HIV-1 Tat-mediated apoptosis in human brain microvascular endothelial cells

The integrity of the blood-brain barrier (BBB) is critical for normal brain function. Neuropathological abnormalities in AIDS patients have been associated with perivascular HIV-infected macrophages, gliosis, and abnormalities in the permeability of the BBB. The processes by which HIV causes these pathological conditions are not well understood. To characterize the mechanism by which HIV-1 Tat protein modulates human brain microvascular endothelial cell (HBMEC) functions, we studied the effects of HIV-1 Tat in modulating HBMEC apoptosis and permeability. Treatment of HBMEC with HIV-1 Tat led to Flk-1/KDR and Flt-4 receptor activation and the release of NO. The protein levels of endothelial NO synthase (NOS) and inducible NOS were increased by HIV-1 Tat stimulation. Importantly, HIV-1 Tat caused apoptosis of HBMEC, as evidenced by changes in the cleavage of poly(A)DP-ribose polymerase, DNA laddering, and incorporation of fluorescein into the nicked chromosomal DNA (TUNEL assay). HIV-1 Tat-mediated apoptosis in HBMEC was significantly inhibited in the presence of N-nitro-L-arginine methyl ester (an inhibitor of NOS) and wortmannin (a phosphoinositol 3-kinase inhibitor). Furthermore, HIV-1 Tat treatment significantly increased HBMEC permeability, and pretreatment with both N-nitro-L-arginine methyl ester and wortmannin inhibited the Tat-induced permeability. Taken together, these results indicate that dysregulated production of NO by HIV-1 Tat plays a pivotal role in brain endothelial injury, resulting in the irreversible loss of BBB integrity, which may lead to enhanced infiltration of virus-carrying cells across the BBB.     

Direct analysis of protein sedimentation equilibrium in detergent solutions without density matching

Characterizing membrane proteins by sedimentation equilibrium is challenging because detergents and/or lipid molecules, usually required for solubilization, form a complex with the protein. The most common way to overcome this problem is Tanford and Reynolds' density matching method, which eliminates the buoyant mass contributions of detergents/lipids by adjusting the solvent density with D2O/H2O mixtures to render either detergent or lipid molecules neutrally buoyant. Unfortunately, the method is practical only for detergent densities between 1.0 (H2O) and 1.1 (D2O) g ml(-1), excluding many of the more commonly used detergents for membrane protein studies. Here, we present a modern variant of Tanford and Reynolds' method that (1) is applicable to any detergent regardless of its specific density, (2) does not compromise accuracy and precision, and (3) provides additional information about the number of detergent molecules that are bound to each protein. The new method was applied successfully to Delta(1-43)A-I, an amino-terminal deletion mutant of human apolipoprotein A-I. Interestingly, we observed a significantly lower Delta(1-43)A-I/octyl-glucoside complex partial specific volume than that expected from volume additivity rules, indicative of specific protein-detergent interactions.     

Persistence of apoptosis and inflammatory responses in the heart and bone marrow of mice following whole-body exposure to 28Silicon (28Si) ions

It has been well established that the bone marrow (BM) is a radiosensitive tissue, but the radiosensitivity of the heart is poorly understood. In this study, we investigated the comparative effects of ²⁸Silicon (²⁸Si) ions (one type of heavy ion found in space) on tissue from the heart and the BM of exposed mice. We gave adult male CBA/CaJ mice a whole-body exposure to a total dose of 0, 0.1, 0.25, or 0.5 Gy of 300 MeV/nucleon (n) ²⁸Si ions, using a fractionated schedule (two exposures, 15 days apart that totaled each selected dose). The heart and BM were collected from 5 mice per treatment group at various times up to 6 months post-irradiation. In each mouse, we obtained tissue lysates from the heart and from the total population of BM cells for measuring the levels of cleaved poly (ADP-ribose) polymerase (cleaved PARP, a marker of apoptotic cell death) and the levels of activated nuclear factor-kappa B (NF-κB) and selected NF-κB-regulated cytokines known to be involved in inflammatory responses. Our data showed that, up to 6 months post-irradiation, the levels of apoptotic cell death and inflammatory responses in tissues from the heart and BM collected from exposed mice were statistically higher than those in sham controls. Hence, these findings are suggestive of chronic apoptotic cell death and inflammation in both tissues after exposure to ²⁸Si ions. In summary, our data are indicative of a possible association between exposure to ²⁸Si ions during space flight and long-term health risk.     

Age-related effects in enzyme catalysis

Summary Rat muscle glyceraldehyde-3-phosphate dehydrogenase is one of several enzymes which have been found to undergo age-related modifications. While the amount of this enzyme in muscle tissue does not change with age, both its specific activity and affinity towards its co-enzyme are significantly reduced in the old tissue.Age-related structural changes were found to exist in the nicotinamide binding site of the enzyme and the reactions leading to the activity loss in old glyceraldehyde-3-phosphate dehydrogenase were shown to involve a reversible modification of the essential cysteine-149 residue at the active site of the enzyme. The aging effects were simulated by a controlled oxidation of cys-149 in samples of young glyceraldehyde-3-phosphate dehydrogenase and subsequent reduction of this residue by 2-mercaptoethanol. The enzyme modified in this way closely resembles native old glyceraldehyde-3-phosphate dehydrogenase, indicating that the structural modifications in the latter enzyme are indeed introduced by a post-translational process. The mechanism for aging of glyceraldehyde-3-phosphate dehydrogenase which is proposed, based on these observations, thus assumes an oxidation of cys-149 as its first step followed by irreversible conformational changes in the enzyme molecule. The aging of glyceraldehyde-3-phosphate dehydrogenase may thus be triggered by the reduced ability of old muscle tissue to protect its constituents against oxidation.Abbreviations CPL circular polarization of luminescence - DTNB 5,5-dithiobis (2-nitrobenzoic acid) - GPDH D-glyceraldehyde-3-phosphate dehydrogenase - ENAD⁺ nicotinamide 1,N⁶-ethenoadenine dinucleotide     

Improved metabolic profiles in insulin-treated diabetic patients given an alpha-glucosidehydrolase inhibitor.

An alpha-glucosidehydrolase inhibitor (acarbose; BAY g 5421) taken with food was compared with dummy tablets in seven insulin-treated diabetic patients over eight-hour periods that included breakfast, lunch, and two snacks. Acarbose diminished the postprandial increases in blood glucose, lactate, and pyruvate concentrations and may therefore be of value in the management of insulin-dependent diabetes.