Atypical manifestations of coronavirus disease 2019 (COVID-19)-associated autoimmune thrombotic thrombocytopenic purpura.

Patients with coronavirus disease 2019 (COVID-19) infection can have various abnormal hematologic parameters. This report illustrates a case with unusual presentation of COVID-19-associated thrombotic thrombocytopenic purpura, in which the patient did not develop any typical respiratory signs or symptoms.

Disulfiram induces apoptosis in human melanoma cells: a redox-related process.

Melanoma is highly resistant to conventional chemotherapy. We have demonstrated that redox regulation in melanoma cells is aberrant, and redox-modulating agents can induce cell apoptosis. We have currently explored the effect of disulfiram (DSF), a member of the dithiocarbamate family, on apoptosis of melanoma cells in vitro. Human metastatic melanoma cells c81-46A, c81-61, and c83-2C were treated with DSF and apoptosis measured. DSF, at a dose of 25-50 ng/ml, consistently caused a 4-6-fold increase in apoptosis. The same dose of DSF did not significantly affect apoptosis in melanocytes. Coincubation of N-acetyl-cysteine reversed the DSF-induced apoptosis. Buthionine sulfoximine (BSO), an inhibitor of gamma-glutamyl-cysteine synthetase, as a single agent caused a approximately 2-fold increase in apoptosis when incubated with melanoma cells for 4 days. BSO slightly enhanced the level of apoptosis induced by DSF (4-10% higher than DSF alone). Intracellular glutathione was remarkably depleted with BSO treatment. DSF did not cause glutathione depletion; however, the ratio of reduced and oxidized glutathione was significantly decreased (14% of control), and N-acetyl-cysteine partially restored the ratio to 30% of control. There was a transient (2-fold) elevation of intracellular superoxide level after 24 h of DSF treatment (before the overt apoptosis). The intracellular H2O2 level progressively decreased with time. DSF decreased the mitochondrial membrane polarization in a time-dependent manner, and there was a significant inverse correlation between apoptosis and mitochondrial membrane polarization. We propose that DSF-induced apoptosis is redox related but involves a different mechanism from BSO-induced apoptosis in tumor cells. Our findings have provided new data for additional understanding of drug-induced apoptosis in melanoma cells and suggests an alternative therapeutic approach to melanoma.

Disulfiram facilitates intracellular Cu uptake and induces apoptosis in human melanoma cells.

The alcohol-abuse deterrent disulfiram (DSF) is shown to have a highly selective toxicity against melanoma in culture, inducing a largely apoptotic response, with much lower toxicity against several other cell lines. Melanoma cell lines derived from different stages (radial, vertical, and metastatic phase) were all sensitive to DSF treatment in vitro; melanocytes were only slightly affected. A required role of extracellular Cu is demonstrated for DSF toxicity. Low concentrations of DSF alone decreased the number of viable cells, and the addition of CuCl(2) significantly enhanced the DSF-induced cell death to less than 10% of control. Significantly, the intracellular Cu concentration of melanoma cells increased rapidly upon DSF treatment. Both the intracellular Cu uptake and the toxicity induced by DSF were blocked by co-incubation with bathocuproine disulfonic acid (BCPD, 100 muM), a non-membrane-permeable Cu chelator. Chemical studies demonstrated a complicated, extracellular redox reaction between Cu(II) and DSF, which forms the complex Cu(deDTC)(2) in high yield, accompanied by oxidative decomposition of small amounts of disulfiram. The Cu complex has somewhat higher activity against melanoma and is suggested to be the active agent in DSF-induced toxicity. The redox conversion of DSF was unique to Cu(II) and not engendered by the other common biological metal ions Fe(II or III), Mn(III), and Zn(II). The implications of this work are significant both in the possible treatment of melanoma as well as in limiting the known side-effects of DSF, which we propose may be diminished by cotreatment to decrease adventitious Cu.

Comparative expression of NFkappaB proteins in melanocytes of normal skin vs. benign intradermal naevus and human metastatic melanoma biopsies.

Nuclear factor kappa B (NFkappaB) is an essential regulator of gene transcription for hundreds of genes, including many critically involved in apoptosis. NFkappaB complexes containing cRel generally activate pro-apoptotic genes, while those with RelA activate anti-apoptotic genes. We have previously shown that NFkappaB binding by RelA is constitutively elevated in human metastatic melanoma cultures relative to normal melanocytes. Here we extended our investigation to immunohistochemical analysis of human tissue biopsies. We found that RelA expression is significantly elevated in melanocytes of human naevi and melanomas relative to normal skin, but expression of its inhibitor IkappaB-alpha is significantly lower in metastatic melanomas than in intradermal naevi. Antibodies specific for the nuclear localization signal of RelA also showed significantly increased staining in metastatic melanoma biopsies. Notably, in melanomas and in naevi, we also found that RelA is phosphorylated at serine 529, and this activated form accumulates in the nuclei of melanomas. This suggests that increased expression and phosphorylation of RelA occurs at the stage of the benign naevus, but IkappaB-alpha is able to sequester RelA in the cytoplasm and regulate RelA transcriptional transactivation. We also found that antibodies against cRel show a progressive increase in staining from naevi to melanoma. However, staining for IkappaB-epsilon, which primarily inhibits the nuclear localization of cRel was also progressively increased, and cRel expression was predominantly cytoplasmic in melanomas. These results confirm that the altered expression of RelA found in metastatic melanoma cells in tissue culture is relevant to human tumors and offer new insights into the deregulation of NFkappaB signaling.