Cardiac Preconditioning With Local Laser-Induced Hyperthermia

Rickettsiae induce microvascular hyperpermeability via phosphorylation of VE-cadherins: evidence from atomic force microscopy and biochemical studies

The most prominent pathophysiological effect of spotted fever group (SFG) rickettsial infection of microvascular endothelial cells (ECs) is an enhanced vascular permeability, promoting vasogenic cerebral edema and non-cardiogenic pulmonary edema, which are responsible for most of the morbidity and mortality in severe cases. To date, the cellular and molecular mechanisms by which SFG Rickettsia increase EC permeability are largely unknown. In the present study we used atomic force microscopy (AFM) to study the interactive forces between vascular endothelial (VE)-cadherin and human cerebral microvascular EC infected with R. montanensis, which is genetically similar to R. rickettsii and R. conorii, and displays a similar ability to invade cells, but is non-pathogenic and can be experimentally manipulated under Biosafety Level 2 (BSL2) conditions. We found that infected ECs show a significant decrease in VE-cadherin-EC interactions. In addition, we applied immunofluorescent staining, immunoprecipitation phosphorylation assay, and an in vitro endothelial permeability assay to study the biochemical mechanisms that may participate in the enhanced vascular permeability as an underlying pathologic alteration of SFG rickettsial infection. A major finding is that infection of R. montanensis significantly activated tyrosine phosphorylation of VE-cadherin beginning at 48 hr and reaching a peak at 72 hr p.i. In vitro permeability assay showed an enhanced microvascular permeability at 72 hr p.i. On the other hand, AFM experiments showed a dramatic reduction in VE-cadherin-EC interactive forces at 48 hr p.i. We conclude that upon infection by SFG rickettsiae, phosphorylation of VE-cadherin directly attenuates homophilic protein-protein interactions at the endothelial adherens junctions, and may lead to endothelial paracellular barrier dysfunction causing microvascular hyperpermeability. These new approaches should prove useful in characterizing the antigenically related SFG rickettsiae R. conorii and R. rickettsii in a BSL3 environment. Future studies may lead to the development of new therapeutic strategies to inhibit the VE-cadherin-associated microvascular hyperpermeability in SFG rickettsioses.

Kinetics of chaperone activity of proteins Hsp70 and Hdj1 in human leukemia u-937 cells after preconditioning with thermal shock or compound u-133

Kinetics of the chaperone activity of proteins Hsp70 and Hdj1 were analyzed in human U-937 promonocytes during their response to heat shock or to treatment with the echinochrome triacetyl glucoside derivative U-133. To measure the chaperone activity of both proteins, a special test was developed for their recognition and binding of a denatured protein. Using this test, the chaperone activity could be concurrently estimated in large numbers of cellular or tissue extracts. We also estimated the contents of both chaperones in cells by immunoblotting. The values for contents of Hsp70 and Hdj1 obtained by two independent test systems coincided, and this suggested that the substrate-binding activity could change proportionally to the chaperone content in the protein mixture. Therefore, the test developed by us can be employed for high throughput screening of drugs activating cellular chaperones. The analysis of quantity and activity of two cellular chaperones during the cell response to heat stress or to the drug-like substance U-133 showed that both factors caused the accumulation of chaperones with similar kinetics. We conclude that the efficiency of drug preconditioning could be close to the efficiency of hyperthermia and that the high activity of chaperones could be retained in human cells for no less than 1.5 days.