Sulphur and skin: from Satan to Saddam!

Microorganisms uptake zero-valent sulfur via membrane lipid dissolution of octasulfur and intracellular solubilization as persulfide

Zero-valent sulfur, commonly utilized as a fertilizer or fungicide, is prevalent in various environmental contexts. Its most stable and predominant form, octasulfur (S8), plays a crucial role in microbial sulfur metabolism, either through oxidation or reduction. However, the mechanism underlying its cellular uptake remains elusive. We presented evidence that zero-valent sulfur was adsorbed to the cell surface and then dissolved into the membrane lipid layer as lipid-soluble S8 molecules, which reacted with cellular low-molecular thiols to form persulfide, e.g., glutathione persulfide (GSSH), in the cytoplasm. The process brought extracellular zero-valent sulfur into the cells. When persulfide dioxygenase is present in the cells, GSSH will be oxidized. Otherwise, GSSH will react with another glutathione (GSH) to produce glutathione disulfide (GSSG) and hydrogen sulfide (H2S). The mechanism is different from simple diffusion, as insoluble S8 becomes soluble GSSH after crossing the cytoplasmic membrane. The uptake process is limited by physical contact of insoluble zero-valent sulfur with microbial cells and the regeneration of cellular thiols. Our findings elucidate the cellular uptake mechanism of zero-valent sulfur, which provides critical information for its application in agricultural practices and the bioremediation of sulfur contaminants and heavy metals.

Comparative evaluation of therapeutic efficacy and safety of black peel versus 25% trichloroacetic acid peel in mild to moderate acne vulgaris: a split face study

Introduction

Peeling has withstood the test of time as a simple, minimally invasive method to renew the skin, despite the introduction of more advanced procedures like lasers.

Materials and Methods

Thirty patients (or 60 sites) with age ranging from 15 to 45 years with mild-to-moderate acne vulgaris were included in the study. Assessment at baseline was done by the global acne grading system score for including mild and moderate acne patients.

Results

On grading the improvement according to the 5-point Global Assessment Scale (GAS), it was found that in area A (black peel), 6.7% of patients showed excellent improvement, 86.7% of patients showed good improvement, and 6.7% of patients showed fair improvement. In area B (25%TCA peel), 6.7% of patients showed excellent improvement, 80% of patients showed good improvement, and 13.3% of patients showed fair improvement.

Discussion

None of the patients showed poor or worse outcomes in any of the areas. The difference between the groups was not significant (P = 0.688).

Conclusion

There is a paucity of data in the literature regarding the comparison of black peel with other conventional peels in the treatment of acne vulgaris. To the best of our knowledge, this is the first study comparing black peel with TCA peel in the treatment of acne vulgaris.

The Pleiotropic Regulator AdpA Regulates the Removal of Excessive Sulfane Sulfur in Streptomyces coelicolor

Reactive sulfane sulfur (RSS), including persulfide, polysulfide, and elemental sulfur (S₈), has important physiological functions, such as resisting antibiotics in Pseudomonas aeruginosa and Escherichia coli and regulating secondary metabolites production in Streptomyces spp. However, at excessive levels it is toxic. Streptomyces cells may use known enzymes to remove extra sulfane sulfur, and an unknown regulator is involved in the regulation of these enzymes. AdpA is a multi-functional transcriptional regulator universally present in Streptomyces spp. Herein, we report that AdpA was essential for Streptomyces coelicolor survival when facing external RSS stress. AdpA deletion also resulted in intracellular RSS accumulation. Thioredoxins and thioredoxin reductases were responsible for anti-RSS stress via reducing RSS to gaseous hydrogen sulfide (H₂S). AdpA directly activated the expression of these enzymes at the presence of excess RSS. Since AdpA and thioredoxin systems are widely present in Streptomyces, this finding unveiled a new mechanism of anti-RSS stress by these bacteria.

Elemental Sulfur Inhibits Yeast Growth via Producing Toxic Sulfide and Causing Disulfide Stress

Elemental sulfur is a common fungicide, but its inhibition mechanism is unclear. Here, we investigated the effects of elemental sulfur on the single-celled fungus Saccharomyces cerevisiae and showed that the inhibition was due to its function as a strong oxidant. It rapidly entered S. cerevisiae. Inside the cytoplasm, it reacted with glutathione to generate glutathione persulfide that then reacted with another glutathione to produce H₂S and glutathione disulfide. H₂S reversibly inhibited the oxygen consumption by the mitochondrial electron transport chain, and the accumulation of glutathione disulfide caused disulfide stress and increased reactive oxygen species in S. cerevisiae. Elemental sulfur inhibited the growth of S. cerevisiae; however, it did not kill the yeast for up to 2 h exposure. The combined action of elemental sulfur and hosts’ immune responses may lead to the demise of fungal pathogens.

Plinia cauliflora (Mart.) Kausel: toxicological assays, biological activities, and elemental analysis of organic compounds

Jaboticaba, Plinia cauliflora (Mart.) Kausel, is a Brazilian berry traditionally used in folk medicine as treatment for some health conditions. Phenolic compounds such as flavonoids and anthocyanins have previously been detected in the fruit. This current study aimed to evaluate the toxicological effects of jaboticaba peel extract (JPE) on Artemia salina, L929, and MDA-MB-231 cell lines. Besides, JPE antioxidant, acetylcholinesterase, and antifungal activities, and elemental analysis CHNS were also tested. JPE had moderate toxicity (LD₅₀ = 360.92 μg mL^-1) on A. salina, non-toxic effect on L929 cell line, and decreased the viability of cancer cell line MDA at 1,000 µg mL^-1 and 500 µg mL^-1 concentrations. The antioxidant activity toward 2,2-diphenyl-1-picrylhydrazyl (DPPH) performed IC₅₀ = 37.45 ± 0.17 µg mL^-1, whereas 45.7% of acetylcholinesterase activity was inhibited. By its elemental composition, JPE is an alternative food supplement and dermocosmetic component. Antifungal potential toward Candida strains was not observed.

Ahram mineral water-induced sulfate keratopathy: histopathologic, electron microscopic, and confocal scan features

PURPOSE

To characterize histopathologic, electron microscopic, and confocal scan features of Ahram mineral water (AMW)-induced keratopathy in cadaver corneas.

METHODS

Seven cadaver globes were examined, 5 of which were exposed to AMW from the corneal side for different durations (30 seconds and 3, 15, 30, and 60 minutes) and the other 2 were considered as control. After performing confocal scan on each cornea, we excised the corneoscleral rim and sent it for histopathologic evaluation. Scanning electron microscopic and transmission electron microscopic examinations were performed on the cornea exposed to AMW for 60 minutes.

RESULTS

Depending on the time of exposure, the confocal scan features varied from intraepithelial high-contrast deposits to subepithelial bulla formation. The histopathologic features ranged from diffuse intracytoplasmic sulfur deposits to subepithelial bulla formation. Scanning electron microscopic examination disclosed rather diffuse irregular bright deposits of high sulfur content over the surface epithelium and together with focal cellular destruction and micro-hole formation in the case with 60-minute exposure. On transmission electron microscopy, electron-lucent bulky deposits were found underneath the basal epithelial cells and between their basement membrane and Bowman layer. Confocal scan of the control corneas disclosed nonspecific anterior stromal haze and Descemet folds, with no evidence of intraepithelial deposits. No pathologic finding was noted on histopathologic examination of the control corneas.

CONCLUSIONS

AMW induces sulfate keratopathy of mainly anterior corneal involvement and with various histopathologic, confocal microscopic, and electron microscopic features even with short-time exposure.

Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

Sulfur nanoparticles were synthesized from hazardous H₂S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe³⁺–malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 andn-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H₂S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5–15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.