RESUMO
Rifamycin derivatives, such as rifampicin, have potent antibiotic activity and have long been used in the clinic as mainstay components for the treatment of tuberculosis, leprosy, and AIDS-associated mycobacterial infections. However, the extensive usage of these antibiotics has resulted in the rapid development of bacterial resistance. The resistance mechanisms mainly include mutations of the rifamycin target RNA polymerase of bacteria and enzymatic modifications of rifamycin antibiotics. One modification is the recently characterized rifamycin degradation catalyzed by Rox enzymes, which belong to the widely occurring flavin monooxygenases. Intriguingly, our recent sequence analysis revealed the rifamycin producers also encode Rox homologs that are not yet characterized. In this work, we expanded the study of the Rox-catalyzed rifamycin degradation. We first showed that the Rox proteins from rifamycin producers have the enzymatic rifamycin SV-degrading activity. Then we used the structurally diverse rifamycin compounds rifampicin and 16-demethylrifamycin W to probe the substrate scope and found that they each have a slightly different substrate scope. Finally, we demonstrated that Rox proteins can also catalyze the transformation of 16-demethylsalinisporamycin to 16-demethylsaliniketal A. Since 16-demethylsalinisporamycin and 16-demethylsaliniketal A are the counterpart analogs of salinisporamycin and saliniketal A, our biochemical findings not only uncover a previously uncharacterized self-resistance mechanism in the rifamycin producers, but also bridge the gap between the biosynthesis of the potential antitumor compound saliniketal A.
RESUMO
BACKGROUND: Vitiligo is characterized by the loss and/or dysfunction of melanocytes in the skin and has a profound impact on the social interactions of patients. Although there are many treatment options for vitiligo, the outcome is frequently unsatisfactory, especially for patients with stable vitiligo. OBJECTIVES: To study the biological properties of melanocytes derived from human hair follicles and to observe the efficacy of using transplants of autologous hair follicle cells to treat patients with stable vitiligo. METHODS: From February 2014 to March 2017, 26 patients with stable vitiligo, who were refractory to all current routine therapy, underwent treatment with transplanted autologous hair follicle cells. The skin graft from each patient's occipital region was trimmed to remove excess adipose tissue and some of the upper part of the dermis. The remaining tissue, including hair follicles and dermal papillae, was cut into pieces and incubated in collagenase type IV and then in trypsin-ethylenediaminetetraacetic acid solutions. The cells were recovered, resuspended in the patient's own serum and then applied to the recipient area. Clinical observations continued for 6 months to 1 year. Laboratory experiments were also performed during this time on scalp specimens obtained from normal human volunteers. Cells migrating from the outer root sheath and the dermal papillae at various times of culture were observed using a microscope. RESULTS: Most of the repigmentation in the vitiligo areas appeared within 8 weeks of transplantation of autologous hair follicle cells. Early skin repigmentation was not uniform and appeared more repigmented than the surrounding normal skin. As time went by, the repigmentation became more obvious and matched the color of the skin around the lesion. Most of the pigmentation presented as a diffuse pattern and was not localized around the hair follicles. Among the 26 patients, 9 (34.6%) achieved excellent repigmentation, while 13 (50.0%) had good, 3 (11.5%) fair and 1 (3.9%) poor repigmentation. During the follow-up visit at 1 year, no excess hair growth was observed in the recipient areas and there was no scarring or ulcer formation in the donor or recipient areas. In the experimental part of the study, many keratinocytes, melanocytes and fibroblasts migrated from the adherent outer root sheath. In later subcultures using a specialized medium, pure melanocytes were obtained that had a strong proliferative capacity and had bipolar or poly-dendritic shapes. On the other hand, cells from the dermal papillae grew radially in primary culture and were almost fibroblast-like. However, a few bipolar melanocytes appeared in the later stage of culture. CONCLUSIONS: The results of our study show that transplantation of autologous hair follicle cells is a simple and effective method to treat patients with stable vitiligo. Hair follicles (especially the outer root sheath) harbor many melanocytes with potential proliferative ability. LIMITATIONS: There are a few limitations of the present study: a small sample size, a short follow-up period, no cell counting or viability testing.