Epidermal hydrogen peroxide is not increased in lesional and non-lesional skin of vitiligo

Caffeic acid derivative WSY6 protects melanocytes from oxidative stress by reducing ROS production and MAPK activation

Purpose

Vitiligo is a chronic depigmentation disease caused by a loss of functioning melanocytes and melanin from the epidermis. Oxidative stress-induced damage to melanocytes is key in the pathogenesis of vitiligo. WSY6 is a caffeic acid derivative synthesized from epigallocatechin-3-gallate (EGCG). This study is to investigate whether the new chemical WSY6 protected melanocytes from H2O2-induced cell damage and to elucidate the underlying molecular mechanism.

Patients and methods

The present study compared the antioxidative potential of WSY6 with EGCG in hydrogen peroxide (H2O2)-treated PIG1 cells. Western blotting was used to study the protein expression of cyto-c, cleaved-caspase3, cleaved-caspase9, and the activation of MAPK family members, including p38, ERK1/2, JNK and their phosphorylation in melanocytes. ROS assay kit to detect intracellular reactive oxygen species production; CCK8 and lactate dehydrogenase leak assay to detect cytotoxicity.

Results

EGCG and WSY6 ameliorated H2O2-induced oxidative stress damage in PIG1 cells in a does-dependent manner, while WSY6 was much more effective. WSY6 reduced cellular ROS production, cytochrome c release, downregulated caspase-3 and caspase-9 activation. MAPK pathway signaling including phosphorylated p38, ERK and JNK were observed under oxidative stress and can be much protected by pre-treatment of WSY6.

Conclusion

These results indicated that WSY6 could be a more powerful antioxidant than EGCG and protect melanocytes against oxidative cytotoxicity.

Label-free in vivo assessment of brain mitochondrial redox states during the development of diabetic cognitive impairment using Raman spectroscopy

Mitochondrial redox imbalance has been recognized as a unifying cause for diabetic cognitive impairment. Currently, a robust method for the in vivo assessment of brain mitochondrial redox imbalance is still lacking. Here, we conducted a spectral study to assess brain mitochondrial redox imbalance in the process of diabetic cognitive impairment by using label-free resonance Raman spectroscopy (RRS). Our findings showed that mitochondrial redox imbalance in cultured neurons and organotypic cortical slices exposed to high glucose were quantified by the reduction of Raman peak area at 750 cm^-1 and 1128 cm^-1, which were also associated with synaptic injury and neuron apoptosis. Raman peak area at 750 cm^-1 and 1128 cm^-1 were also decreased in db/db mice at the age of 8, 16 and 24 weeks, and had a high correlation with the mitochondrial NAD⁺/NADH redox couple. Of note, this mitochondrial redox imbalance occurred before measurable cognitive decline in 8-week-old diabetic mice, and might signal impending diabetic cognitive impairment. In summary, RRS-based mitochondrial redox states assay enabled the in vivo assessment of brain mitochondrial redox imbalance, and might provide an early indicator to enhance the prediction of diabetic cognitive impairment and inform on the response to therapies targeting mitochondrial redox imbalance.

Clinical and Molecular Aspects of Vitiligo Treatments

Vitiligo is an asymptomatic but cosmetically disfiguring disorder that results in the formation of depigmented patches on skin and/or mucosae. Vitiligo can be segmental or non-segmental depending upon the morphology of the clinical involvement. It can also be classified as progressing or stable based on the activity of the disease. Further, the extent of involvement can be limited (localized disease) or extensive (generalized disease). The treatment of vitiligo therefore depends on the clinical classification/characteristics of the disease and usually comprises of 2 strategies. The first involves arresting the progression of active disease (to provide stability) in order to limit the area involved by depigmentation. The second strategy aims at repigmentation of the depigmented area. It is also important to maintain the disease in a stable phase and to prevent relapse. Accordingly, a holistic treatment approach for vitiligo should be individualistic and should take care of all these considerations. In this review, we shall discuss the vitiligo treatments and their important clinical and molecular aspects.