Isolation and screening of rare Actinobacteria, a new insight for finding natural products with antivascular calcification activity

AimVascular calcification (VC) is a significant pathological process in some life-threatening diseases. Several pathological mechanisms, including transdifferentiation of vascular smooth muscle cells to osteoblast-like cells and apoptosis are involved in VC. Compounds with an inhibitory effect on these processes are potentially efficient medications. In consideration of the multiple biological activities of Actinobacteria, this research was aimed at finding anti-VC metabolite-producing Actinobacteria. Methods and ResultsAfter the isolation and identification of Actinobacteria, the effect of their fermentation broth extracts on the apoptosis rate was measured using various methods, for example, ethidium bromide/acridine orange staining, DNA laddering and diphenylamine assays. The effect of the most effective fermentation broth extract of Actinobacteria (FBEA) on the mRNA expression of runt-related transcription factor 2 (Runx2) and osteopontin (OPN) was examined. Finally, the most effective FBEA was fractionated and the chemical composition of anti-VC fractions was analysed using GC-MS. Various VC inhibition rates were observed in the tested FBEA (20gml(-1); 179-6015%). The inhibition of DNA fragmentation was 7-48%. The FBE with the greatest anticalcification activity belonged to Kribbella sp. UTMC 267 and, according to 16S rRNA analysis, Kribbella sancticallisti with a similarity of 9853% is its nearest neighbour. The FBE of Kribbella sp. UTMC 267 reduced Runx2 mRNA expression by 295-fold and OPN mRNA expression by 2857-fold, both of which are considered significant (P<005). Finally, GC-MS analysis showed the existence of potent anti-oxidative and anti-inflammation agents in FBE of Kribbella sp. UTMC 267. ConclusionsActinobacterial metabolites can provide a new strategy for treating VC diseases by reducing the expression of osteogenic genes, the apoptosis rate and oxidative stress. Significance and Impact of the StudyThis study highlights the therapeutic potential of Kribbella sp. metabolites and Actinobacteria as a new natural source for drug discovery programs in the nonantibiotic bioactivity field.