Glucocorticoid hormones reduce the expression of major histocompatibility class I antigens on human epithelial cells

Dexamethasone Modulates IL-13 and IL-10 Expression

Interleukin (IL-)-10 and IL-13 are Th2-cell-associated cytokines with a variety of biologic activities in immune and inflammatory responses. It is known that glucocorticoids (GCs) modulate inflammatory and immune functions. In fact, GCs are involved to regulate the transcription of cytokines which are relevant in chronic inflammation and cell-mediated immune response.

In the present study we analyzed, in vitro, the effects of DEX on the expression of the IL-10 and IL-13 lymphokines in murine spleen and thymus cells. DEX-stimulation induced down-regulation of the expression of IL-10 and IL-13 mRNA.

This effect was already evident 0.5 hr after treatment and persisted in time, in both resting and activated lymphocytes. These results suggest that GCs could have inhibitory effect on Th2 cytokine production.

Management and prevention of post-transplant malignancies in kidney transplant recipients

The central issue in organ transplantation remains suppression of allograft rejection. Thus, the development of immunosuppressive drugs has been the key to successful allograft function. The increased immunosuppressive efficiency obtained in the last two decades in kidney transplantation dramatically reduced the incidence of acute rejection. However, the inevitable trade-off was an increased rate of post-transplant infections and malignancies. Since the incidence of cancer in immunosuppressed transplant recipients becomes greater over time, and the introduction of new immunosuppressive strategies are expected to extend significantly allograft survival, the problem might grow exponentially in the near future. Thus, cancer is becoming a major cause of morbidity and mortality in patients otherwise successfully treated by organ transplantation. There are at least four distinct areas requiring consideration, which have a potentially serious impact on recipient outcome after transplantation: (i) the risk of transmitting a malignancy to the recipient within the donor organ; (ii) the problems of previously diagnosed and treated malignancy in the recipient; (iii) the prevention of de novo post-transplant malignant diseases and (iv) the management of these complex and often life-threatening clinical problems. In this scenario, the direct and indirect oncogenic potential of immunosuppressive therapy should be always carefully considered.

Immunosuppressive therapy and malignancy in organ transplant recipients: a systematic review

Post-transplant malignancy is recognised as being a major limitation to the success of solid organ transplantation and it is currently considered one of the unavoidable costs of long-term immunosuppressive therapy. However, the continual introduction of new immunosuppressive drugs and the growing knowledge about their different oncogenic profiles, requires a continuous evaluation of the available evidence on this topic. The incidence and risk of malignancy is elevated in solid organ transplant recipients compared with the general population. As proof of the relationship between immunosuppressive therapy and post-transplant malignancy, epidemiological data reveal that the length of exposure to immunosuppressive therapy and the intensity of therapy are clearly related to the post-transplant risk of malignancy, and that once cancer has developed, more intense immunosuppression can translate into more aggressive tumour progression in terms of accelerated growth and metastasis and lower patient survival. The association between malignancy and immunosuppressive therapy is mediated through several pathogenic factors. Indirectly, immunosuppressive drugs greatly increase the post-transplant risk of malignancy by impairing cancer surveillance and facilitating the action of oncogenic viruses. However, the direct pro- and anti-oncogenic actions of immunosuppressants also play an important role. The cancer-promoting effect of calcineurin inhibitors, independently of depressed immunosurveillance, has been demonstrated in recent years, and currently only mammalian target of rapamycin (mTOR) inhibitors have shown simultaneous immunosuppressive and antitumour properties. Reports of the initial results of the reduced incidence of cancer in organ transplant recipients receiving mTOR inhibitor therapy strongly indicate separate pathways for pharmacological immunosuppression and oncogenesis. The role of mTOR inhibitors has been firmly established for the treatment of post-transplant Kaposi's sarcoma and its role in the management of patients with other post-transplant malignancies should be clarified as soon as possible. Prevention of morbidity and mortality resulting from post-transplant malignancy should become a main endpoint in solid organ transplant programmes, and the choice and management of immunosuppressive therapy in each phase of transplantation plays a central role in this objective. Although comprehensive and rigorous information about the management of immunosuppressive therapy in transplant recipients at risk of or affected by cancer is still lacking, new experimental and clinical data about mTOR inhibitors offers novel approaches to this problem.

Glucocorticoid use in prostate cancer and other solid tumours: implications for effectiveness of cytotoxic treatment and metastases

Glucocorticoids have been used widely in conjunction with other treatment for patients with cancer because they have potent proapoptotic properties in lymphoid cells, can reduce nausea, and alleviate acute toxic effects in healthy tissue. However, glucocorticoids are used in a supportive-care role, even though to our knowledge no prospective clinical studies have assessed the effect of these steroids on the growth of solid tumours. Data from preclinical and, to some extent, clinical studies, suggest that glucocorticoids induce treatment resistance in solid tumours, including prostate cancer. Research has focussed on disseminated cells that have been shed by the tumour: the potential of glucocorticoids to render these cells resistant to apoptosis--and to downregulate the immune response--might contribute to tumour metastasis. Here, we review the benefits of glucocorticoids and their negative effects, such as induction of resistance in tumour cells and concomitant induction of apoptosis in immune cells, with particular emphasis on prostate cancer.

Differential expression of class I MHC mRNA in the hypothalamus of Lewis and Fischer rats

The expression of class I major histocompatibility complex (MHC) mRNA was compared in the brains of inflammatory susceptible, hypothalamic-pituitary-adrenal (HPA)-axis blunted Lewis rats and inflammatory resistant, HPA-axis hyperresponsive Fischer rats by quantitative in situ hybridization following lipopolysaccharide (LPS) or vehicle administration. Lewis rats showed lower levels of class I MHC in the hypothalamic paraventricular nucleus (PVN) and retrochiasmatic area (RCA) compared to Fischer rats under both vehicle and LPS conditions. No differences were detected in other brain structures. Differential class I MHC expression in Lewis rats suggests an alteration in mechanisms related to cellular activity of neuroendocrine cells rather than alterations specific to neuroendocrine molecules.

Resistance to glucocorticoid-induced apoptosis in PLP peptide-specific T cell clones from patients with progressive MS

Glucocorticoids (GC) are commonly used to treat inflammatory disorders such as multiple sclerosis (MS) and may exert their immunosuppressive activity by inducing apoptosis in activated lymphocytes. However, unlike relapsing-remitting MS patients, those with progressive disease respond poorly to GC treatment. The data in this communication indicate that PLP peptide-specific T cell clones from progressive, but not relapsing-remitting MS patients are resistant to GC-induced apoptosis in vitro, in a fashion associated with expression of B-7 co-stimulatory molecules. Thus, failure to respond to GC treatment may reflect defect in apoptosis that develop during the progressive stages of chronic inflammatory disease.

Inhibition of radiation-induced apoptosis by dexamethasone in cervical carcinoma cell lines depends upon increased HPV E6/E7

Through a glucocorticoid-responsive promoter, glucocorticoids can regulate the transcription of the human papillomavirus (HPV) E6 and E7 viral genes which target the tumour suppressor proteins p53 and Rb respectively. In C4-1 cells, the glucocorticoid dexamethasone up-regulated HPV E6/E7 mRNA and decreased radiation-induced apoptosis. In contrast, dexamethasone had no effect on apoptosis of cells that either lack the HPV genome (C33-a) or in which HPV E6/E7 transcription is repressed by dexamethasone (SW756). Irradiated C4-1 cells showed increased p53 expression, while dexamethasone treatment prior to irradiation decreased p53 protein expression. In addition, p21 mRNA was regulated by irradiation and dexamethasone in accordance with the observed changes in p53. Overall, glucocorticoids decreased radiation-induced apoptosis in cervical carcinoma cells which exhibit increased HPV E6/E7 transcription and decreased p53 expression. Therefore, in HPV-infected cervical epithelial cells, p53-dependent apoptosis appears to depend upon the levels of HPV E6/E7 mRNA.

RU486 increases radiosensitivity and restores apoptosis through modulation of HPV E6/E7 in dexamethasone-treated cervical carcinoma cells

OBJECTIVE

Cervical carcinoma tumors containing radioresistant cells are associated with decreased local control and survival. Therefore, strategies to increase cell kill during radiotherapy have a clear rationale. It was previously determined that treatment with the corticosteroid dexamethasone increased radioresistance and decreased apoptosis in C4-1 cervical carcinoma cells. The goal of this study was to determine whether hormone antagonists, specifically Mifepristone (RU486), could reverse the effects of dexamethasone on clonogenic survival and apoptosis following gamma-irradiation.

METHODS

Cervical carcinoma cell line C4-1 cells were exposed to 1 microM dexamethasone in the presence or absence of 1 microM Mifepristone (RU486), a hormone antagonist, and irradiation. Cells were analyzed for steroid-dependent HPV E6/E7 mRNA expression (by Northern blot analysis), clonogenic survival, and apoptosis (by Annexin V staining and the DNA fragmentation assay). In addition, p53 protein levels were determined by Western blot analysis.

RESULTS

The hormone antagonist RU486 reversed dexamethasone-dependent upregulation of E6/E7 mRNA and restored radiation-induced p53 expression, apoptosis, and clonogenic survival to levels similar to those observed following irradiation alone.

CONCLUSION

RU486 reverses glucocorticoid-dependent upregulation of HPV E6/E7, which corresponds to restoration of p53 expression, and restores radiosensitivity and apoptosis following gamma-irradiation. Therefore, it appears that along with radiation, RU486 may be a beneficial agent in the treatment of hormone-reactive cervical tumors.

The inflammatory reaction following 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine intoxication in mouse

In degenerative disorders of the CNS an immune system involvement in the pathological process is postulated. The MPTP model of Parkinson's disease seem to be a good model for studying an inflammation following toxic neurodegeneration. In this model, microglial and astroglial reactions were previously found around impaired neurons. In the present work we showed an immune reaction, including lymphocytic infiltration of CD4+ and CD8+ T cells in the substantia nigra and striatum and elevated MHC class I and II antigens expression on microglia. Many activated lymphocytes were present, showing increased LFA-1 and CD44 antigen expression. We found also that ICAM-1 expression increased on the endothelium and appeared on microglia in the injured regions. Treatment with dexamethasone inhibited T-cell infiltration and MHC class II expression, lessened the glial reaction, and also diminished neuronal impairment. These findings suggest that an immune mechanism may contribute to the neuronal damage following MPTP administration.

HIV-1 Vpr suppresses immune activation and apoptosis through regulation of nuclear factor kappa B

The HIV-1 accessory gene product Vpr can influence viral pathogenesis by affecting viral replication as well as host cell transcription and proliferation. We have investigated the effects of Vpr on host cell activation and confirm that it influences cellular proliferation. However, we have also found that Vpr modulates T-cell receptor (TCR)-triggered apoptosis in a manner similar to that of glucocorticoids. In the absence of TCR-mediated activation, Vpr induces apoptosis whereas in its presence, Vpr interrupts the expected induction of apoptosis. This regulation of apoptosis is linked to Vpr suppression of NF-kappa B activity via the induction of I kappa B, an inhibitor of NF-kappa B. Further, Vpr suppresses expression of IL-2, IL-10, IL-12, TNF alpha and IL-4, all of which are NF-kappa B-dependent. The effects of Vpr could be reversed by RU486. Our finding that Vpr can regulate NF-kappa B supports the hypothesis that some aspects of viral pathogenesis are the consequence of cell dysregulation by Vpr.

Chronic administration of dexamethasone results in Fc receptor up-regulation and inhibition of class I antigen expression on macrophages from MRL/lpr autoimmune mice

The MRL/lpr mouse develops, after approximately 8 weeks of age, a severe autoimmune syndrome with many features resembling human systemic lupus erythematosus, including autoantibodies against DNA and basement membranes resulting in immune complexes, vasculitis, and multiorgan disease. While this murine model of lupus has been used for the identification of therapeutics with potential efficacy in human autoimmune disease, the long-term impact of chronic immunosuppressive therapy on macrophage function in this paradigm is not understood. To this end, MRL/lpr mice were treated prophylactically with dexamethasone at 0.01, 0.1, and 1 mg/kg of body weight for 20 weeks or were allowed to develop autoimmune disease and, at 15 weeks of age, treated therapeutically with 1-mg/kg dexamethasone for 8 additional weeks. Analysis of surface antigens on resident peritoneal macrophages demonstrated a progressive loss in class I expression with a concomitant increase in Fc receptor expression. Neither phagocytosis nor CD11b expression was modulated with chronic steroid treatment. Furthermore, dexamethasone treatment was associated with a reduction in anti-DNA antibodies and total immunoglobulin G and yet an elevation in serum cholesterol due to an increase in high-density lipoproteins. Therefore, the MRL/lpr mouse serves not only as a small-animal model of autoimmune disease but also as one in which the negative and positive sequelae associated with chronic immunosuppression can be further understood.

Glucocorticosteroids as immunosuppressive agents

When administered at pharmacological dosages, glucocorticosteroid hormones alter leukocyte kinetics, phagocytic cell function, cell-mediated immunity, and, to a lesser extent, humoral immunity. These properties are used to advantage in the treatment of immunologically mediated disease. Corticosteroids are used to suppress pathological immune responses associated with autoimmunity, inhibit rejection of allogenic tissues after organ transplantation, and to diminish inflammation associated with a wide variety of hypersensitivity disorders. The mechanisms by which corticosteroids relieve these conditions are still not completely understood but have recently become more comprehensible. By understanding how corticosteroids exert their effects, we can make better clinical decisions in the management of immune-mediated disease.

Transcriptional regulation of the MHC class I HLA-A11 promoter by the zinc finger protein ZFX

Regulation of the human MHC class I HLA-A11 promoter is governed by a complex array of regulatory elements. One of these elements, shown here to be critical for the transcriptional activity of the promoter, was used to screen a lambda gt11 library and allowed the identification of a cDNA which coded for the zinc finger protein ZFX. ZFX was shown to bind the sequences AGGGCCCCA and AGGCCCCGA, located respectively at positions -271 to -263 and -242 to -234 of the HLA-A11 promoter, with similar affinities through its three C-terminal zinc fingers. ZFX575, a short isoform of ZFX, activates transcription from the HLA-All promoter in a Leydig cell line.

Immunosuppression by glucocorticoids: inhibition of NF-kappa B activity through induction of I kappa B synthesis

Glucocorticoids are among the most potent anti-inflammatory and immunosuppressive agents. They inhibit synthesis of almost all known cytokines and of several cell surface molecules required for immune function, but the mechanism underlying this activity has been unclear. Here it is shown that glucocorticoids are potent inhibitors of nuclear factor kappa B (NF-kappa B) activation in mice and cultured cells. This inhibition is mediated by induction of the I kappa B alpha inhibitory protein, which traps activated NF-kappa B in inactive cytoplasmic complexes. Because NF-kappa B activates many immunoregulatory genes in response to pro-inflammatory stimuli, the inhibition of its activity can be a major component of the anti-inflammatory activity of glucocorticoids.

Hormonal modulation of major histocompatibility complex class I gene expression involves an enhancer A-binding complex consisting of Fra-2 and the p50 subunit of NF-kappa B

Hydrocortisone decreases major histocompatibility complex (MHC) class I gene expression in rat thyroid cells and counteracts increases induced by interferons. Using FRTL-5 cells transfected with class I promoter-reporter gene chimeras, we show that hydrocortisone action is transcriptional and mediated by an element located between 180 and 170 base pairs upstream of the start of transcription. Gel shift assays reveal that hydrocortisone causes the decrease of a specific protein-DNA complex; this same complex, referred to as Mod-1, is increased by interferon. Oligonucleotide competition assays reveal that the Mod-1 complex is associated with enhancer A of the class I gene, -180 to -170 base pairs (5'-GGGGAGTCCCC-3'), immediately upstream of the interferon response element. Antibodies to fra-2, a fos family member, and to the p50, but not the p65, subunit of NF-kappa B supershift the Mod-1 complex. We suggest that hydrocortisone decreases MHC class I gene expression by reducing the formation of Mod-1, which contains both p50 and fra-2; interferon reverses the hydrocortisone effect and increases Mod-1 formation. These observations are relevant to the molecular basis of hydrocortisone therapy in autoimmune thyroid disease and to the actions of interferon to exacerbate or induce autoimmune disease.

Reversible repression of papillomavirus oncogene expression in cervical carcinoma cells: consequences for the phenotype and E6-p53 and E7-pRB interactions

The transforming genes E6 and E7 of high-risk human papillomaviruses are consistently expressed in papillomavirus-associated neoplasms of the anogenital tract. In papillomavirus type 18-associated SW 756 cervical carcinoma cells, transcription of the viral E6-E7 genes is blocked by dexamethasone. Herein we show that dexamethasone-mediated repression of the E6-E7 genes results in loss of the neoplastic phenotype of SW 756 cells. Withdrawal of dexamethasone restores E6-E7 expression and neoplastic growth. Moreover, reconstitution of E6-E7 gene expression by a dexamethasone-inducible expression vector renders the neoplastic phenotype resistant to dexamethasone. These results clearly indicate that the continuous expression of the viral E6-E7 oncogenes is required to maintain the neoplastic growth properties of SW 756 cervical cancer cells. The viral E6 protein destabilizes the p53 tumor suppressor gene product in vitro. Since low levels of p53 have been observed in papillomavirus-transformed keratinocyte cell lines, it was speculated that degradation of p53 by E6 contributes to papillomavirus-associated growth deregulation. Consistent with this hypothesis, we detected a significant increase in p53 levels upon dexamethasone-induced repression of papillomavirus E6-E7 oncogene expression. No p53 increase was observed in dexamethasone-treated cells in which the viral oncogene expression was restored. The viral E7 protein has been shown to complex with the retinoblastoma tumor suppressor gene product (pRB). In some cells, this interaction has been shown shown to release the transcription factor E2F from its complex with pRB, and it has been hypothesized that E7-induced, increased levels of free E2F contribute to the transforming potential of the viral oncogenes. In gel shift experiments, we detected relatively stable complexes of pRB and E2F in all SW 756-derived cells, independent of the level of E7 expression. This suggests that E7-mediated release of E2F from its complex with pRB might not be required to maintain the neoplastic phenotype of human papillomavirus-associated cancer cells, although a possibly relevant partial E7-mediated release of E2F from pRB cannot be excluded.

Effects of dexamethasone on microglial activation in vivo: selective downregulation of major histocompatibility complex class II expression in regenerating facial nucleus

Following axotomy of the facial nerve microglial cells in the facial nucleus become activated, proliferate, and newly express class I and class II major histocompatibility complex (MHC) antigens. Dexamethasone treatment, starting 2 days prior to axotomy at 1 mg/kg/day, selectively inhibited axotomy-induced MHC class II expression on microglial and perivascular cells. In contrast, MHC class I expression was not significantly affected, nor was the expression of other microglial activation markers and the light microscopic morphology of activated microglia. A recently suggested inducer of MHC expression in rat nervous tissue, neuronal gamma interferon-like immunoreactive material, was also unaffected, as was glial fibrillary acidic protein immunoreactivity as a marker for concomitant astroglial activation. The differential effects of the drug suggest the presence of distinct regulatory pathways for different aspects of microglial activation. Inhibition of class II expression on activated microglia might be one mechanism how glucocorticoids act in the suppression of neuroinflammatory disease.

Influence of chromosomal integration on glucocorticoid-regulated transcription of growth-stimulating papillomavirus genes E6 and E7 in cervical carcinoma cells

In most cervical carcinoma cells the E6 and E7 genes of specific human papillomaviruses are transcribed from viral sequences integrated into host cell chromosomes. Glucocorticoids activate the promoter elements of various human papillomaviruses in transient-expression assays. We have analyzed the effect of dexamethasone on the transcription rate of human papillomavirus 18 E6 and E7 genes integrated at different chromosomal sites in four cervical cancer cell lines. Dexamethasone led to an increase in the transcription rate of the integrated E6-E7 sequences in C4-1 and C4-2 cells but led to a decrease in SW 756 cells and did not affect the transcription rate in HeLa cells. However, when the viral promoter elements derived from HeLa or SW 756 cells, in which dexamethasone does not activate transcription of the integrated E6-E7 sequences, were tested in transient-expression assays within the same cell lines, dexamethasone consistently activated the viral promoter. It thus appears that dominant regulatory mechanisms presumably depending on the chromosomal integration site are able to override the response of the viral promoter to steroid hormones. The growth rate of all dexamethasone-treated cell lines correlated consistently with the expression of the papillomavirus E6 and E7 genes, supporting their role in the maintenance of the proliferative phenotype of cervical carcinoma cells. Since human papillomaviruses are integrated into the host cell genome at variable, presumably randomly selected chromosomal loci, regulatory mechanisms that influence viral gene expression, and hence cell growth, may differ among cancers of independent clonal origin.