A novel Rap-Phr system in Bacillus velezensis NAU-B3 regulates surfactin production and sporulation via interaction with ComA.

Several quorum sensing systems occurring in Bacillus subtilis, e.g. Rap-Phr systems, were reported to interact with major regulatory proteins, such as ComA, DegU, and Spo0A, in order to regulate competence, sporulation, and synthesis of secondary metabolites. In this study, we characterized a novel Rap-Phr system, RapA4-PhrA4, in Bacillus velezensis NAU-B3. We found that the rapA4 and phrA4 genes were co-transcribed in NAU-B3. When rapA4 was expressed in the heterologous host Bacillus subtilis OKB105, surfactin production and sporulation were severely inhibited. However, when the phrA4 was co-expressed, the RapA4 activity was inhibited. The transcription of the surfactin synthetase srfA gene and sporulation-related genes were also regulated by the RapA4-PhrA4 system. In vitro results obtained from electrophoretic mobility shift assay (EMSA) proved that RapA4 inhibits ComA binding to the promoter of the srfA operon, and the PhrA4 pentapeptide acts as anti-activator of RapA4. We also found that the F24 residue plays a key role in RapA4 function. This study indicated that the novel RapA4-PhrA4 system regulates the surfactin synthesis and sporulation via interaction with ComA, thereby supporting the bacterium to compete and to survive in a hostile environment. KEY POINTS: •Bacillus velezensis NAU-B3 has a novel Rap-Phr quorum sensing system, which does not occur in model strains Bacillus subtilis 168 and B. velezensis FZB42. •RapA4-PhrA4 regulates surfactin production and sporulation. •RapA4-PhrA4 interacts with the ComA protein from ComP/ComA two-component system.

Chronic Kidney Disease Induces Cognitive Impairment in the Early Stage.

OBJECTIVE: Previous research indicates a link between cognitive impairment and chronic kidney disease (CKD), but the underlying factors are not fully understood. This study aimed to investigate the progression of CKD-induced cognitive impairment and the involvement of cognition-related proteins by developing early- and late-stage CKD models in Sprague-Dawley rats. METHODS: The Morris water maze test and the step-down passive avoidance task were performed to evaluate the cognitive abilities of the rats at 24 weeks after surgery. Histopathologic examinations were conducted to examine renal and hippocampal damage. Real-time PCR, Western blotting analysis, and immunohistochemical staining were carried out to determine the hippocampal expression of brain-derived neurotrophic factor (BDNF), choline acetyltransferase (ChAT), and synaptophysin (SYP). RESULTS: Compared with the control rats, the rats with early-stage CKD exhibited mild renal damage, while those with late-stage CKD showed significantly increased serum creatinine levels as well as apparent renal and brain damage. The rats with early-stage CKD also demonstrated significantly impaired learning abilities and memory compared with the control rats, with further deterioration observed in the rats with late-stage CKD. Additionally, we observed a significant downregulation of cognition-related proteins in the hippocampus of rats with early-stage CKD, which was further exacerbated with declining renal function as well as worsening brain and renal damage in rats with late-stage CKD. CONCLUSION: These results suggest the importance of early screening to identify CKD-induced cognitive dysfunction promptly. In addition, the downregulation of cognition-related proteins may play a role in the progression of cognitive dysfunction.

Tanshinone IIA is superior to paricalcitol in ameliorating tubulointerstitial fibrosis through regulation of VDR/Wnt/ß-catenin pathway in rats with diabetic nephropathy.

Glomerulosclerosis and tubulointerstitial fibrosis (TIF) are closely involved in the development of diabetic nephropathy (DN). Moreover, the development of TIF is closely related to epithelial-to-mesenchymal transition (EMT). Tanshinone IIA (Tan) has various pharmacological effects, especially the anti-fibrotic effect. And it is mainly used in the clinical treatment of cardiovascular diseases. Currently, the protective effect of Tan on DN and its possible mechanism have not been clearly elucidated. Our previous studies illustrated that Tan could improve the EMT of HK-2 cells induced by high glucose by regulating the vitamin D receptor (VDR)/Wnt/ß-catenin pathway. Here, we collected demographic information and laboratory results from the National Health and Nutrition Examination Survey (NHANES) database in order to investigate the relationship between VD and DN. Then, we established a DN model and treated DN rats with Tan and paricalcitol (Par) for 6 weeks. We subsequently compared the changes in general condition, renal function, pathological changes, and TIF-related protein expression levels of control rats, DN rats induced by STZ, DN rats with Tan at 5.4 mg/kg, DN rats with Tan at 10.8 mg/kg, and DN rats with Par at 0.054 µg/kg, to explore the effect and mechanism of Tan and Par on DN rats. The results showed that VD had a protective effect against DN in diabetic patients. And we found that Tan had a protective effect on renal fibrosis in DN rats, which was superior to Par in improving the symptoms of "three more and one less," reducing fasting blood glucose level, improving renal index, BUN/SCr, and UACR, reducing histopathological damage of kidney, and improving the expression of fibrosis-related proteins in kidney tissue by regulating VDR/Wnt/ß-catenin pathway. Tan was superior to Par in ameliorating tubulointerstitial fibrosis by regulating VDR/Wnt/ß-catenin pathway in rats with diabetic nephropathy.