Felix Geissler

Gender difference in ifosfamide metabolism by human liver microsomes

SummaryPharmacokinetic gender-dependent differences in cytochrome P450-mediated drug metabolism, especially CYP3A4, and their clinical implications are increasingly apparent. CYP3A4 seems to be the most important CYP isoform in both bioactivation and N-dechloroethylation of the alkylating prodrug ifosfamide, but informations about possible gender-related differences are lacking. Therefore we compared in 10 male and 10 female liver microsomal preparations the contents and activities of specific isoenzymes, involved in both metabolic pathways, especially CYP3A4, further CYP2A6, CYP2C9 and CYP2B6 and measured the in vitro activities of these microsomes in the ifosfamide 4-hydroxylation and N-dechloroethylation using high-sensitive HPLC/MS and--UV detection methods.Statistically significant differences between male and female livers were found in the mean CYP3A4 contents and activities. These differences had no consequences on the ifosfamide 4-hydroxylation activities of liver microsomes in vitro. In contrast, in the ifosfamide N-dechloroethylation reaction we found a statistically significant difference between the liver microsomes of male and female patients (0.13 ± 0.05 nmol/min · nmolP450 vs. 0.28 ± 0.13 nmol/min · nmolP450, respectively).In conclusion, we firstly demonstrated such gender-related difference in the ifosfamide N-dechloroethylation, which could result in a higher risk of partly severe neurotoxic side effects in female patients.

Quality of life in chronic pancreatitis: a prospective trial comparing classical whipple procedure and duodenum-preserving pancreatic head resection.

Few data are available with respect to quality of life after pancreatic head resection in patients with chronic pancreatitis. The aim of this study was to compare the classical Whipple pancreatoduodenectomy (PD) with the Beger duodenum-preserving pancreatic head resection (DPPHR), in terms of quality of life, using standardized, valid, and reliable questionnaires. Sixty-five consecutive patients were included in this study. The PD procedure was chosen when pancreatic cancer could not be ruled out (n = 30); otherwise DPPHR was performed (n = 35). Quality of life was measured prospectively three times with the European Organization for Research and Treatment of Cancer (EORTC) Quality-of-Life Questionnaire (QLQ-C30) and the Gastrointestinal Quality-of-Life Index (GIQLI). Both procedures led to a significant improvement in quality of life, especially with regard to pain status. However, at the second follow-up examination (18 to 24 months postoperatively), all functional scales and the most important symptom scales of the EORTC QLQ-C30 revealed a better quality of life in the DPPHR group compared to the PD group. After classical PD, more patients seem to develop diabetes mellitus. The EORTC QLQ-C30 was found to be a better tool for quality-of-life assessment than the GIQLI in patients with chronic pancreatitis.

EndothelinA Receptor Blockade Reduces Ischemia/Reperfusion Injury in Pig Pancreas Transplantation

Objective The effect of prophylactic administration of a selective endothelinA receptor antagonist (ETA-RA) on ischemia/reperfusion injury in an experimental model of graft pancreatitis after pancreas transplantation was evaluated. Summary Background Data It is well established that endothelin-1 (ET-1), a powerful vasoconstrictor, plays an important role in the development of pancreatitis. Recent studies have shown a beneficial effect of endothelin receptor antagonists in the therapy for experimental pancreatitis. Methods Relevant ischemia/reperfusion injury was induced in pig pancreas transplants after 6 hours hypothermic preservation in University of Wisconsin solution. The recipients were randomized into 2 groups: control pigs received isotonic saline and the treated group received the selective ETA-RA BSF 208075 at the beginning of reperfusion. On postoperative days 2 and 5, animals were relaparotomized to obtain tissue specimens. Blood monitoring included lipase, amylase, C-reactive protein, trypsinogen-activation peptide, thiobarbituric acid-reacting substances, and ET-1. Partial oxygen tension (ptiO2) was measured by a Clarke-type electrode and blood flow by laser doppler. A semiquantitative score index was used for assessment of histologic injury and for immunohistochemical analysis of ET-1 and ETA receptor expression. Tissue mRNA levels of prepro ET-1, ETA receptor, pro-interleukin (IL)-6, and pro-IL-1&bgr; were quantified using TaqMan real-time reverse transcription-polymerase chain reaction (RT-PCR). Results Prophylactic treatment with ETA-RA significantly reduced the severity of graft pancreatitis evidenced by C-reactive protein. The finding of transient capillary perfusion at the beginning of reperfusion supports the application of the ETA-RA during this period. The dramatic increase of plasma ET-1 in the therapy group is a clear evidence of effective receptor blockade. Mean trypsinogen-activation peptide levels from the portal venous effluent, but not mean systemic plasma TAP values were significantly lower in the treated group. Analysis of ptiO2 and blood flow revealed a significant improvement of capillary perfusion and blood flow in the treated group and was associated with relevant reduction of tissue injury. Intrapancreatic ET-1 and IL-6 mRNA expression and ET-1 protein levels were significantly lower in the therapy group as compared with the control group. In contrast, ETA mRNA showed a marked up-regulation by ETA receptor blockade. Conclusion Application of a ETA-RA reduces ischemia/reperfusion induced graft pancreatitis in a pig transplantation model by improving microcirculation and reducing tissue injury.

Human liver allograft acceptance and the "tolerance assay": in vitro anti-donor T cell assays show hyporeactivity to donor cells, but unlike DTH, fail to detect linked suppression.

Human allograft acceptance is associated with immune regulation, characterized by donor-antigen-linked suppression of delayed-type hypersensitivity (DTH). We wished to determine if “classical” in vitro assays of alloreactivity could also detect linked suppression and thus be useful in the clinical diagnosis of active immune regulation. We analyzed peripheral blood mononuclear cells from a group of eight liver transplant recipients, one of whom had stopped all immunosuppression 4.5 years ago yet continues to have good graft function (graft acceptor). The regulator phenotype was defined as the ability to suppress a DTH response to a recall antigen in the presence of donor antigen. Using the trans vivo DTH test, we identified four regulators, and four nonregulators. When we tested two of the regulators for in vitro mixed lymphocyte culture (MLC) and cytotoxic T lymphocyte (CTL) responses to B-lymphoblastoid cell lines (B-LCL), we found both patients to be specifically hyporesponsive to donor compared with third-party B-LCL stimulators. However, in contrast to the linked suppression of DTH seen when a given B-LCL expressed donor-type HLA-B antigens, there was no evidence of linked suppression in vitro, either in CTL, proliferative, or interferon-&ggr; cytokine release assays. The primary CTL hyporesponsiveness to donor B-LCL could not be reversed by neutralizing antibodies to transforming growth factor &bgr; or interleukin-10, which could restore a strong DTH response to donor B-LCL. We conclude that DTH analysis can readily detect donor antigen-linked suppression in liver transplant recipients. CTL and MLC tests failed to do so. These findings may be relevant to the development of a tolerance assay suitable for use in clinical trials.

Does donor-specific tolerance occur clinically?

There is little literature on clinical transplant patients who have stopped receiving immunosuppression. This review summarizes the recent literature, including studies of the mechanism of allograft acceptance in kidney and liver transplant patients who removed themselves from immunosuppression. A model of peripheral tolerance that involves immunoregulation and microchimerism is favored to account for these rare instances of successful noncompliance. In contrast, clonal deletion may be the principal mechanism of tolerance in the setting of kidney transplantation after successful donor bone marrow transplantation.