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Biomedical subjects

Gary M Halliday

Publications and source records attributed to Gary M Halliday.

At least 19 recordsLinked to original sources
PubMed2006

Photoprotection by 1,25 dihydroxyvitamin D3 is associated with an increase in p53 and a decrease in nitric oxide products.

Vitamin D is produced in skin by UVB radiation (290-320 nm) acting on 7-dehydrocholesterol. The hypotheses that the active vitamin D hormone, 1,25 dihydroxyvitamin D3 (1,25(OH)2D3), would increase the survival of skin cells after UV irradiation and that surviving cells after 1,25(OH)2D3 treatment would have no increase in DNA damage were tested. The survival of keratinocytes post-UVR was significantly greater after treatment with 1,25(OH)2D3 compared to vehicle (P<0.01). Significant reductions in thymine dimers (TDs) in surviving keratinocytes after UVR were noted in the presence of 1,25(OH)2D3 (P<0.001). Nuclear p53 protein expression increased after UVR and was significantly higher in keratinocytes treated with 1,25(OH)2D3 (P<0.01), whereas NO products were significantly reduced (P<0.05). Both the increase in nuclear accumulation of p53 protein and reduced formation of nitric oxide products may contribute to the reduction in TDs seen with 1,25(OH)2D3 after UVR. Reductions in numbers of sunburn cells (P<0.01) and in TDs (P<0.05) were observed 24 hours after UVR in skin sections from Skh:hr1 mice treated with 1,25(OH)2D3. These results are consistent with the proposal that the vitamin D system in skin may be part of an intrinsic protective mechanism against UV damage.

Animals↗
PubMed2006

[Nle4-D-Phe7]-alpha-melanocyte-stimulating hormone significantly increased pigmentation and decreased UV damage in fair-skinned Caucasian volunteers.

Epidermal melanin reduces some effects of UV radiation, the major cause of skin cancer. To examine whether induced melanin can provide protection from sunburn injury, 65 subjects completed a trial with the potent synthetic melanotropin, [Nle4-D-Phe7]-alpha-melanocyte-stimulating hormone ([Nle4-D-Phe7]-alpha-MSH) delivered by subcutaneous injection into the abdomen at 0.16 mg/kg for three 10-day cycles over 3 months. Melanin density, measured by reflectance spectroscopy, increased significantly in all [Nle4-D-Phe7]-alpha-MSH-treated subjects. The highest increases were in volunteers with lowest baseline skin melanin levels. In subjects with low minimal erythemal dose (MED) skin type, melanin increased by an average of 41% (from 2.55 to 3.59, P < 0.0001 vs placebo) over eight separate skin sites compared with only 12% (from 4.18 to 4.70, P < 0.0001 vs placebo) in subjects with a high-MED skin type. Epidermal sunburn cells resulting from exposure to 3 MED of UV radiation were reduced by more than 50% after [Nle4-D-Phe7]-alpha-MSH treatment in the volunteers with low baseline MED. Thymine dimer formation was also shown to be reduced by 59% (P = 0.002) in the epidermal basal layer. This study has shown for the first time the potential ability of a synthetic hormone that augments melanin production to provide photoprotection to people who normally burn in direct sunlight.

Adult↗
PubMed2006

The induction of immunity to a protein antigen using an adjuvant is significantly compromised by ultraviolet A radiation.

Ultraviolet (UV) radiation from sunlight causes skin cancer and inhibits priming of the immune system during vaccination. However the dose related effects of the different components of sunlight (UVA and UVB) are complex and require further investigation. Using ovalbumin as a model protein vaccine with saponin as adjuvant we show that both UVA and UVB can suppress the DTH response to a poorly immunogenic protein. Increasing doses of UVB induced increased levels of immunosuppression and tolerance. UVA however, caused a bi-phasic dose response with intermediate but not low or high doses causing primary immunosuppression. No dose of UVA caused significant tolerance. Similar results were observed in both C57BL/6 and Balb/c mice. Our data confirms the complex immunomodulatory dose effects of UVA and UVB for a protein antigen, and shows that both UVB and UVA can suppress immunity induced by a protein with adjuvant. This highlights the importance of considering sun exposure patterns in the future success of both preventing skin cancer development and enhancing vaccination regimes.

Adjuvants, Immunologic↗
PubMed2006

Spectral and dose dependence of ultraviolet radiation-induced immunosuppression.

Ultraviolet radiation (UV) wavelength and dose dependence has been demonstrated for a number of cutaneous endpoints such as erythema, pigment darkening, DNA damage, and photocarcinogenesis. More recently, a number of in-vitro and in-vivo models of UV immunosuppression have implicated UVA (320-400 nm) in immune protection as well as immune suppression. While the wavelength dependencies for immunosuppression within UVB have been well established in mice, the exact role of specific UVA wavelengths has been less clear. Moreover, in humans, the spectral dependence of UV immunosuppression is even less well established. This review firstly outlines the established UV action spectra for a variety of cutaneous effects. The waveband and dose dependence of UV immunosuppression and its mechanisms are explored with a focus on in-vivo models. Finally, since UV immunosuppression along with DNA damage is thought to play a central role in the development of skin cancer, a clearer understanding of the immunosuppressive potential of discrete UV wavebands will allow a more rational approach to our understanding and prevention of skin cancer.

Aging↗
PubMed2006

Verapamil induces upregulation of P-glycoprotein expression on human monocyte derived dendritic cells.

Overexpression of P-glycoprotein, a transmembrane drug efflux pump that mediates efflux of chemotherapeutic agents contributes to drug resistance in many leukaemia and other cancerous cells. Non-malignant cells including leukocytes also express P-glycoprotein, but physiologic functions for P-glycoprotein are poorly defined. Recently, P-glycoprotein expression has been described in human mononuclear phagocytes and Langerhans cells. It has been shown to play a role in phagocytic cell transmigration through endothelial-lined vessels in an ablumenal-lumenal direction, a process that mimics their migration into lymphatic vessels. Using the monoclonal antibody 4E3, and the P-glycoprotein antagonist, verapamil, the expression of P-glycoprotein on human monocyte-derived dendritic cells was evaluated. Dendritic cells used in this study were CD1a+, CD11c+, CD14-, CD80+, CD83+, CD86+ and MHC-II(High). The expression of these markers increased significantly as the cells matured. P-glycoprotein expression was upregulated as the dendritic cells matured as well as in the presence of the "inflammatory stress" of the pathogenic bacteria Strept. pyogenes. Addition of verapamil or Strept. pyogenes to the culture medium during the final 24 hours significantly upregulated P-glycoprotein expression. Immortalized cell lines did not upregulate P-glycoprotein in the presence of verapamil. Evaluation of other normal cells showed that P-glycoprotein upregulation in the presence of verapamil was also a characteristic of macrophages. This novel observation of the upregulation of P-glycoprotein in the presence of verapamil appears to be a characteristic of activated myeloid derived antigen presenting cells and suggest that P-glycoprotein is essential for these cells as when it is blocked, they respond by increasing expression of this protein. In summary, this work describes that human dendritic cells generated from plastic-adherent monocytes rapidly upregulate expression of P-glycoprotein as they mature, and in the presence of inflammatory stress and the pharmacological agent verapamil, which blocks P-glycoprotein activity, suggesting that P-glycoprotein may play a role in activation as well as in migration of dendritic cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2006

Melanin differentially protects from the initiation and progression of threshold UV-induced erythema depending on UV waveband.

BACKGROUND/PURPOSE: This study aimed to determine the relationship between various measures of constitutive skin pigmentation and erythema caused by solar-simulated UV (ssUV), 290 and 310 nm UV. METHODS: Skin pigmentation was assessed clinically by skin typing as well as objectively by measurement of the melanin index (MI) by reflectance spectroscopy. Subjects having Fitzpatrick skin types I-IV were exposed to graded doses of ssUV and either narrowband 310 nm (n=70) or 290 nm (n=69) UV, and assessed 24 h after exposure. Minimal erythema dose (MED) was assessed visually as the lowest dose that caused minimally perceptible erythema. Susceptibility to further development of erythema with higher exposure doses was measured by the gradient of erythema dose-response curves. This was determined by linear regression using reflectance spectrometry data beyond the MED. RESULTS: Although there was considerable variation within each skin type, MI and ssUV MED increased with increasing Fitzpatrick skin type. MI correlated with ssUV MED and 310 nm UV MED, but not 290 nm UV MED. There was also a significant negative correlation between MI and erythema dose-response gradients caused by ssUV, 310 and 290 nm UV. CONCLUSION: Melanin situated near the basal epidermis may not protect from the initial development of threshold erythema caused by 290 nm UV because it penetrates poorly past the stratum corneum and is not well absorbed by melanin in vivo compared with 310 nm UV. Higher erythemal 290 nm UV doses may reach basal epidermal melanin, which may then afford protection against further 290 nm UV erythema.

Adult↗
PubMed2006

Effect of topical melatonin on ultraviolet radiation-induced suppression of Mantoux reactions in humans.

BACKGROUND: Melatonin, the central neurohormone in circadian rhythm pathways, is recognized to have a variety of immune-enhancing effects. It has previously been shown to reduce ultraviolet (UV) radiation-induced erythema in mice and in humans, but there are as yet no published studies on the effects of melatonin on UV-induced immunosuppression in humans. METHODS: We investigated the effects of topical melatonin on solar-simulated (ss) UV-induced suppression of Mantoux reactions in 16 healthy, Mantoux-positive volunteers. Melatonin (5%) and its vehicle were applied in a double-blinded manner to separate areas on the lower back, immediately after each of three consecutive daily ssUV exposures. Various sites on the back received either no irradiation or one of three-graded ssUV doses. Mantoux testing was performed at each site 24 h after the final irradiation, and assessed 72 h later using a reflectance erythema meter. In a separate group of 19 volunteers, the effect of melatonin on minimal erythema dose was assessed both visually and with an erythema meter. RESULTS: We found dose-responsive UV-induced suppression of the Mantoux response in the presence of both vehicle and melatonin; melatonin did not prevent UV-induced immunosuppression in this model. Melatonin was also found to have no effect on the minimal erythema dose. CONCLUSIONS: Melatonin conferred no protection against immune suppression or sunburn when applied topically to human skin immediately after irradiation.

Adjuvants, Immunologic↗
PubMed2005

Cyclobutane pyrimidine dimer formation is a molecular trigger for solar-simulated ultraviolet radiation-induced suppression of memory immunity in humans.

We tested the hypothesis that DNA is a target for solar-simulated ultraviolet radiation (ssUVR)-induced suppression of the reactivation of memory immunity in humans. T4N5 liposomes contain the DNA repair enzyme T4 endonuclease V. This cleaves DNA at the site of ultraviolet radiation (UVR)-induced cyclobutane pyrimidine dimers (CPD), initiating DNA repair. It has previously been used to show that CPDs are a key molecular trigger for UVR-induced immunosuppression in mice. To determine whether CPD formation is involved in UVR immunosuppression in humans, nickel-allergic volunteers were irradiated with a range of doses of ssUVR. T4N5 or empty liposomes were then applied after irradiation. Nickel-induced recall immunity was assessed by reflectance spectrometry. T4N5 liposomes inhibited immunosuppression and prevented ssUVR from reducing the number of epidermal dendritic cells. T4N5 liposomes also reduced macrophage infiltration into irradiated epidermis. These studies show that enhanced removal of CPDs from human skin protects from immunosuppression, hence demonstrating that these photolesions are an important molecular event in ssUVR-induced immunosuppression in humans. CPDs also triggered loss of dendritic cells and infiltration by macrophages. It is possible that these changes to antigen presenting cells contribute to ssUVR induced suppression of recall immunity to nickel in humans.

Adult↗
PubMed2005

Inflammation, gene mutation and photoimmunosuppression in response to UVR-induced oxidative damage contributes to photocarcinogenesis.

Ultraviolet (UV) radiation causes inflammation, gene mutation and immunosuppression in the skin. These biological changes are responsible for photocarcinogenesis. UV radiation in sunlight is divided into two wavebands, UVB and UVA, both of which contribute to these biological changes, and therefore probably to skin cancer in humans and animal models. Oxidative damage caused by UV contributes to inflammation, gene mutation and immunosuppression. This article reviews evidence for the hypothesis that UV oxidative damage to these processes contributes to photocarcinogenesis. UVA makes a larger impact on oxidative stress in the skin than UVB by inducing reactive oxygen and nitrogen species which damage DNA, protein and lipids and which also lead to NAD+ depletion, and therefore energy loss from the cell. Lipid peroxidation induces prostaglandin production that in association with UV-induced nitric oxide production causes inflammation. Inflammation drives benign human solar keratosis (SK) to undergo malignant conversion into squamous cell carcinoma (SCC) probably because the inflammatory cells produce reactive oxygen species, thus increasing oxidative damage to DNA and the immune system. Reactive oxygen or nitrogen appears to cause the increase in mutational burden as SK progress into SCC in humans. UVA is particularly important in causing immunosuppression in both humans and mice, and UV lipid peroxidation induced prostaglandin production and UV activation of nitric oxide synthase is important mediators of this event. Other immunosuppressive events are likely to be initiated by UV oxidative stress. Antioxidants have also been shown to reduce photocarcinogenesis. While most of this evidence comes from studies in mice, there is supporting evidence in humans that UV-induced oxidative damage contributes to inflammation, gene mutation and immunosuppression. Available evidence implicates oxidative damage as an important contributor to sunlight-induced carcinogenesis in humans.

Animals↗
PubMed2005

Transforming growth factor-beta1 immobilises dendritic cells within skin tumours and facilitates tumour escape from the immune system.

Human skin tumours often regress spontaneously due to immune rejection. Murine skin tumours model this behaviour; some regress and others progress in syngeneic immunocompetent hosts. Previous studies have shown that progressor but not regressor skin tumours inhibit dendritic cell (DC) migration from the tumour to draining lymph nodes, and transforming growth factor-beta1 (TGF-beta1) has been identified as a responsible factor. To determine whether increased production of TGF-beta1 in the absence of other differences inhibits DC migration from the tumour and enables it to evade immune destruction, a murine regressor squamous cell carcinoma clone was transfected with the gene for TGF-beta1. This enhanced growth in vitro and in vivo, causing it to become a progressor. TGF-beta1 transfection reduced the number of infiltrating DCs by about 25%. Quantitation of CD11c+ E-cadherin+ (epidermally derived) DCs in lymph nodes determined that TGF-beta1 reduced the number of DCs that migrated from the tumour to undetectable levels. This was supported by showing that TGF-beta1 reduced DC migration from cultured tumour explants by greater than tenfold. TGF-beta1 transfection also reduced the number of infiltrating CD4 and CD8 T cells. Thus, TGF-beta1 production by skin tumours is sufficient to immobilise DCs within the tumour, preventing their migration to lymph nodes. This reduces the number of T cells that infiltrate the tumour, preventing regression. Thus, TGF-beta1 is a key regulator of whether skin tumours regress or progress.

Animals↗
PubMed2005

B cells activated in lymph nodes in response to ultraviolet irradiation or by interleukin-10 inhibit dendritic cell induction of immunity.

Ultraviolet (UV) radiation suppresses systemic immunity. We explored these cellular mechanisms by exposing mice to systemically immunosuppressive doses of UV radiation and then analyzing cell phenotype and function in the lymphoid organs. Although UV radiation increased total cell number in the draining lymph nodes (DLN), it did not alter the activation state of dendritic cells (DC). Rather, UV radiation selectively activated lymph node B cells, with these cells being larger and expressing higher levels of both anti-major histocompatibility complex II and B220 but not co-stimulatory molecules. This phenotype resembled that of a B cell geared toward immune tolerance. To test whether UV radiation-activated B cells were responsible for immunosuppression, DC and B cells were conjugated to antigen ex vivo and transferred into naive hosts. Although DC by themselves activated T cells, when the B cells from UV radiation-irradiated mice were co-injected with DC, they suppressed DC activation of immunity. Interleukin (IL)-10-activated B cells also suppressed DC induction of immunity, suggesting that IL-10 may be involved in this suppressive effect of UV radiation. These results demonstrate a new mechanism of UV radiation immunosuppression whereby UV radiation activates B cells in the skin-DLN that can suppress DC activation of T cell-mediated immunity.

Animals↗
PubMed2005

Sunlight-induced immunosuppression in humans is initially because of UVB, then UVA, followed by interactive effects.

Solar-simulated ultraviolet radiation (ssUV) suppresses immunity in humans. The ultraviolet B (UVB) waveband is recognized as immunosuppressive; however the relative significance of UVA to ssUV immunosuppression is unknown. We created dose and time-response curves for UVB-, UVA-, and ssUV-induced suppression of memory immunity to nickel in humans. UVB caused immunosuppression within 24 h. UVA immunosuppression required 48 h and was normalized by 72 h. UVB alone accounts for ssUV immunosuppression at 24 h, but both UVB and UVA contributed at 48 h. By 72 h neither waveband accounted for ssUV immunosuppression. An interaction between these wavebands was therefore the major contributor. To confirm this dose-response curves were used to determine immune protection factors (IPF) for sunscreens with nickel challenge 72 h following ssUV. A sunscreen with good UVA protection had an IPF twice that of a poor UVA protector, despite providing similar protection from sunburn. Thus UVA was a major contributor to ssUV-induced immunosuppression at 72 h but only with the cooperation of UVB. Hence, UVB initiates immunosuppressive signals within 24 h, followed by UVA at 48 h, then an interaction between UVB and UVA. By 72 h following ssUV exposure, neither UVB nor UVA, but an interaction between them is the major cause of sunlight-induced immunosuppression.

Adolescent↗
PubMed2004

Single chain antibody fragments for the selective targeting of antigens to dendritic cells.

In order to target antigens (Ags) selectively to dendritic cells (DC), we derived single chain antibody fragments (scFvs) from NLDC-145 and N418, two monoclonal antibodies binding the mouse dendritic cell-restricted surface molecules DEC-205 and CD11c. Recombinant hexahistidine-tagged forms of the scFvs (scNLDC and scN418) were efficiently produced in a baculovirus expression system. Both scFvs bound DEC-205(+) Langerhans cells and CD11c(+) fetal skin-derived dendritic cells (FSDCs) comparably to their parental antibodies. Immunization of C57BL/6 mice with a DNA vaccine encoding a model protein antigen fused to scNLDC stimulated specific immune responses in both the humoral and cellular compartments, in contrast to DNA vaccines expressing scN418-targeted or untargeted antigen. Our results show that antigen targeting to DCs via a DEC-205 binding scFv leads to enhanced immunogenicity. Further, this work suggests that scFvs fused to protein antigens and delivered as DNA vaccines may provide a generic means for delivering vaccinal molecules to selected cell populations.

Animals↗
PubMed2004

The basal layer in human squamous tumors harbors more UVA than UVB fingerprint mutations: a role for UVA in human skin carcinogenesis.

We hypothesized that a substantial portion of the mutagenic alterations produced in the basal layer of human skin by sunlight are induced by wavelengths in the UVA range. Using laser capture microdissection we examined separately basal and suprabasal keratinocytes from human skin squamous cell carcinomas and premalignant solar keratosis for both UVA- and UVB-induced adduct formation and signature mutations. We found that UVA fingerprint mutations were detectable in human skin squamous cell carcinomas and solar keratosis, mostly in the basal germinative layer, which contrasted with a predominantly suprabasal localization of UVB fingerprint mutations in these lesions. The epidermal layer bias was confirmed by immunohistochemical analyses with a superficial localization of cyclobutane thymine dimers contrasting with the localization of 8-hydroxy-2'-deoxyguanine adducts to the basal epithelial layers. If unrepaired, these adducts may lead to fixed genomic mutations. The basal location of UVA-rather than UVB-induced DNA damage suggests that longer-wavelength UVR is an important carcinogen in the stem cell compartment of the skin. Given the traditional emphasis on UVB, these results may have profound implications for future public health initiatives for skin cancer prevention.

Carcinoma, Squamous Cell↗
PubMed2004

The suppression of immunity by ultraviolet radiation: UVA, nitric oxide and DNA damage.

We have examined the mechanism by which solar-simulated ultraviolet radiation (ssUV) suppresses memory immunity to nickel in allergic humans. In initial studies, we used inbred mice to determine the contribution of different wavebands to sunlight-induced immunosuppression. We found that low dose UVA can enhance memory, medium dose UVA (half the amount in one minimum erythemal dose of ssUV) is immunosuppressive, but higher doses protect from UVB. This is genetically dependent, as it is not observed in all mouse strains. UVA caused a similar dose-related change in recall immunity in humans. ssUV dose responses determined the limits of protection provided by sunscreens from immunosuppression in humans. Immune protection factors calculated from these data correlated with UVA protection, but not with sun protection factor, showing that in commercial sunscreens that provide good UVB protection, UVA protection limits prevention of immunosuppression. N(G)-monomethyl-l-arginine acetate (l-NMMA) was used to inhibit nitric oxide (NO) production and T4N5 liposomes containing T4 endonuclease V to enhance DNA repair. Sub-erythemal ssUV caused a dose-related local suppression of recall immunity to nickel in humans. l-NMMA and the liposomes protected the nickel reaction, suggesting that NO and DNA damage are mediators of UV-induced immunosuppression in humans.

Animals↗
PubMed2004

Rapid downregulation of antigen processing enzymes in ex vivo generated human monocyte derived dendritic cells occur endogenously in extended cultures.

Dendritic cells, the most potent antigen presenting cells, have been shown in murine models to induce immune responses against many antigens. Their role in the initiation of antitumour immunity has received enormous attention. Their ability to process and present antigen is dependent on their state of maturation. This study examines the activity of human monocyte-derived dendritic cells at two different time points and the corresponding changes in the proteolytic enzyme activity. Dendritic cells were produced from peripheral blood mononuclear cells of normal volunteers. Plastic adherent cells were cultured for 5 or 7 days with recombinant human (rh)GM-CSF and rhIL-4. Flow cytometry showed that day 5 dendritic cells (DC) were less mature than day 7 DC as indicated by the expression of CD1a, CD11c, CD14, CD80, CD83, CD86 and MHC-II. Proteolytic activity of the enzymes cathepsin C and cathepsin G and phagocytosis of particulate antigens also showed significant differences between d5 dendritic cells and d7 dendritic cells. Allogeneic costimulatory activity of d7 dendritic cells was also significantly increased. Induction of immunity requires active presentation of antigens by antigen processing cells on their MHC-I and/or MHC-II molecules. Study of peptide carriers and peptide precursor molecules showed a significant decrease in CLIP levels in the day 7 DC, suggesting their decreased ability to process antigens but no difference in their ability to load MHC-II molecules. These findings indicate that the length of time in culture, in the absence of exogenous maturation - inducing stimuli affects dendritic cell maturation. Intracellular enzymatic activities of dendritic cells also changed rapidly with small changes in phenotype.

Antigen Presentation↗