Inhibitors of sphingolipid synthesis modulate interferon (IFN)-gamma-induced intercellular adhesion molecule (ICAM)-1 and human leukocyte antigen (HLA)-DR expression on cultured normal human keratinocytes: possible involvement of ceramide in biologic action of IFN-gamma

Opaganib (ABC294640) Induces Immunogenic Tumor Cell Death and Enhances Checkpoint Antibody Therapy

Antibody-based cancer drugs that target the checkpoint proteins CTLA-4, PD-1 and PD-L1 provide marked improvement in some patients with deadly diseases such as lung cancer and melanoma. However, most patients are either unresponsive or relapse following an initial response, underscoring the need for further improvement in immunotherapy. Certain drugs induce immunogenic cell death (ICD) in tumor cells in which the dying cells promote immunologic responses in the host that may enhance the in vivo activity of checkpoint antibodies. Sphingolipid metabolism is a key pathway in cancer biology, in which ceramides and sphingosine 1-phosphate (S1P) regulate tumor cell death, proliferation and drug resistance, as well as host inflammation and immunity. In particular, sphingosine kinases are key sites for manipulation of the ceramide/S1P balance that regulates tumor cell proliferation and sensitivity to radiation and chemotherapy. We and others have demonstrated that inhibition of sphingosine kinase-2 by the small-molecule investigational drug opaganib (formerly ABC294640) kills tumor cells and increases their sensitivities to other drugs and radiation. Because sphingolipids have been shown to regulate ICD, opaganib may induce ICD and improve the efficacy of checkpoint antibodies for cancer therapy. This was demonstrated by showing that in vitro treatment with opaganib increases the surface expression of the ICD marker calreticulin on a variety of tumor cell types. In vivo confirmation was achieved using the gold standard immunization assay in which B16 melanoma, Lewis lung carcinoma (LLC) or Neuro-2a neuroblastoma cells were treated with opaganib in vitro and then injected subcutaneously into syngeneic mice, followed by implantation of untreated tumor cells 7 days later. In all cases, immunization with opaganib-treated cells strongly suppressed the growth of subsequently injected tumor cells. Interestingly, opaganib treatment induced crossover immunity in that opaganib-treated B16 cells suppressed the growth of both untreated B16 and LLC cells and opaganib-treated LLC cells inhibited the growth of both untreated LLC and B16 cells. Next, the effects of opaganib in combination with a checkpoint antibody on tumor growth in vivo were assessed. Opaganib and anti-PD-1 antibody each slowed the growth of B16 tumors and improved mouse survival, while the combination of opaganib plus anti-PD-1 strongly suppressed tumor growth and improved survival (p < 0.0001). Individually, opaganib and anti-CTLA-4 antibody had modest effects on the growth of LLC tumors and mouse survival, whereas the combination of opaganib with anti-CTLA-4 substantially inhibited tumor growth and increased survival (p < 0.001). Finally, the survival of mice bearing B16 tumors was only marginally improved by opaganib or anti-PD-L1 antibody alone but was nearly doubled by the drugs in combination (p < 0.005). Overall, these studies demonstrate the ability of opaganib to induce ICD in tumor cells, which improves the antitumor activity of checkpoint antibodies.

Orosomucoid-like protein 3, rhinovirus and asthma

The genetic variants of orosomucoid-like protein 3 (ORMDL3) gene are associated with highly significant increases in the number of human rhinovirus (HRV)-induced wheezing episodes in children. Recent investigations have been focused on the mechanisms of ORMDL3 in rhinovirus infection for asthma and asthma exacerbations. ORMDL3 not only regulates major human rhinovirus receptor intercellular adhesion molecule 1 expression, but also plays pivotal roles in viral infection through metabolisms of ceramide and sphingosine-1-phosphate, endoplasmic reticulum (ER) stress, ER-Golgi interface and glycolysis. Research on the roles of ORMDL3 in HRV infection will lead us to identify new biomarkers and novel therapeutic targets in childhood asthma and viral induced asthma exacerbations.

Targeting Sphingosine Kinases for the Treatment of Cancer

Sphingosine kinases (SK1 and SK2) are key, druggable targets within the sphingolipid metabolism pathway that promote tumor growth and pathologic inflammation. A variety of isozyme-selective and dual inhibitors of SK1 and SK2 have been described in the literature, and at least one compound has reached clinical testing in cancer patients. In this chapter, we will review the rationale for targeting SKs and summarize the preclinical and emerging clinical data for ABC294640 as the first-in-class selective inhibitor of SK2.

Ceramide signaling in mammalian epidermis

Ceramide, the backbone structure of all sphingolipids, as well as a minor component of cellular membranes, has a unique role in the skin, by forming the epidermal permeability barrier at the extracellular domains of the outermost layer of the skin, the stratum corneum, which is required for terrestrial mammalian survival. In contrast to the role of ceramide in forming the permeability barrier, the signaling roles of ceramide and its metabolites have not yet been recognized. Ceramide and/or its metabolites regulate proliferation, differentiation, and apoptosis in epidermal keratinocytes. Recent studies have further demonstrated that a ceramide metabolite, sphingosine-1-phosphate, modulates innate immune function. Ceramide has already been applied to therapeutic approaches for treatment of eczema associated with attenuated epidermal permeability barrier function. Pharmacological modulation of ceramide and its metabolites' signaling can also be applied to cutaneous disease prevention and therapy. The author here describes the signaling roles of ceramide and its metabolites in mammalian cells and tissues, including the epidermis. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias.

Dermatophagoides farinae house dust mite allergen challenges reduce stratum corneum ceramides in an experimental dog model of acute atopic dermatitis

BACKGROUND

Ceramides are essential stratum corneum (SC) lipids and they play a pivotal role in maintaining effective cutaneous barrier function.

OBJECTIVES

The present study aimed at determining the effect of a Dermatophagoides farinae house dust mite (Df-HDM) allergen challenge on SC ceramides of atopic dogs experimentally sensitized to these allergens.

ANIMALS

Six Df-HDM-sensitized atopic Maltese-beagle dogs were used.

METHODS

Prechallenge SC was obtained by cyanoacrylate stripping. One week later, the dogs were challenged topically with Df-HDM allergens, which resulted in mild to moderate inflammation 24 h later. Two weeks after challenge, SC of lesional and nonlesional skin was obtained. Finally, SC was collected from challenge sites 2 months after lesion resolution. The different SC lipids were quantified blindly by thin-layer chromatography.

RESULTS

Significantly lower amounts of ceramides [AH], [AP], [AS], [NP], [EOP], [NS] and [EOS] were observed in lesional SC compared with prechallenge samples, while no significant effect was found on the amount of other lipids, including cholesterol and free fatty acids. The ceramide profile of nonlesional skin generally showed the same postchallenge reduction pattern. Ceramide amounts returned to normal within 2 months after lesion remission.

CONCLUSION AND CLINICAL IMPORTANCE

These findings suggest that the allergic reactions caused by Df-HDM allergens lead to a selective reduction of SC ceramides, not only at sites of inflammation but also at sites away from those of allergen application. There is normalization of ceramide amounts after inflammation subsides. These observations suggest that the deficiency of ceramides observed in canine atopic skin occurs, at least in part, secondary to inflammation.

Ceramidases: regulators of cellular responses mediated by ceramide, sphingosine, and sphingosine-1-phosphate

Ceramidases catalyze hydrolysis of ceramides to generate sphingosine (SPH), which is phosphorylated to form sphingosine-1-phosphate (S1P). Ceramide, SPH, and S1P are bioactive lipids that mediate cell proliferation, differentiation, apoptosis, adhesion, and migration. Presently, 5 human ceramidases encoded by 5 distinct genes have been cloned: acid ceramidase (AC), neutral ceramidase (NC), alkaline ceramidase 1 (ACER1), alkaline ceramidase 2 (ACER2), and alkaline ceramidase 3 (ACER3). Each human ceramidase has a mouse counterpart. AC, NC, and ACER1-3 have maximal activities in acidic, neutral, and alkaline environments, respectively. ACER1-3 have similar protein sequences but no homology to AC and NC. AC and NC also have distinct protein sequences. The human AC (hAC) was implicated in Farber disease, and hAC may be important for cell survival. The mouse AC (mAC) is needed for early embryo survival. NC is protective against inflammatory cytokines, and the mouse NC (mNC) is required for the catabolism of ceramides in the digestive tract. ACER1 is critical in mediating cell differentiation by controlling the generation of SPH and S1P and that ACER2's role in cell proliferation and survival depends on its expression or the cell type in which it is found. Here, we discuss the role of each ceramidase in regulating cellular responses mediated by ceramides, SPH, and S1P.

Ceramide-Dependent Regulation of Human Epidermal Keratinocyte CD1d Expression during Terminal Differentiation

Human keratinocytes (KC), when cultured under conditions to remain undifferentiated or to terminally differentiate, changed their cellular distribution of CD1d. As studied by confocal microscopy, undifferentiated KC had a pool of cytoplasmic CD1d, whereas after terminal differentiation, this molecule localized in the cell membrane, which recapitulates CD1d expression in vivo. A comparison of undifferentiated and differentiated cultured KC did not reveal any differences in the association with beta(2)-microglobulin, invariant chain of class II MHC, or patterns of glycosylation, suggesting that these biochemical properties are not regulating the cellular distribution of CD1d. Time-course studies of CD1d gene expression indicated that KC slowly increased gene expression with CaCl(2)-induced terminal differentiation. Increased CD1d gene expression was dependent on ceramide synthesis, because fumonisin B1, a ceramide synthetase inhibitor, blocked the increase in CD1d gene expression during terminal differentiation. Similarly, exogenous ceramide or the ceramidase inhibitor, B13, induced CD1d gene expression by undifferentiated, but not terminally differentiated, KC. A protein kinase C-zeta (PKC-zeta) inhibitor (a pseudosubstrate oligopeptide), but not a PKC-alphabeta inhibitor, significantly decreased CD1d gene expression by undifferentiated or ceramide-stimulated cultured, undifferentiated KC. As expected, downstream signaling events of PKC-zeta (JNK phosphorylation and NF-kappaBeta accumulation in the nucleus) were also attenuated. The calcineurin phosphatase inhibitor cyclosporine A, which blocks KC terminal differentiation, also blocked CD1d gene expression by cultured KC. In conclusion, this novel function of cellular ceramides extends the importance of this class of biologically active lipids beyond that of terminal differentiation and barrier function in normal human skin.

Mechanism of action of sphingolipids and their metabolites in the toxicity of fumonisin B1

Fumonisins are a group of mycotoxins produced primarily by Fusarium moniliforme. Several fumonisins have been isolated through out the years but only fumonisin B1, B2 and B3 are the ones present in naturally contaminated foods, with B1 being the most toxic between them. The structural similarity between sphinganine and fumonisin B1 suggests that the mechanism of action of this mycotoxin is mainly via disruption of sphingolipid metabolism, this is an important step in the cascade of events leading to altered cell growth, differentiation and cell injury. Sphingolipids are a second type of lipid found in cell membranes, particularly nerve cells and brain tissues. Toxicity of fumonisin B1 is given via inhibition of ceramide synthase that catalyzes the formation of dihydroceramide from sphingosine. This mechanism of action may explain the wide variety of health effects observed when this mycotoxin is ingested like high rate of human oesophageal cancer and promotion of primary liver cancer.

Interleukin-4 suppresses the enhancement of ceramide synthesis and cutaneous permeability barrier functions induced by tumor necrosis factor-alpha and interferon-gamma in human epidermis

Ceramide is an integral part of the extracellular lipid bilayer of the stratum corneum (SC) that forms the permeability barrier of the skin. The production of SC ceramides is catalyzed by sphingomyelinase (SMase) and glucocerebrosidase (GCase). Acid-ceramidase (acid-CDase) catalyzes the hydrolysis of ceramide in the SC. We examined the effects of T helper (Th)1 and Th2 cytokines on levels of transcripts of genes for acid-CDase, acid-SMase, and GCase, on levels of ceramide, and on the extent of transepidermal water loss (TEWL) in the human epidermis in an effort to determine whether these cytokines affect the permeability barrier functions. Levels of transcripts for acid-SMase and GCase and the amount of ceramide in human epidermal sheets were enhanced by tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma and these effects were inhibited in the presence of interleukin (IL)-4. In epidermal keratinocytes cultured under submerged conditions, however, no similar inhibitory effects of IL-4 were observed. Consistent with these results, TEWL was suppressed by TNF-alpha and IFN-gamma, and these effects were also inhibited by IL-4. The balance between Th1 and Th2 might affect the construction and/or the repair of the epidermal permeability barrier via regulation of the production of ceramide.

Characterization of the Formation and Localization of Sulfamethoxazole and Dapsone-Associated Drug-Protein Adducts in Human Epidermal Keratinocytes

Sulfonamide- and sulfone-induced hypersensitivity reactions are thought to be mediated through bioactivation of parent drug molecule(s) to their respective reactive metabolite(s). Recent studies have demonstrated that keratinocytes can bioactivate sulfonamides and sulfones. Using enzyme-linked immunosorbent assay and hapten-specific rabbit antisera developed in our laboratory, we found that incubation of either normal human epidermal keratinocytes (NHEKs) or an immortalized human keratinocyte cell line (HaCaT) with sulfamethoxazole (SMX) or dapsone (DDS) resulted in the formation of drug/metabolite protein adducts. The formation of these adducts with SMX was increased in the presence of ascorbic acid, whereas N-acetylcysteine decreased adduct formation with both SMX and DDS. Adduct formation was confirmed using confocal microscopy when NHEKs were incubated with SMX, DDS, or their respective arylhydroxylamine metabolites. Cellular distribution of adducts was compared in permeable versus nonpermeable NHEKs. Exposure to SMX, DDS, or dapsone hydroxylamine resulted in the formation of intracellular adducts, whereas SMX hydroxylamine also resulted in the presence of adducts on the cell surface. In summary, our work shows that keratinocytes can bioactivate SMX/DDS to form drug-protein adducts, which may be acquired by antigen-presenting cells upon keratinocyte cell death, evoking an immune response. In addition, keratinocytes may themselves present antigen to hapten-specific cytotoxic T lymphocytes. Furthermore, our results also suggest that different sulfonamides/sulfones may have different protein targets for in situ haptenation in keratinocytes.

C2-ceramide induces apoptosis in a human squamous cell carcinoma cell line

BACKGROUND

Previous studies have demonstrated that synthetic cell-permeable analogues of ceramide promote differentiation and inhibit proliferation of keratinocytes, and that the vitamin D3 inducible sphingomyelin cycle generates ceramide in keratinocytes. Although it has been suggested that exogenous ceramide induces apoptosis of keratinocytes, which is similar to their effect on other cell types, such as leukaemia cells, only a few studies have reported ceramide-induced apoptosis of keratinocytes.

OBJECTIVE

To determine whether ceramide induces apoptosis of keratinocytes, we used the synthetic ceramide analogue, C2-ceramide (N-acetylsphingosine) and a human squamous cell carcinoma cell line, HSC-I.

METHODS

We treated HSC-I cells with C2-ceramide, followed by a viability assay, morphological observations, nick end-labelling (TUNEL), DNA electrophoresis, and electron microscopy.

RESULTS

In the viability assay, C2-ceramide was toxic to HSC-I cells in a dose-dependent manner. Manifestations of apoptotic morphology occurred in the ceramide-treated cells, whereas these morphological changes did not occur in cells treated with dihydroceramide (N-acetylsphinganine). TUNEL revealed that many of the ceramide-treated cells showed positive reactivity. DNA electrophoresis demonstrated that C2-ceramide caused internucleosomal fragmentation in a dose- and time-dependent manner. Electron microscopy revealed that the ceramide-treated cells manifested morphological characteristics typical of apoptosis.

CONCLUSIONS

The present results demonstrate that C2-ceramide induces apoptosis of transformed human keratinocytes, whereas C2-dihydroceramide does not have such an effect. The fact that ceramide induces apoptosis of keratinocyctes raises the possibility that intracellular ceramide, which is increased with differentiation of the epidermis, might be involved in terminal differentiation, a specialized form of apoptosis of keratinocytes.

Induction of tissue factor production but not the upregulation of adhesion molecule expression by ceramide in human vascular endothelial cells

Binding of tumor necrosis factor-alpha (TNF-alpha) to p60 TNF-alpha receptor induces the activation of sphingomyelinase to generate ceramide, which in turn activates certain protein kinases and phosphatases, resulting in various TNF-alpha-mediated biological effects. We have investigated the role for the sphingomyelin/ceramide pathway in the TNF-alpha-induced upregulation of adhesion molecule expression and tissue factor production of human endothelial cells. TNF-alpha stimulated human umbilical vascular endothelial cells (HUVECs) to upregulate the expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and HLA class I molecules in addition to the induction of procoagulant tissue factor production. C2-ceramide, a highly cell-permeable ceramide analog, was able to stimulate HUVECs to produce tissue factor activity as well as TNF-alpha. However, C2-ceramide did not stimulate HUVECs to upregulate the expression of VCAM-1, ICAM-1 and HLA class I molecules. These results suggest that there exist both the ceramide-dependent and -independent pathways in TNF-alpha signal transduction system in human vascular endothelial cells.

The antisense oligonucleotide ISIS 2922 prevents cytomegalovirus-induced upregulation of IL-8 and ICAM-1 in cultured human fibroblasts

Human cytomegalovirus (HCMV) infection is associated with excessive proinflammatory immune responses such as cytokine/chemokine production or upregulation of adhesion molecules on the host cells. It is assumed that these features of HCMV-related immunopathology can not be treated effectively with currently available anti HCMV drugs. In the present study the efficacy of ganciclovir (GCV), foscarnet (PFA), cidofovir (HPMPC), and ISIS 2922, an antisense oligonucleotide complementary to HCMV immediate-early (IE) mRNA, was investigated on HCMV-induced secretion and functional activity of the C-X-C chemokine IL-8 and the expression of the intercellular adhesion molecule-1 (ICAM-1). As compared with mock-infected cells IL-8 production was increased up to 9-fold and ICAM-1 expression up to 4-fold in HCMV-infected fibroblasts. Treatment of infected cells with GCV (40 microM), PFA (200 microM) or HPMPC (2 microM) suppressed completely virus replication as demonstrated by quantification of late (L) antigen expression and infectious virus production. These drugs, however, failed to inhibit IE antigen expression and did not prevent HCMV-induced upregulation of IL-8 and ICAM-1. In contrast, ISIS 2922 (1 microM) suppressed both IE and L antigen expression by 99% and inhibited infectious virus production by 10(4)-fold. Moreover, ISIS 2922 significantly suppressed HCMV-induced upregulation of both IL-8 and ICAM-1 expression on the transcriptional and on the protein level. Our results indicate that ISIS 2922 but not inhibitors of HCMV DNA prevents HCMV-induced upregulation of IL-8 and ICAM-1, both hallmarks of inflammatory processes. Thus, inhibition of HCMV IE expression with ISIS 2922 may be an important strategy for the treatment of HCMV-related immunopathogenesis.

Interferon-gamma-induced differentiation and apoptosis of HT29 cells: dissociation of (glucosyl)ceramide signaling

Recently, (glyco)sphingolipids (SL) like ceramide (Cer) and glucosylceramide (GlcCer) have been shown to be involved in signaling pathways leading to differentiation and apoptosis in several cell types, including the colon adenocarcinoma cell line HT29. Intracellular levels of Cer can be modulated by ligands such as interferon-gamma (IFN gamma). In the present study we show that IFN gamma, depending on its concentration, has both differentiation- and apoptosis-inducing effects on HT29 cells. Since both phenomena have been related to SL-mediated signaling in other cell types, we next examined whether IFN gamma was able to induce changes in the SL levels of HT29 cells. Remarkably, no significant changes in these levels could be revealed, implying that SL are not involved in IFN gamma-induced differentiation and/or apoptosis of HT29 cells. This observation provides evidence for the hypothesis that SL-mediated signaling pathways might be more cell type specific than is generally assumed.

A potential role for ceramide in the regulation of mouse epidermal keratinocyte proliferation and differentiation

We have previously determined that sustained phospholipase D (PLD) activation is associated with differentiation induction in primary mouse epidermal keratinocytes. We therefore investigated the effect of two bacterial PLD on keratinocyte proliferation and differentiation. We found that Streptomyces sp. PLD was much less potent at inhibiting proliferation than S. chromofuscus PLD, with a half-maximal inhibitory concentration of 0.05 versus less than 0.001 IU per ml for S. chromofuscus PLD. Similarly, S. chromofuscus PLD stimulated transglutaminase activity more effectively and potently than S. sp. PLD. When we examined the formation of products by the two PLD, we found that the S. sp. PLD showed higher activity at all concentrations. Whereas the PLD from S. sp. is relatively inactive on sphingomyelin, S. chromofuscus PLD is known to hydrolyze both glycerophospholipids and sphingomyelin. Based on recent data indicating a role for ceramide in regulating cell growth and differentiation, we hypothesized that the ability of S. chromofuscus PLD to hydrolyze sphingomyelin might underlie its greater potency. Therefore, we examined the effect of exogenous sphingomyelinase and synthetic ceramides on DNA synthesis. We found that sphingomyelinase exhibited a potent concentration-dependent effect on [3H]thymidine incorporation, much like S. chromofuscus PLD. Synthetic cell-permeable ceramides (C6- and C2-ceramide) also concentration dependently inhibited DNA synthesis, with a half-maximal inhibitory concentration of approximately 12 microM. Finally, we obtained evidence suggesting that ceramide is generated in response to a physiologically relevant agent, because tumor necrosis factor-alpha, a known effector of sphingomyelin turnover in other systems and a cytokine that is produced and released by keratinocytes, increased ceramide levels in primary epidermal keratinocytes.

The effects of inflammatory cytokines on the isolated human sebaceous infundibulum

The human sebaceous pilosebaceous infundibulum was isolated and maintained in medium for up to 7 d. Freshly isolated infundibula were found to express keratins 1, 5, 6, 16, and 17, as determined by immunohistochemistry. In addition, freshly isolated infundibula expressed filaggrin, profilaggrin, involucrin, cornifin alpha, and loricrin. This pattern of expression was retained over 7 d. The addition of 100 U interferon (IFN)-gamma per ml over 3 d and 1 nM phorbol myristate acetate over 24 h resulted in the expression of intercellular adhesion molecule (ICAM)-1 and HLA-DR by infundibular keratinocytes, as determined by immunohistochemistry. Ten nanograms tumor necrosis factor-alpha per ml and 10 ng IL-6 per ml both caused expression of ICAM-1 alone. IL-1alpha had no effect on the expression of ICAM-1 or HLA-DR over 3 d, but addition of 1 ng IL-1alpha per ml over 7 d in culture resulted in hypercornification of the keratinocytes of the infundibulum, apparently brought about by early keratinocyte cornification. These data suggest that the isolated, maintained, infundibulum is a good model for studying the effects of inflammatory cytokines on the infundibulum, and that IL-1alpha acts on infundibular keratinocytes to promote cornification.

Cetirizine and hydrocortisone differentially regulate ICAM-1 expression and chemokine release in cultured human keratinocytes

BACKGROUND

Cetirizine is a H1 histamine antagonist which possesses anti-inflammatory properties through inhibition of leucocyte recruitment and activation, and reduction of ICAM-1 expression on mucosal epithelial cells. No studies have addressed the potential anti-inflammatory activities of cetirizine on skin keratinocytes.

OBJECTIVES

Cetirizine and hydrocortisone were compared in their capacity to counteract human keratinocytes activation by IFNgamma. In particular, expression of immuno-modulatory membrane molecules and chemokine release have been examined.

METHODS

Keratinocyte cultures established from normal skin of healthy donors were activated by IFNgamma (100-500 U/mL) in the absence or presence of cetirizine (10(-3)-10(3) microM) or hydrocortisone (10(-3)-10(2) microM), and tested for expression of ICAM-1, HLA-DR, MHC class I and CD40 as well as for release of RANTES, IL-8, macrophage chemotactic protein-1 (MCP-1) and granulocyte macrophage-colony stimulating factor (GM-CSF).

RESULTS

Cetirizine at high concentrations (10(2)-10(3) microM) markedly inhibited IFNgamma-induced expression of membrane ICAM-1, HLA-DR and up-regulation of MHC class I, but had no effect on CD40 expression. In contrast, hydrocortisone (10(2) microM) enhanced IFNgamma-induced membrane ICAM-1, reduced expression of HLA-DR and did not alter expression of MHC class I and CD40. Consistently, high doses of cetirizine decreased, whereas hydrocortisone increased, soluble ICAM-1 levels in the supernatants of IFNgamma-treated keratinocytes. The inhibiting and stimulating effects of cetirizine and hydrocortisone, respectively, on ICAM-1 expression were confirmed at the mRNA level by Northern blot analysis. Finally, cetirizine, but not hydrocortisone, inhibited the release of MCP-1 and RANTES from IFNgamma-stimulated keratinocytes. In contrast, hydrocortisone, but not cetirizine, reduced GM-CSF and IL-8 release.

CONCLUSIONS

The results indicate that cetirizine has the capacity to block the IFNgamma-induced activation of keratinocytes, and thus can exert important regulatory effects on TH1 cell-mediated immune responses in the skin. The high doses required for evidencing these activities suggest the potential benefits of a topical use of cetirizine.