cumulative pathology from chronic exposures. In this paper, we perform a comprehensive review of H₂S poisoning including perspectives on past, present, and future.

Tight Junctions, the Epithelial Barrier, and Toll-like Receptor-4 During Lung Injury

Lung epithelium is constantly exposed to the environment and is critically important for the orchestration of initial responses to infectious organisms, toxins, and allergic stimuli, and maintenance of normal gaseous exchange and pulmonary function. The integrity of lung epithelium, fluid balance, and transport of molecules is dictated by the tight junctions (TJs). The TJs are formed between adjacent cells. We have focused on the topic of the TJ structure and function in lung epithelial cells. This review includes a summary of the last twenty years of literature reports published on the disrupted TJs and epithelial barrier in various lung conditions and expression and regulation of specific TJ proteins against pathogenic stimuli. We discuss the molecular signaling and crosstalk among signaling pathways that control the TJ structure and function. The Toll-like receptor-4 (TLR4) recognizes the pathogen- and damage-associated molecular patterns released during lung injury and inflammation and coordinates cellular responses. The molecular aspects of TLR4 signaling in the context of TJs or the epithelial barrier are not fully known. We describe the current knowledge and possible networking of the TLR4-signaling with cellular and molecular mechanisms of TJs, lung epithelial barrier function, and resistance to treatment strategies.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.