A TAT-frataxin fusion protein increases lifespan and cardiac function in a conditional Friedreich's ataxia mouse model.

Friedreich's ataxia (FRDA) is the most common inherited human ataxia and results from a deficiency of the mitochondrial protein, frataxin (FXN), which is encoded in the nucleus. This deficiency is associated with an iron-sulfur (Fe-S) cluster enzyme deficit leading to progressive ataxia and a frequently fatal cardiomyopathy. There is no cure.

Effect of arylhydroxylamine metabolites of sulfamethoxazole and dapsone on stress signal expression in human keratinocytes.

The initiation of an immune response to small molecules is believed to require the release of stress/danger signals that activate resident dendritic cells, presumably secondary to the formation of reactive metabolites. We hypothesized that exposure to arylhydroxylamine metabolites of dapsone and sulfamethoxazole lead to the expression/release of numerous stress signals in the skin. To test this hypothesis, we examined the effect of these metabolites on the expression of selected heat shock proteins, uric acid, cytokines, adhesion molecules, and costimulatory molecules in normal human epidermal keratinocytes (NHEKs).

Formation and uptake of arylhydroxylamine-haptenated proteins in human dendritic cells.

Bioactivation of sulfonamides and the subsequent formation of haptenated proteins is believed to be a critical step in the development of hypersensitivity reactions to these drugs. Numerous lines of evidence suggest that the presence of such adducts in dendritic cells (DCs) migrating to draining lymph nodes is essential for the development of cutaneous reactions to xenobiotics. Our objective was to determine the ability of human DCs to form drug-protein covalent adducts when exposed to sulfamethoxazole (SMX), dapsone (DDS), or their arylhydroxylamine metabolites [sulfamethoxazole hydroxylamine (S-NOH) and dapsone hydroxylamine (D-NOH)] and to take up preformed adduct.

Enzyme-mediated protein haptenation of dapsone and sulfamethoxazole in human keratinocytes: I. Expression and role of cytochromes P450.

Cutaneous drug reactions (CDRs) are among the most common adverse drug reactions and are responsible for numerous minor to life-threatening complications. Several arylamine drugs, such as sulfamethoxazole (SMX) and dapsone (DDS), undergo bioactivation, resulting in adduction to cellular proteins. These adducted proteins may initiate the immune response that ultimately results in a CDR.

Bioactivation, protein haptenation, and toxicity of sulfamethoxazole and dapsone in normal human dermal fibroblasts.

Cutaneous drug reactions (CDRs) associated with sulfonamides are believed to be mediated through the formation of reactive metabolites that result in cellular toxicity and protein haptenation. We evaluated the bioactivation and toxicity of sulfamethoxazole (SMX) and dapsone (DDS) in normal human dermal fibroblasts (NHDF). Incubation of cells with DDS or its metabolite (D-NOH) resulted in protein haptenation readily detected by confocal microscopy and ELISA.

Effect of pro-inflammatory cytokines on the toxicity of the arylhydroxylamine metabolites of sulphamethoxazole and dapsone in normal human keratinocytes.

Sulphonamides, such as sulphamethoxazole (SMX) and the related sulphone dapsone (DDS), show a higher incidence of cutaneous drug reactions (CDRs) in patients with the acquired immunodeficiency syndrome (AIDS) compared with human immunodeficiency virus (HIV) negative patients. During HIV infection, pro-inflammatory cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) are increased. We hypothesized that this increase in pro-inflammatory cytokines may increase the toxicity of the arylhydroxylamine metabolites of SMX (S-NOH) and DDS (D-NOH) in keratinocytes through a reduction in glutathione (GSH) content.

Role of human cyclooxygenase-2 in the bioactivation of dapsone and sulfamethoxazole.

Sulfamethoxazole (SMX) and dapsone (4,4'-diaminodiphenylsulfone, DDS) are believed to mediate their adverse effects subsequent to bioactivation to their respective arylhydroxylamine and arylnitroso metabolites, resulting in covalent adduct formation with intracellular proteins. Various bioactivating enzymes, such as cytochromes P450 and myeloperoxidase, have been shown to be capable of catalyzing the N-oxidation of these compounds. We assessed the role of human cyclooxygenase-2 (COX-2) in the metabolism and subsequent adduct formation of DDS and SMX using recombinant human COX-2.

Reactive oxygen species generation and its role in the differential cytotoxicity of the arylhydroxylamine metabolites of sulfamethoxazole and dapsone in normal human epidermal keratinocytes.

Cutaneous drug reactions (CDR) are responsible for numerous minor to life-threatening complications. Though the exact mechanism for CDR is not completely understood, evidence suggests that bioactivation of drugs to reactive oxygen or nitrogen species is an important factor in the initiation of these reactions. Several CDR-inducing drugs having an arylamine functional group, such as sulfamethoxazole (SMX) and dapsone (DDS), undergo bioactivation to reactive arylhydroxylamine metabolites.

Characterization of the formation and localization of sulfamethoxazole and dapsone-associated drug-protein adducts in human epidermal keratinocytes.

Sulfonamide- and sulfone-induced hypersensitivity reactions are thought to be mediated through bioactivation of parent drug molecule(s) to their respective reactive metabolite(s). Recent studies have demonstrated that keratinocytes can bioactivate sulfonamides and sulfones. Using enzyme-linked immunosorbent assay and hapten-specific rabbit antisera developed in our laboratory, we found that incubation of either normal human epidermal keratinocytes (NHEKs) or an immortalized human keratinocyte cell line (HaCaT) with sulfamethoxazole (SMX) or dapsone (DDS) resulted in the formation of drug/metabolite protein adducts.