Anti-inflammatory activity of ansamycins

Structural diversity and biological relevance of benzenoid and atypical ansamycins and their congeners

Covering: 2011 to 2021The structural division of ansamycins, including those of atypical cores and different lengths of the ansa chains, is presented. Recently discovered benzenoid and atypical ansamycin scaffolds are presented in relation to their natural source and biosynthetic routes realized in bacteria as well as their muta and semisynthetic modifications influencing biological properties. To better understand the structure-activity relationships among benzenoid ansamycins structural aspects together with mechanisms of action regarding different targets in cells, are discussed. The most promising directions for structural optimizations of benzenoid ansamycins, characterized by predominant anticancer properties, were discussed in view of their potential medical and pharmaceutical applications. The bibliography of the review covers mainly years from 2011 to 2021.

Modifications, biological origin and antibacterial activity of naphthalenoid ansamycins

Covering: 2011 to 2021Structural division of natural naphthalenoid ansamycins, regarding the type of the core and length of the ansa chain, and their biosynthetic pathways in microorganisms are discussed. The great biosynthetic plasticity of natural naphthalenoid ansamycins is reflected in their structural variety due to the alterations within ansa bridge or naphthalenoid core portions. A comparison between the biological potency of natural and semisynthetic naphthalenoid ansamycins was performed and discussed in relation to the molecular targets in cells. The antibacterial potency of naphthalenoid ansamycins seems to be dependent on the ansa chain length and conformational flexibility - the higher flexibility of the ansa chain the better biological outcome is noted.

Chronic pancreatitis with IBS-like syndrome: approach to therapy

Aim.To determine approaches of the exacerbations treatment of chronic pancreatitis (CP) with IBS (irritable bowel syndrome)-like syndrome. Materials and methods.312 patients with exacerbation of CP were observed and received standard therapy: antispasmodics, enzymes, proton pump inhibitors. 85 (27.2%) patients had no response to treatment. After excluding obstructive CP, celiac disease, decompensation of diabetes (DD), ischemic and microscopic colitis, small intestinal bacterial overgrowth (SIBO) as a cause of abdominal pain and intestinal dysfunction, a group of 54 patients with exacerbation of CP and IBS-like syndrome was isolated. They were divided into 2 groups: group 1 persons receiving with standard treatment of CP ciprofloxacin in a dose of 500 mg 2 times a day for 10 days (26 patients), group 2 rifaximin 400 mg 3 times a day for 10 days (28 patients). The dynamics of clinical picture, biocenosis indices, endoscopic, morphological features of the colon, interleukin-2 (IL-2), IL-6, IL-8 concentration in the colon mucosa (CA) were evaluated. Results.IBS-like syndrome was determined in 54 (63.5%) patients with prolonged (more than 4 weeks) exacerbation of CP. A modification of therapy is proposed with the results of clinical and instrumental, laboratory, bacteriological studies. 68% of patients with exacerbation of CP, receiving in addition to the standard regimen rifaximin, achieved clinical improvement, normalization of intestinal biocenosis, reduced concentrations of cytokines in tissues, reducing signs of chronic inflammation in the colon mucosa with reducing concentrations of IL-2, IL-6, IL-8 in colon mucosa (p0.05). Conclusion.Exacerbation of CP, resistant to standard therapy, may be associated with the formation of IBS-like syndrome. The inclusion of rifaximin in the complex therapy of prolonged exacerbation of CP contributes to the relief of intestinal dysfunction, abdominal pain of intestine, improves biocenosis, reduces inflammatory modifications, and reduces the concentration of cytokines in the colon mucosa.

Effect of rifampin on production of inflammatory mediators in HepG2 liver epithelial cells

Rifampin, a potent antibacterial agent, is one of the main drugs used in the treatment of mycobacterial infections. Hepatotoxicity is a well-documented adverse event. The aim of this study was to investigate the effect of rifampin on the production of inflammatory mediators in human epithelial HepG2 liver cells in the absence or presence of proinflammatory cytokines. Incubation of HepG2 cells with a cytokine mix plus rifampin was associated with a significant dose-dependent increase in the production of nitric oxide compared to incubation with the cytokine mix alone (P < 0.05) as well as with an increase in inducible nitric oxide synthase protein and mRNA expression. Rifampin significantly increased the secretion of interleukin 8 (IL-8) in both untreated cells (P < 0.001) and cytokine-treated cells (P < 0.006). An array screening assay revealed that rifampin stimulated the production of IL-1β and gamma interferon-induced protein-10 (IP-10) in untreated cells and increased the secretion of RANTES in cytokine-treated cells. Together, these results indicate that rifampin may exert proinflammatory effects on liver cells.

Pretreatment of epithelial cells with rifaximin alters bacterial attachment and internalization profiles

Rifaximin is a poorly absorbed semisynthetic antibiotic derivative of rifampin licensed for use in the treatment of traveler's diarrhea. Rifaximin reduces the symptoms of enteric infection, often without pathogen eradication and with limited effects on intestinal flora. Epithelial cells (HEp-2 [laryngeal], HCT-8 [ileocecal], A549 [lung], and HeLa [cervical]) were pretreated with rifaximin (or control antibiotics) prior to the addition of enteroaggregative Escherichia coli (EAEC). EAEC adherence was significantly reduced following rifaximin pretreatment compared to pretreatment with rifampin or doxycycline for three of the four cell lines tested. The rifaximin-mediated changes to epithelial cells were explored further by testing the attachment and internalization of either Bacillus anthracis or Shigella sonnei into A549 or HeLa cells, respectively. The attachment and internalization of B. anthracis were significantly reduced following rifaximin pretreatment. In contrast, neither the attachment nor the internalization of S. sonnei was affected by rifaximin pretreatment of HeLa cells, suggesting that rifaximin-mediated modulation of host cell physiology affected bacteria utilizing distinct attachment/internalization mechanisms differently. In addition, rifaximin pretreatment of HEp-2 cells led to reduced concentrations of inflammatory cytokines from uninfected cells. The study provides evidence that rifaximin-mediated changes in epithelial cell physiology are associated with changes in bacterial attachment/internalization and reduced inflammatory cytokine release.

Roles of NF-kappaB activation and peroxisome proliferator-activated receptor gamma inhibition in the effect of rifampin on inducible nitric oxide synthase transcription in human lung epithelial cells

Rifampin (rifampicin), an important antibiotic agent and a major drug used for the treatment of tuberculosis, exerts immunomodulatory effects. Previous studies have found that rifampin increases inducible nitric oxide (NO) synthase (iNOS) expression and NO production. The present study investigated the potential mechanism(s) underlying these actions. The incubation of human lung epithelial A549 cells with a cytokine mix (interleukin-1beta, tumor necrosis factor alpha, and gamma interferon) induced the expression of iNOS mRNA. The addition of rifampin increased the iNOS level by 1.9 +/- 0.3-fold at a dose of 10 microg/ml (P < 0.01) and by 4.0 +/- 0.3-fold at a dose of 50 microg/ml (P < 0.001). Rifampin treatment also affected the transcription factors that regulate iNOS mRNA: there was an increased and prolonged degradation of the inhibitory subunit of NF-kappaB, a corresponding increase in the level of cytokine-induced DNA binding of NF-kappaB (2.1 +/- 0.2-fold), and a decrease in the level of expression of peroxisome proliferator-activated receptor gamma (PPARgamma). Specifically, the level of PPARgamma expression dropped by 15% in response to cytokine stimulation and by an additional 40% when rifampin was added (P < 0.001). Rifampin had no effect on the activation of mitogen-activated protein kinases or the signal transducer and transcription activator (STAT-1). In conclusion, rifampin augments NO production by upregulating iNOS mRNA. It also increases the level of NF-kappaB activation and decreases the level of PPARgamma expression. The increases in the levels of NF-kappaB activation and NO production probably contribute to the therapeutic effects of rifampin. However, given the role of NF-kappaB in upregulating many inflammatory genes and the roles of PPARgamma in downregulating inflammatory genes and in lipid and glucose metabolism, these findings have implications for potential adverse effects of rifampin in patients with chronic inflammatory diseases and glucose or lipid disorders.

Antibacterials as anti-inflammatory agents: dual action agents for oral health

BACKGROUND

Inflammatory processes with a range of specialized cells and biochemical mediators form a complex network of inter-related signal transducing pathways that relay information to preserve normal functions. Advances in molecular analyses of the information relay pathways for their constituents and principal ligands along with mechanisms utilized by the host for microbial recognition have stimulated interest in therapeutic agents with dual functionalities i.e. antibacterial and anti-inflammatory effects.

AIM

This review examines clinically tested agents for oral health applications with both antimicrobial and anti-inflammatory effects to include antibiotics, antimicrobials and phenolics.

RESULTS

Bis-phenols such as triclosan, representing a unique dual functional therapeutic for routine oral hygiene, with its demonstrated clinical effects on inhibiting the dental plaque biofilm, reducing inflammation (gingivitis) and subsequent periodontitis is described. Cyclines, comprising another class of approved anti-inflammatory agents used at the patient level for oral health is discussed. Dual active agents in current clinical practice for systemic conditions are highlighted to summarize the clinical validity of dual function agents as an emerging therapeutic strategy.

CONCLUSIONS

Clinical studies demonstrate therapeutic benefits of agents with dual functionality with their effects on microorganisms and the concomitant host inflammatory response. Advances in microbial pathogenesis and resultant inflammation will facilitate progress in this emerging area poised to be a significant milestone for dental therapeutics.

Interaction of rifalazil with oxidant-generating systems of human polymorphonuclear neutrophils

It is well acknowledged that ansamycins display immunosuppressive and anti-inflammatory properties in vitro and in vivo. Rifalazil, a new ansamycin derivative, has not been studied in the context of inflammation. In particular, there are no data on the possible interference of rifalazil with oxidant production by phagocytes. We have compared the antioxidant properties of rifalazil to those of rifampin, a drug well known in this context, by using cellular and acellular oxidant-generating systems. Oxidant production by polymorphonuclear neutrophils was measured in terms of cytochrome c reduction, lucigenin-amplified chemiluminescence (Lu-ACL), and the 2',7'-dichlorofluorescin diacetate H2 (DCFDA-H2) technique (intracellular oxidant production). Rifalazil impaired O2- production in a concentration-dependent manner, with 50% inhibitory concentrations (IC50) (concentrations which inhibit 50% of the response) of 5.4 (30 and 60 min of incubation) and 6.4 (30 min) mg/liter, respectively, for phorbol myristate acetate (PMA) and formyl-methionyl-leucyl-phenylalanine (fMLP) stimulation. In agreement with the published fMLP-like activity of rifampin, the inhibitory effect of rifampin was significantly greater for fMLP (IC50 of 5.6 mg/liter) than for PMA (IC50 of 58 mg/liter) stimulation. Alteration of intracellular oxidant production was also observed with IC50 values similar to those obtained by the cytochrome assay. In addition, rifalazil and rifampin (> or = 25 mg/liter) scavenged O2-, as demonstrated by the acellular (hypoxanthine-xanthine oxidase) system. Interference with light detection systems was evidenced for both drugs by Lu-ACL. The clinical relevance of the antioxidant effect of rifalazil demonstrated in vitro, in particular its potential anti-inflammatory activity, requires further investigation.