The "Dutch DNA Repair Group", in retrospect

The cerebro-morphological fingerprint of a progeroid syndrome: white matter changes correlate with neurological symptoms in xeroderma pigmentosum

Background

Xeroderma pigmentosum (XP) is a rare autosomal recessive progeroid syndrome. It has recently been shown that the underlying DNA repair defect plays a central role in the aging process. In addition to skin symptoms, various premature neurological abnormalities have been reported.

Methodology/Principal Findings

We present the clinical neurological phenotype in 14 XP patients (seven subtypes), in seven of these patients together with conventional and multiparametric advanced MRI data to assess the macrostructural and microstructural cerebral morphology in comparison to controls, including volumetric measurements, MR spectroscopy (¹H MRS), and diffusion tensor imaging (DTI). Clinical hallmarks were spinocerebellar ataxia, pyramidal tract signs, and mild cognitive deficits. DTI demonstrated significantly reduced WM directionality in all regions investigated, i.e. the thalamus, the corticospinal tracts and the dorsal corpus callosum. Single patients showed a marked relative hippocampal volume reduction, but the patients were not different from controls in the volumetric measurements of hippocampal and whole brain volumes at group level. However, ¹H MRS demonstrated that the hippocampal formation was metabolically altered.

Conclusions

The most prominent feature was the white matter affectation, as assessed by DTI, with volume and directionality reductions of the fiber projections involving both the craniocaudal fibers and the interhemispheric connections. These findings, although heterogeneous among the study sample, could be correlated with the clinico-neurological symptoms. The imaging findings support the position that myelin structures degrade prematurely in the brain of XP patients.

Effect of sulphur mustard on human skin cell lines with differential agent sensitivity

The ability of sulphur mustard (HD) to induce DNA damage places limits on the efficacy of approaches aimed at protecting human cells from the cytotoxic effects of HD using a variety of protective agents such as thiol-containing esters and protease inhibitors. In the present study, potential alternative strategies were investigated by examining the differential effects of HD on G361, SVK14, HaCaT and NCTC 2544 human skin cells. The G361 cell line was more resistant to the cytotoxic effects of HD than the NCTC, HaCaT and SVK14 cell lines at HD doses of >3 and <100 microM HD as determined by the MTT assay. At 72 h after exposure to 60 microM HD there was up to an 8.8-fold difference (P < 0.0001) between G361 and SVK14 cell culture viability. Buthionine sulphoximine (BSO) pretreatment increased the sensitivity of all four cell lines to HD. A substantial proportion of the resistance of G361 cells to HD was attributable to BSO-mediated effects on antioxidant-mediated metabolism, although G361 cultures still retained a high degree of viability at 30 microM HD following BSO pretreatment. Cell cycle analysis confirmed that SVK14 cells were relatively more sensitive to HD, as shown by the 2.1-fold reduction (P < 0.0001) in the percentage of cells in G0/G1 phase 24 h after HD exposure compared with control cultures. This compared well with a 1.2-fold increase (P < 0.05) in the percentage of G361 cells in G0/G1 phase following HD exposure, suggesting the existence of a more efficient G0/G1 checkpoint control mechanism in this cell line. Manipulation of the cell cycle using various modulating agents did not increase the resistance of cell lines to the cytotoxic effects of HD.