Kynurenine serves as useful biomarker in acute, Long- and Post-COVID-19 diagnostics

Introduction

In patients with SARS-CoV-2, innate immunity is playing a central role, depicted by hyperinflammation and longer lasting inflammatory response. Reliable inflammatory markers that cover both acute and long-lasting COVID-19 monitoring are still lacking. Thus, we investigated one specific inflammatory marker involved as one key player of the immune system, kynurenine (Kyn), and its use for diagnosis/detection of the Long-/Post-COVID syndrome in comparison to currently used markers in both serum and saliva samples.

Material and methods

The study compromised in total 151 inpatients with a SARS-CoV-2 infection hospitalized between 03/2020 and 09/2021. The group NC (normal controls) included blood bank donors (n=302, 144f/158m, mean age 47.1 ± 18.3 years (range 18-75)). Two further groups were generated based on Group A (n=85, 27f/58m, mean age 63.1 ± 18.3 years (range 19-90), acute admission to the hospital) and Group B (n=66, 22f/44m, mean age 66.6 ± 17.6 years (range 17-90), admitted either for weaning or for rehabilitation period due to Long-COVID symptoms/syndrome). Plasma concentrations of Kyn, C-Reactive Protein (CRP) and interleukin-6 (IL-6) were measured on admission. In Group B we determined Kyn 4 weeks after the negative PCR-test. In a subset of patients (n=11) concentrations of Kyn and CRP were measured in sera and saliva two, three and four months after dismission. We identified 12 patients with Post-COVID symptoms >20 weeks with still significant elevated Kyn-levels.

Results

Mean values for NC used as reference were 2.79 ± 0.61 µM, range 1.2-4.1 µM. On admission, patients showed significantly higher concentrations of Kyn compared to NC (p-values < 0.001). Kyn significantly correlated with IL-6 peak-values (r=0.411; p-values <0.001) and CRP (r=0.488, p-values<0.001). Kyn values in Group B (Long-/Post-COVID) showed still significant higher values (8.77 ± 1.72 µM, range 5.5-16.6 µM), whereas CRP values in Group B were in the normal range.

Conclusion

Serum and saliva Kyn are reflecting the acute and long-term pathophysiology of the SARS-CoV-2 disease concerning the innate immune response and thus may serve a useful biomarker for diagnosis and monitoring both Long- and Post-COVID syndrome and its therapy.

Differences in Immune Response During Competition and Preparation Phase in Elite Rowers

Background: Metabolic stress is high during training and competition of Olympic rowers, but there is a lack of biomedical markers allowing to quantify training load on the molecular level. We aimed to identify such markers applying a complex approach involving inflammatory and immunologic variables. Methods: Eleven international elite male rowers (age 22.7 ± 2.4 yrs.; VO₂max 71 ± 5 ml·min^-1·kg^-1) of the German National Rowing team were monitored at competition phase (COMP) vs. preparation phase (PREP), representing high vs. low load. Perceived stress and recovery were assessed by a Recovery Stress Questionnaire for Athletes (RESTQ-76 Sport). Immune cell activation (dendritic cell (DC)/macrophage/monocytes/T-cells) was evaluated via fluorescent activated cell sorting. Cytokines, High-Mobility Group Protein B1 (HMGB1), cell-free DNA (cfDNA), creatine kinase (CK), uric acid (UA), and kynurenine (KYN) were measured in venous blood. Results: Rowers experienced more general stress and less recovery during COMP, but sports-related stress and recovery did not differ from PREP. During COMP, DC/macrophage/monocyte and T-regulatory cells (T_reg-cell) increased (p = 0.001 and 0.010). HMGB1 and cfDNA increased in most athletes during COMP (p = 0.001 and 0.048), while CK, UA, and KYN remained unaltered (p = 0.053, 0.304, and 0.211). Pro-inflammatory cytokines IL-1β (p = 0.002), TNF-α (p < 0.001), and the chemokine IL-8 (p = 0.001) were elevated during COMP, while anti-inflammatory Il-10 was lower (p = 0.002). Conclusion: COMP resulted in an increase in biomarkers reflecting tissue damage, with plausible evidence of immune cell activation that appeared to be compensated by anti-inflammatory mechanisms, such as T_reg-cell proliferation. We suggest an anti-inflammatory and immunological matrix approach to optimize training load quantification in elite athletes.

PTA Plus Stent Implantation Versus PTA Alone for Central Venous Stenoses

From 1990 through 1992, 17 severely stenosed central venous segments were diagnosed in 13 patients. In 9 patients, 11 stenoses were detected during follow-up after trans- femoral venous thrombectomy. The other 6 stenoses occurred in the venous outflow tract of 4 hemodialysis shunts. Six stenoses were treated by percutaneous transvenous angio plasty (PTA) alone, and 11 stenoses by PTA plus stent implantation (PTA+S). For PTA+S, a flexible, self-expanding stent was used.

Acute procedure-related complications were not observed. After a median follow-up time of eighteen months (three to thirty-six months), all patients were examined clinically, duplex-sonographically, and angiographically. Following PTA alone (n = 6), there was only 1 excellent result, and 5 patients developed high-grade restenoses. Two of these patients had to be reoperated on, and 1 patient underwent another PTA with stent placement. PTA+S (n = 11) for initial treatment of central venous stenoses gave excellent results in 8 cases, a good result in 1 case, and 2 insufficient results caused by intimal hyperplasia within the stent. These restenoses were successfully treated by another PTA.

Treatment of Severe Arterial Occlusive Disease by Epidural Spinal Electrical Stimulation

In 10 cases with advanced vascular occlusive disease the effect of epidural spinal electrical stimulation (ESES) on peripheral circulation has been tested by use of transcutaneous oxygen measurement (TcPO2), telethermography, and laser-speckle measurements. The values in all cases increased. Improvement was more pronounced during the first two to three weeks. Indications and limitations of this treatment modality are discussed.

Dynamics and Diagnostic Relevance of Kynurenine Serum Level after Kidney Transplantation

BACKGROUND

Inflammatory events after kidney transplantation (Tx) may lead to activation of the tryptophane-catabolizing enzyme indoleamine 2,3-dioxygenase followed by the formation of kynurenine (KYN). Post-transplant KYN serum levels in kidney allograft recipients were analyzed for their diagnostic value.

MATERIAL AND METHODS

This was a retrospective analysis of KYN levels (normal value: 2.7±0.6 nmol/ml) measured in 4083 blood samples collected from 355 kidney graft recipients in connection with uncomplicated courses, acute rejections (ARs), infections, and type of immunosuppression. We performed descriptive data analysis and analysis of variance.

RESULTS

In 212 recipients with immediately functioning grafts, the KYN levels dropped from pre-Tx 13.3±5.9 nmol/ml to nearly normal values at day 5 (5.8±3.0 nmol/ml). In patients with delayed graft function, the KYN reduction started only after the last hemodialysis treatment. With respect to ARs in recipients with creatinine values <300 µmol/l pre-AR, the increase of KYN levels depended on the severity of ARs (steroid-sensitive ARs: from 4.5±1.4 to 6.0±6.1 nmol/ml; steroid-resistant ARs: from 6.1±3.1 to 12.9±7.1 nmol/ml; vascular rejections: from 5.8±3.0 to 16.9±9.1 nmol/ml). In patients with creatinine values ≥300 µmol/l pre-AR, a further increase of the KYN level (from 10.1 to 13.2 nmol/ml) was only observed in severe, steroid-resistant ARs. With respect to infections evaluated, the KYN levels before diagnosis/start of treatment were 5.7±3.4 nmol/ml in asymptomatic CMV infections, 7.5±4.4 nmol/ml in CMV diseases, 8.3±3.3 nmol/ml in pneumonia, and 10.4±6.5 nmol/ml in bacterial sepsis.

CONCLUSIONS

Serum KYN seems to be a reliable diagnostic tool for the assessment of post-transplant inflammatory complications, already in an early stage, and for monitoring the efficacy of therapeutic interventions. Prospective studies are recommended.

Relationship of hepatitis B or C virus prevalences, risk factors, and outcomes in renal transplant recipients: analysis of German data

BACKGROUND

Chronic liver disease resulting from hepatitis B (HBV) and hepatitis C (HCV) virus infections is still a major concern in kidney recipients. Our aim was to evaluate the prevalences, risk factors, and impact of HBV and HCV infections in adult renal transplant recipients in Germany.

MATERIALS AND METHODS

Data were collected on 1633 kidney recipients transplanted between 1989 and 2002 at the 21 German renal transplant centers participating in MOST, the prospective Multinational Observational Study in Transplantation. Subgroup analyses compared HBV- and HCV-positive patients vs those with HBV/HCV-negative serology at the time of transplantation.

RESULTS

The prevalences of 4.4% (n = 72) for HBV and 5.8% (n = 94) for HCV showed a marked decline over the last 15 years. Retransplantations were significantly more common among HBV+ (29%) and HCV+ (36%) than HBV-/HCV- patients (12%). HCV+ patients experienced significantly longer dialysis times and received significantly more pretransplantation blood transfusions. Between all groups, no significant differences were observed in acute rejection rate at 12 months or in renal graft function up to 5 years posttransplantation (mean glomerular filtration rate: HBV+, 57.3 mL/min; HCV+, 58.5 mL/min; HBV-/HCV-, 59 mL/min). No progressive elevations in liver enzymes and bilirubin were noted during the 5-year observation period.

CONCLUSIONS

HBV and HCV infections currently have a low prevalence among German kidney graft recipients. Long dialysis times, blood transfusions, and retransplantations were identified as risk factors for hepatitis infections. At 5 years posttransplantation, kidney and liver functions did not differ significantly between HBV+ and HCV+ vs HBV-/HCV- renal transplant recipients.

Severe graft rejection, increased immunosuppression, and active CMV infection in renal transplantation

Associations between active cytomegalovirus (CMV) infection, graft rejection, rejection therapy, and clinical signs and symptoms have been shown repeatedly. However, the causes and the sequence of events remain an area of debate. Two hundred twenty five patients with cadaveric renal transplant were included in the present study. Clinical signs and symptoms, and the development of active CMV infections were recorded during the first 3 months after renal transplantation. CMV monitoring by pp65-antigenemia was performed followed by preemptive antiviral therapy. Delayed graft function and severe graft rejection followed by anti T-cell antibody therapy was associated with the development of active CMV infection. In contrast, the induction therapy with anti-T-cell antibodies was not associated with more active CMV infections. Post-transplant morbidity determined by fever, pneumonia, and duration of hospital stay was increased significantly in patients with active CMV infection. However, in times of preemptive antiviral therapy an increased morbidity occurred in association with severe graft rejection and not with active CMV infection alone. In patients with renal transplantation and preemptive antiviral therapy, the morbidity was no more influenced by the CMV serostatus although the prevalence of active CMV infection was obviously different between CMV exposed (D+/R+,D+/R-, D-/R+) and unexposed (D-/R-) patients. Severe graft rejection and increased immunosuppression could stimulate cooperatively active CMV infections whereas immunosuppression alone may not be as effective. Prevention of severe graft rejection may be important to decrease early post-transplant morbidity and also the development of active CMV infections after renal transplantation.

Renal ischemia/reperfusion and its influence on telomere length and expression of cell cycle regulatory genes

The aim of the study was to evaluate the influence of renal ischemia/reperfusion (I/R) on telomere (T) length and tissue expression of cyclin-dependent kinase inhibitor genes (CDKIG). An experimental model of ex-vivo hemoperfusion of the kidney was used as described earlier. Telomere length measurement and expression of p16((INK4a)), p21((WAF1/CIP1)) and p27((Kip1)) CDKIGs was studied immunohistochemically in kidney biopsy samples at baseline and different time points after the reperfusion. The mean T length decreased after reperfusion from 5.56+/-0.60 kbp to 5.46+/-0.36 kbp (p=NS). All 3 genes were up-regulated in kidney tissue however their activation was different in diverse renal cells according to the reperfusion time. Expression of p16 significantly increased in tubular cells at 180 min of reperfusion as compared with the baseline. Activation of the p27 in glomerular cells was significantly higher at 60, 120 and 180 min of reperfusion as compared with 0 and 15 min. The marker started increasing in tubular cells at 15 min and was elevated at every time point afterwards. p21 was significantly over-expressed in all renal cells after the reperfusion. The current study shows that renal I/R causes T shortening and over-expression of CDKIGs indicating on substantial DNA damage and/or accelerated tissue senescence. The tissue expression of CDKIGs is positively related with the reperfusion time.

Up-regulation of cell cycle regulatory genes after renal ischemia/reperfusion: differential expression of p16(INK4a), p21(WAF1/CIP1) and p27(Kip1) cyclin-dependent kinase inhibitor genes depending on reperfusion time

The aim of this study was to evaluate the influence of renal ischemia, cold preservation and reperfusion on the degree of renal kidney senescence. An experimental model of ex vivo renal hemoperfusion was used. Expression of p16(INK4a), p21(WAF1/CIP1) and p27(Kip1) cyclin-dependent kinase inhibitor genes (CDKIGs) was studied immunohistochemically in kidney biopsy samples at baseline and different time points after reperfusion. All three markers were up-regulated in kidney tissue after the reperfusion; however, their activation in different renal cells varied according to the reperfusion time. Expression of p16 was significantly increased in tubular cells at 180 min of reperfusion when compared with the baseline. Activation of p27 was detected in glomerular cells at 15 min and was significantly higher at 60, 120 and 180 min of reperfusion. The marker started increasing in tubular cells at 15 min and was elevated at every time point afterwards. p21 was significantly over-expressed in all renal cells after the reperfusion. It has been shown by the results of the current study that renal ischemia/reperfusion is associated with over-expression of CDKIGs indicating on substantial DNA damage and/or accelerated tissue senescence. For the first time it has been shown that tissue expression of CDKIGs is positively related with the reperfusion time.

Cyclosporine C2 levels in de novo renal allograft recipients: a German multicenter prospective observational study

This ongoing multicenter prospective observational study was undertaken in de novo renal allograft recipients managed with cyclosporine (CsA) trough (C0) and 2-hour postdose (C2) level monitoring at defined times so as to assess the risk for an acute rejection episode or allograft dysfunction. The renal transplant recipients (n = 159) were enrolled at 11 German centers. The 6-month posttransplant data from 138 patients were evaluable for this interim analysis. Mean C2 levels (ng/mL), which were measured by liquid chromatography-tandem mass spectrometry at a central laboratory, were: days 3 to 5: 873.1 +/- 391.9; days 7 to 10: 939.1 +/- 422.8; days 14 to 28: 1116.3 +/- 497.6; 3 months: 905.0 +/- 316.8; and after 6 months: 787.0 +/- 276.5. To identify patients at higher risk for acute rejection or allograft dysfunction, we calculated the relative CsA absorption capacity (C2 [ng/mL]/morning dose [mg/kg]; CsA-Abs), yielding mean values on days 3 to 5: 284.4 +/- 115.1; days 7 to 10: 306.7 +/- 134.8; days 14 to 28: 382.5 +/- 164.7; month 3: 501.5 +/- 168.8; month 6: 512.7 +/- 176.5. Three groups were distinguished by CsA-Abs at days 7 to 10: low absorbers (CsA-Abs < 200), normal absorbers (CsA-Abs 200 to 350), and high absorbers (CsA-Abs > 350). A between-group comparison of absorption level at 6 months posttransplant revealed the incidences of biopsy-proven acute rejection and Cockcroft-Gault formula-based mean glomerular filtration rates of 23.8% and 54.7 +/- 19.0 mL/min, 22.6% and 59.5 +/- 20.7 mL/min, and 17.6% and 67.7 +/- 23.5, respectively. In conclusion, mean C2 levels >1000 ng/mL are attained within 2 to 4 weeks, with CsA-Abs increasing continuously over the first 6 posttransplant months. High CsA absorbers show a propensity toward good allograft function and lower acute rejection rates at 6 months after renal transplantation.

Cyclosporine-Based Immunosuppressive Strategies for Kidney Recipients: Interim Analysis of German Data From the Multinational Observational Study (MOST)

INTRODUCTION

We collected data from kidney recipients with a functioning graft at German kidney transplant centers in order to analyze the efficacy of various cyclosporine (CsA)-based immunosuppressive strategies, the effects of different perioperative and maintenance regimens, and the impact of donor source on clinical outcome.

METHODS

As part of the ongoing prospective Multinational Observational Study in Transplantation (MOST), data for both prospective and retrospective analysis were collected from kidney recipients over 18 years bearing a functioning graft that was transplanted at 21 German kidney transplant centers between 1987 and 2002.

RESULTS

Data from 1223 renal graft recipients, including their CsA-based immunosuppressive regimens, were stratified as: 402 de novo patients (median 6.8 months posttransplant) and 821 patients on maintenance therapy (median 71 months posttransplant). Triple regimens with CsA + mycophenolate mofetil (MMF) + steroids (Ste) currently comprise the major perioperative immunosuppressive strategies in Germany (de novo 65%). IL-2 receptor antagonist (IL-2Ra) use is increasing (de novo 18%, maintenance 4%), while mono and dual regimen use de novo is declining (de novo 4%, maintenance 20%). Among 689 patients transplanted between 1987 and 2002 with outcome data, the mean incidence of acute rejection during the first posttransplant year was 21.6%. Rejection rates on initial therapy with CsA + MMF + Ste +/- antibodies (n = 517) averaged 17.8%.

CONCLUSIONS

Between 1987 and 2002, CsA-based immunosuppression combined with MMF and Ste became the most commonly used strategy for both initial and maintenance therapy after kidney transplantation in Germany, yielding the low acute rejection rates particularly when combined with IL-2Ra.

Rapamycin rescue therapy in patients after kidney transplantation: first clinical experience

This study was aimed at analysing rapamycin (RAPA) rescue therapy with calcineurin inhibitor (CNI) withdrawal in renal transplant patients primarily presenting with CNI-nephrotoxicity (CNI-Neph), chronic allograft nephropathy (CAN) without [CAN(a)] and with histological changes suggestive of chronic rejection [CAN(b)]. In 36 patient with CNI-Neph (n = 6), CAN(b) (n = 21), CAN(a) (n = 7), and others (n = 2) RAPA therapy was started 4.4-115 months (median 30.6 months) after renal transplantation. During a follow up of 3-33 months (median 19 months) parameters of kidney function were recorded. Three patients on haemodialysis did not show any recovery of graft function. Of the remaining 33 patients renal function improved in 22 (66.7%), was stable in three (9%) but deteriorated in eight (24%) patients, of whom seven (21%) required haemodialysis thereafter. Success rate of RAPA therapy differed with respect to the histological diagnosis: 70% in CAN(b), 80% in CNI-Neph and 33% in CAN(a). Furthermore, in patients with creatinine levels above 400 mum (n = 6) graft function rarely improved (n = 2, 33%). The RAPA rescue therapy with CNI withdrawal appears promising in a special cohort of patients with chronic renal allograft dysfunction even late after transplantation.

Experience with therapeutic drug monitoring of cyclosporine

During the past 20 years, cyclosporine (CsA) has become the main part of immunosuppressive protocols. Its impact to improve the quality and quantity of transplantation surgery has been enormous. Immunosuppression in allograft recipients 10 years after renal transplantation CsA continued to demonstrate benefits on graft survival without evidence of long-term morbidity. The pharmacokinetic properties of CsA show wide interpatient variation. After being subject of intense investigation for more than 20 years, it only recently has the full potential of the drug been realized, primarily due to two advances: first, the development of a microemulsified formulation, (Neoral), that improves drug delivery; second, substantial improvements in CsA monitoring. Sparse-sampling algorithms were developed specifically to predict AUCs. We prospectively investigated the practicality, intrapatient variability, and impact on the outcomes of toxicity and rejection episodes using an algorithm. Rejection episodes were diminished by 43.5% in the first 3 months compared to the results in the previous 3 years. Furthermore, the relation of the trough versus C2 concentrations performed at day 3 to 5 and 10 to 12 predicted the probability of an acute rejection episode. Using a truncated AUC to identify patients at risk for rejection episodes early provides optimal and individualized immunosuppression. This pharmacokinetic rationale has now eventuated in an international consensus statement that represents a further step toward optimal immunosuppression.

Influence of ischaemia/reperfusion and LFA-1 inhibition on telomere lengths and CDKI genes in ex vivo haemoperfusion of primate kidneys

The telomere (T) length, p21(WAF1/CIP1) and p27(Kip1) cyclin-dependent kinase inhibitor (CDKI) genes are the markers of cell senescence and DNA damage. The aim of the study was to determine the influence of renal ischaemia/reperfusion (I/R) and anti-lymphocyte function-associated antigen-1 (LFA-1) monoclonal antibody (mAb) treatment on the value of the above-mentioned markers. Significantly higher levels of p21 and p27 were expressed by the glomeruli (P=0.001 and P=0.0001), tubules (P=0.0065 and P=0.0006), and interstitial cells (P=0.0017 and P=0.0022, respectively) of the xenoperfused kidneys. The mean T length of non-perfused renal specimens (5.56+/-0.60 kbp) was longer than that of the xenoperfused kidneys (5.46+/-0.36 kbp) [P= non-significant (NS)]. Addition of anti-LFA-1 mAb did not significantly influence the gene expression profile in the xenoperfused kidneys. The mean T length was longer in the kidneys with anti-LFA-1 mAb than in those without the medication (5.7+/-0.11 vs 5.13+/-0.31 kbp) (P=0.0661). Kidney I/R is associated with telomere shortening and an over-expression of p21 and p27 CDKIs, which indicates substantial DNA damage and/or accelerated tissue senescence. Although anti-LFA-1 mAb had some protective effect on the telomeres, it did not influence the gene expression profile in this study.

Effect of ischemia/reperfusion on telomere length and CDKI genes expression in a concordant ex-vivo hemoperfusion model of primate kidneys

OBJECTIVES

The telomere (T) length, p21(WAF1/CIP1) and p27(Kip1) cyclin dependent kinase inhibitor (CDKI) genes are considered the markers of cell senescence and DNA damage. The aim of the study was to evaluate the influence of renal ischemia/reperfusion (I/R) on the value of above-mentioned markers.

METHODS

13 Macaque cynomolgus monkey kidneys were harvested and placed in Eurocollins solution. 9 kidneys were ex-vivo perfused with human blood and 4 kidneys were not perfused at all (control group). Tissue expression of p21(WAF1/CIP1) and p27(Kip1) was evaluated immunohistochemically and the T lengths were measured by southern blotting technique.

RESULTS

Significantly higher levels of p21 and p27 were expressed by the glomeruli (p = 0.001 and 0.0001), tubules (p = 0.0065 and 0.0006) and interstitial cells (p = 0.0017 and 0.0022, respectively) of the xenoperfused kidneys. The mean T length was higher in the control group (5.56 +/- 0.60 kbp) than in the study group kidneys (5.46 +/- 0.36 kbp) (P = NS).

CONCLUSION

Renal I/R is associated with telomere shortening and an over-expression of p21 and p27 genes indicating substantial DNA damage and/or accelerated tissue senescence.

Ex-vivo hemoperfusion (eHPS) of pig-lungs with whole human blood: effects of complement inhibition with a soluble C1-esterase-inhibitor

OBJECTIVES

Xenotransplantation could be a future alternative to allotransplantation due to increasing organ shortage. Complement activation plays a major role in hyperacute rejection (HAR) in pig-to-human combinations. We developed an ex-vivo hemoperfusion (EHP) system to investigate pathophysiology of HAR in the lung. After standardizing the model, the effect of a soluble complement inhibitor (C1-INH, Berinert) was investigated.

METHODS

Pig lungs were harvested following cold perfusion with Celsior preservation solution. EHP was performed using fresh heparinized human blood plus C1-INH (n = 6) or heparinized human blood as control (n = 4). Bloodgas analyses (BGA), pulmonalarterial pressure (PAP) were monitored. P-selectin and L-selectin were measured. Tissue samples were taken and microscopic changes evaluated.

RESULTS

BGA, PAP, macroscopic and microscopic changes in the control group showed HAR, while the C1-INH group showed significantly longer function. Leucocytes and platelets were markedly activated in the control, whereas in the treated group L-selectin and P-selectin values indicated lower activation. HE stainings showed maintained lung architecture after perfusion of pig-lungs with human blood plus C1-INH. Immunohistochemistry showed less C1q, C3, C5b-9 activation in the C1-INH group.

CONCLUSIONS

Investigation of interaction of human blood with pig lung endothelium could be done in this model. C1-INH attenuates HAR in a pig-to-human lung transplantation model by decreasing the activation of adhesion molecules. C1-INH could play a role in induction therapy of future lung xenotransplantation.

Urinary endotoxin excretion and urinary tract infection following kidney transplantation

Following kidney transplantation, urine endotoxin levels were measured among 44 patients and compared to bacterial cultures. Urine samples were collected either via transurethral catheters or - after removal of the catheter on postoperative day 4 - by midstream void. In a control group of ten healthy volunteers, urine endotoxin levels were measured daily for 10 days. Urinary endotoxin concentration was measured by means of a chromogenically modified Limulus amebocyte lysate (LAL) test. The levels among patients with positive bacteriological findings (n = 21) were always elevated ( > 0.7 EU/ml). Furthermore, there was a marked, statistically significant difference in endotoxin values between samples with bacterial growth and samples with fungal or without any growth (P < 0.001). All 21 of the 44 patients with urinary tract infection (UTI) were endotoxin-positive. Seven more patients who received antibiotics had elevated urinary endotoxin levels, but no bacterial growth in the urine culture. No bacterial infection or significant urinary endotoxin was found in the control group. In summary, the detection of urinary endotoxin in samples obtained by either suprapubic/transurethral catheters or midstream void is an early, sensitive, and specific means of diagnosis that can be carried out even during antibiotic treatment.

Production of proinflammatory cytokines and adhesion molecules in ex-vivo xenogeneic kidney perfusion

Xenogeneic transplantation of solid organs is limited due to hyperacute rejection. In concordant systems, the mechanisms of rejection can be studied due to cross-reactivity of mediators with anti-human monoclonal antibodies. The aim of this study was to obtain information about the kinetics of proinflammatory cytokines and production of soluble adhesion molecules in the acute phase of reperfusion, eight kidneys from rhesus monkeys were perfused ex-vivo with human blood (group B/0) for 1 hour in a closed system. Blood levels of IL-1b, IL-6, TNFalpha, soluble ICAM, and E-selectin were measured using an ELISA technique under steady-state conditions. Cytokine levels rose significantly within the 60-min interval (IL-1b, 6.1 +/- 2.6-161.1 +/- 98.5 pg/ml; IL-6, 30.2 +/- 7.7-274.2 +/- 75.8 pg/ml; TNFalpha, 544.2 +/- 363.6-1651.0 +/- 25.7 pg/ml; P < 0.05). Immediately after the beginning of reperfusion, soluble ICAM-1 and selectin levels were abnormally high and rose constantly throughout the observation period, reaching significance at 60 min. High levels of proinflammatory cytokines may lead to an induction of adhesion molecules, thus, upregulating the leukocyte-endothelial interaction in a complement-independent mechanism. Specific pretreatment with monoclonal antibodies against ICAM-1, LFA-1, or other soluble mediators may be useful in down-regulating hyperacute rejection in trans-species transplantation.

Long-term follow-up of lipid metabolism and rheologic properties after successful pancreas and kidney transplantation

The long-term effect of pancreatic and kidney transplantation (spkt) on blood viscosity, lipid metabolism and skin microcirculation in insulin-dependent diabetes mellitus (IDDM) was studied because impaired rheological properties of blood may play a role in the development of diabetic micro- and macroangiopathy. 46 IDDM-patients (16 f/30 m; 23 +/- 34 y mean duration of diabetes; 60 +/- 14 mos mean follow up period) underwent spkt (Gr.I: n = 28) or solitary kidney (Gr.II: n = 18) transplantation, and were compared with healthy controls (C). Rheological measurements were performed with Mooney-Ewart rotation-viscosimeter determining whole blood viscosity (WBV), at shear rates 1, 5, 10, 20, 50, 100, 200 sec(-1). Triglycerides, total and HDL-, LDL- and VLDL cholesterol and fibrinogen were measured. Microcirculation was estimated by transcutaneous oxygen tension measurement (tcpO2) and laser speckle method, in the forefoot area. Hemoglobin A1 was normalized only in group I (I: 7.2 +/- 0.2%; II: 8.3 +/- 0.3%; C: < 8%). WBV at low shear (1, 5, 10) was increased in both groups, when compared to healthy controls (I: 12.4 +/- 2; 12.5 +/- 1; 6.8 +/- 0.5 mpas; II: 18.7 +/- 2; 13.4 +/- 15; 9.4 +/- 1 mpas; C: 7.5 +/- 0.5; 6.7 +/- 0.3; 5.4 +/- 0.2 mpas; P < 0.05). Plasma fibrinogen was elevated in both groups compared to normals: (I: 384 +/- 19; II: 448 +/- 20; C: 250 +/- 50 mg/dl; P < 0.05). There was a positive influence of spkt on skin microcirculation: tcpO2/prior tx: I: 44 +/- 3; II: 49 +/- 6 mmHg; post tx: I: 59 +/- 4; II: 42 +/- 3 mmHg. Laser speckle prior tx I: 3.3 +/- 0.3; II: 4.7 +/- 0.2 rel. U.; post tx: 3.8 +/- 0.2; II: 4.3 +/- 0.2 rel. U. Patients with progression of angiopathy showed still higher fibrinogen and shear rates (P < 0.05). There was no significant difference for total HDL-, LDL- and VLDL cholesterol. Despite normalization of glucose metabolism and significant improvement of microcirculation in spkt patients, fibrinogen and the shear rates are increased indicating a persisting "individual" vascular risk. It is suggested that an additional hemorheological approach in the treatment posttrransplant might prevent the progression of vascular complications.

Possible oxcarbazepine interaction with cyclosporine serum levels: a single case study

We studied the influence of an add-on medication with oxcarbazepine on the cyclosporine trough level in a kidney transplant recipient with pharmacoresistant epilepsy. Two weeks after the beginning of the trial we observed a decrease of the cyclosporine trough and the Na serum levels. Both could be corrected by a small-dose reduction of oxcarbazepine, an augmentation of the cyclosporine dosis, and oral sodium chloride substitution. After this episode the cyclosporine trough and the Na serum levels remained stable. Seizure frequency was reduced by 95%. The influence of oxcarbazepine on the cyclosporine serum level has to be studied carefully in other patients after transplantation before the use of oxcarbazepine can be recommended in patients with an immunosuppressive medication with cyclosporine. Our data suggest that oxcarbazepine may be an effective drug with tolerable side effects in this group of patients.

Development and application of a high-performance liquid chromatography-based assay for determination of the activity of inosine 5'-monophosphate dehydrogenase in whole blood and isolated mononuclear cells

With the objective of pharmacodynamic monitoring of the immunosuppressive efficacy of mycophenolate mofetil (MMF) (CellCept, Hoffman-LaRoche, Grenzach-Wyhlen, Germany), a method for determination of the inosine monophosphate dehydrogenase (IMPDH) activity in whole blood cell (WBC) lysates and mononuclear cells (MNCs) was developed. The assay is based on the incubation of WBC lysates or lysed MNCs in the presence of supplemented inosine 5'-monophosphate (IMP) and nicotimamide adenine dinucleotide (NAD). The formation of xanthosine 5'-monophosphate (XMP) was determined by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The analytical method was validated, and the obtained data demonstrated that the amount of XMP in WBC and MNC lysates can be reliably determined by this method. Under assay conditions the rate of XMP formation remained constant within the incubation period of 60 minutes and a quantification of product formation at 30 and 60 minutes proved to be sufficient to reliably characterize the IMPDH activity. Applications of this assay with whole blood indicated extremely high IMPDH-activities in samples from patients with renal transplant receiving MMF. IMPDH monitoring within 10 hours after administration of the morning dose demonstrated a marked enzyme inhibition between 2 hours and 3 hours postdosing, but the activities returned to predose levels within one dose interval. The analysis of isolated cell fractions indicated that the IMPDH-activity is predominantly located in erythrocytes. The contribution of MNCs to the whole blood activity remained below 10%. In order to simulate the in vivo exposure of MNCs to mycophenolic acid, an "erythrocyte- and platelet-free" whole blood was reconstituted by resuspension of isolated MNCs with plasma. This strategy allowed for the reliable measurement of IMPDH activity in the target cells of immunosuppression.

[Human xenogenic kidney transplantation from the clinical viewpoint]

Pig-to-primate transplantations of hDAF-transgenic kidneys achieved survival times of up to 70 days. Pilot projects for clinical kidney xenotransplantation seem to be possible in the near future. The problems of hyperacute rejection seem to be solved. Delayed xenograft rejection remains a serious problem. Further medical, ethical and practical issues have to be solved, before Phase-I-studies can be anticipated. In contrast to other organs, kidney xenotransplantation is associated with low operative risk. Xenotransplant dysfunction or rejection could be treated with conventional hemodialysis.

Cardiovascular risk profile after simultaneous pancreas and kidney transplantation

The positive influence of simultaneous pancreas and kidney transplantation (PKT) on the development of diabetic microvascular lesions is well established. On the other hand, little is known on its impact on diabetic macrovascular disease, which is still the major cause of death in diabetes, including patients after PKT. In order to evaluate the influence of PKT on the cardiovascular risk profile, we performed a cross-sectional study on 55 patients. Special attention was given to the hemorheological parameters fibrinogen and plasma viscosity, two important cardiovascular risk factors, which so far have found no attention in the field of PKT research. The patients were subdivided into three groups according to their graft function: group 1-26 patients after successful PKT (no insulin dependency, serum creatinine <2 mg%), group 2-23 patients after PKT and rejection of the pancreas graft (insulin dependency, serum creatinine <2 mg%), group 3-6 patients after PKT with pancreas rejection and renal insufficiency (insulin dependency, serum creatinine >2 mg%, no dialysis). There was a high prevalence of arterial hypertension after PKT (group 1: 65%, group 2: 70%, group 3: 100%). Serum lipids were in the normal range as long as renal function was intact. In renal insufficiency, however, LDL-cholesterol and triglycerides were significantly elevated (p < 0.05). Fibrinogen was significantly raised after PKT (p < 0.001), as was plasma viscosity when the pancreas graft was rejected (p < 0.02). There was a tendency towards elevated fibrinogen levels with decreasing graft function. In conclusion, a number of cardiovascular risk factors were identified in patients after PKT, predominantly arterial hypertension and impaired hemorheology, with elevated fibrinogen levels and plasma viscosity. There is a further enhancement with decreasing graft function.

Do apnea monitors decrease emotional distress in parents of infants at high risk for cardiopulmonary arrest?

INTRODUCTION

The immediate post-partum period is stressful for most parents. The need to use a home apnea monitor may tax parental coping skills even further. Therefore, we conducted a study to assess the psychosocial consequences of apnea monitoring on parental emotional distress and family functioning.

METHOD

We studied 104 parents of infants at high risk for cardiopulmonary arrest. Fifty-two parents had infants who used home apnea monitors, and 52 parents were age-matched and gender-matched control subjects. Data were collected during the infant's hospitalization, and then at 2 weeks, 3 months, and 6 months after discharge. At 1 year, parents were interviewed about their attitudes toward using the apnea monitor.

RESULTS

Both groups experienced elevated levels of emotional distress, but the group with infants who used the monitors had significant increases in depression and hostility immediately following discharge from the hospital compared with baseline, whereas the non-monitored group had a significant increase in hostility at 6 months. At 1-year follow-up, the majority of the parents reported that they used the monitor every night, felt more secure in using it, and judged it helpful.

DISCUSSION

The immediate period following hospital discharge of infants who need to use a home apnea monitor is characterized by significant emotional distress for the parents, which resolves over time. Anticipatory education and counseling of parents is recommended.

Screening for basiliximab exposure-response relationships in renal allotransplantation

The immunosuppressant basiliximab--a chimeric monoclonal antibody specific to the interleukin-2 receptor on activated T-lymphocytes--significantly reduces the incidence of acute cellular rejection following renal transplantation. Screening for exposure-response relationships was performed within a randomized, blinded, placebo-controlled efficacy trial in which patients received 40 mg basiliximab (20 mg on days 0 and 4) by intravenous infusion in addition to cyclosporine and corticosteroids. In a subset of patients, serum samples were collected pre-transplant and once in weeks 2, 3 and 4 for determination of basiliximab concentrations. A population pharmacostatistical model was used to derive individual empirical Bayes estimates of each patient's pharmacokinetic parameters. Biopsy-confirmed acute rejection episodes were recorded to month 6 post-transplant. Forty basiliximab-treated patients were evaluated, 30 men and 10 women, aged 48 +/- 12 yr (range, 24-73) and weighing 72.4 +/- 12.9 kg (range, 52.5-107.5). The basiliximab distribution volume was 7.5 +/- 1.7 L, the half-life 7.5 +/- 2.5 d and the clearance 33 +/- 12 mL/h. There was no clinically relevant influence of weight, age, or gender on basiliximab disposition. Receptor-saturating serum basiliximab concentrations (> 0.2 microgram/mL) were maintained for 41 +/- 23 d. Twenty-five patients remained rejection-free over the 6-month observation period, while a total of 26 biopsy-confirmed acute rejection episodes occurred in the remaining 14 patients. Of these episodes, 12 occurred during receptor blockade. No apparent relationship to basiliximab concentration on the day of onset was observed range, 0.1-9.0 microgram/mL) nor did the time of suppression offset represent a period of increased risk for rejection episodes. Fourteen rejection episodes occurred after basiliximab had cleared from the serum. The durations of receptor suppression preceding these events did not differ compared with those in patients who remained rejection-free: 32 +/- 11 versus 45 +/- 26 d, respectively (p = 0.1269). Given the durations of receptor saturation achieved with the chosen basiliximab regimen, this screen for exposure-response relationships did not identify the duration of receptor saturation in peripheral blood as a predictive factor for acute rejection episodes. Further exploration for exposure-effect relationships in a larger population is warranted.

[Transgenic swine as potential organ donors? Results of the ex-vivo hemoperfusion hDAF transgenic kidney with human blood]

Kidney xenotransplantation is not yet a realistic clinical treatment modality. However, during the last decades more than 30 kidneys from other species have been transplanted into humans; some of the kidneys sustained some function up to 60 days. Recent progress in genetic engineering has raised the possibility to create large transgenic animals which express human complement regulatory proteins (CRP). Since early complement activation is believed to be the main triggering event for xenograft destruction, complement regulation by species-specific CRP should avoid hyperacute rejection in transspecies transplantation. The perfusion of hDAF-transgenic pig kidneys with human blood was not associated with the morphological signs of hyperacute rejection when compared to non-transgenic control organs. Specific immunohistology could demonstrate that the transgene was sufficient to regulate complement activation beyond C3 despite the endothelial deposition of xenoantibodies. In the future, these organs could be further optimized and ultimately tested in a clinical pilot protocol under appropriate immunosuppression.

[Prevention of ischemia before cold ischemia by pharmcologic donor conditioning--experimental findings]

The loop-diuretic piretanide was used to study the influence of pharmacological donor pretreatment on immediate postischemic function in a pig model of kidney transplantation based on the results of a clinical pilot study [4]. Following laparotomy, both kidneys were flushed via a transaortal catheter with Eurocollins-solution and surgically removed. A cold ischemic period of 1 or 24 h was chosen. After that period, kidneys were reperfused with intraoperatively drawn heparinized blood for one hour. We used a special instrument for hemoperfusion of isolated organs which allows perfusion for several hours under steady-state conditions. Four groups were formed: Control and piretanide, 1 or 24 h cold ischemia. The perfusion of piretanide-treated organs resulted in a lower perfusion-resistance, calculated as pressure/flow-ratio or as pressure/glomerular filtrationratio. The flow in the pretreated group was higher, thus excluding a higher shunt-volume. In parallel, oxygen consumption as a parameter of postischemic function start and creatinine clearance were higher in the piretanide treated groups. The experiments demonstrate a superior postischemic function of pretreated kidneys in comparison to control organs after 1 and 24 hours of cold ischemia in this model.

Immunopathological observations after xenogeneic liver perfusions using donor pigs transgenic for human decay-accelerating factor

BACKGROUND

Donor pigs transgenic for human decay-accelerating factor (hDAF) were used in a xenogeneic ex vivo liver perfusion model to study the effect of this modification on the development of hyperacute rejection.

METHODS

Three transgenic pigs were hepatectomized after hypothermic portal and transaortal gravity perfusion. Livers from six nontransgenic pigs served as controls. All livers were perfused for 3 hr with human blood from two donors diluted to a hematocrit of 30%. Particular importance was placed on the use of an optimal perfusion technique incorporating the floating suspension of the organs in a waterbath and intermittent external pressurization. Biochemical, physiological, and immunological parameters were assessed. Tissue specimens taken before and after perfusion were analyzed using routine histology, electron microscopy, and immunohistology.

RESULTS

Complement activation was more pronounced in the control group. AP50 and CH50 values fell to about 60% of the initial levels in control experiments, whereas they remained at 80% of the initial levels during perfusion of hDAF livers. After 180 min, pig tumor necrosis factor alpha levels were 7862+/-1645 pg/ml for unmodified livers and 2830+/-734 pg/ml in the hDAF group. Human tumor necrosis factor alpha levels were similar in both groups. Control livers showed marked morphological alterations and distinct deposition of complement factors, whereas livers expressing hDAF showed no signs of hepatocellular necrosis and almost no complement deposition beyond C3 activation.

CONCLUSIONS

These results confirm that the transgenic expression of the human complement regulatory protein hDAF reduces complement activation and prevents hyperacute rejection in a xenogeneic liver perfusion model over the 3-hr evaluation period used in this study.

Morphology of hDAF (CD55) transgenic pig kidneys following ex-vivo hemoperfusion with human blood

Discordant xenotransplantation of pig kidneys into man may be possible in the future using transgenic organs which regulate complement activity. It was the aim of this experimental study to characterize morphologic alterations of organs transgenic for human decay accelerating factor (hDAF/CD55) perfused with human blood since no data on function of these organs after exposure to human blood are available. An ex-vivo system was developed that allows computer driven pressure-controlled perfusion of kidneys including a separate cartridge oxygenator circuit. Following cold ischemia time of 1-4 hr, 8 kidneys from heterozygote transgenic animals (TG) and 9 control kidneys (C) were perfused with 500 ml freshly drawn heparinized human blood at physiological conditions. A histologic grading system from 0 to +4 was used to describe the histologic findings. Using a mouse antihuman DAF moAB, hDAF was stained on all TG kidneys both on glomerular capillary (4+) and vascular endothelium (2+), but there was no detectable hDAF-expression on controls. No difference in xenoantibody deposition on vascular endothelium was seen between both groups. There was comparable staining for complement fraction C4 in both groups, but significant reduction of C3 and C9 staining on glomerular and vascular endothelium in TG. P-selectin was expressed on a higher level in C (+4) compared with TG (+2). Neutrophil extravasation [NP-57 elastase] was higher in C (80.2 vs. 32.2 C vs. TG [values as n/high power field]). Tubular epithelial cell swelling and mild necrosis was paralleled by glomerular hemorrhage and platelet microthrombus formation in both groups as seen in transmission electron microscopy. The observed results allow the conclusion that hDAF expression on transgenic pig kidneys was sufficient to inhibit complement activation beyond C3 during xenoperfusion with human blood despite xenoantibody deposition.

Stenting of central venous stenoses in hemodialysis patients: long-term results

From November 1992 through July 1996, 15 Wallstents were implanted for the treatment of symptomatic central arm vein obstructions in 14 hemodialysis patients (10 subclavian, 2 brachiocephalic vein stenoses, 2 subclavian vein occlusions). There were no acute complications. All patients were investigated by clinical examination and color-duplex sonography at regular three month intervals. When recurrent swelling predicted restenosis, phlebography was also performed. During the follow-up, high grade stenoses at the central or peripheral ends of four stents were successfully treated with five overlapping stents, giving a total of 20 Wallstent implantations. Complete occlusion of another subclavian vein distally to the stent at 16 months required ligation of the patient's arteriovenous fistula. Life table analysis including all 20 stents revealed a cumulative primary one year (two year) stent patency of 70% (50%). The cumulative secondary one year (two year) stent patency was 100% (85%). We believe that in hemodialysis patients, PTA plus Wallstent implantation is a safe and effective procedure in the treatment of central venous stenoses and even shorter occlusions. Consequent follow-up allows for timely diagnosis and treatment of restenoses, thus guaranteeing long-term patency rates comparable to those of veno-venous bypass surgery.