Significance of the melanocortin 1 receptor in the DNA damage response of human melanocytes to ultraviolet radiation.

Activation of the melanocortin 1 receptor (MC1R) by α-melanocortin (α-MSH) stimulates eumelanin synthesis and enhances repair of ultraviolet radiation (UV)-induced DNA damage. We report on the DNA damage response (DDR) of human melanocytes to UV and its enhancement by α-MSH. α-MSH up-regulated the levels of XPC, the enzyme that recognizes DNA damage sites, enhanced the UV-induced phosphorylation of the DNA damage sensors ataxia telangiectasia and Rad3-related (ATR) and ataxia telangiectasia mutated (ATM) and their respect-ive substrates checkpoint kinases 1 and 2, and increased phosphorylated H2AX (γH2AX) formation.

Oral tungstate (Na2WO4) exposure reduces adaptive immune responses in mice after challenge.

Tungstate (WO²⁻₄) has been identified as a ground water contaminant at military firing ranges and can be absorbed by ingestion. In this study, C57BL6 mice were exposed to sodium tungstate (Na2WO4·2H2O) (0, 2, 62.5, 125, and 200 mg/kg/day) in their drinking water for an initial 28-day screen and in a one-generation (one-gen) model.

The human DEK oncogene regulates DNA damage response signaling and repair.

The human DEK gene is frequently overexpressed and sometimes amplified in human cancer. Consistent with oncogenic functions, Dek knockout mice are partially resistant to chemically induced papilloma formation. Additionally, DEK knockdown in vitro sensitizes cancer cells to DNA damaging agents and induces cell death via p53-dependent and -independent mechanisms.

Neutrophils, not monocyte/macrophages, are the major splenic source of postburn IL-10.

Burn induces myeloid-derived suppressor cells (MDSCs), a heterogeneous population of immature polymorphonuclear neutrophils (PMNs) and monocytes, which protect against infection. Previous work from our laboratory demonstrated that inflammatory monocytes (iMos) were the major MDSC source of TNF-α in the postburn spleen, and we hypothesized that they were also the major source of postburn IL-10. To test this hypothesis, we examined cytokine production by postburn CCR2 knockout (KO) mice, which have fewer iMos than burn wild-type (WT) splenocytes, but equal numbers of PMNs and F4/80 macrophages.

The burn wound inflammatory response is influenced by midazolam.

Burn patients requiring hospitalization are often treated for anxiety with benzodiazepines (BDZs). Benzodiazepines are reported to influence immune system function. Immune system alterations are a major cause of burn-induced mortality.

Epidermal keratinocytes from light vs. dark skin exhibit differential degradation of melanosomes.

Modification of skin complexion coloration has traditionally been accomplished by interruption or attenuation of melanogenesis and/or melanosome transfer. Post-transfer modification of pigmented melanosomes provides an attractive and distinct avenue of modulating skin pigmentation. The processing of melanosomes during keratinocyte (KC) terminal differentiation and the degradative variability observed between light and dark skin (LS and DS) remains enigmatic.

Mismatch and base excision repair proficiency in murine embryonic stem cells.

Accumulation of mutations in embryonic stem (ES) cells would be detrimental to an embryo derived from these cells, and would adversely affect multiple organ systems and tissue types. ES cells have evolved multiple mechanisms to preserve genomic integrity that extend beyond those found in differentiated cell types. The present study queried whether mismatch repair (MMR) and base-excision repair (BER) may play a role in the maintenance of murine ES cell genomes.

Melanocortin 1 receptor genotype: an important determinant of the damage response of melanocytes to ultraviolet radiation.

The melanocortin 1 receptor gene is a main determinant of human pigmentation, and a melanoma susceptibility gene, because its variants that are strongly associated with red hair color increase melanoma risk. To test experimentally the association between melanocortin 1 receptor genotype and melanoma susceptibility, we compared the responses of primary human melanocyte cultures naturally expressing different melanocortin 1 receptor variants to α-melanocortin and ultraviolet radiation. We found that expression of 2 red hair variants abolished the response to α-melanocortin and its photoprotective effects, evidenced by lack of functional coupling of the receptor, and absence of reduction in ultraviolet radiation-induced hydrogen peroxide generation or enhancement of repair of DNA photoproducts, respectively.

Mouse embryonic stem cells, but not somatic cells, predominantly use homologous recombination to repair double-strand DNA breaks.

Embryonic stem (ES) cells give rise to all cell types of an organism. Since mutations at this embryonic stage would affect all cells and be detrimental to the overall health of an organism, robust mechanisms must exist to ensure that genomic integrity is maintained. To test this proposition, we compared the capacity of murine ES cells to repair DNA double-strand breaks with that of differentiated cells.

A ribonucleotide reductase inhibitor reverses burn-induced inflammatory defects.

Immature myeloid cells have been implicated as a source of postburn inflammation, and the appearance of these cells correlates with enhanced upregulation of hematopoiesis. The role of proliferative cells in postburn immune changes has not been directly tested. Gemcitabine, a ribonucleotide reductase inhibitor, has been shown to deplete proliferative immature myeloid cells in tumor models while sparing mature cells, leading to restored lymphocyte function and tumor regression.

Sodium tungstate (Na2WO4) exposure increases apoptosis in human peripheral blood lymphocytes.

The potential for adverse health effects of using tungsten and its alloys in military munitions are an important concern to both civilians and the US military. The toxicological implications of exposure to tungsten, its alloys, and the soluble tungstate (Na(2)WO(4)) are currently under investigation. To examine tungstate toxicity, a series of experiments to determine its in vitro effects on cells of the immune system were performed.

Bisphenol A and estradiol are equipotent in antagonizing cisplatin-induced cytotoxicity in breast cancer cells.

Resistance to chemotherapy is a major problem facing breast cancer patients. Cisplatin, a highly effective DNA-damaging drug, has shown only little success in breast cancer treatment. We are reporting that low nanomolar doses of bisphenol A (BPA) or estradiol antagonize cisplatin cytotoxicity in breast cancer cells, with their effects not mediated via classical estrogen receptors.

Employing a recombinant HLA-DR3 expression system to dissect major histocompatibility complex II-thyroglobulin peptide dynamism: a genetic, biochemical, and reverse immunological perspective.

Previously, we have shown that statistical synergism between amino acid variants in thyroglobulin (Tg) and specific HLA-DR3 pocket sequence signatures conferred a high risk for autoimmune thyroid disease (AITD). Therefore, we hypothesized that this statistical synergism mirrors a biochemical interaction between Tg peptides and HLA-DR3, which is key to the pathoetiology of AITD. To test this hypothesis, we designed a recombinant HLA-DR3 expression system that was used to express HLA-DR molecules harboring either AITD susceptibility or resistance DR pocket sequences.

Prolactin confers resistance against cisplatin in breast cancer cells by activating glutathione-S-transferase.

Resistance to chemotherapy is a major obstacle for successful treatment of breast cancer patients. Given that prolactin (PRL) acts as an anti-apoptotic/survival factor in the breast, we postulated that it antagonizes cytotoxicity by chemotherapeutic drugs. Treatment of breast cancer cells with PRL caused variable resistance to taxol, vinblastine, doxorubicin and cisplatin.

Absence of nucleolar disruption after impairment of 40S ribosome biogenesis reveals an rpL11-translation-dependent mechanism of p53 induction.

Impaired ribosome biogenesis is attributed to nucleolar disruption and diffusion of a subset of 60S ribosomal proteins, particularly ribosomal protein (rp)L11, into the nucleoplasm, where they inhibit MDM2, leading to p53 induction and cell-cycle arrest. Previously, we demonstrated that deletion of the 40S rpS6 gene in mouse liver prevents hepatocytes from re-entering the cell cycle after partial hepatectomy. Here, we show that this response leads to an increase in p53, which is recapitulated in culture by rpS6-siRNA treatment and rescued by the simultaneous depletion of p53.

Promiscuous recombination of LoxP alleles during gametogenesis in cornea Cre driver mice.

Purpose: To examine whether promiscuous Cre/LoxP recombination happens during gametogenesis in double transgenic mice carrying LoxP modified alleles and Cre transgene driven by tissue-specific promoter outside the gonads of adult mice.

Methods: Cre driver mice were crossbred with reporter mouse lines (e.g.

Stress and prolactin effects on bone marrow myeloid cells, serum chemokine and serum glucocorticoid levels in mice.

Objective: Current evidence supports the conclusion that prolactin (PRL) is not an obligate immunoregulatory hormone and influences the immune system predominantly during stress conditions. In this study, we examined the impact of PRL on the psychogenic stress-induced responses of myeloid cells.

Methods: Seven-week-old PRL+/- (normal) and PRL-/- (deficient) mice were exposed to a predator for 1 h/day on 3 consecutive days.

Thermal injury elevates the inflammatory monocyte subpopulation in multiple compartments.

Recent publications have demonstrated that human resident and inflammatory monocyte (IM) subpopulations have equivalents in rodents. The effect of thermal injury upon these subpopulations has not been studied. Mice were given a scald burn and killed on postburn days (PBDs) 2, 4, and 8.

Ligand-independent regulation of transforming growth factor beta1 expression and cell cycle progression by the aryl hydrocarbon receptor.

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxic effects of its xenobiotic ligands and acts as an environmental checkpoint during the cell cycle. We expressed stably integrated, Tet-Off-regulated AHR variants in fibroblasts from AHR-null mice to further investigate the AHR role in cell cycle regulation. Ahr+/+ fibroblasts proliferated significantly faster than Ahr-/- fibroblasts did, and exposure to a prototypical AHR ligand or deletion of the ligand-binding domain did not change their proliferation rates, indicating that the AHR function in cell cycle was ligand independent.

RB loss promotes aberrant ploidy by deregulating levels and activity of DNA replication factors.

The retinoblastoma tumor suppressor (RB) is functionally inactivated in many human cancers. Classically, RB functions to repress E2F-mediated transcription and inhibit cell cycle progression. Consequently, RB ablation leads to loss of cell cycle control and aberrant expression of E2F target genes.

LS14 cells: a model for chemoresistance in liposarcoma.

Liposarcoma, a malignancy of adipose tissue, is the most common soft tissue sarcoma. Patients whose primary tumor cannot be resected or those who have developed metastasis, have poor prognosis since liposarcomas are highly resistant to chemotherapy. We recently generated a spontaneously immortalized cell line, named LS14, from a patient with metastatic liposarcoma.

Postburn monocytes are the major producers of TNF-alpha in the heterogeneous splenic macrophage population.

Increased tumor necrosis factor (TNF)-alpha production by postburn splenic macrophages is well documented. Splenic macrophages are a heterogeneous population, and the effect of thermal injury on these subpopulations has not been documented. We examined the effects of scald injury on myeloid cells with the phenotype of red pulp, white pulp, and marginal zone monocyte/macrophages.

Psychogenic stress prior to burn injury has differential effects on bone marrow and cytokine responses.

It is well known that many burn patients experience psychopathological disorders prior to burn injury. However, it is not known whether individuals that have been exposed to chronic psychological stresses will respond differently than unstressed individuals when challenged by a burn injury. In this study, we assessed whether chronic psychogenic stress prior to burn injury had any significant impact on burn injury-induced alterations in the myeloid compartment in the bone marrow and serum cytokine levels utilizing a well-controlled purely psychogenic stress model (predator exposure).

Bisphenol A facilitates bypass of androgen ablation therapy in prostate cancer.

Prostatic adenocarcinomas depend on androgen for growth and survival. First line treatment of disseminated disease exploits this dependence by specifically targeting androgen receptor function. Clinical evidence has shown that androgen receptor is reactivated in recurrent tumors despite the continuance of androgen deprivation therapy.

Increased expression of integrins and decreased apoptosis correlate with increased melanocyte retention in cultured skin substitutes.

Losses of human melanocytes (HM) in transplantation of cultured skin substitutes (CSS) may result from poor cellular attachments. To test this hypothesis, HM integrin expression was measured in four culture media: (a) melanocyte growth medium (MGM), an HM proliferation medium; (b) UCMC 160, a CSS maturation medium; (c) mMGM, modified MGM with 1.8 mM calcium; and (d) modified UCMC 160 with HM supplements (mUCMC 160).