Correction to: Polymyxin B causes DNA damage in HK-2 cells and mice.

In the original publication of the article, part of Fig. 6 is missing. The missing subpanels, Fig. 6c, d are given below.

Polymyxin B causes DNA damage in HK-2 cells and mice.

Increasing incidence of multidrug-resistant bacteria presents an imminent risk to global health. Polymyxins are 'last-resort' antibiotics against Gram-negative 'superbugs'; however, nephrotoxicity remains a key impediment in their clinical use. Molecular mechanisms underlying this nephrotoxicity remain poorly defined. Here, we examined the pathways which led to polymyxin B induced cell death in vitro and in vivo. Human proximal tubular cells were treated with polymyxin B (12.5-100 µM) for up to 24 h and showed a significant increase in micronuclei frequency, as well as abnormal mitotic events (over 40% in treated cells, p < 0.05). Time-course studies were performed using a mouse nephrotoxicity model (cumulative 72 mg/kg). Kidneys were collected over 48 h and investigated for histopathology and DNA damage. Notable increases in γH2AX foci (indicative of double-stranded breaks) were observed in both cell culture (up to ~ 44% cells with 5+ foci at 24 h, p < 0.05) and mice treated with polymyxin B (up to ~ 25%, p < 0.05). Consistent with these results, in vitro assays showed high binding affinity of polymyxin B to DNA. Together, our results indicate that polymyxin B nephrotoxicity is associated with DNA damage, leading to chromosome missegregation and genome instability. This novel mechanistic information may lead to new strategies to overcome the nephrotoxicity of this important last-line class of antibiotics.

Follistatin is essential for normal postnatal development and function of mouse oviduct and uterus.

Female mice lacking the follistatin gene but expressing a human follistatin-315 transgene (tghFST315) have reproductive abnormalities (reduced follicles, no corpora lutea and ovarian-uterine inflammation). We hypothesised that the absence of follistatin-288 causes the abnormal reproductive tract via both developmental abnormalities and abnormal ovarian activity. We characterised the morphology of oviducts and uteri in wild type (WT), tghFST315 and follistatin-knockout mice expressing human follistatin-288 (tghFST288). The oviducts and uteri were examined in postnatal Day-0 and adult mice (WT and tghFST315 only) using histology and immunohistochemistry. Adult WT and tghFST315 mice were ovariectomised and treated with vehicle, oestradiol-17ß (100ng injection, dissection 24h later) or progesterone (1mg×three daily injections, dissection 24h later). No differences were observed in the oviducts or uteri at birth, but abnormalities developed by adulthood. Oviducts of tghFST315 mice failed to coil, the myometrium was disorganised, endometrial gland number was reduced and oviducts and uteri contained abundant leukocytes. After ovariectomy, tghFST315 mice had altered uterine cell proliferation, and inflammation was maintained and exacerbated by oestrogen. These studies show that follistatin is crucial to postnatal oviductal-uterine development and function. Further studies differentiating the role of ovarian versus oviductal-uterine follistatin in reproductive tract function at different developmental stages are warranted.

Homeobox gene DLX4 expression is increased in idiopathic human fetal growth restriction.

Idiopathic fetal growth restriction (FGR) is often associated with placental insufficiency. Previously, we isolated and characterized homeobox gene DLX4 from the placenta and provided evidence that DLX4 may regulate placental development. Here, we have investigated whether DLX4 expression levels were altered in idiopathic FGR. FGR-affected placentae were collected based on strict clinical criteria. DLX4 mRNA expression was analysed in placentae obtained from pregnancies complicated by idiopathic FGR and gestation-matched control pregnancies (n = 25 each). Initial RT-PCR results showed a qualitative increase in DLX4 mRNA in both FGR-affected placentae and gestation-matched controls. Real-time PCR showed a 3-fold increase in DLX4 mRNA levels in FGR-affected placentae compared with gestation-matched controls (P < 0.005). Western immunoblotting using a rabbit DLX4 polyclonal antibody revealed significantly increased levels of DLX4 protein in term FGR-affected placentae compared with term controls [5500.1 +/- 21.8 (n = 10) versus 3533.2 +/- 22.4 (n = 10); P < 0.001]. Qualitative immunohistochemical analyses of term placentae showed moderately increased immunoreactivity for DLX4 antigen in the FGR-affected placentae in syncytiotrophoblasts, residual cytotrophoblast cells and endothelial cells of the fetal capillaries compared with gestation-matched control term placentae. We conclude that the increased expression of homeobox gene DLX4 may be a contributing factor to the developmental abnormalities seen in the FGR-affected placentae.