DUOX expression in human keratinocytes and bronchial epithelial cells: Influence of vanadate

DUOX1 in mammalian disease pathophysiology

Dual oxidase 1 (DUOX1) is a member of the protein family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. DUOX1 has several normal physiological, immunological, and biochemical functions in different parts of the body. Dysregulated oxidative metabolism interferes with various disease pathologies and numerous therapeutic options are based on targeting cellular redox pathways. DUOX1 forms an important enzymatic source of biological oxidants, and DUOX1 expression is frequently dysregulated in various diseases. While this review shortly addresses the biochemical and cellular properties and proposed physiological roles of DUOX1, its main purpose is to summarize the current knowledge with respect to the potential role of DUOX1 enzyme in disease pathology, especially in mammalian organisms. Although DUOX1 is normally prominently expressed in epithelial lineages, it is frequently silenced in epithelial-derived cancers by epigenetic mechanisms. While an abundance of information is available on DUOX1 transcription in different diseases, an increasing number of mechanistic studies indicate a causative relationship between DUOX1 function and disease pathophysiology. Additionally, specific functions of the DUOX1 maturation factor, DUOXA1, will also be addressed. Lastly, urgent and outstanding questions on the field of DUOX1 will be discussed that could provide valuable new diagnostic tools and novel therapeutic options.

Off-target effects of protein tyrosine phosphatase inhibitors on oncostatin M-treated human epidermal keratinocytes: the phosphatase targeting STAT1 remains unknown

Cytokine signaling in the epidermis has an important role in maintaining barrier function and is perturbed in pathological conditions. Environmental exposures, such as to metal compounds, are of interest for their potential contribution to skin disease. Present work explores the possibility that vanadate is a more effective protein tyrosine phosphatase inhibitor in human keratinocytes than previously observed in fibroblasts. It focuses on the state of phosphorylation of signal transducer and activator of transcription 1 (STAT1) on tyrosine 701 upon treatment of cultured human keratinocytes with the cytokine oncostatin M, a cutaneous inflammatory mediator that is highly effective in suppressing several differentiation markers and in preserving proliferative potential of keratinocytes. Exposure to sodium vanadate in the medium greatly prolonged the phosphorylation of STAT1, but only at high concentration (>30 µM). Inhibitors of protein tyrosine phosphatases known to dephosphorylate STAT1 (SHP2, TCPTP, PTP1B) were ineffective in mimicking the action of vanadate. The irreversible protein tyrosine phosphatase inhibitor phenyl vinyl sulfonate alone induced STAT1 phosphorylation and appeared to induce its limited cleavage. It also inhibited cross-linked envelope formation, a characteristic step of keratinocyte terminal differentiation, likely due to its reaction with the active site cysteine of keratinocyte transglutaminase. Thus, the key protein tyrosine phosphatase responsible for STAT1 dephosphorylation remains to be identified, and an off-target effect of a potential inhibitor was revealed.