Search PubMed⌕ Search

Biomedical subjects

J J Nordlund

Publications and source records attributed to J J Nordlund.

At least 19 recordsLinked to original sources
PubMed1998

Activation of the cyclic AMP pathway by alpha-melanotropin mediates the response of human melanocytes to ultraviolet B radiation.

A hallmark of sun exposure is increased melanin synthesis by cutaneous melanocytes which protects against photodamage and photocarcinogenesis. Irradiation of human keratinocytes or melanocytes with ultraviolet (UV) rays stimulates the synthesis and release of alpha-melanotropin (alpha-MSH) and adrenocorticotropic hormone (ACTH), which induce cyclic AMP (cAMP) formation and increase the proliferation and melanogenesis of human melanocytes. We report that stimulation of cAMP formation is obligatory for the melanogenic response of cultured normal human melanocytes to UVB radiation. In the absence of cAMP inducers, UVB radiation inhibited, rather than stimulated, melanogenesis. UVB radiation (28 mJ/cm2) arrested melanocytes in the G1 phase of the cell cycle, and concomitant treatment with 0.1 microM alpha-MSH enhanced their proliferation but did not increase the surviving fraction. Irradiation with UVB, with or without alpha-MSH, caused prolonged expression of p53 and p21(waf-1, cip-1), maintained pRB in a hypophosphorylated state, and reduced the expression of Bcl2. However, alpha-MSH allowed UVB-irradiated melanocytes to enter S phase, suggesting that alpha-MSH acts as a mitogen rather than a survival factor, and that overexpression of p53 is mainly a signal for cell death. Our results underscore the importance of the cAMP pathway and its physiological inducers in mediating the response of human melanocytes to UV radiation.

Cyclic AMP↗
PubMed1997

Recent investigations on vitiligo vulgaris.

Vitiligo is a depigmenting disorder of the skin caused by destruction of melanocytes. The depigmented skin has several abnormal functions, including some autonomic nervous functions. The inflammatory response in the depigmented skin is muted. Recent genetic and epidemiologic studies indicate that vitiligo affects men and women equally. The prevalence in the population is about one in 200. Vitiligo seems to be transmitted as a polygenic trait. New data suggest that it is not associated with autoimmune endocrine disorders, but more comprehensive studies are required.

Female↗
PubMed1997

Agouti signaling protein inhibits melanogenesis and the response of human melanocytes to alpha-melanotropin.

In mouse follicular melanocytes, the switch between eumelanin and pheomelanin synthesis is regulated by the extension locus, which encodes the melanocortin-1 receptor (MC1R) and the agouti locus, which encodes a novel paracrine-signaling molecule that inhibits binding of melanocortins to the MC1R. Human melanocytes express the MC1R and respond to melanotropins with increased proliferation and eumelanogenesis, but a potential role for the human homolog of agouti-signaling protein, ASIP, in human pigmentation has not been investigated. Here we report that ASIP blocked the binding of alpha-melanocyte-stimulating hormone (alpha-MSH) to the MC1R and inhibited the effects of alpha-MSH on human melanocytes. Treatment of human melanocytes with 1 nM-10 nM recombinant mouse or human ASIP blocked the stimulatory effects of alpha-MSH on cAMP accumulation, tyrosinase activity, and cell proliferation. In the absence of exogenous alpha-MSH, ASIP inhibited basal levels of tyrosinase activity and cell proliferation and reduced the level of immunoreactive tyrosinase-related protein-1 (TRP-1) without significantly altering the level of immunoreactive tyrosinase. In addition, ASIP blocked the stimulatory effects of forskolin or dibutyryl cAMP, agents that act downstream from the MC1R, on tyrosinase activity and cell proliferation. These results demonstrate that the functional relationship between the agouti and MC1R gene products is similar in mice and humans and suggest a potential physiologic role for ASIP in regulation of human pigmentation.

Agouti Signaling Protein↗
PubMed1996

Unusual skin depigmentation following eyelid cryosurgery.

A 71-year-old African-American man was treated with cryosurgery of the left lower lid for trichiasis. Dramatic depigmentation of the lid skin followed, including substantial pigment loss on the untreated upper lid. Pigmentation returned to nearly normal over a 9-year period. Depigmentation of the skin following cryosurgery is a well-known complication. The clinical course of the depigmentation, however, is not well demonstrated in the literature. This case documents, with clinical photographs, the spontaneous return to nearly normal pigmentation 9 years following the cryosurgery. In addition, the extensive depigmentation seen in this patient cannot be explained by cryoinjury alone. We speculate that the depigmentation was due, in part, to segmental vitiligo initiated at the site treated with cryosurgery.

Aged↗
PubMed1996

Mutation in and lack of expression of tyrosinase-related protein-1 (TRP-1) in melanocytes from an individual with brown oculocutaneous albinism: a new subtype of albinism classified as "OCA3".

Most types of human oculocutaneous albinism (OCA) result from mutations in the gene for tyrosinase (OCA1) or the P protein (OCA2), although other types of OCA have been described but have not been mapped to specific loci. Melanocytes were cultured from an African-American with OCA, who exhibited the phenotype of Brown OCA, and his normal fraternal twin. Melanocytes cultured from the patient with OCA and the normal twin appeared brown versus black, respectively. Melanocytes from both the patient with OCA and the normal twin demonstrated equal amounts of NP-40-soluble melanin; however, melanocytes from the patient with OCA contained only 7% of the amount of insoluble melanin found from the normal twin. Tyrosinase- related protein-1 (TRP-1) was not detected in the OCA melanocytes by use of various anti-TRP-1 probes. Furthermore, transcripts for TRP-1 were absent in cultured OCA melanocytes. The affected twin was homozygous for a single-bp deletion in exon 6, removing an A in codon 368 and leading to a premature stop at codon 384. Tyrosine hydroxylase activity of the OCA melanocytes was comparable to controls when assayed in cell lysates but was only 30% of controls when assayed in intact cells. We conclude that this mutation of the human TRP-1 gene affects its interaction with tyrosinase, resulting in dysregulation of tyrosinase activity, promotes the synthesis of brown versus black melanin, and is responsible for a third genetic type of OCA in humans, which we classify as "OCA3."

Albinism, Oculocutaneous↗
PubMed1995

Isolation of a unique melanogenic inhibitor from human skin xenografts: initial in vitro and in vivo characterization.

Previously, split-thickness human skin grafted onto athymic mice has been shown to become markedly hyperpigmented, but the factor(s) responsible for this hyperpigmentation had not been isolated. The present study describes the isolation and characterization of a potent melanogenic inhibitor from grafted human skin. Extracts from grafted skin inhibited, in a concentration-dependent manner, tyrosinase activity of normal human melanocytes and of Cloudman S91 murine melanoma in culture. Sodium dodecylsulfate-polyacrylamide gel electrophoresis analysis of extracts from pre- and post-grafted skin demonstrated the presence of a protein doublet of approximately 14 kD exclusively in the post-grafted skin. This protein inhibited both tyrosinase activity and cellular proliferation in a concentration-dependent manner. The inhibition of tyrosinase activity in normal human melanocytes was 53% at 0.5 microgram/ml concentration, whereas this inhibition was almost complete in murine melanoma cultures at 1.0 microgram/ml. The protein did not inhibit either cellular proliferation or protein synthesis in normal human fibroblast cultures, and therefore may act specifically on melanocytes. Injections of the inhibitor corresponded with a delay and reduction in the quantity of pigment in human skin 2 weeks after grafting. Multiple injections of the inhibitor into the hyperpigmented xenografts (20 weeks after grafting) reversed the hyperpigmentation with no observable inflammatory or toxic responses. The results indicate that hyperpigmented human skin xenografts contain a potent inhibitor of melanogenesis and melanocyte proliferation.

Animals↗
PubMed1995

Thy-1+ dendritic cells express truncated form of POMC mRNA.

The present study was designed to examine the expression of proopiomelanocortin (POMC) and its related derivative peptide adrenocorticotropic hormone (ACTH) in murine derived Thy-1+ dendritic cells. Immunostaining using a polyclonal antibody specific to ACTH and parent POMC molecule indicated the presence of POMC and its derivative peptide, ACTH, in cultures of Thy-1+ dendritic cells. To explore whether the POMC peptide is present as a reservoir or synthesized de novo in Thy-1+ dendritic cells. Northern blot analysis using 30-mer oligonucleotide probe for alpha-MSH/ACTH precursor POMC was carried out in total RNA from these cells. Northern blot analysis revealed the presence of POMC like mRNA transcript. However, the observed size of transcript was smaller (approximately 0.9 kb) than that expressed by murine AtT20 cells (approximately 1.2 kb), an anterior pituitary tumor cell line used as a positive control. These observations suggest that the epidermal Thy-1+ lymphocytes, like thymic lymphocytes, might serve the epidermis as one source for the synthesis of POMC. The synthesis and presence of POMC in the epidermis may be related to some of the pigmentary anomalies observed in many mucocutaneous disorders.

Adrenocorticotropic Hormone↗
PubMed1995

Low ICAM-1 expression in the epidermis of depigmenting C57BL/6J-mivit/mivit mice: a possible cause of muted contact sensitization.

The depigmenting C57BL/6J-mivit/mivit) (mivit/mivit) mouse, a congenic mutant of the C57BL/6 strain, exhibits an isolated, single immune deficiency. It is unable to mount a normal immune/inflammatory response upon epicutaneous application of DNFB or TNCB, although it does respond normally to oxazalone. The present investigations have been carried out to further study this deficiency. In vivo, C57BL/6 mice could be sensitized by the epicutaneous application of the hapten TNCB, the subcutaneous injection of hapten(TNBS)-conjugated C57BL/6, and hapten conjugated mivit/mivit epidermal cells. In the mivit/mivit mice, however, only subcutaneous injection of haptenized C57BL/6 epidermal cells caused an immune response. The response of these mivit/mivit mice could be documented only by adoptive transfer of splenic lymphocytes into naive C57BL/6 animals which then reacted to challenge doses of TNCB. These observations suggest that mivit/mivit epidermal cells can process and present and mivit/mivit T lymphocytes can react to the antigen. We postulated the presence of a deficient in vivo interaction between epidermal cells and T lymphocytes in the mivit/mivit mice. ICAM-1 is an important adhesion signal regulating epidermal cell/T-lymphocyte interaction. Its expression in mivit/mivit mice was studied using YN1/1 antibody against MALA-2, the murine counterpart of human ICAM-1. In contrast to C57BL/6 animals, the mivit/mivit epidermis essentially did not stain with the antibody after hapten challenge. In vitro after stimulation with TPA or IFN-gamma, the mivit/mivit epidermal cells expressed significantly lesser amounts of ICAM-1 than the C57BL/6 epidermal cells. Lower expression of ICAM-1 by mivit/mivit epidermal cells has also been demonstrated both by direct staining and by flow cytometry. The binding of lymphocytes to mivit/mivit epidermal monolayers, which were stimulated to express ICAM-1 by IFN-gamma, was decreased compared to that of C57BL/6 epidermal cells. We conclude that the muted contact sensitization response detected in vivo in the mivit/mivit mice at least partly results from lower expression of ICAM-1 and thus defective epidermal cell/T-lymphocyte interaction.

Animals↗
PubMed1994

Terminal differentiation and senescence in the human melanocyte: repression of tyrosine-phosphorylation of the extracellular signal-regulated kinase 2 selectively defines the two phenotypes.

Melanocytes are pigmented cells distributed in humans in several organs like the epidermis, the leptomeninges, the eye, and the inner ear. Epidermal melanocytes, whether derived from adult or neonatal skin, proliferate well in a medium supplemented with phorbol esters and other mitogens before they undergo senescence. Potent cAMP inducers like cholera toxin are also growth promoters for neonatal melanocytes but only transient growth stimulators for cells derived from adults. We used this cellular system to delineate biochemical pathways involved in proliferation and in terminal differentiation. Here we show that after a period of 4-8 wk of sustained proliferation in the presence of cholera toxin, the adult melanocytes became round, flat, and enlarged. These changes were associated with terminal growth and preceded by a five- to sixfold increase in cAMP levels and an 8- to 10-fold increase in melanin content. The simultaneous addition of phorbol esters and cholera toxin did not prevent cells from reaching terminal differentiation. Identified targets for phorbol esters are protein kinase C (PKC) and the mitogen-activated kinases (MAPKs), also called extracellular signal-regulated kinases (ERKs). PKC was found to be similarly regulated in proliferating and in terminally differentiated melanocytes. Proliferating melanocytes in early or late passage showed identical activation of the kinase ERK2. This kinase was rapidly phosphorylated upon phorbol 12-myristate 13-acetate (PMA) addition and specifically accumulated in the nucleus of the cells, whereas in unstimulated cells it had a perinuclear distribution. In contrast, senescent and terminally differentiated cells were unable to phosphorylate tyrosine residues of the ERK2 gene product in spite of presenting normal amounts of ERK2 protein. In addition, ERK2 did not show the nuclear accumulation observed in proliferating melanocytes after PMA activation and remained localized in the perinuclear area. These results demonstrate that senescent and terminally differentiated melanocytes share a common block in a critical pathway thought to integrate multiple intracellular signals transmitted by various second messengers and specifically prevent the continuation of the signal transduction cascade initiated by PMA activation of PKC.

Adult↗
PubMed1994

Synthesis of interleukin-1 alpha and beta by normal human melanocytes.

Normal human melanocytes and melanoma cells have been reported to produce several cytokines. Previously we demonstrated that neonatal human melanocyte proliferation and tyrosinase activity are inhibited by interleukin-1 alpha, tumor necrosis factor-alpha, and interleukin-6. We have now also shown that interleukin-1 beta induces an inhibiting effect on neonatal melanocyte tyrosinase activity with little effect on melanocyte proliferation. We investigated the ability of neonatal and adult human melanocytes to synthesize interleukin-1 alpha and beta. By immunocytochemistry, using monoclonal antibodies against interleukin-1 alpha and beta, we observed that neonatal and adult melanocytes stain positively for both cytokines. Flow-cytometric analysis revealed that the percentage of melanocytes positive for interleukin-1 alpha was always greater than that for interleukin-1 beta. The ability of neonatal and adult melanocytes to synthesize interleukin-1 alpha and beta was further confirmed using the polymerase chain reaction. These results clearly indicate that human melanocytes synthesize interleukin-1 alpha and beta, and that these cytokines may function as autocrine and/or paracrine regulators of cells in the epidermis.

Adult↗
PubMed1994

Proliferation and propagation of human melanocytes in vitro are affected by donor age and anatomical site.

We report the effects of two factors, donor age and anatomical site, on the proliferation and melanization of human melanocytes (MC) derived from (1) neonatal foreskins, (2) adult foreskins, or (3) adult breast or arm skin. Two different growth media have been used for this purpose. Medium I supports the long-term proliferation of neonatal MC, and medium II supports the growth of both neonatal and adult MC. We found that neonatal foreskin MC proliferated equally well in both media for more than 12 passages. However, adult MC behaved differently in the two growth media. In very early passages (passages 1-5), all three types of MC proliferated well and reached comparable final cell densities in medium I, but adult foreskin MC proliferated at a higher rate than neonatal or adult non-foreskin MC in medium II. The non-foreskin adult MC had the least proliferative rate in medium II. Unlike neonatal MC, both adult foreskin and non-foreskin MC underwent a drastic reduction in their proliferative rate after only a few (9-10) passages in culture. While the three types of MC differed in their proliferative rates, they responded similarly to melanogenic stimulation by cholera toxin (CT) and isobutyl methylxanthine (IBMX). These results demonstrate that the proliferation of human MC in standard culture media is affected by the donor age and the anatomical site from which these cells are derived. We conclude that human MC are heterogeneous, and caution must be used in extrapolating the results of studies on MC derived from different anatomical sites or age groups.

Adult↗
PubMed1994

Human TRP-1 has tyrosine hydroxylase but no dopa oxidase activity.

Human TRP-1 has been immunopurified from normal human melanocytes cultured from black neonatal subjects and used to investigate the catalytic function of TRP-1 for the two substrates, L-tyrosine and L-DOPA. Immunopurified TRP-1 did not demonstrate DOPA staining on SDS/PAGE nor DOPA oxidase (DO) activity with either routine or modified assays. The purified TRP-1 also demonstrated no tyrosine hydroxylase (TH) activity using the routine Pomerantz assay. However, there was apparent TH activity exhibited by immunopurified TRP-1 under conditions with low tyrosine concentration (< or = 0.8 microCi/ml of 3H-tyrosine), prolonged incubation time (i.e., overnight) and in the absence of the cofactor L-DOPA. Using these latter specific conditions, TH activity was also detected in cell lysates from a tyrosinase-negative albino melanocyte line which exhibited no TH activity with the routine Pomerantz assay. In addition, TH activity under low substrate assay conditions was not exhibited in a melanocyte line derived from a TRP-1 deficient, Brown albino individual. However, the absence of TH in this Brown albino cell line could be compensated for by the addition of L-DOPA to the assay. These results suggested that TRP-1 has some tyrosine hydroxylase but no DOPA oxidase activity. We propose that one function of TRP-1 is to modulate tyrosinase activity by making DOPA available as a cofactor to perpetuate the initial steps in melanogenesis.

Cells, Cultured↗
PubMed1994

Genetic epidemiology of vitiligo: multilocus recessivity cross-validated.

Vitiligo is a dermatological disorder characterized by hypopigmentary patches that tend to become progressive over time. There are reports of extensive familial aggregation. A genetic model for this disorder was earlier proposed by us. This model postulates that recessive alleles at multiple unlinked autosomal loci interact epistatically in the pathogenesis of vitiligo. The present family study was primarily undertaken to cross-validate the proposed genetic model. Data on 194 families from the United States were collected. Each family was ascertained through an affected proband. Analyses of these data reveal that approximately 20% of probands have at least one first-degree relative afflicted with vitiligo. All types of first-degree relatives of probands show a significant risk of developing vitiligo. Results of segregation and robustness analyses reveal that the genetic model postulated by us previously is the most parsimonious model for the present family data set.

Adolescent↗
PubMed1994

On the analysis of the pathophysiology of Chediak-Higashi syndrome. Defects expressed by cultured melanocytes.

BACKGROUND: The Chediak-Higashi syndrome (CHS) is a disorder that affects the synthesis and/or maintenance of storage/secretory granules in various types of cells. Lysosomes of leukocytes and fibroblasts, dense bodies of platelets, azurophilic granules of neutrophils and melanosomes of melanocytes are generally larger in size and irregular in morphology, indicating that a common pathway in storage organellogenesis is affected in patients with CHS. EXPERIMENTAL DESIGN: A pure line of melanocytes has been established using a 2 cm2 shave biopsy from a child with CHS. This 4-week-old male patient had oculocutaneous albinism and expressed neutropenia, impaired platelet function, and no natural killer cell activity. The cultured CHS melanocytes were analyzed for cell biological and biochemical aberrancies. RESULTS: Cultured melanocytes demonstrated some large and/or complexed melanosomes that resembled those observed in melanocytes from ultrastructural sections of the biopsy. Cytoplasmic localization of tyrosinase, tyrosinase-related protein-1 and granulophysin (a 40 kilodalton membrane protein originally identified as a component in dense bodies of platelets) demonstrated a prominent perinuclear accumulation. The basal synthesis of melanin and the activity levels of tyrosine hydroxylase, dihydroxyphenylalanine (DOPA) oxidase, or DOPAchrome tautomerase were comparable to control Caucasian melanocytes in culture. However, melanin synthesis as well as the catalytic activities of tyrosinase were not dramatically upregulated in CHS melanocytes by the addition of isobutyl methylxanthine and cholera toxin in the growth medium when parameters were assayed in cell lysates. In contrast, when assays were performed using live cells, tyrosine hydroxylase demonstrated dramatic upregulation. Medium conditioned by CHS melanocytes demonstrated phenylthiourea-inhibitable tyrosinase activity. Melanocyte lysates and conditioned medium analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and DOPA staining showed an extra, approximately 100 kilodalton soluble protein band with DOPA positivity and tyrosinase immunoreactivity. In addition to tyrosinase, one of three lysosomal enzymes assayed (beta-glucuronidase) was aberrantly secreted into the medium. CONCLUSIONS: These results demonstrate that melanocytes cultured from CHS express a defect in the structure and/or function of the melanosome and abnormal trafficking of some cellular proteins.

Cell Line↗
PubMed1993

Chronic growth stimulation of human adult melanocytes by inflammatory mediators in vitro: implications for nevus formation and initial steps in melanocyte oncogenesis.

In the human epidermis, melanocytes are distributed at a distance from each other. In contrast, melanocytes in nevi, which are considered benign neoplasms of melanocytes, are grouped in nests. Although still not well defined, environmental factors are thought to play an important role in the development of nevi. We found that chronic growth stimulation by leukotriene C4, a compound found in increased amounts in inflamed skin, induced pleiotropic modifications in the normal melanocyte phenotype. These changes include loss of contact inhibition and formation of structures resembling tumor spheroids. In parallel with these changes, there was a constitutive expression of Fos protein. Switching these cultures to medium supplemented with phorbol ester sustained growth with reversion of the altered phenotype. In contrast, a cAMP stimulator, cholera toxin, induced features of terminal differentiation. Our findings suggest a role for inflammatory mediators in human epidermal melanocytes. This observation provides insight into melanocyte growth alterations which may have relevance in early stages of melanocyte oncogenesis.

Adult↗
PubMed1993

Pigmentation and inhibition of wound contraction by cultured skin substitutes with adult melanocytes after transplantation to athymic mice.

Wound closure with cultured skin substitutes results in epithelium that is consistently hypopigmented. Hypothetically, addition of human melanocytes to cultured skin grafts may result in normal pigmentation of healed skin. Skin substitutes were composed of human epidermal keratinocytes and melanocytes, dermal fibroblasts, and collagen-glycosaminoglycan substrates, and were incubated for 12 d in media for keratinocyte growth (KG, n = 4), for keratinocyte differentiation containing four fatty acids and vitamin E with basic fibroblast growth factor (KDF, n = 6) or epidermal growth factor (KDE, n = 6), or for melanocyte growth (MG, n = 6) with phorbol ester and 5% fetal bovine serum. Skin substitutes were grafted orthotopically to full-thickness skin wounds (2 x 2 cm) on athymic mice, and scored for percent original wound size (+/- SEM), visible pigmentation (number pigmented/n), and positive staining for human leukocyte antigens (HLA)-ABC after 6 weeks on the mice. The data show that cultured skin grafts containing human melanocytes that are incubated in KDE or MG media have statistically significant reduction in wound contraction, 1:1 correlation of expression of pigment and HLA-ABC, and increased frequency of pigmentation after healing compared to incubation in KG or KDF media. Transmission electron microscopy confirmed the presence of melanocytes, melanosomes, and pigment transfer to keratinocytes in pigmented skin. These results suggest that survival and differentiated function of cultured epithelium can support melanization of skin, and that skin analogues exposed to phorbol ester in vitro can support skin pigmentation after wound healing.

Adult↗