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Biomedical subjects

Marcia Simon

Publications and source records attributed to Marcia Simon.

9 recordsLinked to original sources
PubMed2006

Inhibition of histone deacetylation promotes abnormal epidermal differentiation and specifically suppresses the expression of the late differentiation marker profilaggrin.

Reversible protein acetylation modulates higher-order chromatin structure and transcription activity of the genome. The reversible acetylation is executed by the intrinsic acetylase and deacetylase activities of co-regulators associated with the regulatory regions. Compounds capable of inhibiting deacetylase activity are a powerful tool for dissecting the role of protein acetylation in gene function. The ability of the deacetylase inhibitors to preferentially affect the homeostasis of transformed cells has also prompted studies for their clinical application. We present evidence that deacetylase inhibition with trichostatin A (TSA) affects the normal epidermal tissue architecture and pattern of expression by a mechanism(s) that does not correlate directly with the hyperacetylated histone status. While promoting abnormal differentiation, TSA specifically represses transcription initiation of the differentiation marker profilaggrin. Multiple factors, among which we have identified decreased Sp1 binding, a local decrease in acetylation activity, and enhanced synthesis and recruitment of a repressor histone demethylase, alter the chromatin configuration over the promoter, ultimately blocking its activation by c-jun. As compromised profilaggrin production leads to epidermal and consequently allergic disorders, our findings emphasize the need for a detailed investigation of the role deacetylase inhibitors may play in the maintenance of epidermal homeostasis in order to optimize their clinical applicability.

Cell Differentiation↗
PubMed2006

Improved wound healing of cutaneous sulfur mustard injuries in a weanling pig model.

OBJECTIVE: The objective was to examine the efficacy of several treatment regimens in improving wound healing of cutaneous sulfur mustard (HD) injuries. METHODS: Wound healing studies were conducted in weanling pigs. Superficial dermal HD injuries were debrided at 48 hours postexposure using an erbium-doped yttrium aluminum garnet (Er:YAG) laser, followed by application of a treatment adjunct. A variety of noninvasive bioengineering methods were conducted during the postsurgical observation period to examine the various cosmetic and functional aspects of the skin. Histopathology was performed at the end of each study (14 or 21 days postsurgery). RESULTS: As noted clinically, reepithelialization was nearly complete by 7 days postsurgery for many of the sites treated with petrolatum and scarlet red dressings. By 21 days, the skin elasticity of the petrolatum-dressed sites was not significantly different from that of sham-exposed skin. Upon dressing removal on postsurgery day 4, the neoepidermis of allograft- and thin film-dressed sites was partially removed, with resultant petechial hemorrhaging. Mean pathology scores for hydrocolloid-dressed sites were significantly lower than those of untreated HD-exposed sites on postsurgery day 14. CONCLUSIONS: Care must be taken during bandage changes, and a nonadherent dressing that could be left in place for a longer period of time (eg, 7 days) would be beneficial. The use of cultured epithelial allograft material may have a potential role if grown on a completely nonadherent backing and left undisturbed for at least a week. Xeroform Petrolatum and Scarlet Red Ointment dressings are effective and inexpensive treatment adjuncts for HD injuries.

Journal Article↗
PubMed2006

Molecular screening for GS2 lipase regulators: inhibition of keratinocyte retinylester hydrolysis by TIP47.

Retinoic acid at nanomolar concentrations modulates epidermal functions by serving as a transcription factor ligand. Under conditions of retinol sufficiency, it is imperative to limit retinoic acid biosynthesis from serum-derived retinol. In the epidermis, this is accomplished by esterifying retinol with long-chain fatty acids. Retinylester (RE) pools serve as a source of retinol for retinoic acid production under retinol deficiency and when required for proper differentiation. We have recently reported that GS2 lipase is expressed in keratinocytes and has the enzymatic properties of keratinocyte RE hydrolase. As GS2 lipase has a robust activity that can affect the intracellular retinol levels, we postulated that its activity must be regulated. Therefore, we screened keratinocyte cDNA expression libraries for the putative inhibitor. Herein, we report the identity of an inhibitor, TIP47, which prevents RE hydrolysis catalyzed by GS2 lipase and hormone-sensitive lipase. This protein was known to transport mannose-6-phosphate receptors from endosome to trans-Golgi and to be distributed between the cytoplasm and lipid droplets. Using a series of deletion mutants, we found two regions involved in the inhibitory activity. Residues within the carboxyl alpha3-alpha4 helices are essential in the context of the full-length protein. Residues within the amino-terminal also contribute depending on the context.

Carboxylic Ester Hydrolases↗
PubMed2006

A metabolic enzyme of the short-chain dehydrogenase/reductase superfamily may moonlight in the nucleus as a repressor of promoter activity.

Transcriptional repression often depends on the action of recruited co-repressor complexes with intrinsic enzymatic activities. The composition of these complexes depends on the nicotine amide dinucleotide co-factors and is thus directly reflective of the metabolic state of the cells. This study provides evidence that an enzyme, hRoDH-E2, with cytoplasmic phosphorylated and reduced forms of NAD-dependent retinol dehydrogenase activity may function in the nucleus as a transcriptional repressor. By using the promoter of the epidermal late differentiation marker profilaggrin as a model, we show that both in vivo and in vitro the protein is recruited over the promoter. hRoDH-E2 represses profilaggrin promoter activity by altering the function of other activators, such as Sp1. The repressive function is associated with the ability of nuclear hRoDH-E2 to modulate the acetylation/deacetylation activity in the vicinity of transcription initiation site. These findings add hRoDH-E2 to the small group of metabolic enzymes, which, by being recruited over promoter regions, could directly link the cytoplasmic and nuclear functions within the cell.

Acetylation↗
PubMed2003

Label-retaining cells (presumptive stem cells) of mice vibrissae do not express gap junction protein connexin 43.

We investigated whether connexin 43, a gap junction protein present in human epidermis and mouse hair follicle, can serve as a negative marker for keratinocyte stem cells. Experiments carried out in mouse pelage and vibrissae hair follicles demonstrated that most of the slowly cycling cells, detected as label-retaining cells, do not express connexin 43. In humans, cells with immunohistochemically undetectable levels of connexin 43 are found in the epidermal basal layer of neonatal foreskin, and in the follicular bulge region. About 10% of the basal keratinocytes are connexin 43 negative, as determined by flow cytometry. These cells are uniformly small and low in granularity suggesting that presumptive keratinocyte stem cells can be identified and separated based on connexin 43 expression.

Animals↗
PubMed2002

Phenotypic differences between dermal fibroblasts from different body sites determine their responses to tension and TGFbeta1.

BACKGROUND: Wounds in the nonglabrous skin of keloid-prone individuals tend to cause large disordered accumulations of collagen which extend beyond the original margins of the wound. In addition to abnormalities in keloid fibroblasts, comparison of dermal fibroblasts derived from nonwounded glabrous or nonglabrous skin revealed differences that may account for the observed location of keloids. METHODS: Fibroblast apoptosis and the cellular content of alpha-smooth-muscle actin, TGFbeta1 receptorII and ED-A fibronectin were estimated by FACS analysis. The effects of TGFbeta1 and serum were examined. RESULTS: In monolayer cultures non-glabrous fibroblasts were slower growing, had higher granularity and accumulated more alpha-smooth-muscle actin than fibroblasts from glabrous tissues. Keloid fibroblasts had the highest level of alpha-smooth-muscle actin in parallel with their expression level of ED-A fibronectin. TGFbeta1 positively regulated alpha-smooth-muscle actin expression in all fibroblast cultures, although its effects on apoptosis in fibroblasts from glabrous and non-glabrous tissues were found to differ. The presence of collagen I in the ECM resulted in reduction of alpha-smooth-muscle actin. A considerable percentage of the apoptotic fibroblasts in attached gels were alpha-smooth-muscle actin positive. The extent of apoptosis correlated positively with increased cell and matrix relaxation. TGFbeta1 was unable to overcome this apoptotic effect of matrix relaxation. CONCLUSION: The presence of myofibroblasts and the apoptosis level can be regulated by both TGFbeta1 and by the extracellular matrix. However, reduction of tension in the matrix is the critical determinant. This predicts that the tension in the wound bed determines the type of scar at different body sites.

Actins↗
PubMed2002

Epidermal stem cells do not communicate through gap junctions.

Although enrichment of putative epidermal stem cells has been achieved, a need for additional markers that can enable isolation of live keratinocytes is crucial for characterization of these cells. Earlier work has shown that connexin proteins are absent from basal cells in the limbal epithelium, a region of the corneal epithelium enriched in corneal stem cells. Accordingly, we investigated whether connexin 43, a gap junction protein present in the basal layer of normal human epidermis, can serve as a negative marker for keratinocyte stem cells. In humans, cells with immunohistochemically undetectable levels of connexin 43 are found in the epidermal basal layer of neonatal foreskin and in the follicular bulge region. About 10% of the basal keratinocytes are connexin 43 negative, as determined by flow cytometry. These cells are uniformly small and low in granularity. Restricted gap junction communication was confirmed by the failure of low molecular weight dyes to transfer between cells. Experiments carried out in mouse epidermis demonstrated that most of the slowly cycling cells, detected as label-retaining cells, do not express connexin 43. Thus, presumptive keratinocyte stem cells can be identified and separated based on connexin 43 expression.

Adult↗
PubMedDate not supplied

Semapimod reduces the depth of injury resulting in enhanced re-epithelialization of partial-thickness burns in swine.

Studies suggest that tumor necrosis factor alpha (TNF-alpha) plays a role in burn pathogenesis. We conducted a randomized controlled experiment in swine to determine whether a novel macrophage inhibitor, semapimod (formerly known as CNI-1493), would blunt the local production of TNF-alpha, interleukin (IL)-1, and IL-6 in burns leading to less injury extension and faster re-epithelialization. After creating second-degree burns, animals received one or two intravenous boluses of semapimod 1 mg/kg or normal saline, and all burns were treated with silver sulfadiazine. The depth of follicular necrosis and thrombosis was reduced by either one or two doses of semapimod (P=.04 and .02, respectively). However, no differences were noted between groups in cytokine levels. Depth of scarring was similar in all groups. We conclude that Semapimod reduces the depth of follicular necrosis and thrombosis after second-degree burns in swine, indirectly resulting in more rapid re-epithelialization. However, this affect does not appear to be mediated by reduced local TNF-alpha, IL-1, or IL-6 protein levels.

Animals↗