Effect of dexamethasone, 6-mercaptopurine and cyclosporine A on intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression

Multiplicity of Glucocorticoid Action in Inhibiting Allograft Rejection

Glucocorticoids (GCs) are used as immunosuppressive and antiinflammatory agents in organ transplantation and in treating autoimmune diseases and inflammatory disorders. GCs were shown to exert their antiproliferative effects directly through blockade of certain elements of an early membrane-associated signal transduction pathway, modulation of the expression of select adhesion molecules, and by suppression of cytokine synthesis and action. GCs may act indirectly by inducing lipocortin synthesis, which in turn, inhibits arachidonic acid release from membrane-bound stores, and also by inducing transforming growth factor (TGF)-β expression that subsequently blocks cytokine synthesis and T cell activation. Furthermore, by preferentially inhibiting the production of Th1 cytokines, GCs may enhance Th2 cell activity and, hence, precipitate a long-lasting state of tolerance through a preferential promotion of a Th2 cytokine-secreting profile. In exerting their antiproliferative effects, GCs influence both transcriptional and posttranscriptional events by binding their cytosolic receptor (GR), which subsequently binds the promoter region of cytokine genes on select DNA sites compatible with the GCs responsible elements (GRE) motif. In addition to direct DNA binding, GCs may also directly bind to, and hence antagonize, nuclear factors required for efficient gene expression, thereby markedly reducing transcriptional rate. The pleiotrophy of the GCs action, coupled with the diverse experimental conditions employed in assessing the GCs effects, indicate that GCs may utilize more than one mechanism in inhibiting T cell activation, and warrant careful scrutiny in assigning a mechanism by which GCs exert their antiproliferative effects. © 1998 Elsevier Science Inc.

Effects of high doses of dexamethasone on hemodynamic and immunohistochemical characteristics of acute paraquat intoxication in rat kidneys

Paraquat (1,1'-dimethyl-4,4'-bipyridinium) (PQ), is a nonselective contact herbicide that is highly toxic to humans. The kidney is affected during PQ intoxication. Dexamethasone (Dexa) has anti-inflammatory effects and is used to treat cases of PQ poisoning. We investigated in rat kidney hemodynamic effects and immunohistochemical characteristics of Dexa treatment in acute PQ poisoning. Adult male rats were divided into four groups: 1, untreated control; 2, treated with 100 mg/kg Dexa; 3, treated with 25 mg/kg PQ; 4, treated with PQ + Dexa. Mean arterial pressure (MAP) and heart rate (HR) were recorded during the experimental period (2 h). Tissues were removed after 2 h and immunohistochemistry was performed after 24 h. Paraffin sections of kidney were prepared and anti-cyclo-oxygenase-1 (COX-1), anti-cyclo-oxygenase-2 (COX-2), anti-angiotensin converting enzyme (ACE), anti-aquaporin-1 (AQU-1), anti-vascular cell adhesion molecule (VCAM) primary antibodies were used for immunohistochemical examination. Immunoreactivities were scored as: (1) minimal, (2) weak, (3) mild, (4) moderate, (5) strong and (6) very strong. MAP and HR were measured at 10 min, 20 min, 1 h and 2 h. MAP at 10 and 20 min and 1 h was increased in the Dexa group. HR also was increased in all groups compared to controls at 2 h. Compared to groups 2 and 4, MAP values decreased significantly in group 3 at 1 h. The intensity of all of immunoreactivities was decreased in group 2. In group 3, immunoreactivities of COX-1, COX-2 and ACE were decreased compared to the control and the other groups, whereas AQU-1 and VCAM immunoreactivities were the same as the control group. ACE and VCAM immunoreactivities were decreased in group 4 compared to the control group, while COX-1, COX-2 and AQU-1 immunoreactivities were close to those of the control group. Dexa appears to be useful for treating PQ intoxication.

Novel Treatments for Drug-Induced Toxic Epidermal Necrolysis (Lyell’s Syndrome)

Drug-induced toxic epidermal necrolysis (TEN) is a life-threatening disease characterized by extensive destruction of the epidermis. It apparently results from the formation of specific toxic drug metabolites by the keratinocytes. The mortality rate which averages 25-30% is mainly due to secondary septicemia, and to ionic and metabolic disturbances following loss of epidermal integrity. Apoptosis is the likely mechanism leading to massive keratinocyte death in TEN. Dysregulations in the tumor necrosis factor-alpha (TNF-alpha) pathway, CD95 system (Fas ligand, CD95L; Fas receptor, CD95R) and calcium homeostasis in the epidermis are involved in this apoptotic process. An active role has also been ascribed to T lymphocytes, macrophages and factor XIIIa-positive dermal dendrocytes. Despite progress, treatment of TEN remains controversial. In the past, systemic glucocorticoids were used in order to target the inflammatory reaction in TEN. However, there was no evidence for improvement of the healing process, while corticosteroids worsened the prognosis by increasing the risk of septicemia. Only a few cases have been treated with other drugs including cyclophosphamide, pentoxyfilline, thalidomide, anti-TNF-alpha antibodies and cyclosporin A. In the recent past, some TEN patients were treated with intravenous human immunoglobulins (IVIG). The rationale for such a treatment was to block the CD95 system on keratinocytes. The early promising clinical results of IVIG treatment in TEN were subsequently challenged. This review compares the effectiveness and drawbacks of the major drugs presently used in TEN treatment. Some future prospects in TEN management are also discussed.

Review of the molecular and cellular mechanisms of action of glucocorticoids for use in asthma

Asthma is characterized by inflammation in the lung and glucocorticoids (GCs) are the most clinically effective treatment available. The success of chronic GC therapy for asthma stems largely from the ability of the GC-GC receptor (GR) complex to alter transcription of a wide array of molecules involved in the inflammatory process. Many of the adverse effects of elevated systemic GC levels have been reduced through the use of inhalation as a method of administration, as opposed to oral GC. GCs exert their effects by binding to the wild-type GR, GR(alpha). The GR(alpha) complex can directly or indirectly alter gene transcription by binding to specific DNA sites or by activating transcription factors. There is also evidence to support GR(alpha) involvement in post-translational activities. In the management of asthma, the GR(alpha) down-regulates proinflammatory mediators such as interleukin-(IL)-1, 3, and 5, and up-regulates anti-inflammatory mediators such as IkappaB [inhibitory molecule for nuclear factor kappaB1 IL-10, and 12. Newer GCs are being designed to increase potency and topical activity. Mometasone furoate (MF), has recently been developed for the treatment of asthma and inhibits key anti-inflammatory processes with a potency equal to or greater than that of fluticasone propionate. A better understanding of the molecular mechanisms involved might provide strategies for optimizing the effectiveness of GC in the treatment of asthma.

Would cyclosporin A be beneficial to mitigate drug-induced toxic epidermal necrolysis?

Drug-induced toxic epidermal necrolysis (TEN) is a rare life-threatening disease whose mortality remains high. The treatment of the disease is badly settled. Several kinds of drugs have been tested, including systemic corticosteroids, cyclophosphamide, pentoxifylline and thalidomide, but without any clear-cut outcome. Cyclosporin A (CsA) has many inhibitory effects on the main cell populations involved in TEN (T lymphocytes, macrophages and keratinocytes). CsA could also act on tumor necrosis factor alpha metabolism, a cytokine which is important in TEN epidermal destruction. Moreover, apoptosis is the mechanism leading to keratinocyte death and CsA has antiapoptotic properties. CsA has already been used successfully on a limited series of TEN patients. We have reviewed the potential theoretical useful effects of CsA in TEN. We conclude that CsA could be a good candidate to reverse TEN progression.

Inhibition of VCAM-1 expression in human bronchial epithelial cells by glucocorticoids

We have demonstrated previously that cytokines induce surface expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on BEAS-2B bronchial epithelial cells in vitro. The present studies demonstrate glucocorticoid inhibition of cytokine-induced VCAM-1 expression as detected using flow cytometry and Northern blot analysis. Several commonly used inhaled glucocorticoids were tested for their ability to inhibit VCAM-1 and ICAM-1 expression. All glucocorticoids tested inhibited VCAM-1 expression in a dose-dependent manner. No inhibition of ICAM-1 expression was observed. The most potent of the glucocorticoids tested for inhibition of VCAM-1 expression were mometasone furoate and fluticasone propionate (FP), which had IC50 values (i.e., concentrations at which each glucocorticoid produced 50% inhibition) of under 10 pM. Budesonide, triamcinolone acetonide, and beclomethasone dipropionate (BDP) had intermediate potency, and hydrocortisone and the BDP metabolite beclomethasone-17-monopropionate were the least potent of the steroids tested. Kinetic analysis of the ability of FP to inhibit VCAM-1 expression revealed that preincubation with FP for 3 h completely inhibited VCAM-1 expression induced by tumor necrosis factor-alpha (TNF-alpha). FP inhibited VCAM-1 expression by 50% even when added as late as 6 h after stimulation with TNF-alpha. Using Northern blot analysis, we confirmed inhibition of VCAM-1 and ICAM-1 messenger RNA (mRNA) expression by FP. Pretreatment with FP (10(-11) M to about 10(-7) M, 24 h) inhibited TNF-alpha-induced VCAM-1 mRNA expression in BEAS-2B in a dose-dependent manner, but did not inhibit expression of ICAM-1 mRNA. Studies with actinomycin D indicate that FP treatment accelerated the degradation of TNF-alpha-induced VCAM-1 mRNA. FP (10(-7) M) also inhibited VCAM-1 mRNA expression induced by TNF-alpha in primary human bronchial epithelial cells as assessed by reverse transcription-polymerase chain reaction. These results suggest that suppression of epithelial VCAM-1 expression by glucocorticoids may contribute to their anti-inflammatory effects.

Methotrexate regulates ICAM-1 expression in recipients of rat cardiac allografts

The means by which methotrexate (MTX) mediates immunosuppression at low doses remains to be elucidated. MTX has been shown to inhibit the adherence of neutrophils and fibroblasts to endothelial cells in vitro. The hypothesis that MTX treatment may affect cellular adherence by downregulating cell adhesion molecule expression formed the rationale for these studies. Previous studies of rat cardiac transplant recipients in our laboratory demonstrated that low-dose MTX treatment alone significantly inhibits the expression of the leucocyte beta 2 integrin subunit, CD18. These investigations have addressed whether low-dose MTX treatment might also affect the expression of the beta-integrin counter-receptor, ICAM-1, a cell adhesion molecule which may be induced on endothelial cells during an immune response. The degree to which low-dose cyclosporine A and low-dose MTX treatment alone, and in combination, impact cell adhesion molecule expression has been studied in Brown Norway (BN) to Lewis (Lew) rat accessory cervical heart allografts. According to both Northern blot and immunohistochemical analysis, ICAM-1 expression was upregulated in graft regional lymph nodes and in the spleen of untreated cardiac allograft recipients within 6 h post-transplantation. Despite induction of VCAM-1 expression, ICAM-1 expression remained low or undetectable in cardiac allograft tissue as measured both by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemical analysis. These data suggest that ICAM-1 may function in leucocyte trafficking through lymphoid organs, such as the lymph nodes and spleen, but not directly in graft leucocyte recruitment during BN to Lew rat cardiac allograft rejection. Despite prolonged allograft survival with cyclosporine A alone and combination cyclosporine A/MTX, these treatments did not result in diminished steady-state ICAM-1 mRNA levels in regional lymph nodes or spleen of cardiac allograft recipients. MTX treatment alone, however, substantially diminished ICAM-1 expression in allograft recipient lymphoid tissues. These studies demonstrate for the first time in vivo using a rat model of acute allograft rejection that MTX but not cyclosporine treatment downregulates cell adhesion molecule expression. Low-dose MTX treatment alone, however, is not sufficient to result in prolonged BN to Lew rat cardiac allograft survival. The means by which combination low-dose cyclosporine A and MTX treatment results in prolonged rat cardiac allograft survival over low-dose cyclosporine treatment alone remain(s) to be clarified.

ICAM-1-, -2- and LFA-1-independent homotypic T cell aggregation induced by a novel activating monoclonal antibody targeting the murine Thy-1 molecule

We have previously reported that the murine T cell line EL-4 has an aggregating phenotype, displaying homotypic aggregation (HTA) when exposed to monoclonal antibodies targeting specific cell surface molecules such as leukocyte function-associated antigen-I (LFA-1). We have used this property of EL-4 cells to isolate additional HTA-inducing MAb by screening a panel of hybridomas that were generated from rats immunized with EL-4 cells. We have isolated a novel anti-Thy-1 MAb (termed FF-10) that is a powerful inducer of HTA in EL-4 cells. In addition to induction of HTA, FF-10 also induces splenocyte proliferation but inhibits anti-CD3-driven T cell proliferation. Thy-1-induced HTA cannot be blocked with MAb targeting intercellular adhesion molecule-I and -2 (ICAM-1, ICAM-2) or LFA-1. Thus, the FF-10 MAb represents a novel and unique tool to investigate the diverse roles of the murine Thy-I molecule in T cell activation, proliferation and apoptosis.

Cyclosporine A regulates T cell-epithelial cell adhesion by altering LFA-1 and ICAM-1 expression

In contrast to the well characterized suppressive effect of cyclosporine A (CsA) on IL-2 gene transcription in T cells, other immunosuppressive effects of CsA have received less attention. We have examined the effect of CsA on the expression of the beta 2 integrin, LFA-1, and its counter receptor, ICAM-1, on a renal Ag-specific murine T cell clone and Ag-expressing renal tubular epithelial cells. We have found that CsA has a concentration dependent effect on the expression of both ICAM-1 mRNA and gene product on renal tubular cells. At 0.1 microgram/ml, CsA exhibits a costimulatory effect, with TNF alpha, on ICAM-1 expression. CsA at 1 to 5 micrograms/ml exhibits concentration dependent inhibition of ICAM-1 cell surface expression by the tubular cells. Although CsA does not inhibit ICAM-1 on T cells, it does inhibit surface expression of LFA-1. The concentration dependent effects of CsA on ICAM-1 expression correlate well with ICAM-1 dependent T cell adhesion to TNF alpha stimulated tubular epithelial cells. TGF-beta 1 has similar effects on ICAM-1 and LFA-1 expression as high dose CsA, but the CsA effects are not mediated through induced TGF-beta 1 expression. Our studies support the conclusion that CsA may bidirectionally alter ICAM-1 dependent cellular adhesive interactions. The inhibition of cytokine stimulated ICAM-1 expression at higher CsA concentrations would contribute to the overall immunosuppressive effect of the drug.