Transmembrane and intracellular signaling events in lipopolysaccharide-stimulated macrophages.
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Animals↗
Biomedical subjects
T A Hamilton
Publications and source records attributed to T A Hamilton.
IFN-gamma and lipopolysaccharide differentially modulate expression of tumor necrosis factor receptor mRNA in murine peritoneal macrophages.
Expression of TNF receptor (TNFR) mRNA has been examined in murine peritoneal macrophages stimulated with LPS and/or IFN-gamma. LPS markedly enhanced expression of a heterogenous population of mRNA, which hybridized with a cDNA encoding the type II TNFR. mRNA expression was optimally induced by 4 to 8 h and returned to baseline by 24 h after stimulation. Interestingly, though IFN-gamma can synergize with LPS for the expression of TNF-alpha, it abrogated the LPS-mediated enhancement of type II TNFR in a dose-dependent fashion. IFN-alpha, though less effective, had a qualitatively comparable effect. These effects were selective for the type II TNFR because levels of mRNA encoding the type I TNFR did not vary appreciably with any of the treatments described. The effects of IFN-gamma on LPS-mediated TNFR expression were dependent on the sequence of exposure; pretreatment with IFN-gamma was most effective at blocking response to LPS, whereas IFN-gamma added 1 h after initiation of LPS treatment had little or no effect. The effects of both LPS and IFN-gamma on type II TNFR expression were mediated at least in part by modulation of transcription. The effects of both LPS and IFN-gamma were also independent of protein synthesis because inclusion of cycloheximide in the treatment protocol did not abrogate either the inductive or the suppressive effects. These findings suggest that IFN-gamma and LPS modulate the physiologic action of TNF through complex mechanisms involving effects on the transcription of TNF-alpha itself and on receptors through which it may act in autocrine or paracrine fashion.
Animals↗
Restoration of collagen formation in photodamaged human skin by tretinoin (retinoic acid)
BACKGROUND: Topical tretinoin (retinoic acid) modifies fine wrinkles and certain other features of human skin damaged by exposure to the sun (photodamage), but histologic changes do not account for this improvement. In mice with photodamage induced by ultraviolet light, effacement of fine wrinkles by tretinoin is correlated with dermal collagen synthesis but not with histologic changes. We investigated whether collagen synthesis was reduced in photodamaged human skin and, if so, whether it could be restored by treatment with topical tretinoin. METHODS: Biopsies of photodamaged skin from the extensor aspect of the forearm and skin from the buttocks, which had been protected from the sun, were performed on 26 healthy subjects. In addition, 29 patients with photodamaged skin were treated for 10 to 12 months with a daily application of 0.1 percent tretinoin cream (15 patients) or vehicle cream (14 patients). Skin-biopsy specimens obtained at base line and after treatment were assessed immunohistologically for evidence of dermal collagen I formation (collagen synthesis). RESULTS: Collagen I formation was 56 percent less in the papillary dermis of photodamaged skin than in skin protected from the sun (P < 0.001) and was correlated with the clinical severity of photodamage (r = -0.58, P = 0.002). Treatment of photodamaged skin with tretinoin produced an 80 percent increase in collagen I formation, as compared with a 14 percent decrease in collagen formation with the use of vehicle alone (P = 0.006). CONCLUSIONS: The formation of collagen I is significantly decreased in photodamaged human skin, and this process is partly restored by treatment with tretinoin.
Adult↗
Synergistic cooperation between T cell lymphokines for induction of the nitric oxide synthase gene in murine peritoneal macrophages.
The ability of T cell-derived cytokines to induce the expression of the nitric oxide synthase (NOS) gene in murine peritoneal macrophages was examined. IL-2 or TNF-alpha alone had no effect either on gene expression or enzyme activity, whereas IFN-gamma had only modest activity. When IL-2 or TNF-alpha were used in combination with IFN-gamma, there was a marked cooperative induction of both mRNA and enzyme activity. The cooperative effects were truly synergistic, as the consequences of combined cytokine treatment were many times greater than was seen with any of the agents acting independently. The expression of NOS mRNA and enzyme activity in response to combined lymphokine treatments was a continuous process reaching optimal levels between 24 and 48 h after stimulation. Concentration dependency for both IL-2 and TNF-alpha suggested that their effects were mediated through interaction with the corresponding defined cell surface receptors. Human rTNF-alpha was as effective a stimulus as murine TNF-alpha; because human TNF-alpha is recognized only by the p55 Type II TNF receptor, this structure appears to mediate the response to TNF-alpha. When IL-2 and TNF-alpha were added at saturating doses in the presence of IFN-gamma, there was an additive effect on NOS mRNA expression suggesting that IL-2 and TNF-alpha cooperate with IFN-gamma through at least partially distinct intracellular signaling pathways. Expression of NOS mRNA in response to IFN-gamma/IL-2 or IFN-gamma/TNF-alpha treatment required protein synthesis, suggesting that cooperative cytokine induction of NOS involves the intermediate expression of new gene products. Such molecular controls for regulation of inducible macrophage gene expression can be contrasted with regulatory control of other inflammatory genes such as IP-10 and TNF-alpha.
Amino Acid Oxidoreductases↗
Topical tretinoin (retinoic acid) therapy for hyperpigmented lesions caused by inflammation of the skin in black patients.
BACKGROUND AND METHODS: Irregular disfiguring skin hyperpigmentation due to inflammation may develop in black persons. We investigated the treatment of this hyperpigmentation with topical tretinoin (0.1 percent retinoic acid cream). Fifty-four subjects completed a 40-week randomized, double-blind, vehicle-controlled study. Twenty-four subjects applied tretinoin daily to the face, arms, or both areas, and 30 subjects applied vehicle cream. At base line and after 40 weeks of treatment, each subject's post-inflammatory hyperpigmented lesions and normal skin were assessed by clinical and colorimetric evaluations and by analysis of biopsy specimens. RESULTS: The facial post-inflammatory hyperpigmented lesions of the tretinoin-treated subjects were significantly lighter after the 40 weeks of therapy than those of the vehicle-treated subjects (P < 0.001); overall improvement was first noted after four weeks of tretinoin treatment. At the end of treatment, colorimetry demonstrated a 40 percent lightening of the lesions toward normal skin color in the tretinoin-treated lesions, as compared with an 18 percent lightening in vehicle-treated lesions (P = 0.05). The epidermal melanin content in the lesions decreased by 23 percent with tretinoin and by 3 percent with vehicle (P = 0.24). Normal skin was minimally lightened by tretinoin as compared with vehicle, according to both clinical evaluation (0.1 vs. -0.1 unit change on an 8-point scale; P = 0.055) and colorimetry (P < 0.001). Retinoid dermatitis developed in 12 of the 24 tretinoin-treated subjects who completed the study (50 percent) and in 1 tretinoin-treated subject who withdrew from the study, but diminished as the study progressed. CONCLUSIONS: Topical application of tretinoin significantly lightens post-inflammatory hyperpigmentation and, to a clinically minimal but statistically significant degree, lightens normal skin in black persons.
Administration, Cutaneous↗
Astrocyte expression of mRNA encoding cytokines IP-10 and JE/MCP-1 in experimental autoimmune encephalomyelitis.
Mononuclear leukocytes preferentially accumulate in the central nervous system (CNS) during the course of experimental autoimmune encephalomyelitis (EAE). To address factors that govern leukocyte trafficking in EAE, we monitored expression of mRNAs encoding IP-10 and JE/MCP-1, which are members of a family of chemoattractant cytokines. A transient burst of IP-10 and JE/MCP-1 mRNA accumulation in the CNS occurred, in close relation to the onset of histologic and clinical disease. In situ hybridizations showed, unexpectedly, that astrocytes were the major source of mRNAs encoding IP-10 and JE/MCP-1. These observations implicate astrocyte-derived cytokines as potential chemoattractants for inflammatory cells during EAE.
Animals↗
Cooperative interaction between interferon (IFN) stimulus response element and kappa B sequence motifs controls IFN gamma- and lipopolysaccharide-stimulated transcription from the murine IP-10 promoter.
The transcriptional regulation of the murine IP-10 gene in lipopolysaccharide (LPS) or interferon gamma (IFN gamma)-treated macrophages was investigated by analysis of regions of the gene that flank the transcription start site. A series of sequence fragments were placed 5' to the chloramphenicol acetyltransferase (CAT) reporter gene and ability to mediate transcription of CAT in response to IFN gamma or LPS treatment was studied following transient transfection in the macrophage-like cell line RAW 264.7. Analysis of larger constructs identified a potential negative regulatory site for IFN gamma response in the region between nucleotide positions -2002 and -930 and a positive regulator for LPS response in the region between bases -930 and -676. A 227-base fragment spanning positions -228 to -2 was the minimal sequence able to mediate LPS- and IFN gamma-dependent transcription of CAT. Deletion of 24 bases, which included a highly conserved IFN stimulus response element (ISRE) from the -228 construct, abolished response to IFN gamma. A 33-base fragment containing the IP-10 ISRE was able to confer both IFN gamma and LPS sensitivity upon a heterologous promoter. The ability of LPS to stimulate CAT via the ISRE was apparently mediated by intermediate expression of endogenous IFN alpha/beta. Elimination of bases -204 to -102 abolished sensitivity to LPS. This region contains two kappa B binding sites. Site-directed mutagenesis of key nucleotides in the ISRE and the two kappa B sites demonstrated that optimal response to IFN gamma required both the ISRE and one of the two kappa B sites, whereas optimal response to LPS required either both kappa B sites or one kappa B site and the ISRE. IFN gamma or LPS treatment induced sequence-specific binding activity for the ISRE and the two kappa B sites. These results indicate that the 230 nucleotides upstream from the transcription start site are important for transcriptional control of the IP-10 gene in response to IFN gamma and LPS. The three defined regulatory elements function in distinct fashion for each of the two stimuli; optimal response to either IFN gamma or LPS requires cooperation between at least two sites.
Amino Acid Sequence↗
T-cells infiltrating renal cell carcinoma display a poor proliferative response even though they can produce interleukin 2 and express interleukin 2 receptors.
The fact that progressing tumors contain a significant infiltrate of T-cells brings into question the competency of the infiltrating T-lymphocytes (T-TIL). We have examined the role of the T-cell receptor/CD3 complex and/or the interleukin 2 receptor (IL2R) in responsiveness of T-cells that infiltrate human renal cell carcinoma. T-TIL display a poor proliferative response to interleukin 2 (IL2) alone, IL2 in combination with antibody to CD3, or mitogen stimulation. The proliferative unresponsiveness was not related to low expression of CD3 or IL2R beta as the percentage of T-cells expressing CD3 and IL2R beta were comparable in both T-TIL and peripheral blood T-cells obtained from the same patient. In contrast to the lack of proliferative activity, stimulation of T-TIL or peripheral blood lymphocytes with phytohemagglutinin or anti-CD3 resulted in comparable levels of both IL2 and gamma-interferon mRNA and protein expression. While levels of IL2R alpha were low in unstimulated T-TIL and peripheral blood lymphocytes, anti-CD3 antibody or IL2 were capable of inducing surface expression of this protein in both cell populations. IL2R alpha mRNA levels were comparable in T-cells from the tumor and peripheral blood although in some experiments both the percentage of IL2R alpha-positive cells and the density of surface expression per cell were reduced in T-TIL. This reduced IL2R alpha expression on T-TIL was not responsible for the proliferative unresponsiveness since T-TIL that expressed both IL2R alpha and/or IL2R beta still failed to respond to high doses of IL2. Thus T-TIL display a selective loss of response to at least two well defined extracellular stimuli. While T-TIL exhibit a poor proliferative response regardless of the form of stimulation these cells remain sensitive to both anti-CD3 and IL2 in terms of IL2 and gamma-interferon or IL2R alpha expression, respectively. The fact that proliferative unresponsiveness exists even though T-TIL can produce IL2 and express IL2R alpha/beta suggests that T-TIL have a selective loss of a common intracellular signaling pathway which is requisite to proliferation but not other aspects of response to antigenic stimulation.
Adult↗
A lipopolysaccharide-inducible macrophage gene (D3) is a new member of an interferon-inducible gene cluster and is selectively expressed in mononuclear phagocytes.
We previously reported the isolation and characterization of cDNA clones encoding novel lipopolysaccharide (LPS)-inducible mRNAs from murine peritoneal macrophages. We now present the complete coding sequence of a cDNA previously termed D3. Analysis of multiple clones from a murine macrophage cDNA library provided a complete cDNA sequence of approximately 1.6 kb. The corresponding RNA contains a single open reading frame encoding a hydrophilic protein composed of 425 amino acids and is characterized by a region including three perfect and two imperfect repeats of a seven-amino-acid sequence. Based on nucleotide and deduced amino acid sequence, this mRNA is a new member of a previously described multigene cluster of interferon-inducible genes termed the Mouse 200 series genes. This new sequence most closely resembles gene 204 because both D3 and 204 genes have segments containing the seven-amino-acid repeat sequence. The Mouse 202 and 204 genes, however, have an approximately 200-amino-acid carboxyl-terminal domain that is absent in the LPS-inducible macrophage-derived cDNA. In addition, D3, 202, and 204 can all be distinguished from one another by virtue of unique 3' noncoding regions 200-300 base pairs in length. The D3 unique sequence is largely restricted to the smallest of the three size classes of this gene family expressed in macrophages and is not detected in interferon- or platelet-derived growth factor-stimulated fibroblasts. Overall, three separate mRNAs have now been described, each of which has three or more of a possible seven nucleotide sequence domains. Although the function(s) of the members of this gene family remains unknown, the multiple forms inducible by diverse stimuli and their restricted cell type expression suggest diverse and important physiologic roles for their products in inflammation.
Amino Acid Sequence↗
An in vivo experimental model for effects of topical retinoic acid in human skin.
An occlusive patch-test assay has been developed for assessment of topical retinoid action in human epidermis. Previous work with this assay has demonstrated marked epidermal hyperplasia in skin treated with topical all-trans-retinoic acid for 4 days and similar effects with the local irritant, sodium lauryl sulphate. To investigate the capabilities of this assay further, a time-course and dose-response were performed with all-trans-retinoic acid, and a comparison made with sodium lauryl sulphate. At no time, between 1 and 4 days, could the clinical or histological effects of 0.1% and 0.025% cream formulations of all-trans-retinoic acid be distinguished from each other. Epidermal hyperplasia was used to generate a 4-day dose-response for all-trans-retinoic acid at concentrations from 0.001 to 0.025% dissolved in a 70% ethanol/30% propylene glycol vehicle. All-trans-retinoic acid could be successfully differentiated from sodium lauryl sulphate at 2 days by virtue of its greater ability to increase epidermal thickness, spongiosis and glycosaminoglycan deposition. It appears that although all-trans-retinoic acid and sodium lauryl sulphate produce similar epidermal histological changes at 4 days, significant differences at earlier time-points suggest differing mechanisms of action. In addition, this in vivo human assay is able to provide potency ranking for doses of all-trans-retinoic acid, and may predict clinical efficacy of retinoids in improvement of acne and/or photodamage.
Administration, Topical↗
Topical tretinoin (retinoic acid) improves melasma. A vehicle-controlled, clinical trial.
Melasma is a common disorder of cutaneous hyperpigmentation predominantly affecting the faces of women. Little is known about the aetiology of melasma, and treatment is frequently disappointing. Topical tretinoin is of benefit in treating other forms of hyperpigmentation, for example liver spots, and we therefore investigated its effectiveness in melasma. Thirty-eight women completed a randomized, vehicle-controlled study, in which they applied 0.1% tretinoin (n = 19) or vehicle cream (n = 19) once daily to the face for 40 weeks. At the end of treatment 13 (68%) of 19 tretinoin-treated patients were clinically rated as improved or much improved, compared with 1 (5%) of 19 in the vehicle group (P = 0.0006). Significant improvement first occurred after 24 weeks of tretinoin treatment. Colorimetry (an objective measure of skin colour) demonstrated a 0.9 unit lightening of tretinoin-treated melasma and a 0.3 unit darkening with vehicle (P = 0.01); these results correlated with clinical lightening (r = 0.55, P = 0.0005). Histologically, epidermal pigment was reduced 36% following tretinoin treatment, compared with a 50% increase with vehicle (P = 0.002). Reduction in epidermal pigment also correlated with clinical lightening (r = -0.41, P = 0.01). Moderate cutaneous side-effects of erythema and desquamation occurred in 88% of tretinoin-treated and 29% of vehicle-treated patients. Topical 0.1% tretinoin produces significant clinical improvement of melasma, mainly due to reduction in epidermal pigment, but improvement is slow.
Administration, Topical↗
Dissociation of lipopolysaccharide (LPS)-inducible gene expression in murine macrophages pretreated with smooth LPS versus monophosphoryl lipid A.
Lipopolysaccharide (LPS) and the nontoxic derivative of lipid A, monophosphoryl lipid A (MPL), were employed to assess the relationship between expression of LPS-inducible inflammatory genes and the induction of tolerance to LPS in murine macrophages. Both LPS and MPL induced expression (as assessed by increased steady-state mRNA levels) of a panel of seven "early" inflammatory genes including the tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta, type 2 TNF receptor (TNFR-2), IP-10, D3, D8, and D2 genes (the last four represent LPS-inducible early genes whose functions remain unknown). In addition, LPS and MPL were both capable of inducing tolerance to LPS. The two stimuli differed in the relative concentration required to induce various outcome measures, with LPS being 100- to 1,000-fold more potent on a mass concentration basis. Characterization of the tolerant state identified three distinct categories of responsiveness. Two genes (IP-10 and D8) exhibited strong desensitization in macrophages pretreated with tolerance-inducing concentrations of either LPS or MPL. In macrophages rendered tolerant by pretreatment with LPS or MPL, a second group of inducible mRNAs (TNF-alpha, interleukin-1 beta, and D3) showed moderate suppression of response to secondary stimulation by LPS. The third category of inducible genes (TNFR-2 and D2) showed increased expression in macrophages pretreated with tolerance-inducing concentrations of either LPS or MPL. All of the LPS-inducible genes examined exhibited modest superinduction with less than tolerance-inducing concentrations of either stimulus, suggesting a priming effect of these adjuvants at low concentration. The differential behavior of the members of this panel of endotoxin-responsive genes thus offers insight into molecular events associated with acquisition of transient tolerance to LPS.
Animals↗
Modulation of lipopolysaccharide-induced macrophage gene expression by Rhodobacter sphaeroides lipid A and SDZ 880.431.
Rhodobacter sphaeroides lipid A (RsDPLA) and SDZ 880.431 (3-aza-lipid X-4-phosphate) are prototypic lipopolysaccharide (LPS) antagonists. Herein, we examined the ability of these structures to regulate murine macrophage tumor necrosis factor (TNF) secretion and LPS-inducible gene expression (tumor necrosis factor alpha [TNF-alpha], interleukin-1 beta [IL-1 beta], IP-10, type 2 TNF receptor [TNFR-2], D3, and D8 genes). We report that RsDPLA alone (> 1 microgram/ml) induced low levels of TNF-alpha secretion and a selective pattern of gene expression in peritoneal exudate macrophages; SDZ 880.431 alone was completely inactive. When LPS was present at a low concentration (1 ng/ml), RsDPLA and SDZ 880.431 blocked TNF secretion and gene induction in a concentration-dependent fashion. In general, gene induction was measurably reduced by 10 to 30 ng of RsDPLA per ml or 300 ng of SDZ 880.431 per ml, but inhibition could be uniformly overridden by increasing the concentration of LPS. Although induction of all six genes by LPS was suppressed by either inhibitor, effective inhibitor concentrations depended on the gene of interest. Induction of TNFR-2 by LPS was relatively resistant to inhibition by RsDPLA, and induction of TNFR-2 and D3 was relatively resistant to inhibition by SDZ 880.431. When LPS was present at > or = 100 ng/ml, correspondingly high concentrations (> or = 20 micrograms/ml) of either inhibitor influenced gene expression in a bidirectional manner. Under these conditions, LPS-induced expression of IP-10, D3, and D8 was suppressed regardless of the LPS concentration used (concentrations tested up to 50 micrograms/ml), while expression of TNF-alpha mRNA was enhanced about fourfold. In toto, RsDPLA and SDZ 880.431, when present at low concentrations, act in a manner consistent with competitive inhibition of LPS, while at higher concentrations, these structures inhibit certain LPS responses noncompetitively and synergize with LPS for other responses.
Animals↗
Retinoic acid metabolites exhibit biological activity in human keratinocytes, mouse melanoma cells and hairless mouse skin in vivo.
Topical all-trans retinoic acid (RA) modulates growth and differentiation of skin and is used in the treatment of various dermatological disorders. RA is metabolized to 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA, which are believed to be markedly less active than RA. 3,4-didehydroretinoic acid (ddRA) is a metabolite of 3,4-didehydroretinol which is present in skin. ddRA is biologically active and acts as a morphogen. We have determined the relative biological activity of ddRA, 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA as assessed by three retinoid responsive systems relevant to skin. RA, ddRA, 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA (10-100 nM) reduced epidermal transglutaminase activity in human keratinocytes to similar extents, and inhibited alpha-melanocyte-stimulating hormone-isobutylmethylxanthine-inducible tyrosinase activity in Cloudman S-91 mouse melanoma cells by 67, 39, 48, 51 and 19%, respectively, at 100 nM. Daily topical application of the retinoids to hairless mouse skin for 4 days resulted in dose-dependent changes in epidermal thickness and global histological score. The relative potencies of RA, ddRA, 4-hydroxy RA, 4-oxo RA and 5,6-epoxy RA, as calculated by parallel line assay, were 1.0, 0.60, 0.34, 0.29 and 0.18, respectively, for epidermal hyperplasia and 1.0, 0.78, 0.23, 0.14 and 0.08, respectively, for global histological score. Interestingly, the compounds exhibited a similar rank order of potency with respect to induction of cellular retinoic acid binding protein-II mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Expression of IP-10, a lipopolysaccharide- and interferon-gamma-inducible protein, in murine mesangial cells in culture.
IP-10 is an early gene induced in multiple cell types by a variety of proinflammatory agents, notably interferons (IFNs) and lipopolysaccharide (LPS). To determine whether this protein might play a role in amplifying immune-mediated glomerular injury, we cultured mouse mesangial cells with several stimuli for various times. Increasing amounts of IFN-gamma (to 100 units/ml) elicited increasing levels of IP-10 messenger RNA (mRNA), sustained to 24 hours, but had no effect on tumor necrosis factor-alpha (TNF-alpha) mRNA. LPS induced transient IP-10 mRNA expression that peaked at 8 hours; TNF-alpha mRNA was also increased. TNF-alpha at doses up to 10 ng/ml and soluble immune complexes up to 150 micrograms/ml antibody evoked 3- to 5-fold increases in IP-10 mRNA expression, much less than the 30- to 70-fold increases seen with IFN-gamma and LPS. We conclude that IFN-gamma, LPS, and other agonists can amplify glomerular immune injury, perhaps via elevated expression of IP-10.
Animals↗
Tumor necrosis factor-alpha induces cell type and tissue-specific expression of chemoattractant cytokines in vivo.
Recombinant murine tumor necrosis factor-alpha (TNF-alpha) was shown to be a strong, systemic stimulus in vivo for members of the chemoattractant cytokine gene families (JE, KC, IP-10). The three genes showed differential sensitivity to TNF-alpha, and their expression demonstrated differential tissue specificity. IP-10 was the most strongly induced messenger RNA and was seen in the liver, kidney, and spleen but very poorly in the lung or skin. JE exhibited a similar pattern, though the magnitude of expression was markedly lower. KC expression was seen only in the liver of TNF-alpha-treated mice. The time course of expression for IP-10 was rapid and transient and showed strong dose dependence. In mice treated with TNF-alpha intravenously, messenger RNA was localized in the splenic stroma but not in adherent macrophages or nonadherent lymphocytes. In situ hybridization found the majority of intercrime expression in the splenic red pulp with little or no expression seen in the white pulp. In vitro, TNF-alpha was a potent stimulus of chemoattractant messenger RNA expression in fibroblasts but not in inflammatory peritoneal macrophages. These results indicate that TNF-alpha may be an important stimulus for chemoattractant cytokine gene expression in vivo, and the primary cell types responsible may be either stromal fibroblasts, microvascular endothelium, and/or a subset of anchored mononuclear phagocytes.
3T3 Cells↗
Comparative morphology of sulfur mustard effects in the hairless guinea pig and a human skin equivalent.
A commercially available human skin equivalent (HSE) was used as an in vitro organotypic skin model to study temporal morphological effects of sulfur mustard gas (HD). Light and electron microscopic analyses of the HD-human skin equivalent model (HD-HSE) were compared to the HD-hairless guinea pig model (HD-HGP). HSE samples were exposed to 10 microliters HD vapor for 8 min and harvested at selected times up to 24 h. Skin sites of HGP were exposed to the same vapor dose or to 2.0 microliters liquid HD for 30 min and collected at 12 and 24 h. In both models, basal cells of the stratum germinativum were selectively affected. The HD-HSE study revealed that basal cell changes began 3 to 6 h following exposure. These early cellular changes included an acantholysis of some basal cells with widening of intercellular spaces, disruption of desmosomal attachments, nuclear pyknosis, perinuclear blebbing and repositioning of cytoplasmic tonofilaments to a perinuclear position. At 12 to 24 h, basal cell pathology progressed to diffuse swelling of endoplasmic reticula, cytoplasmic vacuolations and necrosis which now extended to supra basal cell layers. Comparing basement membrane zone effects, HD-HGP consistently developed characteristic microblisters at the dermal-epidermal junction; however, HD-HSE with its absence of a morphologically distinguishable basement membrane did not. Instead, cellular fragments, granules and debris accumulated early in this area to thicken regions usually assigned to the lamina lucida and lamina densa of a true basement membrane leading to complete separation of dermis from epidermis at later time periods.
Animals↗
Lipopolysaccharide induces DNA binding activity specific for the IFN-stimulated response element in murine peritoneal macrophages.
Several murine macrophage genes that exhibit transcriptional response to LPS (e.g., IP-10, D3) have IFN-stimulated response element (ISRE) sequences present in regions flanking the transcription start sites. In the present study, the ability of LPS to activate proteins in murine peritoneal macrophages capable of binding to the ISRE has been investigated. Nuclear extracts from both LPS-treated and untreated macrophages are capable of forming four distinct complexes with a radiolabeled oligonucleotide containing the ISRE sequence as detected by electrophoretic mobility shift assays. LPS-treated nuclei contained an additional ISRE binding activity (complex I) that was not found in unstimulated cells. The induction of the latter activity by LPS was sensitive to polymyxin B sulfate, a lipid A antagonist, demonstrating that LPS was the primary inducing activity. All five retarded protein-DNA complexes formed were specific for the ISRE sequence as shown by competition with a series of oligonucleotides containing either ISRE-related or -unrelated sequences. Complex I binding activity was dependent upon the concentration of LPS and the time of LPS treatment. Furthermore, complex I was similar to that induced in response to treatment with IFN-beta in terms of electrophoretic mobility and specificity for the ISRE. LPS-induced complex I formation was partially independent of protein synthesis and could not be blocked by including neutralizing antibody to IFN-alpha/beta in the culture medium. Thus, even though LPS is a potent inducer of IFN-beta in murine macrophages, class I IFN expression may not be an obligatory intermediate event in the LPS-driven activation of ISRE binding activity. These results suggest that induction of ISRE binding activity may be an important part of the signaling process initiated by LPS.
Animals↗