Hepatitis C virus (HCV) is yet another example of a pathogen that persists in the presence of a readily apparent immune response. As evidence for both humoral and cellular immune responsiveness is quite strong, our studies have begun to examine whether qualitative defects in CD4 T-cell responses to viral antigens may help to explain why HCV is not eliminated in the vast majority of infections. Direct evidence that CD4 T cells play a role in HCV persistence is lacking, but several observations are consistent with this possibility. Importantly, it does not exclude the role of antibody or killer T cells in the immunopathogenesis of HCV infection. In addition, we discuss the consequences of viral mutation and how naturally occurring variants in immunodominant viral epitopes can effectively suppress helper T-cell responses to wild type virus.
Background: Diabetes may alter renal glucose reabsorption by sodium (Na + )-dependent glucose transporters (SGLTs). Radiolabeled substrates are commonly used for in vitro measurements of SGLT activity in kidney cells. We optimized a method to measure glucose uptake using a fluorescent substrate, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG). Methods: Uptake buffers for 2-NBDG were the same as for 14 C-labeled a-methyl-d-glucopyranoside ([ 14 C]AMG). Cell lysis buffer was optimized for fluorescence of 2-NBDG and Hoechst DNA stain. Uptake was performed on cultures of primary mouse kidney cells (PMKCs), the LLC-PK 1 proximal tubule cell line, or COS-7 cells transiently overexpressing mouse SGLT1 or SGLT2 by incubating cells at 378C in buffer containing 50-200 mM 2-NBDG. Microscopy was performed to visualize uptake in intact cells, while a fluorescence microplate reader was used to measure intracellular concentration of 2-NBDG ([2-NBDG] i ) in cell homogenates. Results: Fluorescent cells were observed in cultures of PMKCs and LLC-PK 1 cells exposed to 2-NBDG in the presence or absence of Na
Many cell types contain metal-ion unsaturated metallothionein (MT). Considering the Zn 2+ binding affinity of metallothionein, the existence of this species in the intracellular environment constitutes a substantial "thermodynamic sink." Indeed, the mM concentration of glutathione may be thought of in the same way. In order to understand how apo-MT and the rest of the Zn-proteome manage to co-exist, experiments examined the in vitro reactivity of Zn-proteome with apo-MT, glutathione (GSH), and a series of common Zn 2+ chelating agents including N,N,N',N'-(2-pyridylethyl) ethylenediammine (TPEN), EDTA, and [(2,2'-oxyproplylene-dinitrilo]tetraacetic acid (EGTA). Less than 10% of Zn-proteome from U87 mg cells reacted with apo-MT or GSH. In contrast, each of the synthetic chelators was 2−3 times more reactive. TPEN, a cell permeant reagent, also reacted rapidly with both Zn-proteome and Zn-MT in LLC-PK 1 cells. Taking a specific zinc finger protein for further study, apo-MT, GSH, and TPEN inhibited the binding of Zn 3 -Sp1 with its cognate DNA site (GC-1) in the sodium-glucose co-transporter promoter of mouse kidney. In contrast, preformation of Zn 3 -Sp1-(GC-1) prevented reaction with apo-MT and GSH; TPEN remained active but at a higher concentration. Whereas, Zn 3 -Sp1 is active in cells containing apo-MT and GSH, exposure of LLC-PK 1 cells to TPEN for 24 h largely inactivated its DNA binding activity. The results help to rationalize the steady state presence of cellular apo-MT in the midst of the many, diverse members of the Znproteome. They also show that TPEN is a robust intracellular chelator of proteomic Zn 2+ .
Diabetes-mediated changes in mRNA expressions of kidney glucose transporters SGLT1 and 2 were investigated in Zucker rats. SGLTs expressions in pre-diabetic obese rats were similar to leans. SGLT1 and SGLT2 levels in diabetic obese rats was 1.6 (P < 0.03) and 4.8 (P < 0.002) folds higher than age-matched leans, respectively.
The present paper centers on mammalian metallothionein 1 and 2 in relationship to cell and tissue injury beginning with its reaction with Cd²⁺ and then considering its role in the toxicology and chemotherapy of both metals and non-metal electrophiles and oxidants. Intertwined is a consideration of MTs role in tumor cell Zn²⁺ metabolism. The paper updates and expands on our recent review by Petering et al. (Met Ions Life Sci 5:353-398, 2009).
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