Immunohistological observations in rat kidney allografts after local steroid administration

KCa1.1 and Kv1.3 channels regulate the interactions between fibroblast-like synoviocytes and T lymphocytes during rheumatoid arthritis

BACKGROUND

Fibroblast-like synoviocytes (FLS) and CCR7- effector memory T (TEM) cells are two of the major cell types implicated in the progression of rheumatoid arthritis (RA). In particular, FLS become highly invasive, whereas TEM cells proliferate and secrete proinflammatory cytokines, during RA. FLS and T cells may also interact and influence each other's phenotypes. Inhibition of the pathogenic phenotypes of both FLS and TEM cells can be accomplished by selectively blocking the predominant potassium channels that they upregulate during RA: KCa1.1 (BK, Slo1, MaxiK, KCNMA1) upregulated by FLS and Kv1.3 (KCNA3) upregulated by activated TEM cells. In this study, we investigated the roles of KCa1.1 and Kv1.3 in regulating the interactions between FLS and TEM cells and determined if combination therapies of KCa1.1- and Kv1.3-selective blockers are more efficacious than monotherapies in ameliorating disease in rat models of RA.

METHODS

We used in vitro functional assays to assess the effects of selective KCa1.1 and Kv1.3 channel inhibitors on the interactions of FLS isolated from rats with collagen-induced arthritis (CIA) with syngeneic TEM cells. We also used flow cytometric analyses to determine the effects of KCa1.1 blockers on the expression of proteins used for antigen presentation on CIA-FLS. Finally, we used the CIA and pristane-induced arthritis models to determine the efficacy of combinatorial therapies of KCa1.1 and Kv1.3 blockers in reducing disease severity compared with monotherapies.

RESULTS

We show that the interactions of FLS from rats with CIA and of rat TEM cells are regulated by KCa1.1 and Kv1.3. Inhibiting KCa1.1 on FLS reduces the ability of FLS to stimulate TEM cell proliferation and migration, and inhibiting Kv1.3 on TEM cells reduces TEM cells' ability to enhance FLS expression of KCa1.1 and major histocompatibility complex class II protein, as well as stimulates their invasion. Furthermore, we show that combination therapies of selective KCa1.1 and Kv1.3 blockers are more efficacious than monotherapies at reducing signs of disease in two rat models of RA.

CONCLUSIONS

Our results demonstrate the importance of KCa1.1 and Kv1.3 in regulating FLS and TEM cells during RA, as well as the value of combined therapies targeting both of these cell types to treat RA.

Renal transplantation: basic concepts and evolution of therapy

Within the last 5 years, dramatic changes in the area of renal transplantation have occurred. There have been shifts in the dominant types of rejection, and in the types and utilization of immunosuppressants. Hyperacute rejection is now rarely seen, and acute cellular rejection within the first 6 to 12 months has been reduced to about 10%. However, humoral/antibody-mediated rejection has become a more prevalent problem. In the area of immunosuppressants, the ability to reduce acute cellular rejection to about 10% has been achieved through more judicious use of calcineurin inhibitors (cyclosporine and tacrolimus), increased use of mycophenolate mofetil, and the recent introduction of sirolimus (rapamycin). The polyclonal antibody (antithymocyte globulin), as well as monoclonal antibodies directed against the alpha chain of CD25 (daclizumab and basilixamab), have added substantially to the improved success of renal allografts. Because of numerous serious toxicities from glucocorticoids and calcineurin inhibitors, particularly cyclosporine, new studies are utilizing calcineurin-free and/or glucocorticoid avoidance or rapid elimination protocols often in combination with a monoclonal antibody and sirolimus. New immunosuppressants such as FTY720 and Campath-1 are also under study. In addition to its use in treating patients with low-level donor-specific antibody before transplantation in order to avoid hyperacute rejection, apheresis is utilized in various combination protocols after transplantation in the management of humoral/antibody-mediated rejection, in the treatment of hemolytic uremia syndrome that sometimes occurs with calcineurin inhibitors and sirolimus, as well as in the treatment of focal segmental glomerulosclerosis that has a major risk of recurrence in renal transplants.

11beta-hydroxysteroid dehydrogenase types 1 and 2: an important pharmacokinetic determinant for the activity of synthetic mineralo- and glucocorticoids

The 11beta-hydroxysteroid dehydrogenase (11beta-HSD) system plays a pivotal role in glucocorticoid (GC) and mineralocorticoid (MC) action. Although 11beta-HSD activities are important determinants for the efficacy of synthetic MCs and GCs, corresponding pharmacokinetic data are scanty. Therefore, we characterized 11beta-HSD profiles for a wide range of steroids often used in clinical practice. 11beta-HSD1 and 11beta-HSD2 were selectively examined in 1) human liver and kidney cortex microsomes, and 2) Chinese hamster ovarian cells stably transfected with 11beta-HSD1 or 11beta-HSD2 expression vectors. Both systems produced concordant evidence for the following conclusions. Oxidation of steroids by 11beta-HSD2 is diminished if they are fluorinated in position 6alpha or 9alpha (e.g. in dexamethasone) or methylated at 2alpha or 6alpha (in methylprednisolone) or 16alpha or 16beta, by a methylene group at 16 (in prednylidene), methyloxazoline at 16, 17 (in deflazacort), or a 2-chlor configuration. Whereas the methyl groups also decrease reductase activity (steric effects), fluorination increases reductase activity (negative inductive effect), leading to a shift to reductase activity. This may explain the strong MC activity of 9alpha-fluorocortisol and should be considered in GC therapy directed to 11beta-HSD2-expressing tissues (kidney, colon, and placentofetal unit). 11beta-HSD2 oxidation of prednisolone is more effective than that of cortisol, explaining the reduced MC activity of prednisolone compared with cortisol. Reduction by 11beta-HSD1 is diminished by 16alpha-methyl, 16beta-methyl, 2alpha-methyl, and 2-chlor substitution, whereas it is increased by the Delta(1)-dehydro configuration in prednisone, resulting in higher hepatic first pass activation of prednisone compared with cortisone. To characterize a GC or a MC as substrate for the different 11betaHSDs may be essential for an optimized steroid therapy.

Metabolism of synthetic corticosteroids by 11 beta-hydroxysteroid-dehydrogenases in man

The presence of an 11 beta-hydroxyl group is essential for the anti-inflammatory and immunosuppressive effects of glucocorticoids. Interconversion of the 11 beta-hydroxyl into the corresponding 11 beta-keto group and vice versa by 11 beta-hydroxysteroid-dehydrogenase (11 beta-HSD) may thus play a pivotal role in the efficacy of these steroids. Therefore, we have compared the metabolism of the endogenous glucocorticoid cortisol (F) with that of synthetic 9 alpha-fluorinated steroids by 11 beta-HSDs in humans in vivo and in vitro. Whereas 30% of the free steroids in urine after oral administration of 5 mg of F is F itself and 70% the inactive keto-product cortisone (E), the urinary excretion of an identical dose of oral 9 alpha-fluorocortisol (9 alpha FF) is 90% 9 alpha FF and 10% inactive 9 alpha-fluorocortisone (9 alpha FE). Kidney slices similarly convert F much faster to E than 9 alpha FF to 9 alpha FE; conversely, renal 11 beta-reduction of 9 alpha FE to 9 alpha FF is much more effective than that of E to F. Kinetic analyses in human kidney cortex microsomes prove that the preference of fluorinated steroids for reduction in human kidney slices is catalyzed by 11 beta-HSD type II: the NADH-dependent conversion of 11-dehydro-dexamethasone (DH-D), another fluorinated steroid, to dexamethasone (D) is very effective (high affinity, high Vmax), whereas reduction of E to F is very slow. In human liver microsomes (11 beta-HSD type I), nonfluorinated (E) and fluorinated 11-dehydrosteroids (DH-D) are both reduced to their corresponding active 11-hydroxyderivatives but with a Michaelis-Menten constant about 20-fold higher than for kidney microsomes (11 beta-HSD-II). Our results suggest that the decreased renal 11 beta-oxidation of 9 alpha-fluorinated steroids may offer pharmacokinetic advantages for renal immunosuppression. Furthermore, administration of fluorinated 11-dehydrosteroids is a new and exciting idea in glucocorticoid therapy in that small amounts of oral DH-D may pass the liver largely unmetabolized (11 beta-HSD-I has low affinity for such steroids) and may then be activated to D by high-affinity 11 beta-HSD-II, thus allowing selective immunosuppression in organs expressing 11 beta-HSD-II (kidney and colon).

Pharmacology of 11 beta-hydroxysteroid dehydrogenase

In clinical practice synthetic glucocorticoids are mainly used as therapy for inflammatory disorders and in suppressing immunological responses to transplanted allografts. The presence of an 11 beta-hydroxyl (11 beta-OH) group is mandatory for the antiinflammatory effects of glucocorticosteroids. The interconversion of the 11 beta-OH into the corresponding 11-keto group and vice versa by 11 beta-OH-steroid dehydrogenase might thus play a pivotal role for the efficacy of these steroids. Estimates of the apparent capacity to interconvert these steroids have been derived from plasma and tissue concentration measurements. Such estimates reveal that the interconversion process is concentration dependent and tissue specific. It remains to be established whether modulating that process might allow the immunosuppressive effect to be targeted within certain organs, thereby increasing the ratio between therapeutic and side effects of glucocorticoid administration.

Local immunosuppressive therapy with monoclonal anti-T cell antibody on renal allograft survival in the rat

Considerable interest in the experimental and clinical use of MoAbs as potential therapeutic agents in allograft rejection has been generated by the recent reports of striking prolongation. In this study we investigated the efficacy of the local administration of MoAb OX-19 which is directed to the rat CD5 equivalent, through the renal artery using a rat kidney transplant model, in order to develop a potent method for modifying rejection while minimizing the systemic side effects. Untreated Lewis rats (LEW, RT-1(1)) rejected Brown-Norway rat (BN, RT-1n) kidney at 7.8 +/- 0.2 days (n = 10). Mean survival time (MST) of recipients treated with OX-19 (75 micrograms/kg per day) as single bolus injections via the dorsal penile vein for 7 days was 7.0 +/- 0.2 days (n = 5, NS). LEW hosts receiving OX-19 (75 micrograms/kg per day) continuously for 7 days via a femoral vein by using an osmotic minipump (IV-treated group) showed a slight prolongation of graft survival (MST = 8.8 +/- 0.9 days, n = 5), but this was not statistically significant. On the other hand, local continuous intrarenal arterial infusion of OX-19 (75 micrograms/kg per day) for 7 days (RA-treated group) significantly prolonged the graft survivals (MST = 16.8 +/- 1.3 days, n = 8, P < 0.01). Histological examination of MoAb-treated LEW hosts on day 6 post-grafting revealed that kidney grafts from RA-treated hosts showed a slight tubular necrosis, but reduced mononuclear cell infiltration, whereas kidney grafts from IV-treated hosts displayed a severe mononuclear cell infiltration around the artery with interstitial oedema. Moreover, the local intrarenal administration of OX-19, even when the dose is delayed until day 4 after renal grafting, has a therapeutic effect for on-going acute allograft rejection (MST = 11.4 +/- 0.8 days, n = 8) compared with administration of OX-19 intravenously from day 4 after grafting (MST = 7.6 +/- 0.2 days, n = 5, P < 0.01) or with no treatment (MST = 7.8 +/- 0.2 days, P < 0.01). The phenotype of graft infiltrating cells (GIC) was investigated on day 6 post-grafting. There was a significantly lower percentage of cells positive for OX-19, OX-8, OX-26 (transferrin receptor), and OX-39 (IL-2 receptor) in the RA group than in the IV group.(ABSTRACT TRUNCATED AT 400 WORDS)

Repression of major histocompatibility complex IA expression by glucocorticoids: the glucocorticoid receptor inhibits the DNA binding of the X box DNA binding protein

Glucocorticoids are effective repressors of major histocompatibility complex (MHC) class II gene expression. The repression occurs in B cells, which constitutively express MHC class II, as well as in macrophages, which only express MHC class II after the cells are treated with interferon gamma. For the MHC class II gene IA beta, this negative regulation has been linked to the X box DNA sequence, located with the IA beta promoter. The addition of the glucocorticoid receptor was shown to inhibit the DNA binding of the X box DNA binding protein to the X box. The DNA binding of two other DNA binding proteins that recognize elements within this promoter was unaffected by the addition of glucocorticoid receptor. It is likely that the repression of IA beta gene expression by glucocorticoids occurs because the X box DNA binding protein is prevented from binding to the DNA and activating transcription.

Spontaneous blastogenesis profiles and IL-2 receptor expression on kidney allograft

To examine immune activation rate of interstitial and glomeruli infiltrating MNC in different conditions of human renal allograft function deterioration, 33 renal transplant biopsies were performed 1-30 months after transplantations. Forty-one patients observed were on immunosuppressives: Pr, Aza, CsA following renal transplantation from a living-related donor parent. The patients were divided according to their histologic diagnosis into the following groups: 1, 15 pts in acute rejection attack (AR); 2, 10 pts with cyclosporine nephrotoxicity (CsN); 3, 10 pts with chronic vascular rejecting kidney (ChR). A conventional histologic investigation and immunohistochemical analyses of CD3 and CD25 molecules were performed in groups 1-3. Spontaneous blastogenesis (SB) of peripheral lymphocytes was simultaneously determined and compared with the controls (C)-30 healthy people, and with patients with stable renal allograft function (S)-8 pts. The highest IL-2R expression on diffuse or focal dense MNC infiltrates in interstitium was observed during AR, without IL-2R+ MNC in glomeruli. Low to moderate focal interstitial infiltrates in damaged areas of renal parenchyma due to CsN, were IL-2R negative. In ChR, moderate IL-2R expression was observed on interstitial spare mild or focal dense MNC infiltrates with IL-2R expression present on glomeruli infiltrating MNC. Significant increases of SB values were recorded during the first week after transplantation and AR in comparison to C. The highest SB values were in ChR group. Values of SB in CsN and S were on the C and before transplantation levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytomegalovirus-specific cell-mediated immune responses in heart and heart-lung transplant recipients are not predictive for the occurrence of symptomatic CMV disease or tissue rejection

To study the predictive value of interferon-gamma (IFN-gamma) production in vitro for the occurrence of symptomatic CMV disease, 17 healthy adult volunteers were tested and 37 heart or heart-lung transplant recipients (CTRs) were studied at various time intervals after transplantation (Tx) for cell-mediated immune (CMI) responses to cytomegalovirus (CMV). At all intervals post Tx, in vitro IFN-gamma production in CTRs was significantly lower than in control subjects. The occurrence of CMV infection was associated with a trend toward inhibited CMI responses prior to the diagnosis, in comparison with CMI responses measured more than 4 weeks prior to or after the diagnosis of CMV infection. The occurrence of acute tissue rejection was associated with a trend toward enhanced CMV responses prior to the diagnosis, on the other hand. In the early post Tx period, the administration of antithymocyte globulin (ATG) or OKT3 monoclonal antibody and peak dosages of azathioprine were associated with significantly inhibited in vitro IFN-gamma production. Despite the demonstrated trends in vitro, IFN-gamma production does not appear to be uniformly predictive for the occurrence of symptomatic CMV disease or of acute tissue rejection in CTRs.

The influence of dose interval on the immunosuppressive potency of methylprednisolone: an experimental organ transplant study in isogenous rats

Groups of isogenous Brown-Norway rats received heterotopic heart transplants from (Brown-Norway/Wistar Furth) x F1 hybrid rats. Methylprednisolone was administered IV in a daily dose of 5-40 mg/kg, using a dose interval of 24, 12, or 0 h (continuous infusion). Continuous infusion proved to be superior when small daily doses were used and then caused a more than threefold increase in graft survival. High daily doses created a substantial mortality with all dose intervals. Moreover, the equipment used for continuous drug administrations was unreliable beyond 4 weeks of infusion.

Local administration of cyclosporin allows reduction of the dose prolonging survival of heart tissue allografts

In the H-2-incompatible donor-recipient combination (BALB/c----CBA/H) local administration of cyclosporin allows a 4-fold reduction in a single dose prolonging survival of heart tissue allografts. These results suggest that local administration of cyclosporin may be useful for certain grafts.

Inhibitory effect of corticosteroids on the secretion of tumour necrosis factor (TNF) by monocytes is dependent on the stimulus inducing TNF synthesis

The cytokine tumour necrosis factor (TNF) is believed to be involved in the pathophysiology of several human disease states, both septic and non-septic. Different pathways of induction are involved in the generation ofTNF in these disease states. We therefore used four different stimulatory agents, lipopolysaccharide, phorbol myristate acetate, silica quartz, and anti-human IgG antibody to study the influence of the corticosteroids prednisolone and budesonide on the secretion of TNF by human monocytes. Both prednisolone and budesonide inhibited TNF secretion induced by these four stimulating agents in a different degree. Inhibition was strong when TNF secretion was induced by lipopolysaccharide or anti-human IgG antibody. A weaker inhibitory effect was observed when TNF secretion was induced by silica quartz. Only minimal inhibition of phorbol myristate acetate induced TNF secretion was observed. Furthermore, it is shown that inhibition is dependent on the dose of corticosteroid, but not or only minimally on the dose of stimulating agent, indicating that inhibition cannot be overcome by increasing the cell-activating stimulus. Finally, optimal inhibition of TNF secretion by corticosteroids is shown to be dependent on the presence of corticosteroids during the phase of cell stimulation.

The role of adaptation in allograft acceptance

The experimental and clinical data suggest that both a decrease of antigen expression and decreased perfusion can protect against immunologically mediated destructive processes. In the adaptation of skin grafts, these factors could be interrelated. Inadequate perfusion might lead to a decreased delivery of substances that stimulate MHC antigen expression. This course of events also could explain the protection in the patient presented here. Immune deposits were completely absent in the protected segment of the kidney, although immune deposits were abundantly present in the remaining part of the kidney, and circulating anti-donor antibodies were demonstrable after the transplanted kidney had been removed. The limited availability of frozen biopsy material has prevented us from comparing the expression of MHC antigens in both kidney segments using monoclonal antibodies. But such studies might be done in experimental kidney transplants with an artificially induced stenosis of the renal artery. Except when an arterial stenosis is present, we have little reason to assume that perfusion gradually decreases in longstanding kidney grafts as it does in skin grafts. Therefore, if adaptation plays a role in the gradual decrease of the sensitivity to rejection in longstanding kidney grafts, this phenomenon must be attributed to a decreased expression of target antigens as a consequence of factors other than decreased perfusion. The most likely candidates are the immunosuppressive drugs, such as cyclosporine and prednisone, which decrease MHC antigen expression. Let me conclude by returning to my main theme of graft adaptation. It seems appropriate to end this review with a quotation from one of Woodruff's original publications on this subject: "If the phenomenon [adaptation] applies to homotransplants of normal tissues to sites other than the eye, I think it almost certain that the clinical homograft problem will be solved; if it does not, the problem may prove insoluble" [9]. Although our insight into the rejection process has increased considerably, we still do not know which factors are most important in determining the long-term survival of primarily vascularized grafts.