Synthesis and preliminary anti-inflammatory and anti-bacterial evaluation of some diflunisal aza-analogs

Diflunisal attenuates acute inflammatory responses through inhibition of NF-κB signaling pathway in Staphylococcus aureus-induced mastitis of lactating mouse model

The cure rate of Staphylococcus aureus mastitis by conventional antibiotic therapy is very poor. Diflunisal (DIF), a difluorophenol derivative of salicylic acid, is reported to have strong anti-bacterial and anti-inflammatory effects against S. aureus infection. The present study aimed to evaluate the potential therapeutic effect of DIF administration against S. aureus-induced mastitis in mouse model by assessing the bacterial load, inflammation and histopathological changes in mammary gland. Eighteen lactating Swiss albino mice were divided into four groups: uninfected control, S. aureus-induced mastitis model, antibiotic (ceftriaxone)-treatment and diflunisal (DIF)-treatment. In S. aureus-induced mastitis mice, markedly increased bacterial load, myeloperoxidase, NF-κB and nitric oxide (NO) levels and up regulations of IL-1β, NF-κB and TNF-α mRNA expressions in mammary tissues with severe necrosis, marked infiltration of neutrophils and fibrosis in histopathology were noticed. Intramammary administration of DIF in S. aureus-induced mastitis mice showed a significant reduction in bacterial load, myeloperoxidase, NF-κB and NO concentrations in mammary tissues. The DIF treatment also suppressed the inflammatory NF-κB signaling in the inflamed mammary tissues by downregulation of IL-1β, NF-κB and TNF-α mRNA expressions. Further, the histopathology of mammary tissues showed mild necrosis with mild inflammatory cells infiltration, few bacterial colonies, moderate fibrosis, and marked regenerative changes with near to normal histological architecture. The findings of the study provide the evidence of therapeutic potential of DIF in S. aureus-induced mastitis by promising antibacterial and anti-inflammatory activities along with ameliorative impact against the histopathological alterations in mammary tissues.

From Ethnobotany to Biotechnology: Wound Healing and Anti-Inflammatory Properties of Sedum telephium L. In Vitro Cultures

Sedum telephium is a succulent plant used in traditional medicine, particularly in Italy, for its efficacy in treating localized inflammation such as burns, warts, and wounds. Fresh leaves or freshly obtained derivatives are directly applied to the injuries for these purposes. However, challenges such as the lack of microbiologically controlled materials and product standardization prompted the exploration of more controlled biotechnological alternatives, utilizing in vitro plant cell cultures of S. telephium. In the present study, we used HPLC-DAD analysis to reveal a characteristic flavonol profile in juices from in vivo leaves and in vitro materials mainly characterized by several kaempferol and quercetin derivatives. The leaf juice exhibited the highest content in total flavonol and kaempferol derivatives, whereas juice from callus grown in medium with hormones and callus suspensions showed elevated levels of quercetin derivatives. The in vitro anti-inflammatory and wound-healing assays evidenced the great potential of callus and suspension cultures in dampening inflammation and fostering wound closure, suggesting quercetin may have a pivotal role in biological activities.

Diflunisal and Analogue Pharmacophores Mediating Suppression of Virulence Phenotypes in Staphylococcus aureus

Invasive methicillin-resistant Staphylococcus aureus (MRSA) infections are leading causes of morbidity and mortality that are complicated by increasing resistance to conventional antibiotics. Thus, minimizing virulence and enhancing antibiotic efficacy against MRSA is a public health imperative. We originally demonstrated that diflunisal (DIF; [2-hydroxy-5-(2,4-difluorophenyl) benzoic acid]) inhibits S. aureus virulence factor expression. To investigate pharmacophores that are active in this function, we evaluated a library of structural analogues for their efficacy to modulate virulence phenotypes in a panel of clinically relevant S. aureus isolates in vitro. Overall, the positions of the phenyl, hydroxyl, and carboxylic moieties and the presence or type of halogen (F vs. Cl) influenced the efficacy of compounds in suppressing hemolysis, proteolysis, and biofilm virulence phenotypes. Analogues lacking halogens inhibited proteolysis to an extent similar to DIF but were ineffective at reducing hemolysis or biofilm production. In contrast, most analogues lacking the hydroxyl or carboxylic acid groups did not suppress proteolysis but did mitigate hemolysis and biofilm production to an extent similar to DIF. Interestingly, chirality and the substitution of fluorine with chlorine resulted in a differential reduction in virulence phenotypes. Together, this pattern of data suggests virulence-suppressing pharmacophores of DIF and structural analogues integrate halogen, hydroxyl, and carboxylic acid moiety stereochemistry. The anti-virulence effects of DIF were achieved using concentrations that are safe in humans, do not impair platelet antimicrobial functions, do not affect S. aureus growth, and do not alter the efficacy of conventional antibiotics. These results offer proof of concept for using novel anti-virulence strategies as adjuvants to antibiotic therapy to address the challenge of MRSA infection.

A novel phenolic derivative inhibits AHL-dependent quorum sensing signaling in Pseudomonas aeruginosa

Increasing antibiotic resistance and the decline in the pharmaceutical industry’s investments have amplified the need for novel treatments for multidrug-resistant bacteria. Quorum sensing (QS) inhibitors reduce pathogens’ virulence without selective pressure on bacteria and provide an alternative to conventional antibiotic-based therapies. P. aeruginosa uses complex QS signaling to control virulence and biofilm formation. We aimed to identify inhibitors of P. aeruginosa QS acting on acyl-homoserine lactones (AHL)-mediated circuits. Bioluminescence and qRT-PCR assays were employed to screen a library of 81 small phenolic derivatives to reduce AHL-dependent signaling. We identified GM-50 as the most active compound inhibiting the expression of AHL-regulated genes but devoid of cytotoxic activity in human epithelial cells and biocidal effects on bacteria. GM-50 reduces virulence factors such as rhamnolipids, pyocyanin, elastase secretion, and swarming motility in P. aeruginosa PAO1 laboratory strain. By molecular docking, we provide evidence that GM-50 highly interacts with RhlR. GM-50 significantly improved aztreonam-mediated biofilm disruption. Moreover, GM-50 prevents adhesion of PAO1 and inflammatory damage in the human A549 cell line and protects Galleria mellonella from PAO1-mediated killing. GM-50 significantly reduces virulence factors in 20 P. aeruginosa clinical isolates from patients with respiratory tract infections. In conclusion, GM-50 inhibits AHL-signaling, reduces virulence factors, enhances the anti-biofilm activity of aztreonam, and protects G. mellonella larvae from damage induced by P. aeruginosa. Since GM-50 is active on clinical strains, it represents a starting point for identifying and developing new phenolic derivatives acting as QS-inhibitors in P. aeruginosa infections.

Problems associated with the use of the term "antibiotics"

The term “antibiotics” is a broadly used misnomer to designate antibacterial drugs. In a recent article, we have proposed to replace, e.g., the term “antibiotics” by “antibacterial drugs”, “antibiosis” by “antibacterial therapy”, “antibiogram” by “antibacteriogram”, and “antibiotic stewardship” by “antibacterial stewardship” (Seifert and Schirmer Trends Microbiol, 2021). In the present article, we show that many traditional terms related to antibiotics are used much more widely in the biomedical literature than the respective scientifically precise terms. This practice should be stopped. Moreover, we provide arguments to end the use of other broadly used terms in the biomedical literature such as “narrow-spectrum antibiotics” and “reserve antibiotics”, “chemotherapeutics”, and “tuberculostatics”. Finally, we provide several examples showing that antibacterial drugs are used for non-antibacterial indications and that some non-antibacterial drugs are used for antibacterial indications now. Thus, the increasing importance of drug repurposing renders it important to drop short designations of drug classes such as “antibiotics”. Rather, the term “drug” should be explicitly used, facilitating the inclusion of newly emerging indications such as antipsychotic and anti-inflammatory. This article is part of an effort to implement a new rational nomenclature of drug classes across the entire field of pharmacology.

A case to stop the use of the term 'antibiotics'

The word 'antibiotics' is an historical, but imprecise, term. Today, 'antibiotics' are also used for other indications and 'non-antibiotics' are repurposed for infectious diseases. This situation calls for a revision of antipathogenic drug terminology. The use of correct terms will facilitate rational antipathogenic treatment and understanding of drug repurposing.

A Novel Aza-Derivative Inhibits agr Quorum Sensing Signaling and Synergizes Methicillin-Resistant Staphylococcus aureus to Clindamycin

Increasing antibiotic resistance and diminishing pharmaceutical industry investments have increased the need for molecules that can treat infections caused by dangerous pathogens such as methicillin-resistant Staphylococcus aureus (MRSA). Quorum Sensing (QS) is a signaling mechanism that regulates bacterial virulence in pathogens. A report demonstrating that the anti-inflammatory drug Diflunisal reduces MRSA virulence factors' expression prompted us to design, synthesize and test 16 aza-analogs as inhibitors of S. aureus virulence factors controlled by the accessory gene regulator (agr) QS system. At first, we evaluated by qRT-PCR the activity of compounds on rnaIII expression, a QS related gene. Azan-7 was the most active molecule tested and it did not show cytotoxic activity in human cell lines. Moreover, we demonstrated that it did not affect bacterial proliferation. Regulation of MRSA virulence genes by Azan-7 was investigated using qRT-PCR and RNAseq. Azan-7 significantly reduced hla, psmα, hysA, agrA, cap1A, and cap1C gene expression. In silico docking demonstrated that Azan-7 binds the response regulator AgrA. This data was confirmed by electrophoretic mobility shift assay (EMSA) reporting that Azan-7 binding to AgrA protein strongly reduced the AgrA-DNA complex formation at the P3 promoter region involved in the regulation of rnaIII transcription. Azan-7 inhibited MRSA-mediated haemolysis, reduced survival of the pathogen at low pH levels, and increased macrophage killing. In addition, Azan-7 enhanced MRSA susceptibility to clindamycin both in planktonic growth and biofilm. Azan-7 did not induce resistance over 10 days in culture. It was equally active against all the AgrA MRSA subtypes encountered among clinical isolates, but it was not active against Staphylococcus epidermidis, although the AgrA proteins show an approximate 80% homology. These results demonstrate that Azan-7 inhibits the expression of MRSA virulence factors by interfering in the QS and synergizes MRSA biofilm with clindamycin, indicating the compound as a promising candidate for the treatment of MRSA infections.