Lipopolysaccharide impairs permeability of pulmonary microvascular endothelial cells via Connexin40.

The endotoxin lipopolysaccharide (LPS)-induced pulmonary endothelial barrier disruption is a key pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, the molecular mechanisms underlying LPS-impaired permeability of pulmonary microvascular endothelial cells (PMVECs) are not fully understood. Gap junctions, particularly Connexin40 (Cx40), are necessary for the maintenance of normal vascular function. In this study, we for the first time investigated the role of Cx40 in LPS-impaired permeability of PMVECs and provided potential therapeutic approaches based on mechanistic findings of Cx40 regulation by LPS stimuli. Rat PMVECs were isolated, cultured and identified with cell morphology, specific markers, ultrastructural characteristics and functional tests. Western blot analysis demonstrated that Cx40 is the major connexin highly expressed in PMVECs. Furthermore, by inhibiting Cx40 in a time-dependent manner, LPS impaired gap junction function and induced permeability injury of PMVECs. The key role of Cx40 decline in mediating detrimental effects of LPS was further confirmed in rescue experiments through Cx40 overexpression. Mechanistically, LPS stress on PMVECs inhibited the protein kinase C (PKC) pathway, which may synergize with the inflammatory nuclear factor kappaB (NFκB) signaling activation in suppressing Cx40 expression level and phosphorylation. Moreover, through pharmacological PKC activation or NFκB inhibition, Cx40 activity in PMVECs could be restored, leading to maintained barrier function under LPS stress. Our findings uncover a previously unrecognized role of Cx40 and its regulatory mechanisms in impaired endothelial integrity under endotoxin and inflammation, shedding light on intervention approaches to improve pulmonary endothelial barrier function in ALI and ARDS.

[Construction of an acellular porcine aortic valve].

OBJECTIVE: To prepare a porcine aortic valve (PAV) free of the cellular components. METHODS: The cellular components of porcine PAV were completely removed using trypsin and Triton X-100, and the acellular PAV was examined microscopically with HE staining with its physical and chemical properties assessed. Transmission electron microscopy was used to observe the integrity of the collagen and elastin and the DNA contents in the PAV was detected to confirm the total removal of the cellular components. With the fresh PAV as the control, small pieces of the acellular PAV were implanted into the subcutaneous tissues of 4 rabbits, and 4 weeks after the implantation, the implants were harvested for microscopic observation. RESULTS: The cellular components were effectively removed from the cusps and roots of the PAV by trypsin and TritonX-100, with marked soluble protein loss [(0.24-/+0.04)% vs (0.48-/+0.12)%] and significantly increased water content [(92.2-/+1.5)% vs (89.2-/+1.6)%]. The acellular PAV still maintained good fibrous scaffold structure and the shrinkage temperature and tension at fracture underwent no significantly changes [(67.9-/+1.0) degrees celsius; vs (68.8-/+0.8) degrees celsius; and (489.3-/+19.0) g/mm2 vs (540.7-/+19.5) g/mm2, respectively]. The PAVs implanted in rabbits showed only mild tissue reaction with a few infiltrating neutrophils, lymphocytes and plasmocytes observed 4 weeks later. The accelular PAV caused obviously milder inflammatory reactions than fresh PAV. CONCLUSIONS: The acellular PAV prepared by treatment with trypsin and Triton X-100 retains good fibrous scaffold structure and mechanical strength with low antigenicity.