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Biomedical subjects

D N Sauder

Publications and source records attributed to D N Sauder.

At least 37 records · Page 2Linked to original sources
PubMed2000

Screening for azathioprine toxicity: a pharmacoeconomic analysis based on a target case.

The risk of azathioprine-induced myelosuppression can be predicted by detecting patients with intermediate or low thiopurine methyltransferase (TPMT) activity. Population studies have shown that 89% of whites have high TPMT activity, 11% have intermediate TPMT activity, and 0.3% have low TPMT activity. Three specific mutations in the TPMT gene that cause decreased TPMT activity have recently been identified. Patients homozygous for the TPMT mutations have low TPMT activity, and patients heterozygous for TPMT mutations have intermediate TPMT activity. This has led to the development of a technique for TPMT genotype analysis that will identify patients at risk of azathioprine-induced myelosuppression. We report a case of a patient with bullous pemphigoid who experienced azathioprine-induced myelosuppression and who was later found to be homozygous for TPMT mutant alleles. Using the cost of treatment required for this patient and the estimated population prevalence of TPMT mutations, we examined the cost impact of screening for TPMT mutations in all patients being considered for azathioprine therapy. We calculated that screening is cost-neutral assuming patients homozygous for TPMT mutations experience myelosuppression, and that it is cost-beneficial assuming patients heterozygous for TPMT mutations also experience myelosuppression while receiving azathioprine. Screening patients for TPMT mutations will reduce the risk of azathioprine-induced myelosuppression, and our study suggests that it may also be a cost-attractive strategy.

Adult↗
PubMed1999

TNF receptor p55 plays a pivotal role in murine keratinocyte apoptosis induced by ultraviolet B irradiation.

Excess exposure of skin to ultraviolet B (UVB) results in the appearance of so-called sunburn cells. Although it has been demonstrated that sunburn cells represent apoptotic keratinocytes, the molecular mechanisms for UVB-induced apoptosis in keratinocytes have not been fully elucidated. The cytokine, TNF-alpha, has been shown to induce apoptosis in a variety of cell types. Since UVB induces keratinocytes to release TNF-alpha, we hypothesized that TNF-alpha is involved in UVB-induced apoptosis in keratinocytes. In order to confirm this hypothesis and to further delineate which type of TNF receptor signaling mediates the apoptosis pathway, we performed both in vivo and in vitro experiments using gene-targeted knockout mice lacking either the TNF p55 receptor or the TNF p75 receptor. In the in vivo study, wild-type and mutant mice were exposed to UVB, and apoptotic keratinocytes were detected by examining DNA fragmentation using in situ nick-end labeling. For the in vitro experiments, keratinocytes derived from the wild-type and mutant mice were irradiated with UVB, and the degree of apoptosis was determined by flow cytometry, nick-end labeling of DNA, and a DNA ladder assay. Both in vivo and in vitro studies demonstrated that the deletion of TNF receptor p55 could suppress UVB-induced apoptosis in keratinocytes. Our observations support the notion that TNF-alpha is involved in UVB-induced keratinocyte apoptosis, and demonstrate that p55 receptor signaling plays a pivotal role in this event.

Animals↗
PubMed1999

Enhanced epidermal Langerhans cell migration in IL-10 knockout mice.

The migration of epidermal Langerhans cells (LC) to lymph nodes (LN) is critical in the initiation of contact hypersensitivity (CHS) responses. Studies suggest that contact allergen-induced epidermal proinflammatory cytokines, including IL-1 and TNF-alpha, play important roles in promoting LC migration. Contact allergens also induce epidermal anti-inflammatory cytokines such as IL-10. Since IL-10 down-regulates proinflammatory cytokine production and inhibits CHS, we hypothesized that IL-10 might inhibit LC migration. To test this hypothesis, IL-10 knockout (KO) mice were epicutaneously sensitized with the hapten, FITC, and 24 h later hapten-bearing cells in the draining LN were examined. The number of hapten-bearing cells in the LN was significantly greater in IL-10 KO mice than in wild-type mice. The mutant mice also had an exaggerated CHS to FITC. Pretreatment with anti-TNF-alpha Ab or IL-1R antagonist significantly reduced the number of hapten-bearing cells in the LN, suggesting that IL-10 modulation of LC migration involves IL-1 and TNF-alpha. Moreover, IL-10 KO mice demonstrated a greater increase in TNF-alpha, IL-1alpha, and IL-1beta mRNAs in the allergen-exposed epidermis, and keratinocytes derived from the mutant mice were able to produce higher amounts of TNF-alpha and IL-1alpha protein. These data suggest that IL-10 plays an inhibitory role in LC migration and that this effect may occur via the down-regulation of TNF-alpha and IL-1 production.

Animals↗
PubMed1999

Role of cytokines in epidermal Langerhans cell migration.

In the epidermal compartment of skin, keratinocytes (KC), Langerhans cells (LC), and their soluble products, i.e. cytokines, constitute a unique immunologic microenvironment. KC participate in cutaneous immune responses by producing various cytokines. LC, a member of the dendritic cell (DC) family, represent the professional antigen-presenting cells in the epidermis. Although it has been demonstrated that migration of LC from skin to lymph nodes is a critical step for the antigen presentation, molecular mechanisms for such an event remain unclear. Recent studies suggest that cytokines are able to modulate LC/DC migration. There is accumulating evidence that proinflammatory cytokines including interleukin (IL)-1 and tumor necrosis factor alpha promote LC emigration from the skin, whereas the anti-inflammatory cytokine IL-10 is a counter-regulator. LC/DC express chemokine receptors. Chemokines generated from lymphatic endothelial cells and lymph node cells play a role in the directional migration of LC/DC into lymph nodes. This article reviews current studies on the role of cytokines in LC/DC migration.

Animals↗
PubMed1999

The etiology of malignant melanoma.

The etiology of malignant melanoma has been intensely studied over the last decade. Much of the recent work focuses on oncongenes and tumour suppressor genes and the role of apoptosis in melanoma. Loss of tumour suppressor proteins such as p16 has been documented in melanoma and correlates with tumour progression. Mutations in the tumour suppressor p53 have also been documented in melanoma. The proto-oncongene Bcl-2 encodes a protein that inhibits apoptosis. Bcl-2 is found in normal melanocytes and benign nevi. However, lower levels are seen in melanoma. To investigate the relationship between melanoma and nevi, in our Basic and Clinical Science section, Dr. Radhi examines the expression of p53, p16, and Bcl in malignant melanoma arriving in benign nevi. P53 immunoreactivity was found only in the malignant component, with no expression being seen in the benign components of the lesion. This suggests that this tumour suppressor gene is involved in the pathogenesis of melanoma.

Humans↗
PubMed1998

The use of low energy photon therapy (LEPT) in venous leg ulcers: a double-blind, placebo-controlled study.

BACKGROUND: Venous ulcers are estimated to be present in 0.2 to 0.4% of the population. Although new therapies have significant promise, nonhealing ulcers still represent a significant problem. OBJECTIVE: To evaluate the efficacy of low energy photon therapy (LEPT) in the treatment of venous leg ulcers. METHODS: A placebo-controlled, double-blind study using low energy photon therapy was performed in nine patients with 12 venous ulcers. Treatment was given three times a week for 10 weeks, using two monochromatic optical sources. One source provided a wavelength (lambda) of 660 nm (red) while the second source delivered a wavelength of 880 nm (infrared). Two optical probes were used, one consisted of an array of 22 monochromatic sources, operating at a wavelength of 660 nm and covering an area 6 x 10 cm2. The second probe had seven infrared sources, operating at a wavelength of 880 nm and covering an area of 4 cm2. The above configuration of optical probes was selected to cover the majority of the ulcer area being treated. The patients who were randomized to placebo treatment received sham therapy from an identical-appearing light source from the same delivery system. RESULTS: Nine patients with 12 venous ulcers were randomized to receive LEPT or placebo therapy. At the conclusion of the study, the percentage of the initial ulcer area remaining unhealed in the LEPT and placebo groups was 24.4% and 84.7%, respectively (P = 0.0008). The decrease in ulcer area (compared to baseline) observed in the LEPT and placebo groups was 193.0 mm2 and 14.7 mm2, respectively (P = 0.0002). One patient dropped out of the study, complaining of lack of treatment efficacy; he was found to be randomized to the placebo group. There were no adverse effects. CONCLUSION: In this placebo-controlled, double-blind study LEPT was an effective modality for the treatment of venous leg ulcers.

Adult↗
PubMed1998

Antiangiogenic properties of a novel shark cartilage extract: potential role in the treatment of psoriasis.

BACKGROUND: A number of inflammatory and immune diseases are associated with vascular changes. Psoriasis, as an example, is a common inflammatory skin disease with dilation of capillaries as an early histological change. In more developed psoriatic lesions there is proliferation of blood vessels and neovascularization. The use of agents that target these vascular changes represents a novel therapeutic strategy in the treatment of inflammatory diseases. Since cartilage is an avascular tissue, it has been hypothesized that there may be factors found in cartilage that inhibit blood vessel formation. OBJECTIVE: The objectives of this study were 1) to determine whether extracts of cartilage could inhibit angiogenesis, and 2) since altered angiogenesis is associated with certain diseases, including psoriasis, to examine whether inhibition of angiogenesis could potentially contribute to the treatment of psoriasis. METHODS: Extracts of shark cartilage were prepared by homogenization and ultrafiltration to derive the active agent termed AE -941. This agent was tested for antiangiogenesis activity using the embryonic vascularization test, which is a modification of the ex vivo chick embryo culture (CAM). Since one of the first steps in angiogenesis is degradation by metalloproteinases of the basement membrane of capillaries, AE -941 was tested for collagenase activity using a fluorogenic peptide substrate. Anti-inflammatory properties were tested using a cutaneous irritation model in humans. RESULTS: A dose dependent inhibition in embryonic neovascularization as well as in collagenase activity by AE -941 was demonstrated. When test compounds were applied on the forearms of test subjects, AE -941 was shown to have anti-inflammatory properties. Anecdotal data suggested that topical AE -941 had a beneficial effect in psoriasis. CONCLUSION: Our results show that AE -941 has anti-angiogenic and anti-inflammatory properties. Antiangiogenesis agents such as AE -941 provide an entirely new class of agents to treat cutaneous and systemic diseases associated with altered vascularity.

Animals↗
PubMed1998

Heparin-induced thrombocytopenia.

OBJECTIVE: To highlight the importance of heparin-induced thrombocytopenia (HIT), a potentially fatal adverse effect of heparin therapy. CASE SUMMARY: There are two types of HIT with distinct etiology. Type 1 HIT is a relatively mild thrombocytopenia of early onset that generally resolves with ongoing heparin therapy. Clinical complications are uncommon. Type 2 HIT, which is more severe, is the main focus of this report. Five patients receiving heparin therapy developed type 2 HIT, which in some cases resulted in complications that required limb amputation, or eventuated in death. DISCUSSION: In a patient receiving heparin therapy, the development of thrombocytopenia should alert the caregiver to the possible development of HIT. Prompt management of HIT can help prevent complications. HIT usually manifests 5-8 days after starting heparin therapy. The platelet count usually decreases to less than 100 x 10(3)/mm3. It generally normalizes within 5-7 days after discontinuing heparin therapy. In spite of the thrombocytopenia, thrombosis or disseminated intravascular coagulation can occur. The management may be subdivided into three clinical situations: mild-to-moderate asymptomatic thrombocytopenia, severe thrombocytopenia with a platelet count of less than 50 x 10(3)/mm3, and thrombosis or embolism complicating HIT. CONCLUSIONS: Heparin-induced thrombocytopenia is an uncommon but potentially serious, and sometimes lethal, complication of heparin therapy. Therefore, it is important to be aware of the possibility of the development of HIT with heparin therapy, to recognize it early, and to manage it appropriately before the manifestation of adverse effects.

Adult↗
PubMed1997

Depressed Langerhans cell migration and reduced contact hypersensitivity response in mice lacking TNF receptor p75.

Epidermal Langerhans cells (LC) belong to the dendritic cell family and represent the major APC within the skin. LC capture epicutaneous Ag, migrate into regional lymph nodes, and present Ag to T cells, thereby initiating primary immune response. The migratory properties of LC are an essential component of their function. The molecular mechanisms responsible for LC migration are far less defined. However, evidence has been accumulating to suggest that TNF-alpha, a major proinflammatory cytokine, plays an important role in promoting DC migration. To confirm the role of TNF-alpha in LC migration and to examine which type of TNF receptor signaling is involved in such an event, we utilized gene-targeted knockout mice lacking TNF receptor p55 or p75. The migration of LC was assessed by examining the frequency of hapten-bearing cells in draining lymph nodes following hapten FITC painting, and the accumulation of dendritic cells in draining lymph nodes after intradermal injection of TNF-alpha. While LC migration was normal in p55-deficient mice, the migration was markedly depressed in p75-deficient mice. Receptor p75-deficient mice also demonstrated a hyporesponsiveness in allergen-induced contact dermatitis, but a normal responsiveness in irritant-induced contact dermatitis. These results suggest that p75-dependent signaling plays a crucial role in the migration of LC and in the initiation of cutaneous immune responses.

Administration, Cutaneous↗
PubMed1997

Alternatively spliced forms of the cGMP-gated channel in human keratinocytes.

Alternatively spliced forms of the alpha subunit of the cGMP-gated channel have been cloned from human keratinocytes. One form encodes a complete channel which is almost identical to the rod photoreceptor. A second spliced variant would encode a protein missing a portion of the intracellular hydrophilic domain and the putative first transmembrane domain. Both complete and spliced variants of the channel also were found in epidermis. The expression of the complete form of the channel was induced by levels of extracellular calcium which promote keratinocyte differentiation. The cGMP-gated channel may play an important role in calcium induced keratinocyte differentiation by mediating Ca2+ entry.

Alternative Splicing↗
PubMed1997

Penetration of keratinocyte-derived cytokines into basement membrane.

Keratinocytes are known to produce a wide variety of cytokines which are believed to play a significant role in cutaneous inflammatory and immunologic reactions. Considering the array of proteolytic enzymes present in the skin and the transient nature of cytokines produced from keratinocytes, it is unclear whether cytokines released by keratinocytes cross the basement membrane and contribute to distal inflammatory and immune reactions. To investigate the ability of cytokines released from human keratinocytes to cross basement membrane, we used a two chamber culture model. Keratinocytes were plated in the upper chamber coated with a reconstituted basement membrane matrix (matrigel) on a microporous membrane. To augment cytokine production, we exposed keratinocytes to 300 J/m2 UVB; 24 h later the supernatants were collected, and the levels of cytokine were measured by ELISA. IL-1alpha, IL-6, and TNF-alpha were found to be increased after UVB irradiation in the upper chamber, and significant amounts (70-80%) of each cytokine were detected in the lower chamber. Our results indicate that keratinocyte-derived cytokines are available for interactions below the basement membrane and present circumstantial evidence that the production of those cytokines from keratinocytes contributes to the elevation of circulation after the UVB exposure.

Basement Membrane↗
PubMed1997

Tumor necrosis factor (TNF) receptor type 1 (p55) is a main mediator for TNF-alpha-induced skin inflammation.

Tumor necrosis factor alpha (TNF-alpha) is a pleiotropic proinflammatory cytokine that elicits a large number of biological effects, including inflammatory and immunoregulatory responses. Biological activities of TNF-alpha are mediated by two distinct TNF receptors, p55 type 1 receptor (TNFR1) and p75 type 2 receptor (TNFR2). To determine the role of TNF-alpha in the induction of inflammatory responses in the skin, gene-targeted mutant mice lacking either TNFR1 or TNFR2 were painted with irritant chemicals. Both phenol and croton oil painting onto the ears induced less inflammation in TNFR1(-) mice than normal and TNFR2(-) mice. Intradermal injection of TNF-alpha (0.2-200 ng for 3 days) into the ear induced less inflammation in TNFR1(-) mice than in normal mice. TNFR2(-) mice developed a normal inflammatory reaction to high doses of TNF-alpha (20-200 ng for 3 days), while they showed minimal reactivity to low doses of TNF-alpha (0.2-2 ng for 3 days). TNF-alpha is known to trigger the release of a series of other cytokines and to induce the expression of cell adhesion molecules, thus contributing to the development of inflammation. The levels of protein and mRNA for interleukin (IL)-6 were elevated in keratinocytes from normal as well as TNFR2(-) mice after treatment with TNF-alpha, while keratinocytes from TNFR1(-) mice did not show any up-regulation of IL-6. TNF-alpha induced intercellular adhesion molecule (ICAM)-1 expression in the keratinocytes from normal and TNFR2(-) mice, but not in those from TNFR1(-) mice. These results indicate that TNFR1 is critical for induction of skin inflammation by TNF-alpha.

Administration, Topical↗
PubMed1997

Costimulation with ultraviolet B and interleukin-1 alpha dramatically increase tumor necrosis factor-alpha production in human dermal fibroblasts.

Ultraviolet light, particularly in wavelengths of 290-320 nm (UVB), is known to induce cytokine synthesis in the skin. Cytokines act in a cascade fashion and can have synergistic or antagonistic actions on regulation of other cytokines. In this study, we sought to determine whether cotreatment with UVB and interleukin-1 alpha (IL-1 alpha) induces tumor necrosis factor-alpha (TNF-alpha) production synergistically by human dermal fibroblasts. UVB irradiation (200 J/m2) or IL-1 alpha (10 ng/ml) independently induced small amount of TNF-alpha (< 25 pg/ml) from human dermal fibroblasts. However, combined treatments with UBV and IL-1 alpha induced 30-40-fold higher levels of TNF-alpha (750 pg/ml) than with either UVB of IL-1 alpha treatment alone. This synergy was also seen with mRNA expression. Maximum synergistic effect was observed when IL-1 alpha was added immediately after irradiation. Considering the fact that UVB is capable of causing release of IL-1 alpha from human keratinocytes and approximately 10% of incident UVB penetrates to the level of dermal fibroblasts, our results suggest that UVB may act in a cascade fashion to induce inflammation by initial release of keratinocyte IL-1 alpha, which then synergizes with UVB on human dermal fibroblasts to significantly increase TNF-alpha production.

Cells, Cultured↗
PubMed1997

Effects of interferons on the production of interleukin-6 and interleukin-8 in human keratinocytes.

Interferons (IFNs) originally described for antiviral activity have been reported to have pleiotropic effects, including the ability to induce interleukin-6 (IL-6) and IL-8 production in several cell types. IL-6 and IL-8 are proinflammatory cytokines and are known to be produced by a wide variety of cells, including human keratinocytes. In the present study, we sought to examine the effects of IFNs on IL-6 and IL-8 production from human keratinocytes. IFN-gamma (10-50 ng/ml) induced IL-6 and IL-8 production dose dependently, but no induction of IL-6 or IL-8 was observed with either IFN-alpha or IFN-beta. Because cytokines often work in a cascade fashion and keratinocytes are a source of primary cytokines, IL-1 alpha, and tumor necrosis factor-alpha (TNF-alpha), we examined whether combined treatment with IFN-gamma and these primary cytokines, IL-1 alpha and TNF-alpha, had a synergistic effect on the production of IL-6 and IL-8. Combined treatment with IFN-gamma and IL-1 alpha induced 6-fold to 7-fold higher levels of IL-6 than IL-1 alpha alone. Combined treatment with IFN-gamma and TNF-alpha induced 11-fold to 12-fold higher levels of IL-6 than TNF-alpha alone. The same treatment induced 3-fold to 4-fold higher levels of IL-8 in both cases. These results suggest that IFN-gamma is a positive regulator for the production of IL-6 and IL-8 from human keratinocytes and likely has an augmentative effect on skin inflammation.

Cells, Cultured↗
PubMed1997

The expression and modulation of IFN-alpha and IFN-beta in human keratinocytes.

In addition to leukocytes and fibroblasts, the classic sources of human interferons (IFN), many other human cells are now known to be capable of producing IFN. Keratinocytes (KC) are abundant in the skin and provide the first line of defense against viruses and other noxious agents. Human KC are a potent source of cytokines and were implicated as forming IFN-like protein(s). We have investigated whether KC form IFN. We found that culture supernatants from unstimulated human KC did not contain detectable amounts of IFN-alpha or IFN-beta. However, those from KC activated with the potent IFN inducer, polyriboinosinic:polriboycytidylic acid (poly rI:rC), had appreciable antiviral activity, which studies with neutralizing sera showed to be caused by IFN-beta. In ELISA tests, we detected IFN-beta protein in the supernatants but not IFN-alpha protein. Nevertheless, reverse transcription PCR showed that both IFN-alpha and IFN-beta mRNA were upregulated in poly rI:rC-treated KC. The levels of these mRNA were also increased in KC exposed to ultraviolet B (UVB) irradiation, interleukin-1alpha (IL-1alpha), tumor necrosis factor-alpha (TNF-alpha), or lipopolysaccharide (LPS). These results show that IFN-beta is among the cytokines secreted from human KC and, together with IFN-alpha, may have a role in host defense mechanisms in the skin.

Antiviral Agents↗
PubMed1997

CD45 molecule in gammadelta T-cell generation: disruption of CD45 exon 6 does not affect Vgamma3 dendritic epidermal T-cell development.

There are two distinct lineages of T cells: T-cell receptor (TCR) alphabeta-bearing cells (alphabeta T cells) and TCR gammadelta-bearing cells (gammadelta T cells). All of the alphabeta T cells and most subsets of gammadelta T cells develop in the thymus. It has been demonstrated that the protein tyrosine phosphatase CD45 plays a pivotal role in the intrathymic development of alphabeta T cells. Thymocyte maturation is arrested at the transitional stage from immature CD4+ CD8+ double-positive to mature CD4+ or CD8+ single-positive cells after CD45 exon 6 gene disruption. In this study, we examined whether Vgamma3 dendritic epidermal T cells (DETC), a subset of thymus-dependent gammadelta T cells uniquely residing in the murine epidermis, are altered in the CD45 exon 6-deficient mice. In situ immunolabeling on epidermal sheets demonstrated that the CD45-deficient mice had a normal density and immunophenotype of Vgamma3 DETC compared with the wild-type control mice. Reverse transcriptase polymerase chain reaction revealed that similar levels of Vgamma3 TCR mRNA were present in the epidermis of CD45-deficient mice and wild-type controls. Flow cytometry demonstrated no significant difference in the proportion of Vgamma3 T cells in the epidermis between the genotypes. In addition, Vgamma2 T cells, another subset of gammadelta T cells, were also examined by flow cytometry. The frequency of Vgamma2 T cells in lymph nodes was normal in the CD45-deficient mice. Our results indicate that although CD45 is crucial for the development of alphabeta T cells, this molecule is not necessary for the thymic maturation of gammadelta T cells, including Vgamma3 DETC and Vgamma2 T cells.

Animals↗