Protective effects of sunscreening agents on photocarcinogenesis, photoaging, and DNA damage in XPA gene knockout mice

We investigated the protective effects of commercial sunscreening agents against UVB-induced photoresponses in group A xeroderma pigmentosum (XPA) model mice. XPA gene-deficient mice are defective in nucleotide excision repair and show a high incidence of skin tumors and severe acute inflammation in response to UVB irradiation, in a similar manner to XP patients. SPF 10 and SPF 60 sunscreens protected partially and almost completely, respectively, ear swelling responses produced by UVB up to 200 mJ/cm2 in (-/-) mice. XPA (-/-) mice were irradiated three times a week to a cumulative dose of 2.6 J/cm2 UVB for a period of 24 weeks with or without SPF 10 or SPF 60 sunscreen. UV-induced skin tumors had developed in all unprotected (-/-) mice (13.3 tumors per mouse) at the completion of UVB irradiation. The SPF 60 sunscreen afforded stronger protection against photocarcinogenesis (1.0 tumors per mouse) than the SPF 10 sunscreen (4.4 tumors per mouse). Regarding photoaging, SPF 60 sunscreen also protected against mast cell infiltration (79% inhibition), elastic fiber accumulation, and dermal cyst proliferation in XPA (-/-) mice compared with unprotected (-/-) mice. In (-/-) mice, the SPF 60 sunscreen provided stronger protection against cyclobutane pyrimidine dimer formation shown immunohistologically following irradiation with 200 mJ/cm2 UVB than the SPF 10 sunscreen. The XPA model mouse is a useful animal for the evaluation of the photoprotective ability of sunscreens because photoresponses, even chronic changes, can be easily and quickly induced experimentally.     

Defects in antioxidant defense and calcium transport in the epidermis of xeroderma pigmentosum patients

Summary A comparative study of the antioxidant enzymes superoxide dismutase, catalase, glutathione reductase and thioredoxin reductase was undertaken in two families with xeroderma pigmentosum (XP) and in healthy controls of corresponding skin phototypes. Epidermal blister roofs obtained from the XP patients revealed significant decreases in catalase, thioredoxin reductase, and superoxide dismutase, but glutathione reductase was unaffected. In addition, keratinocytes established from XP patients contained a significantly higher than normal intracellular calcium concentration compared with control cells from a corresponding skin type. Keratinocytes established from an XP obligate heterozygote revealed intermediate levels of calcium between XP homozygotes and controls. Previously high intracellular calcium has been shown to compromise the redox status of keratinocytes by allosteric inhibition of the thioredoxin reductase/thioredoxin electron transfer system. In XP homozygous keratinocytes from sun-exposed epidermis, the intracellular concentration of reduced thioredoxin was decreased to 50% compared with these cells from unexposed skin. Taken together, the results from this study indicate that the epidermis in XP patients lacks effective defense against free radicals and peroxides. In addition to the well-established defect in the normal rates of unscheduled DNA repair, these findings provide an even better explanation for the multiple cutaneous neoplasms in these patients.     

Triptolide: Progress on research in pharmacodynamics and toxicology

Ethnopharmacological relevance

Tripterygium wilfordii Hook. f. (Tripterygium wilfordii), also known as Huangteng and gelsemium elegan, is a traditional Chinese medicine that has been marketed in China as Tripterygium wilfordii glycoside tablets. Triptolide (TP), an active component in Tripterygium wilfordii extracts, has been used to treat various diseases, including lupus, cancer, rheumatoid arthritis and nephritic syndrome. This review summarizes recent developments in the research on the pharmacodynamics, pharmacokinetics, pharmacy and toxicology of TP, with a focus on its novel mechanism of reducing toxicity. This review provides insight for future studies on traditional Chinese medicine, a field that is both historically and currently important.

Materials and methods

We included studies published primarily within the last five years that were available in online academic databases (e.g., PubMed, Google Scholar, CNKI, SciFinder and Web of Science).

Results

TP has a long history of use in China because it displays multiple pharmacological activities, including anti-rheumatism, anti-inflammatory, anti-tumor and neuroprotective properties. It has been widely used for the treatment of various diseases, such as rheumatoid arthritis, nephritic syndrome, lupus, Behcet?s disease and central nervous system diseases. Recently, numerous breakthroughs have been made in our understanding of the pharmacological efficacy of TP. Although TP has been marketed as a traditional Chinese medicine, its multi-organ toxicity prevents it from being widely used in clinical practice.

Conclusions

Triptolide, a biologically active natural product extracted from the root of Tripterygium wilfordii, has shown promising pharmacological effects, particularly as an anti-tumor agent. Currently, in anti-cancer research, more effort should be devoted to investigating effective anti-tumor targets and confirming the anti-tumor spectrum and clinical indications of novel anti-tumor pro-drugs. To apply TP appropriately, with high efficacy and low toxicity, the safety and non-toxic dose range for specific target organs and diseases should be determined, the altered pathways and mechanisms of exposure need to be clarified, and an early warning system for toxicity needs to be established. With further in-depth study of the efficacy and toxicity of TP, we believe that TP will become a promising multi-use drug with improved clinical efficacy and safety in the future.     

Xeroderma pigmentosum complementation group G patient with a novel homozygous missense mutation and no neurological abnormalities

We describe an unusual xeroderma pigmentosum (XP) patient with a mutation in XP complementation group G, representing only the third reported Japanese XP-G patient. A 40-year-old men (XP3HM), born from consanguineous parents experienced sun sensitivity and pigmentary changes of sun-exposed skin since childhood. He developed a squamous cell carcinoma on his lower lip at the age of 40. He has neither neurological abnormalities nor Cockayne syndrome. The primary fibroblasts of the patient were hypersensitive to killing by UV (D(0) = 0.6 J/m(2)) and the post-UV unscheduled DNA synthesis was 8% of normal. Host cell reactivation complementation analysis implicated XP complementation group G. We identified a novel homozygous mutation (c.194T>C) in a conserved portion of the XPG(ERCC5) gene, resulting in a predicted amino acid change; p.L65P. We confirmed that this genetic change reduced DNA repair thus linking this mutation to increased skin cancer.     

紫外线诱发的细胞染色体畸变与皮肤肿瘤的关系

本文研究两种对日光异常敏感的皮肤病患者的淋巴细胞经紫外线照射后染色体畸变与日光诱发皮肤肿瘤之间的关系。一是着色性干皮病(XP),另一是Cockayne综合征(CS)。两者均系常染色体隐性遗传并伴有DNA修复过程的缺陷,但XP会发展有紫外线诱发的皮肤肿瘤而CS则不会。结果看到两者均有比正常人显著高的紫外线诱发的染色体畸变发生率,各型畸变发生情况也相似,可见紫外线诱发的异常高的染色体畸变不是(至少在CS患者中)紫外线诱发皮肤肿瘤的一个足够的原因。     

XPC Lys939Gln polymorphism is associated with the decreased response to platinum based chemotherapy in advanced non-small-cell lung cancer

Background Platinum-based chemotherapeutics are the most common regimens for advanced non-small-cell lung cancer (NSCLC) patients, and genetic factors are thought to represent important determinants of drug efficacy. We prospectively assessed the status of the XPC Ala499Val and Lys939GIn gene polymorphisms and investigated whether these SNPs can predict the response to cisplatin/carboplatin-based regimens in advanced NSCLC patients in a Chinese population.Methods The treatment outcomes of 96 advanced NSCLC patients who were treated with platinum-based chemotherapy were evaluated. The polymorphic status of xeroderma pigmentosum group C (XPC) gene was genotyped by the 3-D polyacrylamide gel-based DNA microarray method.Results The distributions of XPC Lys939GIn genotypes differed significantly between the response group (complete +partial responses) and the non-response group (stable + progressive disease; P=0.022). The heterozygous A/C genotype carriers had a poorer response rate than the wild A/A genotype carriers in stage Ⅲ (OR, 0.074; 95% CI,0.008-0.704; P=0.023). The XPC Ala499Val polymorphisms were not associated with response to platinum-based chemotherapy.Conclusion Polymorphisms of the XPC gene, Lys939GIn, may be a predictive marker of treatment response for advanced NSCLC patients in stage Ⅲ.     

着色性干皮病C组基因蛋白缺失对膀胱癌细胞自噬的影响

目的 探讨膀胱癌细胞中着色性干皮病C组基因(xeroderma pigmentosum group C,XPC)蛋白缺失对自噬的影响.方法 利用shRNA策略,建立稳定干扰XPC的膀胱癌T24细胞模型,蛋白印迹技术检测干扰XPC后自噬表征蛋白LC3Ⅱ的表达,瞬时转染GFP-LC3,荧光显微镜观察细胞荧光聚集情况,CCK-8法检测细胞的增殖状况,免疫印迹技术检测自噬及凋亡相关蛋白的表达.结果 成功建立干扰XPC的膀胱癌T24细胞模型;干扰XPC后,膀胱癌T24细胞自噬小体的形成[(1.53±0.81)％ vs(3.30 ±0.70)％,P＜0.05]明显减少,顺铂作用下膀胱癌T24细胞自噬小体的形成[(2.19±0.37)％ vs(3.20 ±0.29)％,P＜0.05]明显减少;顺铂促进XPC缺失后的膀胱癌T24细胞自噬;XPC缺失后的自噬为非保护性自噬.结论 XPC蛋白参与调控膀胱癌T24细胞的自噬.     

Metronidazole-induced hepatotoxicity in a patient with xeroderma pigmentosum: A case report

Rationale:Whereas metronidazole-induced hepatotoxicity is quite rare in the general population, in individuals carrying a nucleotide excision repair disorder, namely Cockayne syndrome, there is a high risk of developing this complication.Patient concerns:We report the case of a 44-year-old man, affected by xeroderma pigmentosum, who was admitted to the hospital presenting aspiration pneumoniae caused by worsening dysphagia and with severe hepatotoxicity during the hospitalization.Diagnoses:Acute hepatitis, which was leading to acute liver failure, occurred during antibiotic treatment with metronidazole and ceftazidime with an elevation of liver enzymes consistent with hepatocellular damage pattern.Interventions:Hydration with glucose 5% solution, pantoprazole and vitamin K were administered, meanwhile other causes of hepatitis were ruled out and the ongoing antibiotic treatment was stopped suspecting a drug-induced liver injury.Outcomes:Liver function nearly completely recovered 1 month later with a first rapid improvement, within few days, of aminotransferases and coagulation studies, and slower of cholestatic enzymes.Lessons:We describe the first case available in the literature of hepatotoxicity associated with metronidazole treatment in a xeroderma pigmentosum patient. Clinicians therefore, based on this report and according to the possible underlying mechanism shared by other genetic diseases characterized by alterations in the pathway of DNA-repair, should consider such adverse event also in patients affected by this rare disease.     

EEG and CT abnormalities in xeroderma pigmentosum

Xeroderma pigmentosum associated with neurological abnormalities is a less familiar neurocutaneous disorder. In this report, 35 patients with group A xeroderma pigmentosum were assessed for neurological complications. Of these, 17 showed microcephaly and 24 mental retardation. Of 25 patients over 7 years of age, 22 had sensorineural deafness and 12 showed spinocerebellar signs such as nystagmus, dysarthria, tremor and ataxia, while none below 7 years of age had such neurological complications. Thirty-five EEG studies were performed on 29 patients, and 15 showed intermittent spindles of grouped theta waves with abnormal slow background activity and a poorly developed alpha rhythm, suggesting immature brain development or a regression from normal brain function in many areas including the diencephalon. Twenty-six patients were examined by cranial CT scan, of whom 20 showed abnormal CT findings such as ventricular dilatation, diffuse cortical atrophy, and marked thickening of the calvarial bones. The incidence of abnormal EEG and CT findings increased with advancing age in accordance with the development of neurological complications in the CNS, thus suggesting a chronic progressive degenerative disease.     

The effects of inhibitors of topoisomerase II and quinacrine on ultraviolet-light-induced DNA incision in normal and xeroderma pigmentosum fibroblasts

Summary The aim of our work was to investigate whether DNA topoisomerase II participates in the repair-specific incision of UV-irradiated genomic DNA. Therefore, the influence upon DNA incision of the topoisomerase II inhibitors (nalidixic and oxolinic acid, novobiocin and coumermycin A₁) as well as the intercalating agent quinacrine has been measured in normal human fibroblasts using the alkaline elution technique. In addition, inhibition by novobiocin has been determined in fibroblast strains from 11 normal donors and from 16 xeroderma pigmentosum (XP) patients belonging to the complementation groups A, C, D, E, and XP variant. Nalidixic and oxolonic acid did not inhibit endonucleolytic cleavage, whereas novobiocin was a potent inhibitor of DNA incision. It was observed that in normal and in all XP strains 50% inhibition by novobiocin occurred on average in the dose range 315–590 M. Since inhibition by novobiocin was not paralleled by that with the other topoisomerase II inhibitors nalidixic and oxolinic acid, it must be concluded that reduction of enzyme-catalysed breaks was not due to the participation of topoisomerase II in the incision step, but to the displacement of ATP at the binding site of the DNA-incising enzyme. This enzyme absolutely requires ATP as a cofactor for endonucleolytic cleavage. Quinacrine, however, inhibited DNA incision in normal fibroblasts at a meanK _i of 318 M. Inhibition by this intercalating agent seems to be caused by structural perturbations in DNA, which render it a poor substrate for endonucleolytic cleavage.Abbreviations XP xeroderma pigmentosum - UV ultraviolet light This work was supported by the Deutsche Forschungsgemeinschaft, SFB 136