IntroductionThe mortality of rhabdomyolysis-induced acute kidney injury (AKI) is still high, as there is no effective therapy. It has been shown that bone marrow-derived mesenchymal stem cells (MSCs) can induce M2 macrophages, which mediate MSC protection in other experimental inflammation-related organ injury. This study was designed to investigate the protective effects of macrophage activation in MSC therapy of rhabdomyolysis-induced AKI.MethodsMSCs were injected into glycerol-induced rhabdomyolysis mice. Renal injury was evaluated using the serum creatinine, urea nitrogen, renal pathology and acute tubular necrosis score. The distribution of MSCs was detected using two-photon fluorescence confocal imaging. Immunofluorescence of anti-F4/80 and anti-CD206 was performed to determine macrophages and M2 macrophages in the tissues of the kidney, and M2 macrophage infiltration was also evaluated using western blotting analyses. After depletion of macrophages using clodronate liposomes at the phase of kidney repair, renal injury was re-evaluated. RAW 264.7 macrophages were incubated with lipopolysaccharide and co-cultured with MSCs and subsequently visualised using immunofluorescence staining and flow cytometry analysis. Finally, disparate phenotype macrophages, including normal macrophages (M0), lipopolysaccharide-stimulated macrophages (M1), and MSC-co-cultured macrophages (M2), were infused into mice with AKI, which were pre-treated with liposomal clodronate.ResultsIn vivo infusion of MSCs protected AKI mice from renal function impairment and severe tubular injury, which was accompanied by a time-dependent increase in CD206-positive M2 macrophage infiltration. In addition, depleting macrophages with clodronate delayed restoration of AKI. In vitro, macrophages co-cultured with MSCs acquired an anti-inflammatory M2 phenotype, which was characterised by an increased expression of CD206 and the secretory cytokine interleukin (IL)-10. The concentrations of IL-10, IL-6 and tumor necrosis factor α were evaluated using enzyme-linked immunosorbent assay. Furthermore, macrophage-depleted mice with intramuscular injection of glycerol were subjected to a single injection of different types of RAW 264.7 macrophages. Mice infused with M0 and M1 macrophages suffered a more severe histological and functional injury, while mice transfused with MSC-educated M2 macrophages showed reduced kidney injury.ConclusionsOur findings suggested that MSCs can ameliorate rhabdomyolysis-induced AKI via the activation of macrophages to a trophic M2 phenotype, which supports the transition from tubule injury to tubule repair.

Treatment with MSCs can alleviate sepsis-associated AKI and improve survival in mice with polymicrobial sepsis. These effects may be mediated by the inhibition of IL-17 secretion and balance of the proinflammatory and anti-inflammatory states. Mesenchymal stem cells may be a potential new therapeutic agent for the prevention or reduction of sepsis-associated AKI.

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Fungal conidia serve as active ingredients of fungal insecticides but are sensitive to solar UV irradiation, which impairs double-stranded DNA (dsDNA) by inducing the production of cytotoxic cyclobutane pyrimidine dimers (CPDs) and (6-4)-pyrimidine-pyrimidine photoproducts (6-4PPs). This study aims to elucidate how CPD photolyase (Phr1) and 6-4PP photolyase (Phr2) repair DNA damage and photoreactivate UVB-inactivated cells in Beauveria bassiana, a main source of fungal insecticides. Both Phr1 and Phr2 are proven to exclusively localize in the fungal nuclei. Despite little influence on growth, conidiation, and virulence, singular deletions of phr1 and phr2 resulted in respective reductions of 38% and 19% in conidial tolerance to UVB irradiation, a sunlight component most harmful to formulated conidia. CPDs and 6-4PPs accumulated significantly more in the cells of Δphr1 and Δphr2 mutants than in those of a wild-type strain under lethal UVB irradiation and were largely or completely repaired by Phr1 in the Δphr2 mutant and Phr2 in the Δphr1 mutant after optimal 5-h exposure to visible light. Consequently, UVB-inactivated conidia of the Δphr1 and Δphr2 mutants were much less efficiently photoreactivated than were the wild-type counterparts. In contrast, overexpression of either phr1 or phr2 in the wild-type strain resulted in marked increases in both conidial UVB resistance and photoreactivation efficiency. These findings indicate essential roles of Phr1 and Phr2 in photoprotection of B. bassiana from UVB damage and unveil exploitable values of both photolyase genes for improved UVB resistance and application strategy of fungal insecticides. IMPORTANCE Protecting fungal cells from damage from solar UVB irradiation is critical for development and application of fungal insecticides but is mechanistically not understood in Beauveria bassiana, a classic insect pathogen. We unveil that two intranuclear photolyases, Phr1 and Phr2, play essential roles in repairing UVB-induced dsDNA lesions through respective decomposition of cytotoxic cyclobutane pyrimidine dimers and (6-4)-pyrimidine-pyrimidine photoproducts, hence reactivating UVB-inactivated cells effectively under visible light. Our findings shed light on the high potential of both photolyase genes for use in improving UVB resistance and application strategy of fungal insecticides.