Amphotericin B from antifungal to antiviral therapy: promising modern therapeutic branch

Balancing renal Ang-II/Ang-(1-7) by xanthenone; an ACE2 activator; contributes to the attenuation of Ang-II/p38 MAPK/NF-κB p65 and Bax/caspase-3 pathways in amphotericin B-induced nephrotoxicity in rats

Despite the great importance of amphotericin B for the management of life-threatening systemic fungal infections, its nephrotoxic effect restricts its repeated administration. This study was designed to examine the prospective modulatory effects of xanthenone, an ACE2 activator, against amphotericin B nephrotoxicity. Male Wistar rats were allocated into four groups; control (1^st), Xanthenone (2^nd), Amphotericin B (3^rd), and Xanthenone + Amphotericin B (4^th). The second and fourth groups received xanthenone (2 mg/kg; s.c.) daily for 14 consecutive days. Amphotericin B (18.5 mg/kg; i.p.) was administered to the third and fourth groups daily starting from day 8. After 2 weeks, samples were withdrawn for analysis. The histopathological findings, molecular and biochemical markers showed that amphotericin B caused marked renal injury. Pretreatment with xanthenone ameliorated amphotericin B-induced deterioration in kidney function biomarkers (creatinine, urea, cystatin C, KIM-1) and guarded against the disturbance of serum electrolytes (Na⁺, K⁺, Mg²⁺) due to amphotericin B-induced tubular dysfunction. Besides, the ACE2 activator xanthenone-balanced renal Ang-II/Ang-(1-7), and so the inflammatory signaling p38 MAPK/NF-κB p65 and its downstream inflammatory cytokines (TNF-α, IL-6) were attenuated. Meanwhile, the anti-oxidant signaling Nrf2/HO-1 and glutathione content were preserved, but the lipid peroxidation marker MDA was declined. These regulatory effects of xanthenone eventually enhanced Bcl-2 (anti-apoptotic), but reduced Bax (pro-apoptotic) and cleaved caspase-3 (apoptotic executioner) protein expressions. Collectively, the regulatory effects of xanthenone on renal Ang-II/Ang-(1-7) could at least partially contribute to the mitigation of amphotericin B nephrotoxicity by attenuating inflammatory signaling, oxidative stress, and apoptosis, thus improving the tolerability to amphotericin B.

The Antibacterial Action of Safranin and Gentian Violet

BACKGROUND

The increasing resistance of many bacterial pathogens against antibiotic measures urgently requires new or repurposing therapeutic strategies. Gentian violet is a triarylmethane dye used as a histological stain and for Gram's method of classifying bacteria. It also exerts an antimicrobial effect against certain pathogens, especially dermatological infections. Safranin is the most popular counterstain used in medical laboratories due to its low cost and safe laboratory usage. However, few studies have been conducted on the antimicrobial activity of safranin.

OBJECTIVE

With the growing prevalence of multidrug-resistant bacteria, this study aimed to evaluate the antibacterial efficacy of gentian violet and safranin against multidrug-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa).

METHODS

All tested bacteria were multidrug-resistant (MDR) bacteria isolated from skin infections (abscesses and wounds). Using gentian violet and safranin, antibacterial effects were studied using the well-diffusion method against 20 samples of clinically isolated bacteria, 10 diagnosed as S. aureus, and 10 as P. aeruginosa. Bacteria were diagnosed using the VITEK 2 automated system (bioMérieux, Marcy-l'Étoile, France). Iodine served as the control agent, since both Gram-positive and Gram-negative bacteria are sensitive to it.

RESULTS

Gentian violet dye has been shown to be 100% sensitive to both Gram-positive and Gram-negative bacterial isolates. Although safranin also had high sensitivity (100%) to S. aureus isolates, its sensitivity to P. aeruginosa was only 20%. Staphylococcus aureus was more resistant to iodine (40% sensitivity) compared to P. aeruginosa, which was 100% sensitive to iodine.

CONCLUSIONS

Gentian violet and safranin are low-cost and better tolerated topical agents that have potential for use in dermatological applications. Gentian violet had good antibacterial activity against both Gram-positive and Gram-negative bacteria, making it useful for treating bacterial skin pathogens such as S. aureus and P. aeruginosa especially for MDR bacteria. While safranin has good efficacy against Gram-positive bacteria (S. aureus), its effect against Gram-negative bacteria (e.g. P. aeruginosa) is poor.

Teaching an old dog new tricks: drug discovery by repositioning natural products and their derivatives

Given the substantial cost and low success rate of drug discovery and development, repositioning existing drugs to treat new diseases has gained significant attention in recent years, with potentially lower development costs and shorter time frames. Natural products show great promise in drug repositioning because they have been used for various medical purposes for thousands of years. In this review, we discuss the drug repositioning of six prototypical natural products and their derivatives to reveal new drug-disease associations. We also highlight opportunities and challenges in natural product-based drug repositioning for future reference.