Bacterial lipopeptide triggers massive albuminuria in murine lupus nephritis by activating Toll-like receptor 2 at the glomerular filtration barrier.

What are the molecular mechanisms of bacterial infections triggering or modulating lupus nephritis? In nephritic MRL(lpr/lpr) mice, transient exposure to bacterial cell wall components such as lipopeptide or lipopolysaccharide (LPS) increased splenomegaly, the production of DNA autoantibodies, and serum interleukin (IL)-6, IL-12 and tumour necrosis factor (TNF) levels, and aggravated lupus nephritis. Remarkably, bacterial lipopeptide induced massive albuminuria in nephritic but not in non-nephritic mice. This was associated with down-regulation of renal nephrin mRNA and redistribution from its normal localization at foot processes to the perinuclear podocyte area in nephritic MRL(lpr/lpr) mice. Bacterial lipopeptide activates Toll-like receptor 2 (TLR2), which we found to be expressed on cultured podocytes and glomerular endothelial cells. TNF and interferon (IFN)-gamma induced TLR2 mRNA and receptor expression in both cell types. Albumin permeability was significantly increased in cultured podocytes and glomerular endothelial cells upon stimulation by bacterial lipopeptide. LPS also induced moderate albuminuria. In summary, bacterial lipopeptide and LPS can aggravate glomerulonephritis but only lipopeptide potently induces severe albuminuria in MRL(lpr/lpr) mice.

VEGF regulation of endothelial nitric oxide synthase in glomerular endothelial cells.

BACKGROUND: Vascular endothelial growth factor (VEGF) regulation of endothelial nitric oxide synthase (eNOS) and signaling pathways involved have not been well studied in glomerular endothelial cells (GENCs). METHODS: GENCs grown from tsA58 Immortomice were used. Immunoblotting and in-cell Western blot analysis were employed to assess changes in VEGF receptor signaling pathway and eNOS phosphorylation of ser1177. Immunokinase assay and immunoblotting with phosphospecific antibodies were performed to assess activity of kinases. RESULTS: VEGF rapidly induced tyrosine phosphorylation of type 1 and type 2 VEGF receptors. Physical association between VEGF-receptor 2 (VEGF-R2) and insulin receptor substrate (IRS-1) and phosphatidylinositol 3'-kinase (PI3K) was induced by VEGF, which augmented PI3K activity in VEGF-R2 immunoprecipitates. VEGF stimulated Akt phosphorylation in a PI3K-dependent manner. VEGF increased eNOS phosphorylation on Ser1177. Activation of eNOS was associated with nitric oxide generation as measured by medium nitrite content. Signaling mechanisms involved in VEGF stimulation of eNOS were explored. VEGF-induced eNOS phosphorylation was abolished by SU1498, a VEGF-R2 inhibitor, LY294002, a PI3K inhibitor, and infection of cells with an adenovirus carrying a dominant negative-mutant of Akt, demonstrating the requirement of the VEGF-R2/IRS-1/PI3K/Akt axis for activation of eNOS. VEGF also activated extracellular signal-regulated protein kinase (ERK) in a time-dependent manner; and VEGF-stimulated eNOS phosphorylation on Ser1177 was prevented by PD098059, an upstream inhibitor of ERK, demonstrating that ERK was involved in VEGF regulation of eNOS. ERK phosphorylation was abolished by LY294002, suggesting ERK was downstream of PI3K in VEGF-treated GENC. CONCLUSIONS: Our data demonstrate that in GENC, VEGF stimulates VEGF-R2/IRS-1/PI3K/Akt axis to regulate eNOS phosphorylation on Ser1177 in conjunction with the ERK signaling pathway.

Isolation, culture, and characterization of endothelial cells from mouse glomeruli.

BACKGROUND: Cloned glomerular endothelial cells (GENC) have many potential uses and applications in immunologic and physiologic studies. Propagation of GENC has been difficult and available homogeneous GENC, particularly from mice, are limited. Herein we report isolation, cloning, propagation, and characterization of GENC from mice. METHODS: tsA58 immorto mice were used to isolate glomerular cells. Glomeruli were isolated by differential sieving, and decapsulated explants were cultured in permissive and optimal conditions for endothelial cells. The primary cells from glomerular outgrowths were expanded, taking advantage of the temperature-sensitive tsA58 gene, and then the cells were allowed to undergo spontaneous transformation. The cells were then sorted using anti-CD31 antibodies and their capacity to uptake acetylated-low-density lipoprotein (LDL). Individual subclones isolated by patch cloning were characterized using multiple markers. RESULTS: One of the homogeneous clones was morphologically endothelial-like, positive for CD31, CD106, CD62E, CD54, and acetylated-LDL uptake, formed tubes, and was negative for epithelial and mesangial cell markers. The functional properties of this GENC clone appeared to be intact, and signaling pathway was not altered. Two of the clones displayed the characteristics of either visceral epithelial or mesangial cells. CONCLUSION: The identified clones should have utility in multiple areas of investigation.

Monoclonal anti-idiotypic antibody mimicking the gastrointestinal carcinoma-associated epitope CO17-1A elicits antigen-specific humoral and cellular immune responses in colorectal cancer patients.

Monoclonal rat anti-idiotypic antibody (Ab2) BR3E4 mimicking the colorectal carcinoma (CRC)-associated epitope CO17-1A induced antigen-specific humoral and cellular immune responses in mice and rabbits. Ab2 BR3E4 was administered in a phase I trial to CRC patients either as intact IgG or as F(ab')(2) coupled to keyhole limpet hemocyanin (KLH). There was a trend for the F(ab')(2)-KLH-immunized patients to show higher immune response rates (18/21 and 5/15 patients with anti-anti-idiotypic antibodies and T cells, respectively) than the IgG-immunized patients (15/23 and 3/15 patients positive). Clinical responses were rare in these patients with liver metastases.

A mixed hemadsorption assay for detection of cell surface binding anti-tumor antibodies in human sera.

A practical mixed hemadsorption assay (MHA) was developed for the detection of cell surface binding anti-tumor antigen antibodies (anti-TA Ab) in the human sera. The assay was compared to enzyme-linked immunosorbent assay (ELISA) and dot ELISA in the detection of the antibodies developed against GA733-2 antigen. SW1116 cell line and recombinant GA733-2E protein were used as targets in the MHA and solid phase immunoassays (SPIA), respectively. Sera were obtained from healthy donors and vaccinated-colon carcinoma patients. The sensitivity level of the MHA was very high for detection of anti-TA Ab in sera.