Strains of Aeromonas hydrophila isolated from skin infections of common freshwater fish in Bangladesh were tested for enterotoxin production, hemolysin production, and any correlation between these two activities. We also tested the resistance patterns of A. hydrophila to different drugs, especially in relation to ampicillin. The A. hydrophila strains produced an enterotoxin that was related to their beta-hemolytic activities. Production of beta-hemolysin may thus be an indicator of enterotoxicity. As 50% of the strains of A. hydrophila were found to be susceptible to 12.5 ,ug of ampicillin per ml, media containing this antibiotic may not be suitable for their isolation.

Disrupted epithelial barrier, fluid accumulation, inflammation, and compromised physiology are hallmarks of lung injury. Here we investigated the structural stability of the Toll‐like receptor‐4 (TLR4)‐interacting SPA4 peptide, its effect on Pseudomonas aeruginosa lipopolysaccharide (LPS)‐disrupted epithelial barrier in a human cell system, and lung injury markers in a mouse model of LPS‐induced lung inflammation. The structural properties of SPA4 peptide were investigated using circular dichroism and UV–VIS spectroscopy. The transepithelial electrical resistance (TEER), an indicator of barrier function, was measured after the cells were challenged with 1 μg/ml LPS and treated with 10 or 100 μM SPA4 peptide. The expression and localization of tight junction proteins were studied by immunoblotting and immunocytochemistry, respectively. Mice were intratracheally challenged with 5 μg LPS per g body weight and treated with 50 μg SPA4 peptide. The lung wet/dry weight ratios or edema, surfactant protein‐D (SP‐D) levels in serum, lung function, tissue injury, body weights, and temperature, and survival were determined as study parameters. The spectroscopy results demonstrated that the structure was maintained among different batches of SPA4 peptide throughout the study. Treatment with 100 μM SPA4 peptide restored the LPS‐disrupted epithelial barrier, which correlated with the localization pattern of Zonula Occludens (ZO)‐1 and occludin proteins. Correspondingly, SPA4 peptide treatment helped suppress the lung edema and levels of serum SP‐D, improved some of the lung function parameters, and reduced the mortality risk against LPS challenge. Our results suggest that the anti‐inflammatory activity of the SPA4 peptide facilitates the resolution of lung pathology.

The TLR4-interacting SPA4 peptide suppresses inflammation. We assessed the structural and physicochemical properties and binding of SPA4 peptide to TLR4-MD2. We also studied the changes at the whole transcriptome level, cell morphology, viability, secreted cytokines and chemokines, and cell influx in cell systems and mouse models challenged with LPS and treated with SPA4 peptide. Our results demonstrated that the SPA4 peptide did not alter the cell viability and size and only moderately affected the transcriptome of the cells. Computational docking and rendering suggested that the SPA4 peptide intercalates with LPS-induced TLR4-MD2 complex. Results with alanine mutations of D-2 amino acid and NYTXXXRG-12-19 motif of SPA4 peptide suggested their role in binding to TLR4 and in reducing the cytokine response against LPS stimulus. Furthermore, therapeutically administered SPA4 peptide significantly suppressed the secreted levels of cytokines and chemokines in cells and bronchoalveolar lavage fluids of LPS-challenged mice. The results suggest that the SPA4 peptide intercalates with LPS-induced TLR4 complex and signaling for the suppression of inflammation.

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.

Objective: The inquisitive objective of the study was to observe the antimicrobial, cytotoxicity, and antioxidant activities of some newly synthesized metal complexes of tolfenamic acid. Methods: While antimicrobial activity was studied by disk diffusion method, cytotoxicity was studied by performing brine shrimp lethality bioassay. Moreover, DPPH radical scavenging potential was observed to determine the antioxidant property of the complexes. Results: From the disk diffusion antimicrobial screening of tolfenamic acid and its metal complexes, it was found out that considerable antimicrobial activity in terms of zone of inhibition against the tested organisms had been demonstrated by Cu and Zn complex of tolfenamic acid. In addition, the brine shrimp lethality bioassay corroborated that tolfenamic acid and Cu, Co, Zn complexes of the parent NSAID exhibited cytotoxicity with LC 50 values 1.23 ± 0.91 lg/ml, 1.12 ± 0.12 lg/ml, 1.17 ± 0.56 lg/ml, 1.35 ± 0.24 lg/ ml respectively, compared to the vincristine sulfate had LC 50 value of 0.82 ± 0.09 lg/ml. Furthermore, 1,1diphenyl-2-picrylhydrazyl assay revealed that in comparison with standard BHT had IC 50 of 11.84 ± 0.65, Cu and Co complex of tolfenamic acid exhibited significant antioxidant or radical-scavenging properties with IC 50 values 13.61 ± 0.58 lg/ml and 15.38 ± 0.09 lg/ml, respectively. Conclusion: It can be postulated that metal complexes of tolfenamic acid have auspicious pharmacological effects: antimicrobial, cytotoxicity, and antioxidant potency. Hence, these complexes might have better therapeutic responses in future; notwithstanding, it needs further detailed analysis in other pharmacological perspectives.