Mutilin

14-O-[(4,6-Diaminopyrimidine-2-yl)thioacetyl] mutilin (DPTM) is a promising drug candidate with excellent antibacterial activity against Gram-positive bacteria. The present study was designed to characterize its Cytochrome P450 (CYP) enzymes inhibition activities and the genotoxicity with the standard Ames test. We determined the inhibitory effects of DPTM on CYP1A2, CYP2D1/6, CYP2E1, CYP2C11/9 and CYP3A/4 in rat liver microsomes (RLMs) and in human liver microsomes (HLMs). The mRNA expressions of the above CYP isoforms and their transcriptional regulators were also evaluated using the Hep G2 cell model. The results showed DPTM exhibited a moderate inhibitory potential against CYP3A/4 (IC50values of 10 ± 2 and 8 ± 2 μM, respectively) and weak against the other CYP enzymes based on their IC50values. Compared to the control, CYP isoforms and their transcriptional regulators mRNA expressions significantly increased when the Hep G2 cells were treated with DPTM for a certain period of time. In the Ames test, Salmonella strains TA97, TA98, TA100, TA102 and TA1535 were treated with or without the metabolic activation (S9). Analysis showed the average number of revertant colonies per plate was less in double in the groups treated with DPTM than that in the negative control plate and showed no dose-related increase.

Staphylococcus aureus(S. aureus) is a major human pathogen that requires new antibiotics with unique mechanism. A new pleuromutilin derivative, 14-O-[(4,6-Diamino-pyrimidine-2-yl) thioacetyl] mutilin (DPTM), has been synthesized and proved as a potent antibacterial agent using in vitro and in vivo assays. In the present study, DPTM was further in vitro evaluated against methicillin-resistantStaphylococcus aureus(MRSA) isolated from dairy farms and outperformed tiamulin fumarate, a pleuromutilin drug used for veterinary. Moreover, a murine skin wound model caused by MRSA infection was established, and the healing effect of DPTM was investigated. The results showed that DPTM could promote the healing of MRSA skin infection, reduce the bacterial burden of infected skin MRSA and decrease the secretion of IL-6 and TNF-α inflammatory cytokines in plasma. These results provided the basis for further in-depth drug targeted studies of DPTM as a novel antibacterial agent.

A new pleuromutilin derivative, 14-O-[(4,6-Diaminopyrimidine-2-yl) thioacetyl] mutilin (DPTM), has been synthesized and proven to be a potent agent against Gram-positive pathogens, especially for Staphylococcus aureus (S. aureus). However, its pharmacological activities against α-hemolysin (Hla), a major virulence factor produced by S. aureus, and inflammations related to S. aureus are still unknown. In the present study, we investigated the DPTM inhibition activities against methicillin-resistant S. aureus (MRSA) Hla and protective efficacy of Raw264.7 cells from injury induced by MRSA. The results showed that DPTM with sub-inhibitory concentrations significantly inhibited Hla on the hemolysis of rabbit erythrocytes and down-regulated the gene expressions of Hla and agrA with a dose-dependent fashion. In Raw264.7 cells infected with MRSA, DPTM efficiently attenuated the productions of lactate dehydrogenase (LDH), nitric oxide (NO) and pro-inflammatory cytokines, as well as the express levels of nuclear factor-kappaB (NF-κB), nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, DPTM inhibited the translocation of p-65 to nucleus in RAW264.7 cells infected by MRSA.