A 9-year-old girl with Kawasaki disease and pulmonary nodules

Clinical Rheumatology -     

Mutations in the FHA-domain of ectopically expressed NBS1 lead to radiosensitization and to no increase in somatic mutation rates via a partial suppression of homologous recombination

Ionizing radiation induces DNA double-strand breaks (DSBs). Mammalian cells repair DSBs through multiple pathways, and the repair pathway that is utilized may affect cellular radiation sensitivity. In this study, we examined effects on cellular radiosensitivity resulting from functional alterations in homologous recombination (HR). HR was inhibited by overexpression of the forkhead-associated (FHA) domain-mutated NBS1 (G27D/R28D: FHA-2D) protein in HeLa cells or in hamster cells carrying a human X-chromosome. Cells expressing FHA-2D presented partially (but significantly) HR-deficient phenotypes, which were assayed by the reduction of gene conversion frequencies measured with a reporter assay, a decrease in radiation-induced Mre11 foci formation, and hypersensitivity to camptothecin treatments. Interestingly, ectopic expression of FHA-2D did not increase the frequency of radiation-induced somatic mutations at the HPRT locus, suggesting that a partial reduction of HR efficiency has only a slight effect on genomic stability. The expression of FHA-2D rendered the exponentially growing cell population slightly (but significantly) more sensitive to ionizing radiation. This radiosensitization effect due to the expression of FHA-2D was enhanced when the cells were irradiated with split doses delivered at 24-h intervals. Furthermore, enhancement of radiation sensitivity by split dose irradiation was not seen in contact-inhibited G0/G1 populations, even though the cells expressed FHA-2D. These results suggest that the FHA domain of NBS1 might be an effective molecular target that can be used to induce radiosensitization using low molecular weight chemicals, and that partial inhibition of HR might improve the effectiveness of cancer radiotherapy.     

OPN4 belongs to the photosensitive system of the human skin

The human skin has previously been described to be affected by light; however, the underlying mechanism remains unknown. OPN4 (melanopsin) expression was first identified in the skin of amphibians; however, whether it is also expressed and functioned in the human skin has not yet been identified. Here, we show that OPN4 was expressed in the human skin tissue and cultures of isolated keratinocytes, melanocytes and fibroblasts. Additionally, Ca²⁺ influx in vitro and ex vivo and phosphorylation of extracellular signal‐regulated kinases 1/2 in human fibroblasts were observed by stimulation of blue light irradiation. Notably, our findings showed that this Ca²⁺ influx and phosphorylation of extracellular signal‐regulated kinases 1/2 are promoted in an intensity‐dependent manner, indicating that the light signal is converted to an intracellular signal via OPN4 in the human skin. Overall, in this study we showed that the human skin functions as a photoreceptor by demonstrating that in human skin, the photoreceptive protein was expressed, and photoreception was conducted via photoreceptive protein.     

Glutamate release and neuronal injury after intrathecal injection of local anesthetics

High concentrations of local anesthetics are neurotoxic, but the mechanism for this neurotoxicity is obscure. Here, we report increased concentrations of glutamate in the cerebrospinal fluid after intrathecal injections of high concentrations of tetracaine (a local anesthetic). The peak concentrations of glutamate after administration of 1%, 2%, and 4% tetracaine were 4-fold, 6-fold, and 10-fold higher than baseline values, respectively. Animals in the 1% group were all neurologically normal one week after tetracaine injection. In the group receiving 4%, no animal was able to hop and vacuolation of the white matter and/or central chromatolysis of the motor neurons were observed. Because high concentrations of glutamate are known to be neurotoxic, our results may provide some insight into the mechanisms for neurotoxicity of intrathecal local anesthetics.