No abstract

The pulmonary collectins, surfactant proteins A (SP-A) and D (SP-D), have been reported to bind lipopolysaccharide (LPS), opsonize microorganisms, and enhance the clearance of lung pathogens. In this study, we examined the effect of SP-A and SP-D on the growth and viability of Gram-negative bacteria. The pulmonary clearance of Escherichia coli K12 was reduced in SP-A–null mice and was increased in SP-D–overexpressing mice, compared with strain-matched wild-type controls. Purified SP-A and SP-D inhibited bacterial synthetic functions of several, but not all, strains of E. coli, Klebsiella pneumoniae, and Enterobacter aerogenes. In general, rough E. coli strains were more susceptible than smooth strains, and collectin-mediated growth inhibition was partially blocked by coincubation with rough LPS vesicles. Although both SP-A and SP-D agglutinated E. coli K12 in a calcium-dependent manner, microbial growth inhibition was independent of bacterial aggregation. At least part of the antimicrobial activity of SP-A and SP-D was localized to their C-terminal domains using truncated recombinant proteins. Incubation of E. coli K12 with SP-A or SP-D increased bacterial permeability. Deletion of the E. coli OmpA gene from a collectin-resistant smooth E. coli strain enhanced SP-A and SP-D–mediated growth inhibition. These data indicate that SP-A and SP-D are antimicrobial proteins that directly inhibit the proliferation of Gram-negative bacteria in a macrophage- and aggregation-independent manner by increasing the permeability of the microbial cell membrane

We previously demonstrated that vascular endothelial growth factor (VEGF)-elicited increase in the permeability of coronary venules was blocked by the nitric oxide (NO) synthase inhibitor N G-monomethyl-l-arginine (l-NMMA). The aim of this study was to delineate in more detail the signaling pathways upstream from NO production in VEGF-induced venular hyperpermeability. The apparent permeability coefficient of albumin ( P a) and endothelial cytosolic Ca2+concentration ([Ca2+]i) were measured in intact perfused porcine coronary venules using fluorescence microscopy. VEGF (10−10 M) induced a two- to threefold increase in P a, which was blocked by a monoclonal antibody directed against the VEGF receptor Flk-1/KDR, the phospholipase C (PLC) antagonist U-73122, or the protein kinase C (PKC) antagonist bisindolylmaleimide (BIM). In 12 venules that displayed the [Ca2+]iresponse to bradykinin (10−6M) and ionomycin (10−6 M), only 4 vessels responded to VEGF with a transient increase in [Ca2+]i. Furthermore, Western blot analysis of cultured human umbilical vein endothelial cells showed that VEGF increased tyrosine phosphorylation of PLC-γ and serine phosphorylation of endothelial constitutive NO synthase (ecNOS). The hyperphosphorylation of PLC-γ was greatly attenuated by the KDR receptor antibody and U-73122, but not by BIM orl-NMMA. In contrast, U-73122 and BIM were able to inhibit VEGF-elicited serine phosphorylation of ecNOS. The results suggest that VEGF induces venular hyperpermeability through a KDR receptor-mediated activation of PLC. In turn, ecNOS is activated by PLC-mediated PKC and/or cytosolic Ca2+ elevation stimulation.

No abstract

Background:The pathophysiological importance of autophagy in renal tubules during the development of diabetic nephropathy (DN) has been implicated. Results: Autophagy was inactivated because lysosomal membrane permeabilization and lysosomal dysfunction were triggered by advanced glycation end products. Conclusion:The autophagy-lysosome pathway is disrupted in renal tubules in DN. Significance:The findings open a new field for studying the mechanisms of DN.