Infection of mesangial cells with HIV and SIV: Identification of GPR1 as a coreceptor

Infection of mesangial cells with HIV and SIV: Identification of GPR1 as a coreceptor.BackgroundMesangial cells are an important component of the glomerulus. Dysfunction of mesangial cells is thought to be involved in the development of human immunodeficiency virus type 1 (HIV-1)-associated nephropathy (HIVAN). HIVAN is a structural renal failure frequently observed in patients with acquired immune deficiency syndrome. However, the susceptibility of mesangial cells to HIV-1 is disputable. More than ten G protein-coupled receptors, including chemokine receptors, have been shown to act as HIV-1 coreceptors that determine the susceptibilities of cells to HIV-1 strains with specific cell tropisms.MethodsWe examined the susceptibility of mesangial cells to various HIV-1, HIV type 2 (HIV-2) and simian immunodeficiency virus (SIV) strains. Expression of CD4 and HIV/SIV coreceptors was examined by Western blotting and polymerase chain reaction.ResultsMesangial cells were found to be susceptible to HIV-1 variant and mutants that infect brain-derived cells, but highly resistant to T-tropic (X4), M-tropic (R5) or dual-tropic (X4R5) HIV-1 strains. In addition, mesangial cells were also susceptible to HIV-2 and SIV strains that infect the brain-derived cells. Among HIV/SIV coreceptors we tested, the expression of GPR1 mRNA was detected in mesangial cells. Expression of CD4 mRNA and protein was also detected in them. Mesangial cells and GPR1-transduced CD4-positive cells showed similar susceptibilities to the HIV-1 variant and mutants and HIV-2 and SIV strains.ConclusionsCD4 and GPR1 mRNAs were detected in mesangial cells. Mesangial cells were susceptible to HIV/SIV strains that use GPR1 as a coreceptor. Our findings suggest that an orphan G protein-coupled receptor, GPR1, is a coreceptor expressed in mesangial cells. It remains to be investigated whether the interaction of mesangial cells with specific HIV-1 strains through GPR1 plays a role in the development of HIVAN

Structural continuity of filtration slit (slit diaphragm) to plasma membrane of podocyte

Structural continuity of filtration slit (slit diaphragm) to plasma membrane of podocyte. Murine monoclonal antibody 5-1-6 was reported to bind to the slit membrane and closely related structures in rat renal glomeruli; it induced heavy, reversible proteinuria and appeared to redistribute onto the plasma membrane of epithelial cells after binding at the original target sites. This phenomenon of antigenic movement has not been analyzed in detail to date. In addition to normal kidneys we also studied localization of the antigen recognized by monoclonal antibody 5-1-6 in protamine sulfate-perfused rat kidneys, in which slit diaphragms are known to be functionally modified. Isolated glomeruli as well as ultrathin kidney cryosections were labeled by the immunogold technique to clarify the relation between this antigen and the slit diaphragm. Sequential localization of injected monoclonal antibody was visualized using a post-embedding immunogold method in rats 2 hours to 12 days after injection of antibody. Ultrastructural immunogold labeling demonstrated that under normal conditions antigenic molecules were expressed mainly in the area beneath the slit diaphragms. Occasionally labeling was found at the base of the foot process, facing the glomerular basement membrane. After protamine sulfate treatment antigenic sites were dislocated due to the lifting and disruption of slit diaphragms, indicating that this antigen is associated with slit diaphragms. Injected antibody was localized at the filtration slits at 2 hours, and by 12 hours it had moved onto the apical plasma cell membrane of foot process. In addition, from 3 days onwards patch or cap-like formation on the plasma cell membrane of podocytes was seen. Possible shedding of antibody from podocyte cell surface membrane was occasionally encountered, but internalization of antibody was a minor event. Elution experiments in isolated glomeruli at day 3 indicated that antigen and antibody were both localized on the podocyte cell surface membrane, suggesting redistribution of immune complexes. In conclusion, filtration slits (slit diaphragms) and the apical membrane of foot process of podocytes demonstrate structural continuity, as revealed by the movement of the antigen recognized by monoclonal antibody 5-1-6 as antigen-antibody complexes

Glomerular angiotensinogen protein is enhanced in pediatric IgA nephropathy

Enhanced intrarenal renin-angiotensin system (RAS) is implicated in the development and progression of renal injury. To investigate whether angiotensinogen (AGT) expression is involved in glomerular RAS activity and glomerular injury, we examined glomerular AGT expression and its correlation with expression of other RAS components, and levels of glomerular injury in samples from patients with immunoglobulin A nephropathy (IgAN) (23) and minor glomerular abnormalities (MGA) (8). Immunohistochemistry showed that AGT protein was highly expressed by glomerular endothelial cells (GEC) and mesangial cells in nephritic glomeruli of IgAN compared with glomeruli of MGA. Levels of glomerular AGT protein were well correlated with levels of glomerular angiotensin II (ang II), transforming growth factor-β (TGF-β), α-smooth-muscle actin, glomerular cell number, and glomerulosclerosis score but not with those of glomerular angiotensin-converting enzyme and ang II type 1 receptor. Real-time polymerase chain reaction (RT-PCR) and Western blot analyses using cultured human GEC indicated that ang II upregulated AGT messenger ribonucleic acid (mRNA) and protein expression in a dose- and time-dependent manner. These data suggest that activated glomerular AGT expression is likely involved in elevated local ang II production and, thereby, may contribute to increased TGF-β production and development of glomerular injury in IgAN. Augmentation of GEC-AGT production with ang II stimulation might drive further glomerular injury in a positive-feedback loop

Suction towards a vessel wall by hemodialysis catheters—the establishment of a new experimental extracorporeal circulation system using pig veins

Abstract Background Hemodialysis catheters are commonly used for vascular access in patients undergoing blood purification therapies. However, the sudden dysfunction of catheters represents a serious problem, and while we know that the major causative factor is suction between the catheter and the vessel wall, it is very difficult to evaluate this in vivo. Therefore, we created a new experimental system to investigate this phenomenon ex vivo, using pig veins, which allowed us to quantitatively analyze the effect of suction. Methods We attempted to create a model system for quantitative evaluation using azygos veins from a pig. Four types of catheters were inserted into an extracted pig vein: true circle type 1, true circle type 2, semi-circle type 1, and semi-circle type 2. We then circulated 50% glycerol solution through the vein at a flow rate (Qv) from 100 to 1000 mL/min. Glycerol solution was also circulated within the catheters at a flow rate (Qb) from 100 to 200 mL/min. We measured the frequency of suction towards the vessel wall ten times, under each experimental schedule, at a Qb of both 100 and 200 mL/min. We then measured the pressure between the pre-Qb pump and the blood circuit, when the arterial side opening was positioned approximately in the center of the blood vessel to prevent catheter suction towards the vessel wall. Results Suction towards the vessel wall occurred 8/10 times with the true circle type 1 catheter and 10/10 times with the semi-circle type 2 catheter in the arterial pore of the catheter is only one, when Qb and Qv were 100 and 100 mL/min, respectively. Suction towards the vessel wall occurred 3/10 times with the semi-circle type 2 catheter, when Qb and Qv were 100 and 1000 mL/min, respectively. The true circle type 1 catheter showed a minimum pressure of − 58.6 ± 0.516 mmHg when Qb and Qv were 100 and 300 mL/min, respectively, while the true circle type 2 catheter showed a minimum pressure of − 137 ± 5.96 mmHg when Qb and Qv were 200 and 300 mL/min, respectively. Conclusions We successfully established a novel ex vivo evaluation system for catheters using a pig vein which allowed us to recreate the effect of suction from catheters towards a vessel wall in vivo