Mutant enzyme provides new insights into the cause of ALS

Metal element excretion in 24-h urine in patients with Wilson disease under treatment of D-penicillamine

Wilson disease is an inherited autosomal recessive disorder causing copper accumulation and consequent toxicity. D-Penicillamine, a potent metal chelator, is an important therapy for Wilson disease. To investigate the changes of metal elements under the treatment of D-penicillamine, we determined the levels of Cu, Zn, Mg, Ca, Fe, Se, Mn, Pb, Hg, Cd, As, Tl, and Al by ICP-MS in 24-h urine of 115 Wilson disease patients who had received treatment with D: -penicillamine for 1 month to 22 years at maintenance doses, as well as 115 age-matched, healthy controls. The levels of Cu, Mg, Ca, Zn, Hg, Pb, Tl, Cd, and Mn in the 24-h urine of the cases were significantly higher than those of the controls (P < 0.05), and the observed increases in the levels of Mg, Ca, and Zn were directly correlated with the treatment duration with Pearson Correlation Coefficient (R) of 0.356 (Mg), 0.329 (Ca), and 0.313 (Zn), respectively (P < 0.05). On the other hand, the levels of Al and As in the 24-h urine were lower than those of the controls (P < 0.05) and were negatively correlated with the treatment time with R of -0.337 (Al) and -0.398 (As), respectively, (P < 0.05). Thus, this study indicates that the levels of metal elements may be altered in patients with Wilson disease under the treatment of D-penicillamine.

Caspase-3-like activity is necessary for IL-2 release in activated Jurkat T-cells

The caspase family of proteases has previously been implicated in the biochemical cascade leading to apoptotic cell death. Recently caspase-3 was reported to be cleaved into its catalytically active subunits (17 and 13 kDa) following phytohemagglutinin (PHA) activation of peripheral blood mononuclear cells (C. Miossec et al., J. Biol. Chem. 272, 13459-13462). More recently, J. M. Zapata and colleagues (J. Biol. Chem. 273, 6916-6920, 1998), however, proposed that caspase-3 activity detected during T-cell activation was due to a methodological artifact related to the composition of the cell lysis buffer. Here we show that in PHA-activated Jurkat T-cells using the recommended lysis buffer detailed by Zapata et al., a caspase-3-like protease is activated and is accompanied by cleavage of PARP and alpha-spectrin into cleavage products suggestive of caspase-3 proteolytic activation. LDH release did not increase following PHA stimulation in this paradigm. Two caspase inhibitors, carbobenzoxy-Asp-CH2OC(O)-2,6-dichlorobenzene (Z-D-DCB) and acetyl-Asp-Glu-Val-Asp-CHO, blocked IL-2 release in a dose-dependent manner. Caspase-3-like protease-generated PARP and alpha-spectrin breakdown product formation was also reduced by Z-D-DCB. In addition, Jurkat T-cells costimulated with anti-CD3 plus anti-CD28 produced significant levels of IL-2 that were also blocked by these caspase inhibitors. Importantly, IL-2 was determined in cell culture supernatants, thus avoiding a cell lysis step that might have enabled activation of caspase-3 by granzyme B. Collectively, these data support the role of caspase-3-like protease activity in Jurkat T-cell activation and demonstrate that caspase-3 like activity is necessary for IL-2 release in PHA-activated and anti-CD3/anti-CD28 costimulated Jurkat T-cells.

A purine nucleoside phosphorylase (PNP) inhibitor induces apoptosis via caspase-3-like protease activity in MOLT-4 T cells

Children with congenital homozygous deficiency of purine nucleoside phosphorylase (PNP) have abnormalities in purine metabolism that result in T-cell selective immune deficiency. The mechanism of action for cell death has been attributed to intracellular accumulation of dGTP, a potent inhibitor of ribonucleotide reductase and subsequently DNA synthesis, in thymocytes and T-cells but not B-cells. However, the mode of cell death has not been determined to be either necrosis or apoptosis. To examine the involvement of apoptosis in T-cells following PNP inhibition, MOLT-4 cells, a human T cell leukemia cell line, were co-treated with the PNP inhibitor, CI-1000 (2-amino 3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]-pyrimidin-4-one HCl), and 2'-deoxyguanosine (dGuo) which resulted in a concentration-dependent loss of cell viability (trypan blue) and inhibition of tritiated thymidine ([3H]-TdR) uptake. Staining of cells with the DNA dye Hoechst 33,258 showed nuclear morphology characteristic of apoptosis. Western blots (24 h lysates) were probed with antibodies against several proteins implicated in apoptosis. Anti-PARP revealed the presence of an 85 kD PARP breakdown product while, anti-alpha-spectrin revealed the accumulation a 120 kD breakdown product, both suggestive of CPP32 cleavage (caspase-3; an ICE-like cysteine protease). Western blots also detected the loss of the intact 32 kD caspase-3 isoform, a biochemical event associated with caspase-3 activation. Corresponding fluorometric activity assays detected a marked increase in caspase-3-like activity using the substrate Ac-DEVD-MCA. Lastly, a pan caspase inhibitor (Z-D-DCB) and 2'-deoxycytidine (dCyd), which is known to prevent dGTP accumulation following PNP inhibition, were able to prevent cell death and all indicators of caspase-3-like activity in MOLT-4 cells co-treated with dGuo and CI-1000. In summary, we provided several lines of evidence for the role of apoptosis and the contribution of caspase-3-like proteases in T-cell death following PNP inhibition.