Sirolimus/cyclosporine/tacrolimus interactions on bile flow and biliary excretion of immunosuppressants in a subchronic bile fistula rat model

Biomaterial-enhanced treg cell immunotherapy: A promising approach for transplant medicine and autoimmune disease treatment

Regulatory T cells (Tregs) are crucial for preserving tolerance in the body, rendering Treg immunotherapy a promising treatment option for both organ transplants and autoimmune diseases. Presently, organ transplant recipients must undergo lifelong immunosuppression to prevent allograft rejection, while autoimmune disorders lack definitive cures. In the last years, there has been notable advancement in comprehending the biology of both antigen-specific and polyclonal Tregs. Clinical trials involving Tregs have demonstrated their safety and effectiveness. To maximize the efficacy of Treg immunotherapy, it is essential for these cells to migrate to specific target tissues, maintain stability within local organs, bolster their suppressive capabilities, and ensure their intended function's longevity. In pursuit of these goals, the utilization of biomaterials emerges as an attractive supportive strategy for Treg immunotherapy in addressing these challenges. As a result, the prospect of employing biomaterial-enhanced Treg immunotherapy holds tremendous promise as a treatment option for organ transplant recipients and individuals grappling with autoimmune diseases in the near future. This paper introduces strategies based on biomaterial-assisted Treg immunotherapy to enhance transplant medicine and autoimmune treatments.

Coordinated action of a gut-liver pathway drives alcohol detoxification and consumption

Alcohol use disorder (AUD) affects millions of people worldwide, causing extensive morbidity and mortality with limited pharmacological treatments. The liver is considered as the principal site for the detoxification of ethanol metabolite, acetaldehyde (AcH), by aldehyde dehydrogenase 2 (ALDH2) and as a target for AUD treatment, however, our recent data indicate that the liver only plays a partial role in clearing systemic AcH. Here we show that a liver-gut axis, rather than liver alone, synergistically drives systemic AcH clearance and voluntary alcohol drinking. Mechanistically, we find that after ethanol intake, a substantial proportion of AcH generated in the liver is excreted via the bile into the gastrointestinal tract where AcH is further metabolized by gut ALDH2. Modulating bile flow significantly affects serum AcH level and drinking behaviour. Thus, combined targeting of liver and gut ALDH2, and manipulation of bile flow and secretion are potential therapeutic strategies to treat AUD.

Evidence that decreased expression of sinusoidal bile acid transporters accounts for the inhibition by rapamycin of bile flow recovery following liver ischemia

Rapamycin is employed as an immunosuppressant following organ transplant and, in patients with hepatocellular carcinoma, to inhibit cancer cell regrowth following liver surgery. Preconditioning the liver with rapamycin to induce the expression of antioxidant enzymes is a potential strategy to reduce ischemia reperfusion (IR) injury. However, pre-treatment with rapamycin inhibits bile flow, especially following ischemia. The aim was to investigate the mechanisms involved in this inhibition. In a rat model of segmental hepatic ischemia and reperfusion, acute administration of rapamycin by intravenous injection did not inhibit the basal rate of bile flow. Pre-treatment of rats with rapamycin for 24 h by intraperitoneal injection inhibited the expression of mRNA encoding the sinusoidal influx transporters Ntcp, Oatp1 and 2 and the canalicular efflux transporter Bsep, and increased expression of canalicular Mrp2. Dose-response curves for the actions of rapamycin on the expression of Bsep and Ntcp in cultured rat hepatocytes were biphasic, and monophasic for effects on Oatp1. In cultured tumorigenic H4IIE liver cells, several bile acid transporters were not expressed, or were expressed at very low levels compared to hepatocytes. In H4IIE cells, rapamycin increased expression of Ntcp, Oatp1 and Mrp2, but decreased expression of Oatp2. It is concluded that the inhibition of bile flow recovery following ischemia observed in rapamycin-treated livers is principally due to inhibition of the expression of sinusoidal bile acid transporters. Moreover, in tumorigenic liver tissue the contribution of tumorigenic hepatocytes to total liver bile flow is likely to be small and is unlikely to be greatly affected by rapamycin.

The effects of lipiodol and cyclosporin A on the hepatobiliary disposition of doxorubicin in pigs

Doxorubicin (DOX) emulsified in Lipiodol (LIP) is used as local palliative treatment for unresectable intermediate stage hepatocellular carcinoma. The objective of this study was to examine the poorly understood effects of the main excipient in the drug delivery system, LIP, alone or together with cyclosporin A (CsA), on the in vivo liver disposition of DOX and its active metabolite doxorubicinol (DOXol). The advanced, multi-sampling-site, acute pig model was used; samples were collected from three blood vessels (v. portae, v. hepatica and v. femoralis), bile and urine. The four treatment groups (TI-TIV) all received two intravenous 5 min infusions of DOX into an ear vein: at 0 and 200 min. Before the second dose, the pigs received a portal vein infusion of saline (TI), LIP (TII), CsA (TIII) or LIP and CsA (TIV). Concentrations of DOX and DOXol were analyzed using UPLC-MS/MS. The developed multicompartment model described the distribution of DOX and DOXol in plasma, bile and urine. LIP did not affect the pharmacokinetics of DOX or DOXol. CsA (TIII and TIV) had no effect on the plasma pharmacokinetics of DOX, but a 2-fold increase in exposure to DOXol and a significant decrease in hepatobiliary clearance of DOX and DOXol were observed. Model simulations supported that CsA inhibits 99% of canalicular biliary secretion of both DOX and DOXol, but does not affect the metabolism of DOX to DOXol. In conclusion, LIP did not directly interact with transporters, enzymes and/or biological membranes important for the hepatobiliary disposition of DOX.

Biliary diseases in heart transplanted patients: a comparison between cyclosporine A versus tacrolimus-based immunosuppression

A cyclosporine (CsA)-based immunosuppression is associated with an increased incidence of cholelithiasis after heart transplantation. It is not known if tacrolimus (Tac) has comparable biliary side effects in humans.

We evaluated the incidence of gallbladder sludge and cholelithiasis under Tac-based immunosuppression by ultrasound examinations in 31 cardiac transplants (25 male, 6 female, mean age: 59 ± 11 years). Data were compared to 57 patients (47 male, 10 female, mean age: 58 ± 11 years) who received CsA-based immunosuppression.

6 patients receiving Tac and 6 patients receiving CsA had already gallstones prior to transplantation so that finally 25 patients of the Tac group and 51 patients of the CsA group could be evaluated.

In the Tac group the incidence of biliary sludge was 4% (1 of 25), of gallstones 28% (7 of 25). In comparison, patients receiving CsA developed biliary sludge in also 4% (2 of 51) and gallstones in 25% (13 of 51). Nine of 42 males in the CsA group (21%) and eight of 20 males in the Tac group (40%) developed either gallstones or sludge (n.s). Six of nine females in the CsA group (67%), but none of five females in the Tac group (0%) developed either gallstones or sludge (p = 0.01).

In summary, the incidence of biliary disease in patients with Tac is comparable with CsA-based immunosuppression. We recommend regular sonographical examinations to detect biliary diseases as early as possible. In cases of clinically, laboratory and sonographical signs of cholecystitis cholecystectomy is indicated. It seems that towards lithogenicity female patients benefit more from a Tac-based treatment because the occurrence of gallstones is rare.

Identification of urinary biomarkers useful for distinguishing a difference in mechanism of toxicity in rat model of cholestasis

This (1)H nuclear magnetic resonance metabonomics study was aimed to determine urinary biomarkers of cholestasis resulting from inhibition of biliary secretion of bile or obstruction of bile flow. To inhibit biliary secretion of bile, cyclosporine A was administered to male Sprague-Dawley rats. Obstruction of bile flow was induced by administration of 4,4'-methylene dianiline, alpha-naphthylisothiocyanate or bile duct ligation. Clinical pathological and histopathological examinations were performed to confirm cholestatic injury and (1)H nuclear magnetic resonance spectral data for urine samples were analysed to determine similarities and differences in profiles of metabolites using the Spotfire. In cyclosporine A-treated groups, serum total bilirubin and bile acid were significantly increased but no remarkable hepatic histopathological-changes were observed. In 4,4'-methylene dianiline-, alpha-naphthylisothiocyanate- and bile duct ligation-treated groups, serum alkaline phosphatase, gamma-glutamyltranspeptidase and total bilirubin levels increased significantly, and hepatic histopathological-changes were observed. On urinary (1)H nuclear magnetic resonance spectral analysis, area intensities derived from 0.66 to 1.90 ppm were decreased by cyclosporine A, whereas they were increased by other treatments. These metabolites were identified using the NMR suite as bile acids, branched-chain amino acids, n-butyrate, propionate, methyl malonate and valerate. These metabolites were further investigated by K-means clustering analysis. The cluster of these metabolites is considered to be altered by cholestasis. We conclude that bile acids, valine and methyl malonate have a possibility to be urinary cholestatic biomarkers, which distinguish a difference in mechanism of toxicity. (1)H nuclear magnetic resonance metabonomics thus appears to be useful for determining the mechanisms of toxicity and can be front-loaded in drug safety evaluation and biomarker discovery.

Evaluation of a surgical procedure to measure drug biliary excretion of rats in regulatory safety studies

A surgical procedure was evaluated to allow bile collection from the freely moving male Sprague-Dawley rats for the assessment of drug biliary excretion during regulatory safety studies. A catheter was implanted into the bile duct to divert the bile flow via an exteriorized loop. Following recovery from the surgery and verification of normal hepatic function, the exteriorized catheter was sectioned to allow collection of the bile and replacement with a commercial bile salt solution. Approximately 80% of the catheterized animals (10 females and 10 males) had normal serum liver enzyme levels 2 days after surgery. Then, the effect of acute or repeated administrations of the immunosuppressant tacrolimus on the biliary excretion of 14C diazepam was studied to validate the technique. A first group of 12 rats received an intravenous injection of 10 mg/kg 14C-diazepam and the total and sequential amounts of diazepam excreted in the bile were measured over 72 h. Biliary excretion accounted for 80% of diazepam elimination. These rats were then given an oral administration of 3 mg/kg tacrolimus on days 7 and 8 followed by the same intravenous dose of 14C-diazepam. Another group of 10 catheterized rats was given 21 daily oral doses of 3 mg/kg tacrolimus followed by a single intravenous administration of 14C-diazepam. No significant changes in diazepam biliary excretion were observed following either acute or repeated administration of tacrolimus. This study demonstrates the feasibility of drug biliary excretion investigations under Good Laboratory Practices conditions as a complement to regulatory acute or repeated dose safety studies.

Adding sirolimus to tacrolimus-based immunosuppression in pediatric renal transplant recipients reduces tacrolimus exposure

In adult renal recipients, coadministration of tacrolimus (TAC) and sirolimus (SIR) results in reduced exposure to TAC at SIR doses of 2 mg/day. Eight pediatric renal recipients (median age at transplant 2.0 years, range: 1.2-12.9 years) were converted to TAC- and SIR-based immunosuppression as a rescue therapy. All patients had biopsy-proven chronic allograft nephropathy. TAC levels were measured using a commercially available EMIT assay and SIR levels with a newly developed assay based on the LC-MS MS technology. SIR was started at 0.13+/-0.05 mg/kg/day (3.51+/-1.26 mg/m2/day) in two divided doses. TAC was given at 0.14+/-0.09 mg/kg/day, resulting in a trough level of 6.3+/-2.5 ng/mL. After the addition of SIR, the median dose required to keep TAC blood trough concentrations within the target range increased by 71.2% (range: 21.9-245.4%), dose-normalized TAC exposure (AUC) decreased to 67.1% and the dose-normalized C(max), a surrogate for absorption rate, to 53.8% (both geometric means) while terminal half-life (t1/2), a pharmacokinetic parameter characterizing systemic elimination, remained unchanged (p<0.93). Adding SIR to TAC-based immunosuppression in young pediatric renal transplant recipients results in a significant decrease of TAC exposure. TAC trough levels should be monitored frequently.

Maternal effects and cancer risk in the progeny of mice exposed to X-rays before conception

To investigate in an animal model whether preconceptual X-ray exposure leads to an altered tumor rate and spectrum in the offspring, a transgeneration carcinogenesis study was carried out. Female mice received X-ray irradiation (2 x 2 Gray) 2 weeks prior to mating with untreated males. After weaning, half of the descendants were exposed for 6 months to the immunomodulating and tumor-promoting compound cyclosporine A (CsA) by diet, the others remained untreated. The animals were maintained for their entire lifespan, terminal sacrifices were carried out after 28 months. Complete autopsy was performed, and three protocol organs (lung, liver and spleen) were examined histologically, together with any suspicious lesions in other organs. Fertility and the lifetime of the maternal mice were reduced by the X-ray irradiation, and their incidence of lung and liver tumors was increased as compared to non-irradiated mice. The descendants of all groups revealed comparable body weights and mortality rates. The incidence of hematopoietic/lymphoreticular tissue tumors increased in the female hybrids by 6 months of CsA-treatment. A higher incidence of lung and liver tumors in the sham-treated male progeny of irradiated mothers was detected, pointing to a possible germ cell-transmitted alteration initiated by the preconceptual maternal X-ray exposure.

Benefit-Risk Assessment of Sirolimus in Renal Transplantation

Sirolimus (rapamycin) is a macrocyclic lactone isolated from a strain of Streptomyces hygroscopicus that inhibits the mammalian target of rapamycin (mTOR)-mediated signal-transduction pathways, resulting in the arrest of cell cycle of various cell types, including T- and B-lymphocytes. Sirolimus has been demonstrated to prolong graft survival in various animal models of transplantation, ranging from rodents to primates for both heterotopic, as well as orthotopic organ grafting, bone marrow transplantation and islet cell grafting. In human clinical renal transplantation, sirolimus in combination with ciclosporin (cyclosporine) efficiently reduces the incidence of acute allograft rejection. Because of the synergistic effect of sirolimus on ciclosporin-induced nephrotoxicity, a prolonged combination of the two drugs inevitably leads to progressive irreversible renal allograft damage. Early elimination of calcineurin inhibitor therapy or complete avoidance of the latter by using sirolimus therapy is the optimal strategy for this drug. Prospective randomised phase II and III clinical studies have confirmed this approach, at least for recipients with a low to moderate immunological risk. For patients with a high immunological risk or recipients exposed to delayed graft function, sirolimus might not constitute the best therapeutic choice--despite its ability to enable calcineurin inhibitor sparing in the latter situation--because of its anti-proliferative effects on recovering renal tubular cells. Whether lower doses of sirolimus or a combination with a reduced dose of tacrolimus would be advantageous in these high risk situations remains to be determined. Clinically relevant adverse effects of sirolimus that require a specific therapeutic response or can potentially influence short- and long-term patient morbidity and mortality as well as graft survival include hypercholesterolaemia, hypertriglyceridaemia, infectious and non-infectious pneumonia, anaemia, lymphocele formation and impaired wound healing. These drug-related adverse effects are important determinants in the choice of a tailor-made immunosuppressive drug regimen that complies with the individual patient risk profile. Equally important in the latter decision is the lack of severe intrinsic nephrotoxicity associated with sirolimus and its advantageous effects on arterial hypertension, post-transplantation diabetes mellitus and esthetic changes induced by calcineurin inhibitors. Mild and transient thrombocytopenia, leukopenia, gastrointestinal adverse effects and mucosal ulcerations are all minor complications of sirolimus therapy that have less impact on the decision for choosing this drug as the basis for tailor-made immunosuppressive therapy. It is clear that sirolimus has gained a proper place in the present-day immunosuppressive armament used in renal transplantation and will contribute to the development of a tailor-made immunosuppressive therapy aimed at fulfilling the requirements outlined by the individual patient profile.

Mécanismes des hyperlipidémies dues aux immunosuppresseurs

This article summarises the mechanisms responsible for the hyperlipidaemia observed after immunosuppressive treatment. Much progress has been achieved in the treatment of organ transplantation over the last 10 years, in particular because of the use of new immunosuppressive drugs with less nephrotoxicity. However, hypercholesterolaemia and hypertriglyceridaemia persist among many patients, who are thus more likely to develop cardiovascular diseases. We first reviewed the effects of immunosuppressive drugs on biliary acid biosynthesis, which is the main pathway of cholesterol degradation. The inhibition of this biosynthesis pathway, and especially of some key cytochrome P450s (CYP) such as CYP27A1, could contribute to the increased cholesterolaemia. Immunosuppressive drugs may also modify the activity of lipoprotein receptors or the expression of different apolipoproteins involved in cholesterol and triglyceride transport by lipoproteins. Finally, the fact that hypertriglyceridaemia is more frequently observed after certain immunosuppressive treatments may be partly caused by changes in the synthesis and elimination of triglycerides involving lipoprotein lipase or some apolipoproteins which serve as its cofactors (apoCII or apoCIII).

Everolimus/cyclosporine interactions on bile flow and biliary excretion of bile salts and cholesterol in rats

As a possible explanation for everolimus/cyclosporine-induced hypercholesterolemia seen in transplant recipients, we investigated the interactions of the immunosuppressants everolimus and cyclosporine on bile flow and biliary excretion of bile salts and cholesterol in a subchronic bile fistula model in rats because biliary excretion is a main elimination route of cholesterol. After 2 weeks of daily treatment, everolimus (1 mg/kg i.p.) and cyclosporine (5 mg/kg i.p) decreased bile flow (-45 and -36%) and biliary excretion of bile salts (-34 and -54%) and cholesterol (-25 and -39%) and increased serum concentrations of cholesterol (+40 and +17%) and triglycerides (+220 and +110%). Bile salt serum concentration was elevated only by cyclosporine (+100%), and not by everolimus. Everolimus/cyclosporine slightly enforced the cyclosporine-induced hyperlipidemia but not reduction of bile parameters, while the cyclosporine-induced increase in bile salts in serum was totally prevented. From these results we conclude that bile salt synthesis could be impaired by everolimus, which could be one reason for everolimus-induced hypercholesterolemia.