Differential ultraviolet-B-induced immunomodulation in XPA, XPC, and CSB DNA repair-deficient mice

The Prognostic and Predictive Role of Xeroderma Pigmentosum Gene Expression in Melanoma

Background

Assessment of immune-specific markers is a well-established approach for predicting the response to immune checkpoint inhibitors (ICIs). Promising candidates as ICI predictive biomarkers are the DNA damage response pathway genes. One of those pathways, which are mainly responsible for the repair of DNA damage caused by ultraviolet radiation, is the nucleotide excision repair (NER) pathway. Xeroderma pigmentosum (XP) is a hereditary disease caused by mutations of eight different genes of the NER pathway, or POLH, here together named the nine XP genes. Anecdotal evidence indicated that XP patients with melanoma or other skin tumors responded impressively well to anti-PD-1 ICIs. Hence, we analyzed the expression of the nine XP genes as prognostic and anti-PD-1 ICI predictive biomarkers in melanoma.

Methods

We assessed mRNA gene expression in the TCGA-SKCM dataset (n = 445) and two pooled clinical melanoma cohorts of anti-PD-1 ICI (n = 75). In TCGA-SKCM, we applied hierarchical clustering on XP genes to reveal clusters, further utilized as XP cluster scores. In addition, out of 18 predefined genes representative of a T cell inflamed tumor microenvironment, the TIS score was calculated. Besides these scores, the XP genes, immune-specific single genes (CD8A, CXCL9, CD274, and CXCL13) and tumor mutational burden (TMB) were cross-correlated. Survival analysis in TCGA-SKCM was conducted for the selected parameters. Lastly, the XP response prediction value was calculated for the two pooled anti-PD-1 cohorts by classification models.

Results

In TCGA-SKCM, expression of the XP genes was divided into two clusters, inversely correlated with immune-specific markers. A higher ERCC3 expression was associated with improved survival, particularly in younger patients. The constructed models utilizing XP genes, and the XP cluster scores outperformed the immune-specific gene-based models in predicting response to anti-PD-1 ICI in the pooled clinical cohorts. However, the best prediction was achieved by combining the immune-specific gene CD274 with three XP genes from both clusters.

Conclusion

Our results suggest pre-therapeutic XP gene expression as a potential marker to improve the prediction of anti-PD-1 response in melanoma.

The impact of polyphenols extracted from Tricholoma matsutake on UVB-induced photoaging in mouse skin

BACKGROUND

Despite Tricholoma matsutake has been used as natural health products with multiple medicinal properties, detailed information about its polyphenolic composition as sources of anti-photoaging agents remains to be determined.

OBJECTIVE

To investigate the impact of polyphenols extracted from Tricholoma matsutake (TME) on Ultraviolet B (UVB)-induced skin photoaging.

MATERIALS AND METHODS

Various factors of oxidative stress and inflammation as well as histological and immunohistochemical analysis in the mouse dorsal skin were determined after UVB radiation.

RESULTS

Topical administration with TME suppressed the UVB-induced skin thickness, wrinkles and erythema, and increased skin collagen content. Furthermore, TME decreased reactive oxygen species (ROS) level, upregulated glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT) and glucose-6-phosphate dehydrogenase (G6PDH) activities and inhibited the expression of IL-1, IL-6, IL-8 and TNF-α in mice irradiated with UVB. TME could reduce UVB-induced p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation and effectively inhibited the activity of the transcriptional factor nuclear factor-kappa B (NF-κB), thereby reducing the cyclooxygenase-2 (COX-2) expression, which is an important mediator of inflammatory cascade leading to the inflammatory response.

CONCLUSION

Our data demonstrated that TME had various beneficial effects on UVB-induced skin photoaging due to its antioxidant and anti-inflammatory activities, and it might be exploited as a promising natural product in skin care, anti-photoaging and the therapeutic intervention of skin disorders related to both oxidative stress and inflammation.

Comparative study of cytotoxic effects induced by environmental genotoxins using XPC- and CSB-deficient human lymphoblastoid TK6 cells

Background

The human genome is constantly exposed to numerous environmental genotoxicants. To prevent the detrimental consequences induced by the expansion of damaged cells, cellular protective systems such as nucleotide excision repair (NER) exist and serve as a primary pathway for repairing the various helix-distorting DNA adducts induced by genotoxic agents. NER is further divided into two sub-pathways, namely, global genomic NER (GG-NER) and transcription-coupled NER (TC-NER). Both NER sub-pathways are reportedly involved in the damage response elicited by exposure to genotoxins. However, how disruption of these sub-pathways impacts the toxicity of different types of environmental mutagens in human cells is not well understood.

Results

To evaluate the role of NER sub-pathways on the cytotoxic effects of mutagens, we disrupted XPC and CSB to selectively inactivate GG-NER and TC-NER, respectively, in human lymphoblastoid TK6 cells, a standard cell line used in genotoxicity studies. Using these cells, we then comparatively assessed their respective sensitivities to representative genotoxic agents, including ultraviolet C (UVC) light, benzo [a] pyrene (B(a)P), 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline (MeIQx), 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP), γ-ray, and 2-acetylaminofluorene (2-AAF). CSB^−/− cells exhibited a hyper-sensitivity to UVC, B(a)P, and MeIQx. On the other hand, XPC^−/− cells were highly sensitive to UVC, but not to B(a)P and MeIQx, compared with wild-type cells. In contrast with other genotoxins, the sensitivity of XPC^−/− cells against PhIP was significantly higher than CSB^−/− cells. The toxicity of γ-ray and 2-AAF was not enhanced by disruption of either XPC or CSB in the cells.

Conclusions

Based on our findings, genetically modified TK6 cells appear to be a useful tool for elucidating the detailed roles of the various repair factors that exist to combat genotoxic agents, and should contribute to the improved risk assessment of environmental chemical contaminants.

Cisplatin-Induced Ototoxicity: Effects, Mechanisms and Protection Strategies

Cisplatin is a highly effective chemotherapeutic agent that is widely used to treat solid organ malignancies. However, serious side effects have been associated with its use, such as bilateral, progressive, irreversible, dose-dependent neurosensory hearing loss. Current evidence indicates that cisplatin triggers the production of reactive oxygen species in target tissues in the inner ear. A variety of agents that protect against cisplatin-induced ototoxicity have been successfully tested in cell culture and animal models. However, many of them interfere with the therapeutic effect of cisplatin, and therefore are not suitable for systemic administration in clinical practice. Consequently, local administration strategies, namely intratympanic administration, have been developed to achieve otoprotection, without reducing the antitumoral effect of cisplatin. While a considerable amount of pre-clinical information is available, clinical data on treatments to prevent cisplatin ototoxicity are only just beginning to appear. This review summarizes clinical and experimental studies of cisplatin ototoxicity, and focuses on understanding its toxicity mechanisms, clinical repercussions and prevention strategies.

Role of DNA repair in host immune response and inflammation

In recent years, the understanding of how DNA repair contributes to the development of innate and acquired immunity has emerged. The DNA damage incurred during the inflammatory response triggers the activation of DNA repair pathways, which are required for host-cell survival. Here, we reviewed current understanding of the mechanism by which DNA repair contributes to protection against the oxidized DNA damage generated during infectious and inflammatory diseases and its involvement in innate and adaptive immunity. We discussed the functional role of DNA repair enzymes in the immune activation and the relevance of these processes to: transcriptional regulation of cytokines and other genes involved in the inflammatory response; V(D)J recombination; class-switch recombination (CSR); and somatic hypermutation (SHM). These three last processes of DNA damage repair are required for effective humoral adaptive immunity, creating genetic diversity in developing T and B cells. Furthermore, viral replication is also dependent on host DNA repair mechanisms. Therefore, the elucidation of the pathways of DNA damage and its repair that activate innate and adaptive immunity will be important for a better understanding of the immune and inflammatory disorders and developing new therapeutic interventions for treatment of these diseases and for improving their outcome.

Tannic acid suppresses ultraviolet B-induced inflammatory signaling and complement factor B on human retinal pigment epithelial cells

Ultraviolet B (UVB) radiation may cause the inflammation of retinal pigment epithelium (RPE) cells and play a role in development of age-related macular degeneration (AMD). The activation of the complement factor B (CFB) gene has been shown to be involved in formation of AMD. Here our results revealed that UVB induces IL-6/STAT3 signaling activation and the UVB-induced STAT3 is able to regulate the CFB expression in ARPE-19 cells. Tannic acid (TA) is a kind of water-soluble polyphenol and may have anti-inflammation effects. We also found that TA attenuates the UVB-induced IL-6 protein production, the STAT3 phosphorylation and the CFB expression. Taken together, these findings suggest UVB-induced inflammation of RPE can be mediated through the IL-6/STAT3/CFB pathway, and TA has a protected effect via the inhibition to the inflammatory response.

Cisplatin ototoxicity and protection: clinical and experimental studies

Cisplatin is a chemotherapeutic agent that is widely used to treat a variety of malignant tumors. Serious dose-limiting side effects like ototoxicity, nephrotoxicity and neurotoxicity occur with the use of this agent. This review summarizes recent important clinical and experimental investigations of cisplatin ototoxicity. It also discusses the utility of protective agents employed in patients and in experimental animals. The future strategies for limiting cisplatin ototoxicity will need to avoid interference with the therapeutic effect of cisplatin in order to enhance the quality of life of patients receiving this important anti-tumor agent.

Reactive oxygen species generated by thiopurine/UVA cause irreparable transcription-blocking DNA lesions

Long-term treatment with the anticancer and immunosuppressant thiopurines, azathioprine or 6-mercaptopurine, is associated with acute skin sensitivity to ultraviolet A (UVA) radiation and a high risk of skin cancer. 6-thioguanine (6-TG) that accumulates in the DNA of thiopurine-treated patients interacts with UVA to generate reactive oxygen species. These cause lethal and mutagenic DNA damage. Here we show that the UVA/DNA 6-TG interaction rapidly, and essentially irreversibly, inhibits transcription in cultured human cells and provokes polyubiquitylation of the major subunit of RNA polymerase II (RNAPII). In vitro, 6-TG photoproducts, including the previously characterized guanine-6-sulfonate, in the transcribed DNA strand, are potent blocks to RNAPII transcription whereas 6-TG is only slightly inhibitory. In vivo, guanine-6-sulfonate is removed poorly from DNA and persists to a similar extent in the DNA of nucleotide excision repair-proficient and defective cells. Furthermore, transcription coupled repair-deficient Cockayne syndrome cells are not hypersensitive to UVA/6-TG, indicating that potentially lethal photoproducts are not selectively excised from transcribed DNA. Since persistent transcription-blocking DNA lesions are associated with acute skin responses to sunlight and the development of skin cancer, our findings have implications for skin cancer in patients undergoing thiopurine therapy.

Cisplatin induces cytoplasmic to nuclear translocation of nucleotide excision repair factors among spiral ganglion neurons

Genomic DNA is a high-affinity target for the antineoplastic molecule cisplatin. Cell survival from cisplatin DNA damage is dependent on removal of cisplatin-DNA adducts by nucleotide excision repair (NER) pathways. The rate-limiting steps in the NER pathways are DNA damage identification and verification. These steps are accomplished by xeroderma pigmentosum complementation group C and A (XPC and XPA) and RNA polymerase II. Unlike RNA polymerase II, XPC and XPA have no known cellular function beyond DNA repair. Cisplatin is known to damage spiral ganglion neurons at the basal coil of the cochlea therefore it was posited that cisplatin may target their DNA and mobilize XPC and XPA. Female Fisher344 rats were given two, four day cycles of cisplatin (2mg/kg) or saline, separated by a 10day rest period. A 2 x 3 x 2 factorial design, consisting of two treatment conditions (cisplatin and saline treatment), three survival times (5, 19 and 22 days) and two analysis methods (quantitative RT-PCR and immunohistochemistry) was employed to evaluate the expression and distribution of XPC and XPA. Quantitative RT-PCR revealed statistically significant differences in cochlear XPC and XPA mRNA levels after cisplatin treatment at all times except day 22 for XPA. Immunohistochemistry revealed that a proportion ( approximately 50%) of spiral ganglion neurons in control rats showed cytoplasmic expression of XPC and XPA. After cisplatin treatment, a similar proportion ( approximately 50%) of spiral ganglion neurons showed increased nuclear expression of XPC and XPA, which appears to represent translocation from the cytoplasm. Basal coil spiral ganglion neurons translocated XPC and XPA at later treatment cycles and with less magnitude than apical coil neurons after cisplatin treatment. Therefore, it is suggested that cisplatin treatment induces nuclear translocation of NER proteins among spiral ganglion neurons and that this nuclear translocation is less efficient at the base relative to the apex.

Do heat stress and deficits in DNA repair pathways have a negative impact on male fertility?

In Europe up to one in four couples experience difficulty conceiving and in half of these cases the problem has been attributed to sub or infertility in the male partner. The development of assisted reproductive technologies (ART) such as in vitro fertilization and intra-cytoplasmic spermatozoa injection has allowed some such couples to achieve a pregnancy. Concerns have been raised over the increasing use of ART not least because of the discovery of elevated levels of DNA damage in sperm from subfertile men. The impact of damaged DNA originating in the male germ line is poorly understood, but is thought to contribute to early pregnancy loss (recurrent miscarriage), placental problems and have a long-term impact on the health of the offspring. DNA repair is essential for meiotic recombination and correction of DNA damage in germ cells and proteins involved in all the major repair pathways are expressed in the testis. In this review, we will consider evidence that the production of sperm containing damaged DNA can be the result of suboptimal DNA repair and/or a mild environmental insult, such as heat stress, and how studies in mice may give us insight into the origins and consequences of DNA damage in human sperm.

Differential role of basal keratinocytes in UV-induced immunosuppression and skin cancer

Cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) comprise major UV-induced photolesions. If left unrepaired, these lesions can induce mutations and skin cancer, which is facilitated by UV-induced immunosuppression. Yet the contribution of lesion and cell type specificity to the harmful biological effects of UV exposure remains currently unclear. Using a series of photolyase-transgenic mice to ubiquitously remove either CPDs or 6-4PPs from all cells in the mouse skin or selectively from basal keratinocytes, we show that the majority of UV-induced acute effects to require the presence of CPDs in basal keratinocytes in the mouse skin. At the fundamental level of gene expression, CPDs induce the expression of genes associated with repair and recombinational processing of DNA damage, as well as apoptosis and a response to stress. At the organismal level, photolyase-mediated removal of CPDs, but not 6-4PPs, from the genome of only basal keratinocytes substantially diminishes the incidence of skin tumors; however, it does not affect the UVB-mediated immunosuppression. Taken together, these findings reveal a differential role of basal keratinocytes in these processes, providing novel insights into the skin's acute and chronic responses to UV in a lesion- and cell-type-specific manner.

Selective DNA damage responses in murine Xpa-/-, Xpc-/- and Csb-/- keratinocyte cultures

Cellular DNA damage responses (DDRs) are induced by unrepaired DNA lesions and constitute a protective back-up system that prevents the expansion of damaged cells. These cellular signaling pathways trigger either growth arrest or cell death and are believed to be major components of an early anti-cancer barrier. Cultures of C57BL/6J keratinocytes with various defects in NER sub-pathways allowed us to follow the kinetics of DDRs in an isogenic background and in the proper (physiologically relevant) target cells, supplementing earlier studies in heterogenic human fibroblasts. In a series of well-controlled parallel experiments we have shown that, depending on the NER deficiency, murine keratinocytes elicited highly selective DDRs. After a dose of UV-B that did not affect wild-type keratinocytes, Xpa(-/-) keratinocytes (complete NER deficiency) showed a rapid depletion of DNA replicating S-phase cells, a transient increase in quiescent S-phase cells (not replicating DNA), followed by massive apoptosis. Csb(-/-) keratinocytes (TC-NER deficient) responded by a more sustained increase in QS-phase cells and appeared more resistant to UV-B induced apoptosis than Xpa(-/-). In irradiated Xpc(-/-) keratinocytes (GG-NER deficient) the loss of replicating S-phase cells was associated with a gradual build-up of both QS-phase cells and cells arrested in late-S phase, in complete absence of apoptosis. Our analysis complements and extends previous in vivo investigations and highlights both similarities and differences with earlier fibroblast studies. In vitro cultures of murine keratinocytes provide a new tool to unravel the molecular mechanisms of UV-induced cellular stress responses in great detail and in a physiologically relevant background. This will be essential to fully appreciate the implications of DDRs in tumor suppression and cancer prevention.

The stratum corneum: structure and function in health and disease

Our understanding of the formation, structure, composition, and maturation of the stratum corneum (SC) has progressed enormously over the past 30 years. Today, there is a growing realization that this structure, while faithfully providing a truly magnificent barrier to water loss, is a unique, intricate biosensor that responds to environmental challenges and surface trauma by initiating a series of biologic processes which rapidly seek to repair the damage and restore barrier homeostasis. The detailed ultrastructural, biochemical, and molecular dissection of the classic "bricks and mortar" model of the SC has provided insights into the basis of dry, scaly skin disorders that range from the cosmetic problems of winter xerosis to severe conditions such as psoriasis. With this knowledge comes the promise of increasingly functional topical therapies.

Association of transcription-coupled repair but not global genome repair with ultraviolet-B-induced Langerhans cell depletion and local immunosuppression

Exposure to ultraviolet-B radiation impairs cellular immune responses. This immunosuppression seems to be associated with Langerhans cell migration. DNA damage appears to play a key role because enhanced nucleotide excision repair, a pathway essential for elimination of ultraviolet-B-induced DNA lesions, strongly counteracts immunosuppression. To determine the effect of DNA repair on ultraviolet-B-induced local immunosuppression and Langerhans cell disappearance, three mouse strains carrying different defects in nucleotide excision repair were compared. XPC mice, which were defective in global genome repair, were as sensitive to ultraviolet-B-induced local suppression of contact hypersensitivity to picryl chloride as their wild-type littermates. CSB mice, defective in transcription-coupled repair, were far more sensitive for immunosuppression as were XPA mice, defective in both transcription-coupled repair and global genome repair. Only a moderate depletion of Langerhans cells was observed in XPC mice and wild-type littermates. Ultraviolet-B-induced Langerhans cell depletion was enhanced in CSB and XPA mice. Hence, the major conclusion is that local immunosuppression is only affected when transcription-coupled DNA repair is impaired. Furthermore, a defect in transcription-coupled repair was linked to enhanced ultraviolet-B-induced Langerhans cell depletion. In combination with earlier experiments, it can be concluded that Langerhans cell disappearance is related to ultraviolet-B-induced local but not to systemic immunosuppression.

Excellent response of basal cell carcinomas and pigmentary changes in xeroderma pigmentosum to imiquimod 5% cream

Xeroderma pigmentosum (XP) is an autosomal recessive disease in which patients have a 1000-fold increased risk of developing cutaneous neoplasms. Management of patients with XP is a difficult therapeutic challenge as they usually present with many cutaneous malignancies and continue to form skin tumours at a high rate. We describe a 19-year-old woman with XP who had been previously treated with many different therapeutic approaches. She had an excellent clinical response of her multiple small pigmented basal cell carcinomas and pigmentary changes using imiquimod 5% cream with only minor side-effects.

Inhibition of the elicitation phase of contact hypersensitivity by thymidine dinucleotides is in part mediated by increased expression of interleukin-10 in human keratinocytes

The production of immunomodulatory cytokines such as interleukin-10 (IL-10) from keratinocytes and other target cells in the skin plays a crucial role in UV-induced immunosuppression. Substantial evidence supports an association between DNA damage and immunomodulation. It is also known that small DNA fragments such as thymidine dinucleotides (pTpT) can mimic several UV-induced effects, including inhibition of the induction phase of the contact hypersensitivity response and up-regulation of tumor necrosis factor-alpha (TNF-alpha). To determine whether pTpT also induces IL-10 secretion by keratinocytes, and by inference whether IL-10 production after UV irradiation is a response to DNA damage, we compared the effects of pTpT with those of UV irradiation on primary human keratinocyte cultures. Subconfluent cultures of primary human keratinocytes were treated either with 10 micro M or 100 micro M pTpT or diluent alone, or exposed to solar-simulated light (100 J/m2 of UVB) or sham irradiated. An increase in IL-10 mRNA expression was observed 6-24 h after irradiation and at 24-48 h after treatment with pTpT. Detection of secreted IL-10 protein coincided with up-regulation of IL-10 gene expression at 48 and 72 h as determined by ELISA. Conditioned media from human keratinocytes treated with pTpT, like that from irradiated cells, significantly inhibited lymphocyte proliferation in the allogeneic-mixed lymphocyte reaction (MLR) assay. To determine whether pTpT mimics the suppressive influence of UVB on the elicitation phase of contact hypersensitivity, believed to result largely from IL-10 release, we compared the effects of topical application of pTpT with those of UVB irradiation on C57Bl/6 mice sensitized with dinitrofluorobenzene. Sensitized mice treated with pTpT or UVB irradiation showed markedly suppressed elicitation of ear-swelling responses. These results demonstrate that increased keratinocyte IL-10 mRNA level and IL-10 protein release are among the effects of pTpT and support the hypothesis that pTpT treatment triggers many of the biologic effects of UV irradiation by mimicking UV-induced DNA damage. Finally, regardless of mechanism, the data suggest that topical treatment with pTpT may provide a novel means of suppressing contact hypersensitivity or other lymphocyte-mediated reactions in skin.

Photoimmunology and nucleotide excision repair: impact of transcription coupled and global genome excision repair

Ultraviolet (UV) light generates damage to DNA which is removed by a versatile mechanism called nucleotide excision repair (NER). There are two subpathways for NER: the transcription coupled repair (TCR) pathway which removes DNA damage from actively transcribed genes and the global genome repair pathway which removes damage throughout the genome. Most types of DNA lesions are processed more rapidly by TCR than by GGR. It is widely accepted that immunological processes play a pivotal role in the generation of skin tumours induced by exposure to ultraviolet light and first evidence is emerging that GGR and TCR play different roles in skin reactions such as erythema and delayed type hypersensitivity. The relationship between UV-induced responses of the skin and the two NER subpathways is discussed.

Biological consequences of cyclobutane pyrimidine dimers

In the skin many molecules may absorb ultraviolet (UV) radiation upon exposure. In particular, cellular DNA strongly absorbs shorter wavelength solar UV radiation, resulting in various types of DNA damage. Among the DNA photoproducts produced the cyclobutane pyrimidine dimers (CPDs) are predominant. Although these lesions are efficiently repaired in the skin, this CPD formation results in various acute effects (erythema, inflammatory responses), transient effects (suppression of immune function), and chronic effects (mutation induction and skin cancer). The relationships between the presence of CPD in skin cells and the subsequent biological consequences are the subject of the present review.