Remission of refractory Crohn's disease by high-dose cyclophosphamide and autologous peripheral blood stem cell transplantation

BACKGROUND

Despite advances in immunosuppressive therapy, up to 10% of patients with severe Crohn's disease (CD) remain refractory to conventional treatment. Limited evidence from pilot trials suggests that high-dose immunosuppression and autologous peripheral blood stem cell transplantation (autoPBSCT) may induce remission in these patients, but there is substantial controversy regarding the safety and efficacy of this approach.

AIM

To address this issue, a monocentre phase I/II trial of autoPBSCT was performed in patients with refractory CD in our hospital.

METHODS

Here, we report on the outcome of 12 patients with refractory CD treated with autoPBSCT. Briefly, CD34(+) -selected PBSCs were harvested after mobilisation therapy with cyclophosphamide and granulocyte-colony stimulating factor. Later, immunoablative conditioning therapy with high-dose cyclophosphamide followed by autoPBSCT was applied and clinical and endoscopic responses were analysed after a mean follow-up of 3.1 years (range 0.5-10.3 years).

RESULTS

PBSC harvest following mobilisation chemotherapy was successful in 11/12 patients and resulted in a clinical and endoscopic improvement in 7/12 patients. Subsequent conditioning and autoPBSCT were performed in nine patients and were relatively well tolerated. Among those, five patients achieved a clinical and endoscopic remission within 6 months after autoPBSCT. However, relapses occurred in 7/9 patients during follow-up, but disease activity could be controlled by low-dose corticosteroids and conventional immunosuppressive therapy.

CONCLUSION

Immunoablation by cyclophosphamide and autologous peripheral blood stem cell transplantation is safe and effective to induce remission of refractory Crohn's disease, and should be further evaluated in randomised controlled trials.

Endoscopic diagnosis of acute intestinal GVHD following allogeneic hematopoietic SCT: a retrospective analysis in 175 patients

Diagnosis of acute intestinal GVHD (aGVHD) following allogeneic hematopoietic cell transplantation is based on clinical symptoms and histological lesions. This retrospective analysis aimed to validate the 'Freiburg Criteria' for the endoscopic grading of intestinal aGVHD. Grade 1: no clear-cut criteria; grade 2: spotted erythema; grade 3: aphthous lesions; and grade 4: confluent defects, ulcers, denudation of the mucosa. Having excluded patients with infectious diarrhea, we evaluated 175 consecutive patients between January 2001 and June 2009. Setting a cutoff between grade 1 (no change in therapy) and grade 2 (intensification of immunosuppression), macroscopy had a sensitivity of 89.2% (95% confidence interval (CI): 80.4-94.9%), a specificity of 79.4% (95% CI: 69.6-87.1%), a positive-predictive value of 79.6% (95% CI: 70.0-87.2%) and a negative-predictive value of 89.0% (95% CI: 80.2-94.9%). In all, 20% of patients with aGVHD in the lower gastrointestinal tract (GIT) had lesions only in the terminal ileum. In all patients with aGVHD ≥2 of the upper GIT, typical lesions were also found in the lower GIT. Ileo-colonoscopy showed the highest diagnostic yield for aGVHD. In conclusion, the 'Freiburg Criteria' for macroscopic diagnosis of intestinal aGVHD provide high accuracy for identifying aGVHD ≥2.

A clinical trial on absorption and N-acetylation of oral and rectal mesalazine

BACKGROUND

Mesalazine (5-ASA) is a standard treatment for ulcerative colitis. Extent of absorption and N-acetylation determine systemic exposure to 5-ASA, and are thereby relevant for the safety of the treatment. The aim of the study was to compare absorption and N-acetylation of 5-ASA following rectal or oral drug administration. Healthy subjects were compared to patients with ulcerative colitis to evaluate the impact of chronic inflammation of colorectal mucosa on disposition of 5-ASA.

MATERIALS AND METHODS

First, 12 healthy adults were randomized to receive 2 g of 5-ASA by each of four different formulations: oral delayed release granules, 30 mL enema, 60 mL rectal foam, and 120 mL rectal foam. Second, 12 patients with active ulcerative colitis received 60 mL rectal foam. Pharmacokinetic analysis was performed by determination of 5-ASA and its acetylated, pharmacologically inactive metabolite (Ac-5-ASA) in plasma and urine.

RESULTS

First, systemic exposure to 5-ASA was markedly lower after rectal drug administration as compared to oral dosing (P < 0.001; e.g. median relative bioavailability of 60 mL rectal foam: 36%). Second, N-acetylation of rectal 5-ASA was lower in patients than in healthy subjects [area under the curve (AUC) ratio Ac-5-ASA/5-ASA: 1.6 +/- 0.5 vs. 2.3 +/- 0.4, mean +/- SD, P < 0.01]. High peak plasma concentrations of 5-ASA were correlated with high microscopic disease activity (r = 0.67, P < 0.05).

CONCLUSIONS

Rectal delivery of 5-ASA results in low systemic drug exposure with potentially reduced toxicity in comparison with oral drug administration. Chronic inflammation of colorectal mucosa might be a relevant source of variability in pharmacokinetics of 5-ASA.

[Pathogenesis of chronic inflammatory bowel diseases]

Genetic predisposition, nutritional and environmental influences, intestinal pathogens, psychological stress, and disturbed intestinal barrier function have been accepted as important factors in the pathogenesis of chronic inflammatory bowel diseases. Uncontrolled reactions of T-cells and proinflammatoric cytokines are the common denominator of all factors contributing to pathogenesis. The detection of NOD2 gene mutation in about 25% of patients with Crohn's disease was an important step towards an understanding of the molecular background of the disease. The NOD2 proteins functions as an intracellular sensor of bacterial cell membrane constituents and is a crucial part of the innate immune system. In Crohn's disease, the secretion of defensins, naturally occurring antimicrobial peptides, is disturbed. There is evidence that several pathways involved in the reaction of the innate immune system may be disturbed in CED, ultimately leading to an uncontrolled activity of the adaptive immune system.

Effect of vardenafil, an inhibitor of phosphodiesterase-5, on portal haemodynamics in normal and cirrhotic liver -- results of a pilot study

BACKGROUND

Dysregulation of the cyclic guanosine 3',5' monophosphate-nitric oxide system is in part responsible for portal hypertension in cirrhosis.

AIM

To test the effects of inhibitors of phosphodiesterase-5 on portal haemodynamics.

METHODS

To 18 healthy subjects and 18 patients with Child A liver cirrhosis, 10 mg of vardenafil, an inhibitor of phosphodiesterase-5, were administered orally. Doppler sonographic measurements of hepatic and splanchnic blood flow, systemic blood pressure and heart rate were recorded before, 1 h after, and 48 h after the application. Vardenafil plasma levels were determined after 1 h. In five patients, invasive registration of free and wedged hepatic vein pressure was performed.

RESULTS

Portal venous flow increased in patients from 0.82 +/- 0.30 L/min (mean +/- s.d.) by 26% (CI: 16-37%, P = 0.0004) and in healthy subjects from 0.75 +/- 0.20 L/min (mean +/- s.d.) by 19% (CI: 9-28%; P = 0.0010). Celiac and hepatic artery resistivity indices rose significantly. Systemic blood pressure decreased slightly in patients. The wedged hepatic venous pressure gradient decreased in four of five patients with liver cirrhosis. Vardenafil plasma levels were higher in patients (14 +/- 10 microg/L) than in healthy subjects (9 +/- 6 microg/L; n.s.).

CONCLUSIONS

Inhibition of phosphodiesterase-5 increases portal flow and lowers portal pressure by a decrease in sinusoidal resistance and may be a novel therapeutic strategy for portal hypertension.

Cholestatische Hepatopathien

Zu den autoimmunen cholestatischen Hepatopathien rechnet man die primär biliäre Zirrhose (PBC), die Autoimmuncholangitis (AIC, Synonym: AMA-negative PBC) und die primär sklerosierende Cholangitis (PSC). Überlappungssyndrome weisen sowohl Charakteristika von cholestatischen Leberkrankungen als auch einer Autoimmunhepatitis auf. Bei der PBC sind alkalische Phosphatase und gamma-GT erhöht, in geringerem Ausmaß auch die Transaminasen, die Histologie zeigt Gallengangsläsionen. Anti-mitochondriale Antikörper sind charakteristisch. Die Gabe von Ursodeoxycholsäure (UDC) ist die etablierte Therapie und kann – zumindest in frühen Stadien – die Progredienz aufhalten oder verlangsamen. Bei fehlendem Ansprechen kann eine Immunsuppression versucht werden. Die PSC ist meist mit einer chronisch entzündlichen Darmerkrankung assoziiert. P-ANCA sind häufige Autoimmunmarker. Meist wird die Diagnose durch die typischen Veränderungen der Gallenwege bei der ERCP gestellt. UDC wird zur Therapie eingesetzt. Gallengangsstrikturen oder Cholangitiden sind sekundäre Folgen und können mit Antibiotika oder Dilatationen der Gallenwege behandelt werden. PBC und PSC führen letztlich zur Leberzirrhose. Bei fortgeschrittener Erkrankung ist eine Lebertransplantation indiziert.

Thioguanine-nucleotides do not predict efficacy of tioguanine in Crohn's disease

BACKGROUND

6-Thioguanine-nucleotides seem to be the active metabolites of thiopurine therapy, and their monitoring has been considered a useful tool for optimizing response in inflammatory bowel diseases. Tioguanine (thioguanine) therapy results in much higher levels of 6-thioguanine-nucleotide levels when compared with azathioprine or mercaptopurine.

AIM

To elucidate the influence of 6-thioguanine-nucleotide and methylated 6-thioguanine-nucleotide levels under tioguanine on efficacy and toxicity in Crohn's disease.

METHODS

6-Thioguanine-nucleotide and methylated 6-tioguanine-nucleotide levels were measured regularly in 26 Crohn's disease patients treated with tioguanine. Nucleotide levels were related to efficacy and toxicity.

RESULTS

6-Thioguanine-nucleotide levels rose very high [median 1241 pmol/8 x 10(8) red blood cells (range 313-1853)]. Methylated 6-thioguanine-nucleotide levels were detected in all patients [491 pmol/8 x 10(8) red blood cells (154-1775)]. 6-Thioguanine-nucleotide and methylated 6-thioguanine-nucleotide concentrations correlated significantly (r = 0.7, P < 0.0001). Nucleotide levels from patients achieving remission (n = 14) did not differ significantly from non-remitters (n = 12) [6-thioguanine-nucleotide: 1077 (599-2160) vs. 1210 (534-4665); methylated 6-thioguanine-nucleotide: 510 (214-1222) vs. 421 (145-1284)]. One patient with intermediate thiopurine S-methyltransferase activity experienced bone marrow toxicity upon dose escalation parallel with excessively high thioguanine-nucleotide levels.

CONCLUSIONS

6-Thioguanine-nucleotide as well as methylated 6-thioguanine-nucleotide levels under tioguanine therapy were not related to efficacy. This suggests that monitoring of 6-thioguanine-nucleotide levels is not a useful tool to predict response to thiopurines.

Complete remission of Crohn's disease after high-dose cyclophosphamide and autologous stem cell transplantation

In a 36-year-old male with ileocolic Crohn's disease (CD) no long-lasting remission was obtained by treatment with corticosteroids, mesalazine, azathioprine and antibiotics. Surgical interventions due to relapsing fistulae and abscesses resulted in the removal of >1.5 m of small bowel and left only 40 cm of large bowel. In July 2000, a new fistula and abscess developed. The combination of corticosteroids, mesalazine, ciprofloxacin, metronidazol, azathioprine, formula diet and anti-TNF-alpha antibody largely reduced clinical activity, and resection of fistula and abscess were successful. Despite clinical remission, histology showed activity in the small bowel and the colon. In March 2001, stem cell mobilization chemotherapy with cyclophosphamide was performed. It induced an endoscopic remission for 9 months, which was maintained on azathioprine and corticosteroids. After relapse, in March 2002, high-dose chemotherapy with cyclophosphamide and reinfusion of T-cell-depleted autologous peripheral CD34+ blood stem cells were performed. This led to a complete clinical, endoscopical and histological remission for 9 months without any treatment. Thereafter, endoscopy showed initial aphthous lesions with minimal histological signs of inflammation. The patient is asymptomatic, but low-dose prednisolone and methotrexate are prophylactically given. Immunoablative chemotherapy followed by autologous peripheral blood stem cell transplantation may be a beneficial therapeutic option in complicated refractory CD.

High variation of tioguanine absorption in patients with chronic active Crohn's disease

BACKGROUND

Tioguanine (thioguanine) has been suggested as a therapeutic alternative for patients with Crohn's disease resistant or intolerant to azathioprine or mercaptopurine. However, pharmacokinetic data on tioguanine in inflammatory bowel disease are missing.

AIM

To determine the disposition of three different 40 mg tablet preparations of tioguanine in patients with Crohn's disease.

METHODS

Six patients with chronic active Crohn's disease were included in a randomized, cross-over, single-dose study. Pharmacokinetic analysis was based on plasma concentrations of tioguanine during 6 h after dosing. Tioguanine was measured by a validated high-pressure liquid chromatographic method.

RESULTS

The areas under the curve (AUC) varied 4-7-fold between patients. In two patients, tioguanine was not detected in plasma following the intake of one of the three tablets; another patient did not absorb tioguanine in two of the three different preparations. No significant differences were found in the AUC and Cmax values between the three tablets. In all patients, there was a second peak in plasma concentration following a meal 3 h after drug administration.

CONCLUSIONS

The absorption of tioguanine is highly variable in patients with Crohn's disease, which may be responsible for treatment failure. Therapy with tioguanine may be improved by monitoring tioguanine nucleotides as a surrogate parameter of efficacy.

Remission maintenance by tioguanine in chronic active Crohn's disease

BACKGROUND

Tioguanine may offer an alternative for immunosuppression in chronic active Crohn's disease. Recently, we have shown that tioguanine is effective in inducing rapid remission.

AIM

To evaluate the role of tioguanine in the maintenance of remission in chronic active Crohn's disease.

METHODS

A follow-up study was performed to investigate the long-term efficacy and safety of and tolerance to tioguanine in chronic active Crohn's disease. Sixteen patients who had successfully received 6-tioguanine for remission induction were enrolled. The reasons for immunosuppressive therapy were steroid dependence (n = 10), steroid refractoriness (n = 6) and intolerance (n = 6) or refractoriness (n = 1) to azathioprine. After remission induction therapy for 6 months, patients were treated for another 6 months with a daily dose of 20-40 mg tioguanine. Primary outcomes were remission (Crohn's disease activity index < 150) and complete steroid reduction in steroid-dependent patients at 12 months. Laboratory controls of white blood count and liver enzymes, as well as erythrocyte tioguanine nucleotide levels, were performed regularly.

RESULTS

After 12 months of treatment, 14 of 16 (88%) patients were in remission, and 12 of these were completely free of systemic steroids. Adverse events during maintenance therapy included photosensitivity (one patient), minor viral infections (one), headache (four) and mild alopecia (one). One patient developed elevated liver enzymes, splenomegaly and thrombocytopenia, indicative of nodular regenerative hyperplasia of the liver.

CONCLUSIONS

In responders to tioguanine, the drug appears to be very effective in maintaining remission of chronic active Crohn's disease. Unfortunately, long-term hepatotoxicity seems to be an unpredictable and potentially severe adverse drug reaction. Therefore, to date, tioguanine cannot be recommended for general use outside clinical trials.

6-thioguanine--efficacy and safety in chronic active Crohn's disease

BACKGROUND

: Azathioprine and mercaptopurine are commonly used in chronic active Crohn's disease. They share the disadvantage of a delayed onset of action and potentially serious side-effects, and are metabolized to thioguanine nucleotides which are thought to be the active metabolites. The direct use of 6-thioguanine may offer a more rapid and safer alternative. We conducted an open prospective study to investigate the efficacy and safety of 6-thioguanine in chronic active Crohn's disease.

METHODS

: Thirty-seven patients with chronic active Crohn's disease and a Crohn's disease activity index of > 150 were enrolled in this study. Inclusion criteria were steroid dependence (n = 19), steroid refractoriness (n = 9) and/or intolerance (n = 16) or refractoriness (n = 6) to azathioprine. Patients were treated with 40 mg/day of 6-thioguanine for 24 weeks; a dose escalation to 80 mg was allowed at week 12. Remission was defined as a Crohn's disease activity index of < 150 associated with a decrease of > 70 points; response was defined as a decrease of > 70 points in the Crohn's disease activity index.

RESULTS

: In the intention-to-treat analysis, 13 of 37 patients achieved remission (35%). Twelve of these 13 patients achieved remission after 4 weeks. Fifty-seven per cent of patients (21/37) achieved a response. The mean Crohn's disease activity index decreased from 284 +/- 74 to 153 +/- 101. 6-Thioguanine was more effective in azathioprine-intolerant than in azathioprine-refractory patients. Twelve of 16 patients intolerant to azathioprine tolerated 6-thioguanine. Adverse events included phototoxicity, pancreatitis, headache, nausea, alopecia, arthralgia, minor infections and reversible elevation of transaminases. Six patients required discontinuation of medication, two because of leucopenia.

CONCLUSIONS

: In this patient group with chronic active Crohn's disease, 6-thioguanine appeared to be effective with acceptable short-term toxicity, but long-term controlled trials are clearly needed to further define its role.

6-thioguanine--efficacy and safety in chronic active Crohn's disease

BACKGROUND

: Azathioprine and mercaptopurine are commonly used in chronic active Crohn's disease. They share the disadvantage of a delayed onset of action and potentially serious side-effects, and are metabolized to thioguanine nucleotides which are thought to be the active metabolites. The direct use of 6-thioguanine may offer a more rapid and safer alternative. We conducted an open prospective study to investigate the efficacy and safety of 6-thioguanine in chronic active Crohn's disease.

METHODS

: Thirty-seven patients with chronic active Crohn's disease and a Crohn's disease activity index of > 150 were enrolled in this study. Inclusion criteria were steroid dependence (n = 19), steroid refractoriness (n = 9) and/or intolerance (n = 16) or refractoriness (n = 6) to azathioprine. Patients were treated with 40 mg/day of 6-thioguanine for 24 weeks; a dose escalation to 80 mg was allowed at week 12. Remission was defined as a Crohn's disease activity index of < 150 associated with a decrease of > 70 points; response was defined as a decrease of > 70 points in the Crohn's disease activity index.

RESULTS

: In the intention-to-treat analysis, 13 of 37 patients achieved remission (35%). Twelve of these 13 patients achieved remission after 4 weeks. Fifty-seven per cent of patients (21/37) achieved a response. The mean Crohn's disease activity index decreased from 284 +/- 74 to 153 +/- 101. 6-Thioguanine was more effective in azathioprine-intolerant than in azathioprine-refractory patients. Twelve of 16 patients intolerant to azathioprine tolerated 6-thioguanine. Adverse events included phototoxicity, pancreatitis, headache, nausea, alopecia, arthralgia, minor infections and reversible elevation of transaminases. Six patients required discontinuation of medication, two because of leucopenia.

CONCLUSIONS

: In this patient group with chronic active Crohn's disease, 6-thioguanine appeared to be effective with acceptable short-term toxicity, but long-term controlled trials are clearly needed to further define its role.

A randomized, double-blind, double-dummy, multicenter trial of voriconazole and fluconazole in the treatment of esophageal candidiasis in immunocompromised patients

The efficacy, safety, and tolerability of voriconazole and fluconazole were compared in 391 immunocompromised patients with mycology- and biopsy-proven esophageal candidiasis. Primary efficacy analysis (256 patients) of esophageal treatment as assessed by esophagoscopy revealed success rates of 98.3% with voriconazole and 95.1% with fluconazole. The 95% confidence interval for the difference in success rates ranged from -1.0% to 7.5%. The overall safety and tolerability of both antifungals were acceptable. Fewer patients discontinued voriconazole treatment because of insufficient clinical response (4 patients [2.0%] vs. 5 patients [2.6%]). More patients discontinued voriconazole than fluconazole treatment because of laboratory test abnormalities (7 patients [3.5%] vs. 2 patients [1.0%]) or treatment-related adverse events (5 patients [2.5%] vs. 1 patient [0.5%]). The most frequent adverse events (23%) with voriconazole were mild, transient visual disturbances. Voriconazole (200 mg, b.i.d.) was shown to be at least as effective as fluconazole in the treatment of biopsy-proven esophageal candidiasis in immunocompromised patients.

Neuro-Behçet's syndrome in a patient not fulfilling criteria for Behçet's disease: clinical features and value of brain imaging

Central nervous system involvement is rarely an initial presenting manifestation of Behçet's disease (BD). We report the case of a 33-year-old man with recurrent attacks of fever, oral mucosal ulcers, deep venous thrombosis, diplopia, vertigo and headache. Sequential brain magnetic resonance imaging (MRI) scans showed fluctuating lesions of the brain stem, mesencephalon and thalamus. F-18-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) revealed hypometabolism at the parieto-occipital cortex at both sides and the brain stem. Treatment with prednisone and cyclosporine A led to a complete remission and normalisation of MRI and FDG-PET lesions. The present case illustrates the difficulty in the differential diagnosis of early neuro-BD.

Feasibility and response to budesonide as topical corticosteroid therapy for acute intestinal GVHD

Therapy of acute intestinal GVHD is still one of the main challenges after allogeneic transplantation. Increasing systemic immunosuppression (IS) is the first choice and includes corticosteroids and lymphocyte antibodies, often associated with severe side-effects. In inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, topical steroid therapy is used very successfully. Because of the similarity between these and acute intestinal GVHD we conducted a trial with oral budesonide (Budenofalk), a new topically active glucocorticoid, to treat patients with acute GVHD > or = grade II. After a diagnosis of aGVHD > or = grade II, 22 patients received increased IS, mainly systemic corticosteroids, and additionally budesonide 9 mg/day divided into three doses. Improvement in aGVHD, infectious side-effects, reduction of systemic IS and outcome were documented. Results were compared with the results of 19 control patients, who were treated only by increasing IS dose. In 17/22 patients (70%), treated with budesonide, the acute intestinal GVHD resolved and no relapse occurred after decreasing the systemic IS, while continuing budesonide. In only 8/19 patients in the control group did the acute intestinal GVHD resolve and 2/8 patients had a relapse of intestinal GVHD after decreasing IS, with an overall response of 33%. No severe intestinal infections occurred. We conclude that budesonide may be effective in acute intestinal GVHD as a topical corticosteroid and prospective, randomized studies should demonstrate its efficacy in allowing reduction of systemic immunosuppressive therapy, and its side-effects.

High prevalence of antibodies to calreticulin of the IgA class in primary biliary cirrhosis: a possible role of gut-derived bacterial antigens in its aetiology?

BACKGROUND

In a preliminary study we showed that antibodies to the endoplasmic reticulum protein calreticulin (CR) occur in primary biliary cirrhosis (PBC) and autoimmune hepatitis type 1 (AIH). Since anti-CR antibodies have also been found in patients with infectious diseases, we investigated their prevalence and immunoglobulin classes in patients with various hepatic and intestinal diseases, hoping to get some information on a possible relationship between an infectious trigger and the induction of a certain class of anti-CR antibodies.

METHODS

Sera were tested for anti-CR antibodies of the IgA, IgG, and IgM class by Western blotting, using CR isolated from human liver: in autoimmune liver diseases (primary biliary cirrhosis (PBC) (n = 86) and autoimmune hepatitis (AIH) type 1 (n = 57)), alcoholic liver cirrhosis (ALC) (n = 32), viral liver infections (acute hepatitis A (n = 8), acute hepatitis B (n = 20), and chronic hepatitis C (n = 28)), and intestinal diseases (Crohn disease (CD) (n = 30), acute yersiniosis (n = 26)). Sera from 100 healthy individuals served as negative controls.

RESULTS

The most prominent finding was the high prevalence of anti-CR antibodies of the IgA class and the similarity in the anti-CR antibody class pattern in PBC (IgA, 62%; IgG, 43%; IgM, 55%) and yersiniosis (IgA, 62%; IgG, 39%; IgM, 42%). Class IgA anti-CR antibodies also occurred frequently in ALC (IgA, 44%; IgG, 41%; IgM, 19%). In contrast, in AIH anti-CR antibodies were predominantly of class IgG (IgA, 28%; IgG, 60%; IgM, 33%). In hepatitis A anti-CR antibodies were absent. In the other diseases they had a low prevalence and were mostly of class IgG (acute hepatitis B: IgA, 0%; IgG, 15%; IgM, 0%; chronic hepatitis C: IgA, 7%; IgG, 21%; IgM, 0%; CD: IgA, 13%; IgG, 20%; IgM, 13%). Of the healthy individuals 7% had anti-CR antibodies exclusively of class IgG.

CONCLUSIONS

The high prevalence of anti-CR antibodies of class IgA in patients with PBC and yersiniosis as well as in alcoholic liver disease reflects a reactivity of the gut-associated immune system and could imply that a still undefined gut-derived bacterial (?) agent may trigger PBC.

Intersectoral action for health: a cornerstone for health for all in the 21st century

For many decades, intersectoral action has been recognized as being of critical importance for the promotion and the protection of human health. In 1977, the World Health Assembly identified intersectoral action as an important component in achieving the goal of Health for All by the Year 2000; this has since been reemphasized by a number of international conferences. A major conference entitled "Intersectoral action for health: a cornerstone for health for all in the 21st century" was held in Canada in 1997. Described as "intersectoral action in motion", the conference assessed problems and progress, identifying future policy and strategies appropriate for the 21st century. The main conclusion of the meeting was that while intersectoral action is working, the successes and failures need to be further analysed, assessed and the lessons learned widely disseminated. Strategies need to be modified, adapted and implemented at global, national and subnational levels, in ways that are appropriate to different country situations and contexts. The full potential of intersectoral action for achieving health for all in the context of sustainable human development has yet to be realized.

Partial characterization of a new nucleotide binding glycoprotein of hepatocyte plasma membrane

Hepatocyte plasma membranes contain a glycosylated 230-kDa Ca(2+) -dependent, Mg(2+)-stimulated ATPase (pgp230), which consists of two subunits, one of 120 kDa and the other of 110 kDa. pgp230 can be enriched by the use of affinity chromatography on Concanavalin A-Sepharose, wheat germ lectin-Sepharose, and 5'-AMP-Sepharose. It has a high-affinity Ca2+ binding site. In the presence of Ca2+, it forms a phosphorylated intermediate by autocatalytic transfer of the terminal phosphate residue from ATP. Maximal Ca(2+)-dependent autophosphorylation is observed at pH 5-6. Photoaffinity labeling using 8-azido-[alpha-32P]ATP or [y-32P]ATP confirms the presence of ATP binding sites. Incubation with [alpha-32P]ATP leads to a rapid but transient labeling of pgp230. Various nucleotides, nucleotide receptor agonists, or antagonists inhibit Ca(2+)-dependent phosphorylation by [y-32P]ATP. The concentrations of half-maximal inhibition range from 10(-7) M to 10(-3) M. The rank order of inhibitory potency is: ATP > alpha,beta-methylene-ATP > CTP = TTP > y-4-amino-phenyl-ATP = 2-methyl-thio-ATP > UTP = GTP > GDP = ADP = beta,y-methylene-ATP = beta, y-methylene-TTP = beta,y-methylene-GTP = adenosine-5'-O-2-thiodiphosphate = CMP = AMP > adenosine > cytidine > guanosine = suramin > Reactive blue 2 > iso-butyl-methyl-xanthine > thymidine > uridine. These data suggest a nucleotide binding capacity of this new hepatocyte membrane glycoprotein. Further investigations should be carried out to reveal its biological function.

Renal tubular damage: an extraintestinal manifestation of chronic inflammatory bowel disease

OBJECTIVE

To investigate whether treatment of inflammatory bowel disease (IBD) with 5-aminosalicylate or sulphasalazine in IBD may induce renal tubular damage.

DESIGN AND METHODS

The urinary enzymes beta-N-acetyl-D-glucosaminidase ( beta-NAG), dipeptidylpeptidase 4 (DPP4) and alanine aminopeptidase (AAP) were measured as markers of renal tubular damage in 104 consecutive patients with Crohn's disease and in 43 consecutive patients with ulcerative colitis (all with normal serum creatinine values). Control values were gained from 65 healthy persons.

RESULTS

The normal values (mean +/- SD) for the urinary enzymes investigated (U/g creatinine in the urine) were: DPP4 4.5 +/- 2.2, beta-NAG 1.6 +/- 1.4, AAP 11.4 +/- 6.5. In 28% of the patients with ulcerative colitis elevated beta-NAG levels of more than the mean + 2 x SD were measured. This pathological enzymuria was nearly exclusively found in patients with active disease (CAI > 6): DPP4 15.6 +/- 25.3, beta-NAG 8.3 +/- 10.1, AAP 24.7 +/- 50.1 (all three enzymes were significantly elevated). The highest values were measured in patients with active ulcerative colitis before start of therapy. Nineteen per cent of the patients with Crohn's disease had elevated beta-NAG levels of more than the mean + 2 x SD. There was no significant difference in enzymuria between patients with active (CDAI > 150) and patients with inactive Crohn's disease (CDAI < or = 150). DPP4 and AAP were normal in both groups. A correlation between the enzymuria and the cumulative doses of 5-aminosalicylic acid, sulphasalazine or prednisolone could not be found. The courses of enzymuria in three patients who presented with the first severe manifestation of IBD are described. They were treated with either corticosteroids and 5-aminosalicylic acid or corticosteroids and sulphasalazine. Before onset of therapy, very high urine enzyme values were measured. They almost normalized in the course of successful medical therapy despite increasing cumulative doses of 5-aminosalicylic acid or sulphasalazine.

CONCLUSIONS

Renal tubular damage can frequently be observed in IBD. Our results suggest that this is an extraintestinal manifestation of the disease and not a toxic side-effect of anti-inflammatory therapy using 5-aminosalicylic acid or sulphasalazine.

[Collagenous sprue]

HISTORY AND FINDINGS

A 45-year-old man with type I diabetes mellitus was admitted to hospital because of colicky abdominal pain and 5-6 watery stools daily. Upper gastrointestinal endoscopy showed nearly total atrophy of the villi in the duodenum and jejunum suggesting coeliac disease. However, gluten-free diet for 2 weeks brought no improvement. Another examination of the biopsy 6 weeks after the first endoscopy revealed extensive collagen deposition in the lamina propria of the small intestine, giving the diagnosis of collagenous sprue.

TREATMENT AND COURSE

Parenteral nutrition, lactulose, cisapride, cholestyramine, doxycycline, paromomycin, vancomycin and octreotide failed to affect the loss of fluid from the gut which 12 weeks after admission had increased to 221 daily. However, it was stopped after prednisolone was administered (100mg daily). 7 months after starting the steroid treatment the collagen layer had disappeared and the villous atrophy had partially regressed. Over the next 6 months the prednisolone dosage was decreased to 10 mg daily. Shortly thereafter a perimembranous glomerulonephritis occurred, with proteinuria (up to 60 g/d) and oedema. It regressed to 6 g/d when the steroid dose was increased and cyclosporin, 0.5 g/d, had been added. On maintenance dosage of cyclosporin the histological and clinical remission of the collagenous sprue has now lasted for over 2 years.

CONCLUSIONS

This case suggests that steroid administration is an effective treatment of collagenous sprue. The presence of diabetes and other immune-related diseases in this case also suggests that an immunological mechanism may play a causative role in collagenous sprue.

International program on the health effects of the Chernobyl accident

The International Program on the Health Effects of the Chernobyl Accident (IPHECA) was established by the World Health Organization (WHO) in 1991. Currently, the technical part of IPHECA consists of five projects addressing the following areas of priority health problems or needs: thyroid, hematology, brain damage in utero, epidemiological registry and oral health. Important findings are: 1) a significant increase of thyroid cancer in children in Belarus and Ukraine since 1989, and in Russia since 1992 though not so pronounced. A relationship between detected thyroid cancers and radiation exposure is yet to be established, 2) no increase yet in the incidence of hemoblastoses in the three States, 3) no relationship established between mental retardation and radiation exposure in utero in 4,500 children investigated. The importance of dosimetry and biological indicators of radiation damage has been recognized by IPHECA. Several methods of biological and physical dosimetry are being employed using instrumentation provided by IPHECA. Some preliminary results indicate: 1) unstable aberrations can indicate an integral exposure but it is heavily biased to recent exposures, 2) when comparing healthy persons and patients with hematological diseases in contaminated areas, there is a higher ratio of total aberrations compared to their background and that the level of stable is lower than unstable aberrations, and 3) by applying electron spin resonance (ESR) it has been shown that the individual distribution of doses approaches a log-normal one, especially for adults, and that a peak shift towards higher doses is noticeable for children.

A new type of Ca(2+)-dependent, Mg(2+)-stimulated ATPase of rat liver plasma membrane

Incubation of a glycoprotein fraction obtained from rat liver plasma membrane which has been previously well characterized using [gamma-32P]ATP results in the phosphorylation of a 230-kDa glycoprotein (pgp230). It is composed of a 120-kDa subunit (pgp120) and a 110-kDa subunit (pgp110) linked by interchain disulfide bonds. Peptide maps of pgp120 and pgp110 suggest extensive similarity in their polypeptide chains. Glycan analysis reveals between four and six hybrid-type oligosaccharide chains for both phosphoproteins. Immunoblotting using monoclonal antibodies and endoglycosidase digestion exclude an identity of pgp120 or pgp110 with the hepatocyte plasma membrane glycoproteins dipeptidylpeptidase IV or the taurocholate transport protein, which co-purify and co-migrate in SDS/PAGE. Protein phosphorylation is Ca(2+)-dependent (K0.5(Ca2+) = 0.35 microM, in the absence of Mg2+). In the presence of Mg2+, the glycoprotein undergoes rapid cycles of phosphorylation and dephosphorylation, resulting in ATPase activity. Analysis of phosphorylated amino acids identifies phosphothreonine as the major one. Photoaffinity labeling with 8-azido-[alpha-32P]ATP demonstrates the presence of one or more ATP binding site(s). Preincubation of pgp230 with various purine or pyrimidine nucleotides (ATP, UTP, TTP, ADP, GDP, AMP, CMP) or known P2-purinoceptor agonists or antagonists (adenosine 5'-[alpha,beta-methylene]triphosphate, 2-methyl-thio-adenosine 5'-triphosphate, suramin) inhibits its phosphorylation by [gamma-32P]ATP. The biological function of pgp230 is unknown at present. Several findings of the present study are compatible with the idea that pgp230 may be involved in a P2-purinoceptor function of the hepatocyte. Following this concept, a mechanism is discussed where a cytosolically exposed high-affinity Ca(2+)-binding site of pgp230 would allow for receptor feedback control, via phosphorylation and dephosphorylation, by sensing changes in cytosolic Ca2+ concentration.

[Radiologic differential diagnosis of inflammatory round pulmonary infiltrates in immunocompromised patients. A prospective study using CT and MRT]

In a prospective study we examined the diagnostic ranking of CT and MR in 52 immunocompromised patients with nodular pulmonary lesions and clinical suspicion of invasive pulmonary aspergillosis (IPA). For early diagnosis of IPA (clinical symptoms having existed for less than 10 days) the CT halo sign proved highly sensitive and specific. MRT showed at this time a comparatively high sensitivity but only low specificity that could not be improved upon after Gd-DTPA. At a later stage of the aspergillosis infection (clinical symptoms manifested for more than 10 days) MR identified aspergillus-specific lesions with on-target characteristics (marked enhancement of margins after Gd-DTPA) or the so-called "reverse" target phenomenon (T2-weighted sequences). Such lesions were never seen in the early stage of the disease in patients with nodular pulmonary lesions of different aetiology (pseudomonal or staphylococcal pneumonia).

Immuno-gold electron microscopical detection of heat shock protein 60 (hsp60) in mitochondria of rat hepatocytes and myocardiocytes

We characterize the specificity of a polyclonal antibody against heat shock protein 60 (hsp60) and present an application for ultrastructural localization studies of this protein. The antibody was obtained from an IgG fraction (AB 121) originally raised against the calcium binding protein calsequestrin by immunoabsorption on isolated rat liver hsp60. As shown by partial N-terminal amino acid sequence analysis of immunoprecipitated proteins AB 121 contained reactivities against hsp60, calsequestrin and the glycoprotein fetuin. In rat heart AB 121 recognized calsequestrin and hsp60. In human and rat liver the only reacting protein was hsp60. In rat erythrocytes the antibody bound to 61 kDa and 58 kDa isoforms of fetuin. According to published data no amino acid sequence homologies nor common motifs are found between calsequestrin, hsp60 and fetuin. As the first application the anti-hsp60 antibody was used for immuno-gold electron microscopical localization of hsp60: in myocardiocytes and hepatocytes of the rat strong labelling was obtained exclusively in mitochondria. No extramitochondrial structures were labelled. The specificity of the antibody and its ability to be visualized by immuno-gold electron microscopy offers the possibility to study the expression of this protein in the liver and in other organs. Possible clinical applications of these studies are discussed, since hsp60 could be a target antigen of autoantibodies in diseases such as autoimmune hepatitis, primary sclerosing cholangitis or primary biliary cirrhosis.

Oligosaccharide reprocessing and recycling of a cell surface glycoprotein in cultured rat hepatocytes

The metabolism of the cell surface glycoprotein dipeptidyl peptidase IV(DPPIV) was studied in cultured rat hepatocytes. In pulse-chase labelling experiments using L-[35S]methionine a 100-kDa high-mannose precursor polypeptide is converted into the mature complex-type 110-kDa glycoprotein. Digestion with exo- and endoglycosidases and metabolic labelling with radioactive sugars demonstrate that the 110-kDa form contains about 6 complex-type oligosaccharides which are fucosylated and sialylated. About 25 min after the beginning of the pulse-labelled glycoprotein appears in the sinusoidal membrane. Physiologically only the 110-kDa form is found in the cell surface. If cell surface DPP IV was desialylated by sialidase at 4 degrees C, it is resialylated during incubation at 37 degrees C. This oligosaccharide reprocessing indicates that the surface glycoprotein has been recycled to the cell compartment containing terminal glycosyltransferases (presumably the trans Golgi system). Two different methods demonstrate internalization of cell surface DPP IV: 1) The complex cell surface DPPIV -anti-DPP IV-antibody -L-[35S]methionine-labelled secondary goat-anti-mouse-antibody formed at 4 degrees C becomes less accessible to trypsin during incubation at 37 degrees C. 2) Part of the complex plasma membrane DPP IV-anti-DPP IV-antibody formed in the cold cannot be recognized by the radioactive secondary antibody after rewarming. Internalization is not blocked by inhibition of protein synthesis with cycloheximide. During internalization of plasma membrane DPP IV its concentration in the membrane remains constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of protein N-glycosylation by 2-deoxy-2-fluoro-D-galactose

The effects of 2-deoxy-2-fluoro-D-galactose (dGalF) on N- and O-glycosylation of proteins was studied in rat hepatocyte primary cultures and in human monocytes. In hepatocytes, dGalF at concentrations of 1 mM or higher completely inhibited N-glycosylation of alpha 1-antitrypsin and alpha 1-acid glycoprotein, whereas 4 mM-2-deoxy-D-galactose (dGal) only slightly impaired N-glycosylation. In monocytes, 1 mM- or 4 mM-dGalF blocked N-glycosylation of alpha 1-antitrypsin and of interleukin-6, while O-glycosylation of interleukin-6 remained unaffected. In monocytes, dGal had no effect on protein N-glycosylation. Addition of uridine effectively prevented the UTP deficiency induced by dGalF, but had no effect on the inhibition of protein N-glycosylation by dGalF. Using 19F-n.m.r. spectroscopy, 2-deoxy-2-fluoro-D-galactose 1-phosphate (dGalF-1-P), UDP-dGalF and UDP-dGlcF could be identified as the major metabolites of dGalF in hepatocytes as well as in monocytes. In conclusion, compared with dGal, dGalF is a more efficient inhibitor of protein N-glycosylation. The effect is not caused by the depletion of UTP induced by dGalF, but rather by metabolites of dGalF. dGalF is metabolized not only in hepatocytes but also in peripheral blood monocytes, which can be used for ex vivo studies of disturbances in D-galactose metabolism.

Therapy of invasive aspergillosis with itraconazole: improvement of therapeutic efficacy by early diagnosis

We report on the treatment of invasive aspergillosis with the new triazole antimycotic agent itraconazole. All 11 patients suffered from pulmonary invasive aspergillosis. Two patients also had cerebral aspergillosis; in one of these patients the paranasal sinuses were also invaded. Underlying diseases were acute lymphoblastic leukaemia (n = 3), acute myeloid leukaemia (n = 4); one patient underwent allogeneic bone marrow transplantation before he developed aspergillosis; another was transplanted after successful aspergillosis treatment, liver cirrhosis (n = 1), lung infarction after pulmonary embolism (n = 1), chronic bronchitis after pulmonary tuberculosis (n = 1) and AIDS (n = 1). In five cases initial diagnosis was established by means of mycological methods and clinical signs. In six patients invasive pulmonary aspergillosis was initially diagnosed due to the clinical criteria presented in this paper. Secondary mycological confirmation after onset of therapy was achieved in five out of these six patients. All of the patients initially responded to therapy. One female patient experienced a relapse of aspergillosis and died of cerebral involvement and relapsing leukaemia. Two further patients died due to underlying diseases (pulmonary embolism, relapsing leukaemia). Nine patients (82%) were cured of the mycosis, including the patient with cerebral involvement; two underwent surgical resection of residual pulmonary lesions. Itraconazole is a very effective drug for treatment of invasive aspergillosis. Therapeutic efficacy can be optimized by early diagnosis using clinical criteria and prompt start of treatment.

[Gastroenterologic findings in graft versus host disease after allogenic bone marrow transplantation]

We are reporting on a 25 years old patient with acute myelogenous leukemia, who developed an acute graft-versus-host disease (GVHD) 43 days after allogeneic bone marrow transplantation (BMT). The clinical symptoms included exanthema, diarrhea and abdominal cramps. The patient was treated with cyclosporine A and prednisone and the clinical symptoms disappeared subsequently. At day 225 post BMT the patient became icteric as the clinical manifestation of chronic GVHD. We describe in this case report endoscopical and histological findings during the episodes of acute and chronic graft-versus-host disease. The results obtained by sigmoidoscopy and liver biopsy confirmed the clinical diagnosis. The clinical work up of patients with acute or/and chronic GVHD should also include sigmoidoscopy in order to verify this transplantation related complication.

[Conservative therapy of ulcerative colitis and Crohn disease]

Basis treatment of severe ulcerative colitis and Crohn's disease comprises the systemic administration of corticosteroids. If the conditions are less severe, treatment with oral sulfasalazine or 5-aminosalicylic acid (5-ASA) can be attempted. Distal ulcerative colitis may respond to topical corticosteroids of enemas with sulfasalazine or 5-ASA. In long-term treatment with high-dose corticosteroids, azathioprine and 6-mercaptopurine may be employed to reduce the corticosteroid requirement. There ist no known generally applicable diet for the treatment or prophylaxis of these conditions.

Hepatocyte specific long lasting inhibition of protein N-glycosylation by D-galactosamine

The effect of D-galactosamine on protein N-glycosylation was studied in rat hepatocyte primary cultures for alpha 1-antitrypsin (three complex type oligosaccharide chains) and alpha 1-acid glycoprotein (six complex type oligosaccharide chains). D-Galactosamine at a concentration of 4 mM inhibited partially de novo N-glycosylation leading to the formation of alpha 1-antitrypsin lacking one to two and of alpha 1-acid glycoprotein lacking one to five of its carbohydrate side chains. In addition D-galactosamine interfered with oligosaccharide processing, leading to the formation of some carbohydrate side chains remaining in an endoglucosaminidase H sensitive, i.e., not completely processed, form. D-Galactosamine impaired the secretion of alpha 1-antitrypsin and of alpha 1-acid glycoprotein but did not inhibit the secretion of the unglycosylated albumin. The inhibitory effect of D-galactosamine on de novo glycosylation as well as on oligosaccharide processing lasted for at least 24 h after it had been removed from the cells. D-Galactosamine impaired the glycosylation of alpha 1-antitrypsin only in hepatocytes, but not in human monocytes. Furthermore, D-galactosamine did not impair the N- and O-glycosylation of interleukin-6 in human monocytes and in MRC 5 fibroblasts. The results indicate that the effect of D-galactosamine on protein glycosylation is restricted to D-galactosamine metabolizing hepatocytes and is not exerted by the drug itself but by its metabolites.

[Non-cirrhotic portal hypertension]

A chronic increase of the portal venous pressure is not only a sequel of liver cirrhosis. There is a large group of different diseases leading to "non-cirrhotic portal hypertension". Clinical presentation, diagnosis and treatment are discussed. The discrimination between cirrhotic and non-cirrhotic portal hypertension is important for the understanding of differences in clinical signs and course of the diseases, however.

[Dipeptidyl aminopeptidase IV in hospitalized patients and in galactosamine hepatitis of the rat: Activity and lectin affinity chromatography in serum and hepatic plasma membranes]

The activity of dipeptidyl aminopeptidase IV was studied in the sera of 378 hospitalized patients. The mean activity of dipeptidyl aminopeptidase IV was elevated significantly in patients with neoplasmata and hepatitis, but not in patients with liver cirrhosis. Significant correlations (p less than 0.001) existed with gamma-glutamyl transferase, glutamate dehydrogenase, alkaline phosphatase and leucine aminopeptidase. A significant correlation with lactate dehydrogenase existed only in patients with neoplasmata. Principal component analysis, performed with aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, leucine aminopeptidase, lactate dehydrogenase and dipeptidyl aminopeptidase IV, revealed correlations between the activities of aspartate aminotransferase and alanine aminotransferase, and between alkaline phosphatase and leucine aminopeptidase, but neither dipeptidyl aminopeptidase IV nor lactate dehydrogenase showed any correlation with either of these two groups. In lectin affinity chromatography with concanavalin A and wheat germ lectin sepharose, serum dipeptidyl aminopeptidase IV from liver cirrhosis patients showed the same binding pattern as that from healthy subjects. The activity and glycosylation of dipeptidyl aminopeptidase IV in serum and hepatic plasma membranes was investigated in rats, following the induction of hepatitis with galactosamine. In the serum, dipeptidyl aminopeptidase IV activity was elevated as early as 6 h after galactosamine injection, and the elevated activity persisted until the 7th day. At the same time dipeptidyl aminopeptidase IV activity was also elevated in the hepatic plasma membrane. Ninety eight percent of hepatic dipeptidyl aminopeptidase IV bound to concanavalin A as well as to wheat germ lectin and this value was unchanged during hepatitis. In the serum of control rats, 90% of dipeptidyl aminopeptidase IV bound to concanavalin A but only 39% to wheat germ lectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the alpha-glucosidase inhibitor N-hydroxyethyl-1-deoxynojirimycin (Bay m 1099) on the biosynthesis of liver secretory glycoproteins

The effect of the alpha-glucosidase inhibitor N-hydroxyethyl-1-deoxynojirimycin (Bay m 1099) on the glycosylation and secretion of alpha 1-antitrypsin (three complex type oligosaccharide chains) and of alpha 1-acid glycoprotein (six complex type oligosaccharide chains) was studied in rat hepatocyte primary cultures. In the presence of 4 mM Bay m 1099 the processing of high-mannose to complex type oligosaccharides was partially inhibited leading to the secretion of alpha 1-antitrypsin and alpha 1-acid glycoprotein carrying a mixture of both high-mannose and complex type oligosaccharides. The major part of alpha 1-antitrypsin secreted by Bay m 1099 treated cells still carried two complex type oligosaccharide chains, the majority of alpha 1-acid glycoprotein carried three to five. Despite its effects on protein glycosylation Bay m 1099 did not lead to pronounced changes in the synthesis or secretion of alpha 1-antitrypsin, alpha 1-acid glycoprotein or albumin. At concentrations of Bay m 1099 lower than 0.5 mM no inhibitory effect on oligosaccharide trimming could be observed. After removal of Bay m 1099 from hepatocytes its inhibitory effect on protein glycosylation was immediately reversible.

Remodeling of a rat hepatocyte plasma membrane glycoprotein. De- and reglycosylation of dipeptidyl peptidase IV

The present paper demonstrates the terminal de- and reglycosylation of a rat hepatocyte plasma membrane glycoprotein, dipeptidyl peptidase IV (DPP IV). Cultured hepatocytes were used in pulse-chase experiments with [3H]L-fucose and [14C]N-acetyl-D-mannosamine as markers for terminal carbohydrates, [3H]D-mannose as marker of a core-sugar, and [35S]L-methionine for labeling the protein backbone. Membrane DPP IV was immunoprecipitated with a polyclonal antibody which bound selectively at 4 degrees C to the cell-surface glycoprotein. The times of maximal labeling of hepatocyte plasma membrane DPP IV were 6-9 min for [3H]L-fucose, 20 min for [3H]D-mannose, and 25 min for [35S]L-methionine. When antibodies were bound to cell-surface DPP IV at 4 degrees C, the immune complex remained stable for more than 1 h after rewarming to 37 degrees C, despite ongoing metabolic and membrane transport processes. This was shown by pulse labeling with [35S]L-methionine at 37 degrees C, followed by cooling to 4 degrees C, and addition of antibody against plasma membrane DPP IV. During rewarming, the radioactivity in the complex remained constant. In a similar experiment with [3H]L-fucose, the radioactivity in the immune complex declined rapidly, indicating a defucosylation of the plasma membrane glycoprotein. Using the same experimental design with [3H]D-mannose, the radioactivity in the immune complex remained constant, showing that the core-sugar D-mannose is not cleaved from the membrane glycoprotein. Terminal reglycosylation (refucosylation and resialylation) was demonstrated as follows. Hepatocytes were maintained at 37 degrees C in a medium supplemented with tunicamycin in order to block the de novo synthesis of N-glycosidically bound carbohydrate chains. At 4 degrees C the antibody against DPP IV bound only to cell surface glycoprotein. During the rewarming period at 37 degrees C, radioactivity from [3H]L-fucose and [14C]N-acetyl-D-mannosamine became incorporated into the immune complex. This indicates a fucosylation and sialylation of the glycoprotein originally present at the cell surface. The mechanisms whereby terminal de- and reglycosylation of plasma membrane glycoproteins may occur during membrane recycling are discussed.

Rapid purification of dipeptidyl peptidase IV from rat liver plasma membrane

Dipeptidyl peptidase IV (EC 3.4.14.5) was solubilized from rat liver plasma membranes with sulphobetaine 14 and purified by successive affinity chromatography on Con A-Sepharose, wheat germ lectin-Sepharose and arginine-Sepharose columns. The specific activity of the final preparation was 49.4 mumol Gly-Pro p-nitroanilide/min per mg protein, representing a 1098-fold purification of the homogenate. SDS-polyacrylamide gel electrophoresis of the arginine-Sepharose eluate showed a single protein band with a molecular weight of 105,000. The isoelectric point was determined to be 3.9 under non-denaturing conditions with sulphobetaine 14. The preparation was free of post-proline cleaving enzyme. The content of aminopeptidase M was 0.2% of the total protein.

Modification of the intramolecular turnover of terminal carbohydrates of dipeptidylaminopeptidase IV isolated from rat-liver plasma membrane during liver regeneration

An intramolecular turnover of the terminal carbohydrates L-fucose, N-acetylneuraminic acid and D-galactose is a characteristic property of several liver plasma membrane glycoproteins, first demonstrated for dipeptidylaminopeptidase IV (EC 3.4.14.5., DPP IV). The core carbohydrates D-mannose and N-acetyl-D-glucosamine turn over like the polypeptide chain. The ratio of apparent half-lives of L-fucose and L-methionine of DPP IV is shifted from 0.17 in normal liver to 0.60 in regenerating liver. The ratio of half-lives of N-acetylneuraminic acid and L-methionine is only slightly changed from 0.43 in normal liver to 0.61 in regenerating liver. The ratio of apparent half-lives of D-mannose and L-methionine amounts to 0.80 in normal liver and 0.71 after partial hepatectomy. From this a drastic reduction of the intramolecular turnover of L-fucose on plasma membrane DPP IV in regenerating liver can be derived. The intramolecular N-acetylneuraminic acid turnover is affected to only a minor extent. D-Mannose turns over like the polypeptide in both normal and regenerating liver. The intramolecular L-fucose turnover may be involved in membrane glycoprotein recycling, which presumably is altered in regenerating liver. Additionally, L-fucose could regulate the rate of degradation of DPP IV, since core-fucosylated glycoproteins appear to be resistant to mammalian endo-N-acetylglucosaminidase.

Heterogeneous turnover of terminal and core sugars within the carbohydrate chain of dipeptidylaminopeptidase IV isolated from rat liver plasma membrane

Dipeptidylaminopeptidase IV, a plasma membrane-bound glycoprotein, is characterized by an intramolecular heterogeneous turnover of the protein backbone and carbohydrate chain. The faster turnover of the latter is restricted only to the outer sugars. The inner core sugars D-mannose and N-acetyl-D-glucosamine turn over at the same rate as the protein backbone.