Cyclosporin A for the treatment of graft-versus-host disease in man

Calcineurin inhibitor (CNI)-associated skin cancers: New insights on exploring mechanisms by which CNIs downregulate DNA repair machinery

The use of the calcineurin inhibitors (CNI) cyclosporine (CsA) and tacrolimus remains a cornerstone in post-transplantation immunosuppression. Although these immunosuppressive agents have revolutionized the field of transplantation medicine, its increased skin cancer risk poses a major concern. A key contributor to this phenomenon is a reduced capacity to repair DNA damage caused by exposure to ultraviolet (UV) wavelengths of sunlight. CNIs decrease DNA repair by mechanisms that remain to be fully explored. Though CsA is known to decrease the abundance of key DNA repair enzymes, less is known about how tacrolimus yields this effect. CNIs hold the capacity to inhibit both of the main catalytic calcineurin isoforms (CnAα and CnAβ). However, it is unknown which isoform regulates UV-induced DNA repair, which is the focus of this review. It is with hope that this insight spurs investigative efforts that conclusively addresses these gaps in knowledge. Additionally, this research also raises the possibility that newer CNIs can be developed that effectively blunt the immune response while mitigating the incidence of skin cancers with immunosuppression.

Human CD83-targeted chimeric antigen receptor T cells prevent and treat graft-versus-host disease

Graft-versus-host disease (GVHD) remains an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). For decades, GVHD prophylaxis has included calcineurin inhibitors, despite their incomplete efficacy and impairment of graft-versus-leukemia (GVL). Distinct from pharmacologic immune suppression, we have developed what we believe is a novel, human CD83-targeted chimeric antigen receptor (CAR) T cell for GVHD prevention. CD83 is expressed on allo-activated conventional CD4+ T cells (Tconvs) and proinflammatory dendritic cells (DCs), which are both implicated in GVHD pathogenesis. Human CD83 CAR T cells eradicate pathogenic CD83+ target cells, substantially increase the ratio of regulatory T cells (Tregs) to allo-activated Tconvs, and provide durable prevention of xenogeneic GVHD. CD83 CAR T cells are also capable of treating xenogeneic GVHD. We show that human acute myeloid leukemia (AML) expresses CD83 and that myeloid leukemia cell lines are readily killed by CD83 CAR T cells. Human CD83 CAR T cells are a promising cell-based approach to preventing 2 critical complications of allo-HCT - GVHD and relapse. Thus, the use of human CD83 CAR T cells for GVHD prevention and treatment, as well as for targeting CD83+ AML, warrants clinical investigation.

Modulation of innate immunity by cyclosporine A

Cyclosporine A has long been known to suppress T cell responses by inhibiting the production of IL-2, which drives T cell proliferation, enabling its use as a therapeutic for transplantation or autoimmunity. However, cyclosporine A also impacts on innate immune cells including dendritic cells, macrophages and neutrophils. In dendritic cells, which are essential for T cell priming, cyclosporine A can modulate both expression of surface molecules that engage with T cells and cytokine secretion, leading to altered induction of T cell responses. In macrophages and neutrophils, which play key antimicrobial roles, cyclosporine A reduces the production of cytokines that can play protective roles against pathogens. Some of these molecules, if produced in the context of chronic disease, can also contribute to pathology. There have been a number of elegant recent studies addressing the mechanisms by which cyclosporine A can modulate innate immunity. In particular, cyclosporine A inhibits the release of mitochondrial factors that stimulate the production of type 1 interferons by innate immune cells. This review addresses the emerging literature on modulation of innate immune responses by cyclosporine A, its resultant impact on adaptive immune responses and how this offers potential for new therapeutic applications.

Calcineurin inhibitors: 40 years later, can't live without

Calcineurin inhibitors (CNIs) revolutionized the field of organ transplantation and remain the standard of care 40 years after the discovery of cyclosporine. The early impressive results of cyclosporine in kidney transplant recipients led to its subsequent use in other organ transplant recipients and for treatment of a variety of autoimmune diseases as well. In this review, we examine the discovery of CNIs, their mechanism of action, preclinical and clinical studies with CNIs, and the usage of CNIs in nontransplant recipients. We review the mechanisms of renal toxicity associated with CNIs and the recent efforts to avoid or reduce usage of these drugs. Although minimization strategies are possible, safe, and of potential long-term benefit, complete avoidance of CNIs has proven to be more challenging than initially thought.

Pharmacologic prophylaxis regimens for acute graft-versus-host disease: past, present and future

Abstract Acute graft-versus-host disease (GVHD) has compromised and continues to compromise the benefits associated with allogeneic hematopoietic cell transplant to cure malignant and non-malignant diseases. Pharmacologic interventions to prevent GVHD have emerged as a major objective of research in the immunology and transplant fields. A better understanding of the pathobiology behind the GVHD process has led the way to novel approaches and medications. Here we review the present arsenal of medications used to prevent GVHD, focusing on past experience and the current evidence, and discuss future potential targets.

Should methotrexate plus calcineurin inhibitors be considered standard of care for prophylaxis of acute graft-versus-host disease?

In a rapidly developing field, one can always anticipate that different interpretations of similar data will coexist. Stem cell transplanters can be a contentious lot, especially in the absence of controlled randomized trials. Thus, although improvements in the basic understanding of acute graft-versus-host disease (aGVHD) has led to many testable hypotheses in the management of GVHD, there remains little consensus regarding the most effective and least toxic approach to GVHD prevention. In the 1980s, the comparison would have been between cyclosporine-based regimens and ex vivo T cell depletion (TCD). Although ex vivo TCD is still used in some settings, pharmacologic-based therapy and in vivo TCD with serotherapy now predominate. This review is meant to highlight the advantages and disadvantages of the "standard of care" and assess the prospects for future regimens that may be more effective.

Cyclosporine A: A Review of Current Oral and Intravenous Delivery Systems

As early as 1978, the immunosuppressive effect of cyclosporine A (CsA), a metabolite of the fungus Tolypocladium inflatum (Borel, 1989), was reported to be effective in inhibiting organ rejection in patients receiving kidney transplants from mismatched cadaver donors (Calne et al., 1978) and in the treatment of graft-versus-host disease in patients with acute leukemia following bone marrow transplants (Powles et al., 1978). Today, CsA is still indicated to prevent rejection following solid organ transplantations, prevent and treat graft-vs-host disease following bone marrow transplants, and has also been used in the treatment of autoimmune disease such as psoriasis, rheumatoid arthritis, and nephrotic syndrome (Canadian Pharmacists Association, 2006). The effectiveness of CsA is derived from its ability to specifically and reversibly inhibit immunocompetent lymphocytes in the G(0) and G(1) phase of the cell cycle. The T-helper cells are the main target, but suppression of the T-suppressor cells also occurs. The production and release of lymphokines, including interleukin-2 are also inhibited (Novartis, 2005a). CsA can be administered intravenously as well as orally in the form of a solution or a soft gelatin capsule. The following review will focus on the evolution of the emulsion-based oral formulations from the first generation as Sandimmune to the second generation Neoral, both products of Novartis Pharmaceutical, as well as on the Sandimmune commercial intravenous formulation. The potential of alternative delivery systems, including micelles, micro- and nanoparticles, and liposomes, will also be discussed.

Gallstone formation after pancreas and/or kidney transplantation: an analysis of risk factors

Pancreas and kidney transplantation (SPK) is the treatment of choice for patients with type 1 diabetes mellitus and end-stage renal failure. Gallstones are common after SPK transplantation but little is known about the true incidence and etiology of gallstones in this group. We therefore evaluated the incidence of gallstones and the presence of transplant-related risk factors in patients after SPK and kidney transplantation alone (KTA). Data were evaluated of 56 consecutive patients who underwent SPK transplantation and compared the results with those of 91 consecutive nondiabetic patients who underwent KTA transplantation at the Leiden University Medical Center between 1987 and 1994. Of the 58 evaluable KTA patients, 20.7% developed gallstones during 7.7 yr of follow-up and in the SPK group 43.9% of the 41 evaluable patients developed gallstones during 7.1 yr of follow-up. Postoperative weight loss and cyclosporin A-related hepatotoxicity correlated with gallstone formation both in SPK and KTA patients. In addition, the duration of postoperative fasting and autonomic neuropathy correlated with gallstones in SPK patients. It is concluded that both in patients after SPK transplantation and in patients after KTA transplantation, the risk to develop gallstones is significantly increased. Physicians should be aware of the high incidence of gallstones in SPK recipients.

Use of cyclosporine in hematopoietic cell transplantation

Early attempts to perform successful allogeneic hematopoietic stem cell transplants were plagued by graft rejection and graft-versus-host disease, leading many investigators to lose hope that bone marrow transplantation could ever become a useful therapeutic approach in clinical medicine. Although many subsequent discoveries contributed to the successful transformation of this area of research into lifesaving therapy, there can be no doubt that the discovery of cyclosporine (CsA) constituted one of the major advances. Even today, more than 25 years after the first description of its use in humans, CsA remains one of the cornerstones of therapy for the majority of patients undergoing allogeneic hematopoietic cell transplantation (HCT). In this review we will recount the events that have established CsA as a foundation of HCT.

Pharmacology of calcineurin antagonists

Cyclosporine and tacrolimus share the same pharmacodynamic property of activated T-cell suppression via inhibition of calcineurin. The introduction of these drugs to the immunosuppressive repertoire of transplant management has greatly improved the outcomes in organ transplantation and constitutes arguably one of the major breakthroughs in modern medicine. To this date, calcineurin inhibitors are the mainstay of prevention of allograft rejection. The experience gained from the laboratory and clinical use of cyclosporine and tacrolimus has greatly advanced our knowledge about the nature of many aspects of immune response. However, the clinical practice still struggles with the shortcomings of these drugs: the significant inter- and intraindividual variability of their pharmacokinetics, the unpredictability of their pharmacodynamic effects, as well as complexity of interactions with other agents in transplant recipients. This article briefly reviews the pharmacological aspects of calcineurin antagonists as they relate to the mode of action and pharmacokinetics as well as drug interactions and monitoring.

Cyclosporine-associated hyperkalemia: report of four allogeneic blood stem-cell transplant cases

BACKGROUND

Nephrotoxicity is a well-known effect of cyclosporine (CsA) that causes a reduction in glomerular filtration rate through vasoconstriction of the afferent glomerular arterioles and may result in acute renal failure. Isolated CsA-induced hyperkalemia occurring through different mechanisms is also common. However, there are only a few "case reports" addressing this phenomenon in allogeneic bone marrow transplantation patients. In this report, we propose mechanisms and methods of managing CsA-associated hyperkalemia in allogeneic transplantation.

METHODS

We report on four allogeneic blood stem- cell transplant cases and a review of the literature.

RESULTS

Four adult leukemia patients underwent allogeneic peripheral blood stem cell transplantation and received CsA as a part of their graft-versus-host disease prophylaxis. The patients developed hyperkalemia, despite adequate kidney function. CsA seemed to be the only pharmaceutical agent to which this electrolyte abnormality could be attributed. Renal tubule dysfunction and secondary hypoaldosteronism seemed to be the reasons for CsA-associated hyperkalemia.

CONCLUSION

This report of four cases demonstrates that CsA should be considered among the possible causes of hyperkalemia in bone marrow transplantation. There may be a need for urgent intervention depending on the severity of hyperkalemia. Monitoring of blood CsA level and dose adjustment are important for the prevention of this complication.

Non-ribosomal peptide synthetases as technological platforms for the synthesis of highly modified peptide bioeffectors – Cyclosporin synthetase as a complex example

Many microbial peptide secondary metabolites possess important medicinal properties, of which the immunosuppressant cyclosporin A is an example. The enormous structural and functional diversity of these low-molecular weight peptides is attributable to their mode of biosynthesis. Peptide secondary metabolites are assembled non-ribosomally by multi-functional enzymes, termed non-ribosomal peptide synthetases. These systems consist of a multi-modular arrangement of the functional domains responsible for the catalysis of the partial reactions of peptide assembly. The extensive homology shared among NRPS systems allows for the generalisation of the knowledge garnered from studies of systems of diverse origins. In this review we shall focus the contemporary knowledge of non-ribosomal peptide biosynthesis on the structure and function of the cyclosporin biosynthetic system, with some emphasis on the re-direction of the biosynthetic potential of this system by combinatorial approaches.

Development of allogeneic hematopoietic stem cell transplantation (HSCT)

The field of BMT has entered a new phase based on insights into basic molecular and cellular biology. The mechanism of cure mediated by allogeneic HSCT is now believed to be at least partially mediated by cellular attack against tumor-associated antigens. Better understanding of these cellular targets and the means of targeting them specifically will allow a more precise application of cellular therapy than is currently possible. This in turn may make it possible to design therapies that are increasingly selective without the collateral toxicities of GVHD, infection, and direct organ damage that currently are the limiting features of allogeneic HSCT as practiced until recently. However, it remains a challenge to demonstrate that disease-control using reduced intensity preparative regimens is at least comparable to that achieved by traditional myeloablative HSCT. This will require carefully controlled studies in each the major diseases that have shown sensitivity to the immune-mediated effects of HSCT. The chapters below will highlight progress towards the goals of elucidating the role of NST.

Historic landmarks in clinical transplantation: conclusions from the consensus conference at the University of California, Los Angeles

The transplantation of organs, cells, and tissues has burgeoned during the last quarter century, with the development of multiple new specialty fields. However, the basic principles that made this possible were established over a three-decade period, beginning during World War II and ending in 1974. At the historical consensus conference held at UCLA in March 1999, 11 early workers in the basic science or clinical practice of transplantation (or both) reached agreement on the most significant contributions of this era that ultimately made transplantation the robust clinical discipline it is today. These discoveries and achievements are summarized here in six tables and annotated with references.

Long-term outcome of adult acute leukemia patients who are alive and well two years after allogeneic bone marrow transplantation from an HLA-identical sibling

We studied the long-term outcome of 136 adults with acute leukemia (age 15-48 years at transplant, median 28; 112 myeloid, 22 lymphoblastic, 2 undifferentiated) who were alive in continuous remission two years after allografting from HLA-identical sibling donors. Six relapsed 25-46 months (median 30) after BMT. Fourteen (10%) died of non-relapse causes (12 transplant-related and 2 unrelated) 24-140 months (median 73) after BMT; mainly due to complications of chronic GVHD (8 infections, 3 secondary malignancies). One hundred and seventeen (86%) patients are alive in remission 25-226 months (median 103) after BMT; 116 (85%) in continuous remission. Eight survivors have symptomatic chronic GVHD requiring therapy (Karnofsky scores 60-90%, median 80%). The majority of those without chronic GVHD have Karnofsky scores of 100%. The 10-year probabilities of survival, toxic death, and relapse (from the 2-year mark) are 81%, 13%, and 5%. Twenty-two (19%) survivors had creatinine levels of > 110 mumol/L (one more than double), and 11 (9%) had bilirubin levels of > 17 mmol/L (one more than double) at the last follow-up. The absence of chronic GVHD at the 2-year mark (RR 3.5, P = .004), and female sex (RR 2.9, P = .04) influenced overall survival favorably, and the absence of chronic GVHD at the 2-year mark (RR 8.1, P = .001) influenced toxic death favorably. We conclude that patients with acute leukemia who are alive and well without chronic GVHD two years following an allograft have a high probability of being cured, whereas patients with active chronic GVHD requiring immunosuppression continue to be at risk of non-relapse death. The incidence of long-term liver and kidney dysfunction measured by serum bilirubin and creatinine is low.

Drug delivery systems for cyclosporine: achievements and complications

The review deals with the preparation, properties, and analysis of different kinds of cyclosporine delivery systems, such as solid formulations, liposomes, emulsions and microemulsions and targeted cyclosporine formulations. The review points out a key role of delivery systems in increasing the therapeutic effectiveness of cyclosporine. Comparative studies of the prior marketed formulation, Sandimmune, with a new microemulsion formulation, Neoral, are discussed including some data on clinical development of Neoral.

Pharmacokinetics of cyclosporine as a function of energy--protein deficiency in children with chronic renal failure

The present study was conducted to determine whether malnutrition in patients with chronic renal failure requiring cyclosporine therapy for renal transplantation has some effect on the clinical pharmacokinetics of cyclosporine. Eleven pediatric patients were enrolled in this study before renal transplantation and divided into two groups (group I: six well-nourished patients with a deficit in weight/height ratio < or = 7%; group II: five malnourished patients with a deficit in weight/height > 8%). The patients received a single oral dose of cyclosporine (3.0 mg/kg). Blood samples were collected for a 26-hour period, and serum concentrations of cyclosporine were measured using fluorescence-polarization immunoassay technology. The results suggest that, when malnutrition is present, the median Cmax of cyclosporine decreases by almost threefold (from 387.5 ng/mL in group I to 136.1 ng/mL in group II). An observed 52% reduction in AUC0-infinity (from 2,856.0 ng/mL/hr in group I to 1,481.4 ng/mL/hr in group II) was caused by the increased volume of distribution (from 4.6 L/kg in group I to 11.1 L/kg in group II). The elimination half-life (t1/2) was longer in group II compared with that of group I (12.4 hr for group II; range, 7.8-13.5 hr versus 8.9 hr for group I; range, 5.2-16.0 hr). Differences in t1/2 were not statistically significant at 5% confidence intervals. The effects of energy malnutrition on the pharmacokinetics of cyclosporine could explain in part some of the interindividual variability. This study provides pharmacokinetic guidelines for the use of cyclosporine.

The history of cyclosporin A (Sandimmune) revisited: another point of view

The immunosuppressant cyclosporin A (Sandimmune) has become the first line treatment for preventing rejection of transplanted organs and for certain autoimmune diseases. The discovery of that drug and its preclinical development are described, and it is shown that most earlier accounts of the history of this compound are, in important respects, incorrect and misleading.

Nephrotoxicity of xenobiotics

Nephrotoxicity can be grouped by the xenobiotics place of action, by the clinical presentation or by the generic toxic effect. The latter can be dose related, indirect, idiosyncratic or allergic. Nephrotoxicity of lithium, demeclocycline, aminoglycosides, cyclosporine, mercuric ion, nonsteroidal anti-inflammatory drugs, methoxyflurane, ethylene glycol, D-penicillamine and methicillin is reviewed in light of all these three viewpoints, but emphasis is on toxic mechanisms.

From a historical outline of transplants to the concept of biological ego

A chronology of the biological preliminaries of human transplantation science is proposed together with a chronological listing of the applications which transplants have had in clinical medicine in general and in pediatrics in particular. The most significantly immunological elements which surface from this assortment of experiences (in which those of pediatric interest have a considerable role) contribute easily to a more deeply perceived culture of man's biological individuality.

Lichen planus

Lichen planus, a papulosquamous disease, in its classical presentation is characterized by pruritic violaceous papules most commonly on the extremities of middle-aged adults. It may or may not be accompanied by oral and genital mucous membrane involvement. Its course is generally self-limited for a period of several months to years, but it may last indefinitely. There are many clinical variants described, ranging from lichenoid drug eruptions to association with other diseases such as diabetes mellitus, autoimmune disease, and the graft-versus-host reaction. The relationship of these, if any, to classical lichen planus is questionable. Multiple therapeutic options exist including corticosteroids, retinoids, griseofulvin, PUVA, and cyclosporine.

FK-506 and cyclosporin A: selective inhibition of calcium ionophore-induced polymorphonuclear leukocyte degranulation

This paper investigates the abilities of FK-506 and cyclosporin A (CsA) to inhibit human polymorphonuclear leukocyte (PMNL) degranulation. PMNLs, purified from human blood, were stimulated in vitro with A23187, ionomycin, the complement derived peptide C5a, formylmethionylleucinylphenylalanine (FMLP) or phorbol myristate acetate (PMA). Degranulation was assessed by measuring the release of either lactoferrin or N-acetyl-beta-D-glucosaminidase (NAG). Both FK-506 and CsA produced a concentration-related inhibition of degranulation induced by either A23187 or ionomycin but did not affect C5a-, FMLP- or PMA-induced degranulation. The IC50 values for inhibition of degranulation (approximately 0.7 nM for FK-506 and 33.7 nM for CsA) are very close to the published values for inhibition of human T-cell proliferation. Removal of calcium from the incubation medium with ethyleneglycolbis(aminoethylether)tetra-acetate (EGTA) totally inhibited calcium ionophore-induced degranulation but had no effect against C5a-, FMLP- or PMA-induced degranulation. Preincubation of PMNLs with actinomycin D or cycloheximide did not affect either A23187- or PMA-induced degranulation. Non-immunosuppressive analogs of CsA were ineffective at inhibiting degranulation. Rapamycin, a macrolide structurally related to FK-506, did not inhibit degranulation but it did antagonize the inhibition produced by FK-506. Given the similar profiles of activity of FK-506 and CsA in neutrophils and T cells, we conclude that similar activation or signal transduction pathways may be present in both T cells and neutrophils. Because A23187-induced PMNL degranulation was not sensitive to either actinomycin D or cycloheximide, it is apparent that the signal transduction pathways ultimately control different cellular functions.

Cyclosporine and liver regeneration studied by in vivo 31P nuclear magnetic resonance spectroscopy

The changes in fructose-1-phosphate (F-1-P), intracellular pH, and ATP content of the liver after a fructose challenge were investigated noninvasively in vivo using phosphorus-31 nuclear magnetic resonance spectroscopy of dog liver four days after a portacaval shunt (PCS) with or without portal venous infusion of cyclosporin (CsA). The F-1-P metabolism was slower in PCS dogs (N = 2) as compared to either the normal (N = 2) or PCS + CsA-treated dogs (N = 3) (P less than 0.05). The intracellular pH temporarily decreased from 7.3 +/- 0.05 to 7.0 +/- 0.05 during the fructose challenge. The regenerative indexes were increased in the PCS + CsA group (P less than 0.01). These data obtained in vivo using 31P-NMR spectroscopy in the liver following a portacaval shunt, suggest that: (1) the energy status of the liver and the metabolic response to fructose are reduced in PCS compared to normal animals and (2) CsA treatment enhances the regenerative response of the liver and prevents the reduction in hepatic function associated with portacaval shunting.

Cyclosporin A and its metabolites, distribution in blood and tissues

Cyclosporin A (CsA), a non-myelotoxic immunosuppressant, and its metabolites are widely distributed in the body. Highest concentrations of CsA have been detected in the pancreas, adipose tissue and liver, lowest concentrations in brain, muscle, blood and other body fluids. Metabolites are distributed differently to CsA. In addition to lipid partition, intracellular binding to cyclophilin, a peptidyl-prolyl cis-trans isomerase, appears to play a role in its tissue distribution. The temperature dependence of such binding in erythrocytes poses difficulty in serum or plasma measurements. Tissue specific processes may also influence action and toxicity of CsA and its metabolites; thus, a better understanding of the complex distribution pattern of CsA and its metabolites would be important for establishing improved strategies and selection of appropriate specific methodologies for drug monitoring.

Drug-induced toxic epidermal necrolysis treated with cyclosporin

A 35-year-old woman developed toxic epidermal necrolysis secondary to phenytoin. Because the life-threatening eruption was resistant to prednisone and high-dose methylprednisolone therapy, cyclosporine therapy was initiated. Within 24-48 hours, the eruption stabilized and the patient improved.

Cyclosporine: a review and its specific use in liver transplantation

During the past decade, treatment with cyclosporine, an immunosuppressive agent, has contributed substantially to enhanced allograft and patient survival after liver transplantation. Currently, the 1-year survival rate after liver transplantation is more than 80% in major liver transplantation centers, in contrast with approximately 60% before the availability of cyclosporine. Its predominant immunologic effect is inhibition of lymphokine production and secretion by helper T cells. The use of cyclosporine, however, is associated with numerous adverse effects, the most important of which are nephrotoxicity, hypertension, neurotoxicity, opportunistic infections, and malignant lesions. Acute nephrotoxicity, hypertension, and neurotoxicity usually can be reversed by decreasing the dose of cyclosporine. Measurement of cyclosporine concentrations in the blood is essential for optimization of immunosuppressive therapy and prevention of toxicity.

Cyclosporin A: action and side-effects

Cyclosporin A (CSA) is a new, potent immunosuppressive agent which is of proven value in organ transplantation. The use of CSA is associated with numerous side-effects, of which a dose-dependent nephrotoxicity is the most serious. CSA nephrotoxicity can be divided into two major groups: (i) functional toxicity without significant morphological lesions and (ii) morphological forms of toxicity with tubular and/or vascular-interstitial lesions. Vascular-interstitial toxicity is the most serious form because the renal lesions are irreversible.

Cyclosporine, low-density lipoprotein, and cholesterol

Lipoproteins are known to be able to transport a variety of drugs. This report suggests that low-density lipoprotein not only functions as an important carrier of cyclosporine in plasma but also facilitates transport of cyclosporine across the cell membrane by means of the low-density lipoprotein receptor. Such a mechanism would explain (1) the similar tissue distribution of cyclosporine and the low-density lipoprotein receptor, (2) the increase in immunosuppression and toxicity with low total serum cholesterol levels, and (3) the relative absence of immunosuppression and toxicity with high levels of cyclosporine in the blood in patients with hypertriglyceridemia. In addition to receptor-mediated uptake, a disturbance of the blood-brain barrier is suggested as an explanation of the high frequency of cyclosporine-induced central nervous system toxicity after liver transplantation. Cyclosporine-induced inhibition of the mitochondrial steroid 26-hydroxylase, an enzyme involved in the formation of bile acids from cholesterol and deficient in patients with cerebrotendinous xanthomatosis, may cause or contribute to the observed central nervous system toxicity. It also may explain the similar clinical features of cyclosporine-induced central nervous system toxicity and cerebrotendinous xanthomatosis.

Stage-selective inhibition of rodent malaria by cyclosporine

The relative susceptibility of different developmental stages of Plasmodium berghei to cyclosporine was investigated in vivo. Within 12 h of receiving a single 25-mg/kg (body weight) dose of cyclosporine, mice with patent P. berghei infections uniformly exhibited a rapid fall in asexual parasite stages. Initially, ring forms and mature schizonts disappeared. Subsequently, trophozoites disappeared between 21 and 24 h, whereas gametocytes persisted for 36 h. In contrast, when cyclosporine was administered to mice 1 day before inoculation (100 mg/kg) with P. berghei sporozoites and for 2 consecutive days after inoculation (25 mg/kg), infections developed normally. When mice with patent infections were placed on prolonged cyclosporine therapy (25 mg/kg per day), parasitemia initially disappeared but often recrudesced. Recrudescent parasites were frequently resistant to cyclosporine (Csr). The Csr phenotype remained stable after serial passage of parasites in mice and after transmission through Anopheles stephensi mosquitoes, in which the capacity to produce oocysts was reduced. When infections of untreated mice were initiated with equal numbers of Csr and cyclosporine-susceptible (Css) parasites and then carried through two serial cycles of mosquito-to-mouse transmission without cyclosporine treatment, the Csr phenotype was lost. The results indicate that cyclosporine selectively inhibits asexual blood stages of P. berghei and favors the emergence of Csr parasites with diminished infectivity for mosquitoes.

Graft-versus-host disease: a review

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The histological diagnosis of cutaneous graft versus host disease: relationship of skin changes to marrow purging and other clinical variables

Punch biopsies of skin were taken from allogeneic marrow recipients routinely before transplantation, at 14-22 and 90-107 d after grafting and in the event of a clinical rash. Three histological appearances were encountered: graft versus host disease (GvHD), epidermal abnormalities, and normal. Graft versus host disease was characterized by epidermal basal vacuolation, spongiosis and individual cell necrosis associated with mononuclear cell infiltration of the upper dermis and lower epidermis, while epidermal abnormalities were identical to GvHD but without the mononuclear cell infiltrate. Graft versus host disease occurred only in patients receiving marrow unpurged of T-cells while epidermal abnormalities occurred with equal frequency in recipients of purged and unpurged marrow and were also noted in a high proportion of pre-transplant biopsies. Patients whose skin biopsies exhibited epidermal abnormalities showed no greater incidence of subsequent clinical or histological GvHD than those with normal biopsies. For these reasons, we conclude that epidermal abnormalities cannot be regarded as a minor manifestation of GvHD as has often been previously assumed. We also conclude that they cannot be regarded as the cause of a rash as, unlike GvHD, the incidence was not significantly different in patients with and without rashes. The cause of epidermal abnormalities is not entirely clear; cytotoxic drugs and irradiation appear to play a part but their occurrence in patients with previously normal post-transplant biopsies suggests that other factors may also be important. Some patients with strong clinical evidence of GvHD had negative biopsies; these should be regarded with caution especially within the first 24 h after the onset of a rash as the diagnostic histological picture may take time to develop. In some cases, GvHD was confined to pilosebaceous units; this seems to represent a minor form of the disease with only a limited capacity for progression. Dysplastic epidermal changes which have previously been attributed to the use of cyclosporin A were found with equal frequency in patients who did not receive this drug and must therefore have some other cause.

[Cyclosporin and autoimmune diseases. 1: Experimental bases]

Cyclosporine is an 11 aminoacid cyclic peptide of fungal origin endowed with potent immunosuppressive activity. Unlike the conventional immunosuppressants, cyclosporine does not interfere with DNA metabolism, but it selectively and reversibly inhibits lymphocyte T-helper activation by inhibiting the production of interleukin-2 which plays a role in immune response development. Cyclosporine has little effect on lymphocytes B and does not modify the production of antibodies when it is in progress. The drug is effective in preventing spontaneous or autoantigen-induced auto-immune diseases in animals. The best studied models are experimental allergic encephalomyelitis, uveitis in the rat and spontaneous diabetes of BB rats. However, cyclosporine has no effect on diseases exclusively due to the pathogenic action of antibodies, such as spontaneous thyroiditis of the obese chicken. It is also possible to obtain a curative effect, this type of model being nearer to therapeutic conditions in humans than the previous models.