Chemical Modification of Tiopronin for Dual Management of Cystinuria and Associated Bacterial Infections

Cystinuria is an inherited autosomal recessive disease of the kidneys of recurring nature that contributes to frequent urinary tract infections due to bacterial growth and biofilm formation surrounding the stone microenvironment. In the past, commonly used strategies for managing cystinuria involved the use of (a) cystine crystal growth inhibitors such as l-cystine dimethyl ester and lipoic acid, and (b) thiol-based small molecules such as N-(2-mercaptopropionyl) glycine, commonly known as tiopronin, that reduce the formation of cystine crystals by reacting with excess cystine and generating more soluble disulfide compounds. However, there is a dearth of simplistic chemical approaches that have focused on the dual treatment of cystinuria and the associated microbial infections. This work strategically exploited a single chemical approach to develop a nitric oxide (NO)-releasing therapeutic compound, S-nitroso-2-mercaptopropionyl glycine (tiopronin-NO), for the dual management of cystine stone formation and the related bacterial infections. The results successfully demonstrated that (a) the antibacterial activity of NO rendered tiopronin-NO effective against the stone microenvironment inhabitants, Escherichia coli and Pseudomonas aeruginosa, and (b) tiopronin-NO retained the ability to undergo disulfide exchange with cystine while being reported to be safe against canine kidney and mouse fibroblast cells. Thus, the synthesis of such a facile molecule aimed at the dual management of cystinuria and related infections is unprecedented in the literature.

The antioxidant N-(2-mercaptopropionyl)-glycine (tiopronin) attenuates expression of neuropathic allodynia and hyperalgesia

The current pharmacotherapy of neuropathic pain is inadequate as neuropathic pain involves varied clinical manifestations with multifactorial etiology, modulated by a cascade of physical and molecular events leading to different clinical presentations of pain. There is an accumulating evidence of the involvement of oxidative stress in neuropathy, and antioxidants have shown promise in mitigating neuropathic pain syndromes. To explore the evidence supporting this beneficial proclivity of antioxidants, this study investigated the antinociceptive effectiveness of N-(2-mercaptopropionyl)glycine or tiopronin, a well-recognized aminothiol antioxidant, in a refined chronic constriction injury (CCI) rat model of neuropathic pain. Tiopronin (10, 30, and 90 mg/kg, i.p.) and pregabalin (30 mg/kg, i.p.) were administered daily after CCI surgery. The neuropathic paradigms of mechanical/cold allodynia and mechanical/heat hyperalgesia were assessed on days 3, 7, 14, and 21 post-nerve ligation. At the end of study, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were estimated in the sciatic nerve, dorsal root ganglion, and spinal cord for assessing the extent of oxidative stress. The expression of neuropathic nociception was attenuated by tiopronin which was observed as a significant attenuation of CCI-induced allodynia and hyperalgesia. Tiopronin reversed the neuronal oxidative stress by significantly reducing MDA, and increasing SOD, CAT, and GSH levels. Pregabalin also showed similar beneficial propensity on CCI-induced neuropathic aberrations. These findings suggest prospective neuropathic pain attenuating efficacy of tiopronin and further corroborated the notion that antioxidants are effective in mitigating the development and expression of neuropathic pain and underlying neuronal oxidative stress.

Case Study - Case Studies in Cystinuria

The diagnosis and treatment of patients with rare inherited metabolic disorders associated with recurrent and often obstructive kidney stones are important to the prevention of chronic kidney disease or end stage renal disease. Two case studies in this article describe the diagnosis and management of cystinuria, the most common rare kidney stone disorder.

Genotype and Phenotype Analysis in Pediatric Patients with Cystinuria

Cystinuria is an inherited disorder characterized by defective renal reabsorption of cystine and dibasic amino acids leading to nephrolithiasis. This study was conducted to analyze the genotypes and phenotypes of pediatric patients with cystinuria. Eight children from Seoul National University Hospital and Asan Medical Center presenting with cystinuria from January 2003 to June 2016 were retrospectively analyzed. Mutational studies were performed by direct sequencing. Two of the 8 were male and 6 were female. The median ages at onset and diagnosis were 1.5 (range, 0.3-13.6) and 2.6 (range, 0.7-16.7) years, respectively. The median followed up was 7.7 (range, 3.4-14.0) years. Mutational analyses were performed in 7 patients and revealed biallelic SLC3A1 mutations (AA genotype) in 4 patients, a single heterozygous SLC3A1 mutation (A- genotype) in 1 patient, biallelic SLC7A9 mutations (BB genotype) in 1 patient, and a single heterozygous SLC7A9 mutation (B- genotype) in 1 patient. Two of the mutations were novel. No genotype-phenotype correlations were observed, except for earlier onset age in patients with non-AA genotypes than in patients with the AA genotype. All patients suffered from recurrent attacks of symptomatic nephrolithiasis, which lead to urologic interventions. At the last follow-up, 3 patients had a mild-to-moderate degree of renal dysfunction. This is the first study of genotypic and phenotypic analyses of patients with cystinuria in Korea.

The role of tiopronin for the prevention of chemotherapy-related liver toxicity in advanced colorectal cancer patients treated with mFOLFOX7: a prospective analysis

AIMS AND BACKGROUND

Chemotherapy-related hepatotoxicity is a limitation for the continuation of chemotherapy in patients with advanced colorectal cancer (CRC). This prospective study determined the efficacy of tiopronin infusion in chemotherapy-induced hepatoxicity.

METHODS AND STUDY DESIGN

One hundred and fifty patients having advanced CRC treated with first-line palliative chemotherapy were included, of whom 86 were treated with mFOLFOX7 plus supplementation of tiopronin and 64 were treated with the same regimen without tiopronin. Aspartate aminotransferase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), total bilirubin (TBIL), gamma-glutamyl transferase (γ-GT), alkaline phosphatase (ALP), and albumin (ALB) were recorded before treatment and during every therapy cycle. In addition, course discontinuations, dose reductions, and chemotherapy efficacy were evaluated.

RESULTS

The age and gender of the two groups were comparable (P >0.05). The proportions of abnormal mean ALT (P = 0.042), AST (P = 0.045), TBIL (P = 0.044) and ALB (P = 0.043) were significantly lower in the tiopronin group than the control group. Course discontinuations (P = 0.002), dose reductions (P = 0.005) and efficacy (P = 0.012) were significantly different between the two groups. Multivariate logistic regression analysis showed that the hepatoprotective drug played an important role in clinical outcome (OR = 6.837; 95% CI, 1.845 to 25.333; P = 0.004).

CONCLUSIONS

Tiopronin tends to decrease the incidence of chemotherapy-induced hepatoxicity, enhance patients' tolerance to mFOLFOX7 treatment, and even benefit the efficacy of chemotherapy.

Efficacy of Tiopronin in treatment of severe non-alcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a clinicopathologic syndrome of which the main feature is diffuse macrovesicular hepatic steatosis caused by deposition of excessive free fatty acid and triglyceride in liver parenchyma.

AIM

To observe the efficacy of Tiopronin in treatment of severe nonalcoholic fatty liver disease (NAFLD).

PATIENTS AND METHODS

30 patients with severe NAFLD were treated with Tiopronin for 3 months. 30 healthy people were selected as control. The body mass index (BMI) and plasma levels of endotoxin (ET), leptin, IL-6 and IL-8 were measured before and after treatment.

RESULTS

The serum levels of ET, leptin, IL-6 and IL-8 in severe NAFLD group were significantly higher than those in control group (p < 0.05). After treatment with Tiopronin, these indexes were significantly lower than before (p < 0.05).

CONCLUSIONS

The intestinal endotoxemia (IETM) occurs in patients with severe NAFLD. Leptin, IL-6 and IL-8 play important roles in pathogenesis of NAFLD. Tiopronin can reduce the levels of ET, leptin, IL-6 and IL-8 for treatment of NAFLD.

N-(2-Mercaptopropionyl)-glycine, a diffusible antioxidant, activates HIF-1 by inhibiting HIF prolyl hydroxylase-2: implication in amelioration of rat colitis by the antioxidant

We investigated anti-colitic effects of N-(2-mercaptopropionyl)-glycine (NMPG), a diffusible antioxidant, in TNBS-induced rat colitis model and a potential molecular mechanism underlying the pharmacologic effect of the antioxidant. NMPG alleviated colonic injury and effectively lowered myeloperoxidase activity. Moreover, NMPG substantially attenuated expression of pro-inflammatory mediators in the inflamed colon. NMPG induced hypoxia-inducible factor-1α (HIF-1α) in human colon carcinoma cells, leading to elevated secretion of vascular endothelial growth factor (VEGF), a target gene product of HIF-1 involved in ulcer healing of gastrointestinal mucosa. NMPG induction of HIF-1α occurred by inhibiting HIF prolyl hydroxylase-2 (HPH-2), an enzyme that plays a major role in negatively regulating HIF-1α protein stability. In in vitro Von Hippel-Lindau protein binding assay, the inhibitory effect of NMPG on HPH-2 was attenuated by escalating dose of ascorbate but not 2-ketoglutarate, cofactors of the enzyme. Consistent with this, cell-permeable ascorbate significantly attenuated NMPG induction of HIF-1α in cells. Our data suggest that NMPG is an anti-colitic antioxidant that exerts its pharmacologic effects at least partly through activation of an ulcer healing pathway, HIF-1-VEGF.

Reduced renal function and benefits of treatment in cystinuria vs other forms of nephrolithiasis

A significant study from the USA compares cystine stone formers and routine stone formers; the former group had a higher requirement for therapeutic procedures, but this was less if they took chelating agents, although remaining higher than in the latter group. Other interesting findings are also presented.

OBJECTIVE

First, to compare two types of stone formers (SF), those with cystinuria and those without, for effects of treatments for stones, as cystinuria leads to recurrent stones that are difficult to fragment with shock-wave lithotripsy, and there is disagreement about the efficacy of current treatments. Second, to compare these two groups with respect to blood pressure (BP) and renal function, as cystine stones may be associated with more morbidity than are routine stones.

PATIENTS AND METHODS

Fifty-two cystinuric patients (cystine SF) entering our programme since 1970 were compared with 3215 SF without cystinuria (routine SF), of whom 114 had a single functioning kidney (routine SF + nephrectomy). All patients had three 24-h urine and blood samples taken to determine the risk of stones before their first clinic visit; these studies were repeated after therapy was initiated, and at regular intervals to monitor therapy. Cystine was measured in the urine samples of the cystine SF. All stone-related procedures were recorded, and BP measured at clinic visits. Creatinine clearances (CCr) were calculated from each set of serum and urine values. Cystine supersaturation (SS) was directly measured in 16 urine samples collected before treatment and 13 afterward.

RESULTS

Patients were treated with increased fluid intake, potassium alkali and chelating agents such as alpha-mercapto-propionyl-glycine, as needed. The mean (sd) CCr, corrected for age and gender, was significantly lower at entry in cystine SF than in routine SF, at 91 (6) vs 160 (1) L/day, respectively (P < 0.001), and remained so at the last CCr. Neither systolic nor diastolic BP, similarly corrected, differed between the groups, but cystine SF had significantly more procedures, corrected for time at risk, before treatment than did routine SF, at 4.0 (0.4) vs 1.86 (0.06), respectively (P < 0.001); time-adjusted procedures decreased significantly in both groups during treatment, but remained higher in cystine SF, at 0.88 (0.14) vs 0.23 (0.02), respectively, (P < 0.001). Urine volume and pH were significantly higher in cystine SF than in routine SF, both before and during treatment. Cystine SS decreased during treatment, consistent with the increase in urine volume and decline in procedure rates during treatment.

CONCLUSION

Cystine SF have significantly higher procedure rates than routine SF, but procedure rates decline during therapy, although they remain higher than in routine SF. The lower CCr in cystinurics suggests that treatment to prevent stone recurrence and the need for procedures is particularly important, and emphasizes the need for a close follow-up. Use of cystine SS measurements may allow closer monitoring of the effect of treatment on the risk of stone recurrence.

Effect of Cystine-Binding Thiol Drugs on Urinary Cystine Capacity in Patients with Cystinuria

PURPOSE

To determine the effect of cystine-binding thiol drugs (CBTD) on urinary cystine capacity in patients with cystinuria.

PATIENTS AND METHODS

Seven cystinuric patients performed two sets of urine collections while on and off CBTD while controlling for all other variables: diet and fluid and alkali intake. They monitored and recorded their diet for 3 days and performed urine collections on days 2 and 3. They then stopped the CBTD for 7 days. On days 8, 9, and 10, they replicated their diets of days 1 through 3 and performed two more urine collections on days 9 and 10. Two patients took D-penicillamine, four took tiopronin, and one took tiopronin and captopril. The cystine capacity was determined, and the values obtained when the patient was on and off the CBTD were compared to determine whether CBTDs affect urinary cystine capacity. To measure the cystine capacity, we used a solid-phase assay in which cystine crystals are added to the urine and incubated for 48 hours. The crystals are spun down and resolubilized in high-pH buffer, and the amount of cystine in the crystals is calculated. The solid phase will take up cystine from urine (negative cystine capacity) that is supersaturated and give up cystine to an undersaturated urine (positive cystine capacity).

RESULTS

All seven patients had significant improvement in urinary cystine capacity on CBTDs. The mean cystine capacity off CBTD was -130.6 +/- 280.8, while the value during CBTD use was 43.1 +/- 131.2 (P < 0.05). On CBTDs, two patients still had negative values, but both had important improvements. The mean urinary volumes were similar on and off CBTD, indicating adequate and similar fluid intake. Urine pH values and urinary excretion of sodium and urea also were comparable, indicating consistency of citrate intake and diet.

CONCLUSIONS

Our results demonstrate that CBTDs lower the urinary supersaturation of cystine, as shown by a less-negative or more-positive cystine capacity. Cystine capacity can be measured directly, even in the presence of CBTDs. The value of this measurement lies in the potential to monitor the response to the drug, prescribe the minimum effective dose, and potentially decrease the adverse effects often associated with CBTDs.

Delayed ischemic preconditioning activates nuclear-encoded electron-transfer-chain gene expression in parallel with enhanced postanoxic mitochondrial respiratory recovery

BACKGROUND

Delayed ischemic preconditioning promotes cardioprotection via genomic reprogramming. We hypothesize that molecular regulation of mitochondrial energetics is integral to this cardioprotective program.

METHODS AND RESULTS

Preconditioning was induced by use of 3 episodes of 3-minute coronary artery occlusion separated by 5 minutes of reperfusion. Twenty-four hours later, infarct size was reduced by 58% after preconditioning compared with sham-operated controls (P<0.001). Cardiac mitochondria were isolated from sham and preconditioned rat hearts. Mitochondrial respiration and ATP production were similar between the groups; however, preconditioned mitochondria exhibit modest hyperpolarization of the inner mitochondrial membrane potential (> or =22% versus control, P<0.001). After 35-minute anoxia and reoxygenation, preconditioned mitochondria demonstrated a 191+/-12% improvement in ADP-sensitive respiration (P=0.002) with preservation of electron-transfer-chain (ETC) activity versus controls. This augmented mitochondrial recovery was eradicated when preconditioning was abolished by the antioxidant 2-mercaptopropionyl glycine (2-MPG). These biochemical modulations appear to be regulated at the genomic level in that the expression of genes encoding rate-controlling complexes in the ETC was significantly upregulated in preconditioned myocardium, with a concordant induction of steady-state protein levels of cytochrome oxidase, cytochrome c, and adenine nucleotide translocase-1. 2-MPG abolished preconditioning induction of these transcripts. Moreover, transcripts of nuclear regulatory peptides known to orchestrate mitochondrial biogenesis, nuclear respiratory factor-1 and peroxisome-proliferator-activated receptor gamma coactivator 1alpha, were significantly induced in preconditioned myocardium.

CONCLUSIONS

Delayed preconditioned mitochondria display increased tolerance against anoxia-reoxygenation in association with modifications in mitochondrial bioenergetics, with concordant genomic induction of a mitochondrial energetic gene regulatory program. This program appears to be mediated by reactive oxygen species signaling.

Urinary excretion of total cystine and the dibasic amino acids arginine, lysine and ornithine in relation to genetic findings in patients with cystinuria treated with sulfhydryl compounds

Advances in molecular genetics have brought a deeper understanding of cystinuria. This autosomal recessive disease, which is caused by a defective tubular reabsorption of cystine and the three dibasic amino acids arginine, lysine and ornithine, results in a lifelong risk of renal stone formation because of the low solubility of cystine in urine. Mutations detected within the two genes known to be associated with cystinuria, SLC3A1 (related to type I) and SLC7A9 (related to non-type I), cannot, however, in all cases explain the disease. Inasmuch as a high urinary concentration of cystine is the basis of stone formation in these patients, our aim was to measure urinary total cystine, arginine, lysine and ornithine, in patients currently lacking a full genetic explanation for their disease. Thirty-three patients with cystinuria who were on long-term treatment with tiopronin or D-penicillamine were divided into two groups. Group 1 comprised eight patients who carried mutation in one of the SLC3A1 alleles and two patients who completely lacked mutations both in the SLC3A1 and the SLC7A9 genes, that is genetic findings discordant with the increased urinary excretion of cystine and the dibasic amino acids in these patients. Group 2 comprised 23 patients homozygous for mutations within SLC3A1, that is genetic findings in accordance with the excretion pattern of classic type I cystinuria. When the two groups were compared, Group 1 had a significantly higher total urinary excretion of cystine ( p<0.01) as well as of arginine, lysine and ornithine ( p<0.05) than Group 2. Also, when the two patients without mutations were excluded from the calculations, there still was a significant difference in the urinary excretion of total cystine ( p<0.05). This suggests that the two patients without any detected mutations in the two known cystine transport genes also contributed to the difference. These unexpected findings indicate that an additional gene or genes participate in the urinary cystine reabsorption in the cystinuric patients who currently are without a full genetic explanation for their disease.

[An observation of the effects of Tiopronin on the oxygen free radicals in severely scalded rats receiving delayed fluid resuscitation]

OBJECTIVE

To observe the harmful effects of oxygen free radicals and the protective roles of Tiopronin in severely scalded rats after delayed fluid resuscitation.

METHODS

Rats inflicted with 30% III degree scald on the back were employed as the model. They were divided into delayed resuscitation (D) and Tiopronin treatment (T) groups. The changes in superoxide dismutase (SOD) and malonyldialdehyde (MDA) in plasma and subeschar fluid were determined at 24 to 48 postburn hours (PBHs) by means of electron spin resonance (ESR) technique and other routine methods. And the pathomorphological changes in the heart, liver, kidneys and small intestine, and changes in the blood biochemical indices were simultaneously determined. Normal rats were taken as control group (N).

RESULTS

The plasma SOD level was was lower than that in N group, while the MDA content in plasma and subeschar fluid in D group was much higher than that in N group. Changes in all the blood biochemical and internal organ pathomorphology were more obvious in the D group. on the other hand, the rat plasma SOD level in T group increased obviously (P < 0.01) while the MDA contents was decreased in T group (P < 0.05) when compared with those rats of D group. In addition, the internal organ pathomorphology and blood biochemical indices were improved evidently in T group.

CONCLUSION

Oxidative stress injury was evoked in severely scalded rats after delayed fluid resuscitation, and it could be protected to some extent by Tiopronin.

[Cystinuria - Cystine Stones: Recommendations for Diagnosis, Therapy and Follow-up]

Cystinuria, an autosomal-recessive disorder, is the cause of 1 - 2 % of all kidney stones observed in adults and about 10 % of those observed in infants. Despite increasing understanding of underlying pathomechanisms, patients still form recurrent stones and have to undergo repeated interventions with increasing risk of renal insufficiency. Dietary and medical metaphylaxis may lower the frequency of recurrent stones but are often not practiced. Regular follow-up examinations and optimal therapy significantly enlarge stone-free intervals. This review offers an overview of the underlying pathogenetic mechanisms as well as guidance for diagnosis, monitoring, metaphylaxis and therapy of cystinuria following the recommendations of the Deutsche Gesellschaft für Urologie (DGU) and the European Association of Urology (EAU).

[Long-term study of tiopronin in patients with cystinuria]

Thirty two patients with cystinuria were enrolled in this long-term study and 16 patients were treated with tiopronin for 24 weeks. Tiopronin reduced daily urinary cystine excretion from 901.48 mg (before treatment) to 488.60 mg (on the average of 12th week and 24th week after tiopronin administration) successfully. Tiopronin therapy was tolerated well, but side effects were observed in 13 events in 6 patients. Thus tiopronin was expected to be effective in preventing cystine stone formation and tolerated well.

Effects of sulfhydryl compounds on pancreatic cytoprotection in acute necrotic pancreatitis

OBJECTIVE

To observe sulfhydryl compound variation in the injury of pancreatic cells and the effects of external sulfhydryl compounds on cytoprotection.

METHODS

Male Wistar mice were divided randomly into three groups: groups A and B served as animal models (retrograde duct infusion with 5% sodium taurocholate), in group A, 45 animals were treated with normal saline therapy, in group B, 45 animals were treated with Tiopronin therapy; and group C, 15 animals, were designated as normal control. Animals were killed at 2, 4, 6, 12 and 24 h, and pancreatic tissue was analyzed for total sulfhydryl (TSH), nonprotein sulfhydryl (NPSH) and malondialdehyde (MDA). Histopathology, serum amylase (Sam) and C reactive protein (CRP) were assessed as well.

RESULTS

Levels of Sam and CRP increased in both group A and group B, with corresponding pathological changes of acute nerotic pancreatitis (ANP). Levels of TSH, NPSH and protein sulfhydryl (PSH) in group A decreased markedly during pancreatitis (P < 0.01), but MDA increased significantly (P < 0.01). The depletion of NPSH in group B was markedly ameliorated at 4 h or 6 h, when Tiopronin was prophylactically administered (P < 0.05), after which the level of MDA showed very little increase when compared to group A (P < 0.01). Histopathological damage was attenuated to a certain extent, in regards to serum amylase and CRP.

CONCLUSIONS

All sulfhydryl compounds decreased significantly during ANP; external sulfhydryl compound could protect the pancreatic cells most likely as a type of scavengers of oxygen free radicals, which are critically involved in the pathophysiology of ANP. Sulfhydryl plays an important role in the action of pancreatic cytoprotection.

The protective role of thiola and soybean seeds against the genotoxicity induced by potassium dichromate in mice

The genotoxic potential of potassium dichromate (K(2)Cr(2)O(7)) was evaluated in vivo in mice using different mutagenic end points. Chromosomal aberrations in bone-marrow and spermatocytes as well as sperm abnormalities in the tested mice were determined. The doses used were 3, 6, 12 mg K(2)Cr(2)O(7)kg(-1) body weight which correspond to 1/16, 1/8, 1/4 the experimental LD(50), respectively. The protective roles of i.p. injection with thiola (a synthetic sulfhydryl compound) at 20 mg kg(-1) body weight and feeding treatment with soybean seeds (30% of the diet) were also studied. For chromosomal aberration analysis, subacute treatment for a period of 3 weeks were performed. All the tested doses of K(2)Cr(2)O(7) induced a statistically significant increase in the percentage of chromosomal aberrations in both somatic and germ cells with dose and time relationships. The percentage of the induced chromosomal aberrations was significantly minimized in all groups of mice i.p. treated with thiola or fed soybean seeds during the period of treatment. Potassium dichromate also induced a significant increase (P<0.01) in the percentage of abnormal sperms at the doses 6 and 12 mg kg(-1) body weight. Such percentage reached 7.52+/-0.45, 5.50+/-0.53 and 4.28+/-0.45 in mice treated with the highest tested dose of K(2)Cr(2)O(7), K(2)Cr(2)O(7) and thiola; K(2)Cr(2)O(7) and soybean, respectively compared with 2.14+/-0.33 for the control. In conclusion, the results demonstrate the genotoxic effect of potassium dichromate in mice. The results also confirm the protective role of thiola and soybean seeds against the genotoxicity of potassium dichromate.

Bucillamine prevents myocardial reperfusion injury

Injury during reperfusion can partially offset the benefit of relief of ischemia in myocardial infarctions rapidly treated with thrombolytic drugs or angioplasty. We assessed whether bucillamine (N-[2-mercapto-2-methylpropionyl]-L-cysteine) is potentially useful to treat myocardial reperfusion injury. Bucillamine is a potent sulfhydryl donor not previously tested as a treatment of reperfusion injury. Cardiac myocytes were exposed to hydrogen peroxide or a xanthine/xanthine oxidase system resulting in injury-induced release of lactate dehydrogenase. Bucillamine (125-500 microM) prevented lactate dehydrogenase release in a concentration-dependent manner. Bucillamine, which has two donatable thiol groups, was twice as protective as N-2-mercaptopropionyl glycine, which contains a single donatable thiol group. Dogs were then exposed to 90 min of coronary artery occlusion and 48 h of reperfusion before sacrifice. Beginning at the onset of reperfusion, bucillamine, 11 or 22 mg/kg per hour, or vehicle (saline) was administered intravenously for 3 h. There was a dose-related response to bucillamine for infarct size, normalized for size of the region at risk and adjusted for collateral blood flow to the ischemic region. Infarct size was reduced by 41% in the group treated with bucillamine 22 mg/kg per hour, compared with the vehicle group. Bucillamine, probably through an antioxidant mechanism, reduced infarct size when administered during reperfusion.

Cystine analyses of separate day and night urine as a basis for the management of patients with homozygous cystinuria

Based on previous observations of the diurnal variation of urinary cystine excretion, the use of separate day and night urine collections was proposed. To improve the medical treatment of patients with cystinuria, this strategy was performed to guide the fluid intake and the administration of SH compounds (tiopronin, D-penicillamine, and MESNA).Twenty-six patients (19 treated with SH compounds and seven with alkalinization and hydration only) were followed during two 3.5-year periods. During Period 1, 24-h urine was collected and during Period 2, separate day and night urine was collected. There were 56 episodes of high urinary cystine supersaturation (> 1,200 micromol/l) during Period 2, 47% of which would have evaded detection with 24-h urine analysis. In comparison with Period 1, the urinary cystine concentration was lower (P < 0.05), and the urinary volume was higher (P < 0.05) during Period 2. Patients treated with tiopronin had reduced cystine excretion (P < 0.05) and at the end of Period 2, an increased dose of tiopronin, reflecting a more aggressive treatment. Furthermore, a reduced number of stone episodes and need of active stone removal (P < 0.05) was noted in the whole group of patients. Analyses of separate day and night urine samples can be used advantageously to reveal episodes of high supersaturation with cystine not detected in 24-h urine samples. Such a procedure might be useful for optimizing the treatment of patients with cystinuria.

A comparison of the effects of potassium citrate and sodium bicarbonate in the alkalinization of urine in homozygous cystinuria

For many years, urine alkalinization has been one of the cornerstones in the treatment of homozygous cystinuria. Because of the relationship found between the excretion of urinary sodium and cystine, potassium citrate has emerged as the preferred sodium-free alkalizing agent. To evaluate the usefulness of potassium citrate for urine alkalization in cystinuric patients, sodium bicarbonate and potassium citrate were compared in 14 patients (10 on tiopronin treatment and four without treatment with sulfhydryl compounds). The study started with 1 week without the use of any alkalizing agents (Period 0) followed by 2 weeks with sodium bicarbonate (Period 1) and 2 weeks with potassium citrate (Period 2). Urinary pH, volume, excretion of sodium, potassium, citrate and free cystine, as well as the plasma potassium concentration, were recorded. Potassium citrate was shown to be effective as an alkalizing agent and, in this respect, not significantly different from sodium bicarbonate. Even though a normal diet was used, a significant increase in urinary sodium excretion was observed with sodium bicarbonate (Period 1). Urinary potassium and citrate excretion increased with potassium citrate (Period 2). A significant correlation was found between urinary sodium and cystine in the tio-pronin-treated patients. No significant differences in cystine excretion were recorded in Periods 0, 1 and 2. Plasma potassium was significantly higher during Period 2, but only one patient developed a mild hyperkalemia (5.0 mmol/l). The use of potassium citrate for urine alkalization in homozygous cystinuria is effective and can be recommended in the absence of severe renal impairment.

Cystinuria in the dog: clinical studies during 14 years of medical treatment

The purpose of this study was to summarize 14 years of clinical experience with medical treatment of 88 cystinuric dogs. Of special interest was evaluation of recurrence rate of cystine uroliths and adverse effects during long-term tiopronin treatment. Twenty-six different breeds were recognized, and the most common breeds were Dachshunds, Tibetan Spaniels, and Basset Hounds. In 76 of 88 treated dogs (86%), re-formation of cystine uroliths was prevented. Recurrence rate of cystine uroliths changed from 7 months before to 18 months during tiopronin treatment. On 28 occasions, bladder stones were found, and in about 60% of the dogs, the uroliths dissolved. Quantitative measurement of the urinary excretion of cystine showed a significantly (P < .03) higher excretion of cystine in dogs with recurrent urolith formation than in dogs with only 1 urolith episode. Another finding was a significant (P = .02) decrease in urinary cystine excretion in older (>5 years) than in younger (<5 years) dogs. Adverse effects were found in 11 dogs, and the most severe signs were aggressiveness and myopathy. All signs disappeared when tiopronin treatment was stopped. In conclusion, this study emphasizes the importance of an individual strategy for lifelong treatment of cystinuria. In addition to increasing water intake, chemical modification of the cysteine molecule into a more soluble form by means of tiopronin is useful. In dogs with re-formed cystine uroliths, dissolution may be induced by increasing the tiopronin dosage to 40 mg/kg body weight per day. In dogs with a low urolith recurrence rate and low urinary cystine excretion, the tiopronin dosage may be decreased or treatment discontinued.

CYSTINE CALCULI IN CHILDREN: THE RESULTS OF A METABOLIC EVALUATION AND RESPONSE TO MEDICAL THERAPY

PURPOSE

We describe baseline metabolic abnormalities and evaluate mercaptopropionylglycine plus potassium citrate treatment for urinary abnormalities and to prevent new stone formation in children with cystine stones.

MATERIALS AND METHODS

Daily urinary excretions of calcium, oxalate, citrate, magnesium, urate and phosphorus were determined in 18 children with cystine stone and 24 healthy children. The cystine stone cases were treated with 10 to 15 mg./kg. alpha-mercaptopropionylglycine and 1 mEq./kg. potassium citrate daily for a median 15 months. The potassium citrate dose was adjusted to render urinary pH 6.5 to 7.5.

RESULTS

There was no significant difference in baseline metabolic profile between the cystine stone and control groups except for citrate. The cystine stone group excreted less citrate than the control group (p = 0.044). After treatment median plus or minus standard deviation urinary cystine 245 +/- 233 to 140 +/- 106 mmol./mol. creatinine decreased from (p = 0.015), and urinary citrate increased from 255 +/- 219 to 729 +/- 494 mg./1.73 m.2 (p = 0.003). No serious adverse reaction was noted. Of the 15 patients with followup data 5 (33%) had 8 recurrent calculi (recurrence rate 0.64 per patient year).

CONCLUSIONS

Our results suggest that further investigation of low citrate excretion is needed in cystinuric children. Potassium citrate therapy is effective in increasing urinary pH and urinary citrate. However, high recurrence rate and persistent cystinuria in our patients emphasize the inadequacy of our treatment schedule in the prevention of recurrent cystine calculi.

Prophylaxia of cystine calculosis by alpha-mercaptopropionyl-glycine administered continuously or every other day

We determined the efficacy of alpha-mercaptopropionyl-glycine administered in a low dosage continuously or every other day for prophylaxis of cystine calculosis. Two homozygous cystinuric patients with previous calculosis and renal unilateral hypoplasia and been given preventive treatment with alpha-mercaptopropionyl-glycine continuously administered in a low dosage (1.5-4 mg Kg-1 day-1 for 14 1/2 years and 10(-4) mg Kg-1 day-1 for 9 years respectively). Neither calculosis, nor side effects were observed. Subsequently, the patients were given 4 mg Kg-1 of the drug every second day for 1 and 1-2 years respectively without calculosis or side effect being observed. A low dosage of alpha-mercaptopropionyl-glycine(1.5-4 mg Kg-1 day-1) supplied continuously or, for a short time, 4 mg Kg-1 day-1 supplied every other day can be effective in the prophylaxis of cystine nephrolithiasis in some homozygous patients with renal unilateral hypoplasia, with lower risk of side effects.

[A preliminary study on the activation of superoxide dismutase by Tiopronin in patients with chronic hepatitis B]

OBJECTIVE

To observe the clearance effect of Tiopronin on oxygen free radicals in chronic hepatitis B patients.

METHODS

The ranthine oxidase assay was used to detect superoxide dismutase (SOD) in 80 chronic hepatitis B patients, the ALT, TBil, TP and AIG ratio of the patients were also tested. The 80 chronic hepatitis B patients were divided into two groups, the control group was treated with routine liver protective and jaundice regressing drugs while the treated group was additionally administered with Tiopromin besides the routine treatment.

RESULTS

In two groups of patients with similar ages and sexes, there showed no differences in levels of SOD, ALT, TBil, TP and ALB before treatment, as the SOD in treated group and control group were 106.57 (40.68 NU/ml and 105.18(44.59 NU/ml respectively, while the normal value for SOD in 16 normal persons was 165.9(23.36 NU/ml. After treatment, there were significant differences (P< 0.01) in SOD, ALT, TBil and ALB levels which showed SOD 187.93(35.24 NU/ml, ALT 38.41(22.22 U/L, TBil 23.15(12.46 micromol/L, ALB 43.28 (4.21 g/L in the treated group and SOD 157.96(47.29 NU/ml, ALT 68.52(34.19 U/L, TBil 30.38(21.80 micromol/L and ALB 40.36(5.19 g/L in the control group.

CONCLUSIONS

There showed a good therapeutic effect of Tiopronin on the clearance of oxygen free radicals in chronic hepatitis B patients and also it can improve the liver function.

The long-term outcome of cystinuria in Japan

Recurrence of growth of urinary stone is frequently observed during the clinical course of cystinuria patients. The aim of the present study is to examine the long-term outcome of cystinuria in Japan and clarify the effects of medical treatment on urinary stone. Thirty-one patients with cystinuria who had been followed up longer than 6 months were included. The follow-up period was 6-264 months with a mean of 89.5 months. Stone event was defined as appearance of new stone or radiological evidence of stone growth. All patients were managed with forced hydration and urine alkalization. Twenty-eight patients were treated with administration of thiol such as D-penicillamine or alpha-mercaptopropionylglycine. Stone events per year ranged from 0 to 1.09 with a median of 0.09. Stone events per patient-year was 0.19 for all patients. The average urinary cystine concentration during treatment in the favorable outcome group (stone events per year < 0.3) was lower that that in the unfavorable outcome group (stone events per year >/=0.3); 221.2 +/- 75.2 vs. 303.3 +/- 93.5 mg/l, although the difference was not statistically significant. Prognosis of urinary stone in Japanese patients with cystinuria was relatively good with large variation. The medical treatment to reduce urinary cystine concentration would be useful for the management of cystinuria.

A modified cyanide-nitroprusside method for quantifying urinary cystine concentration that corrects for creatinine interference

Cystinuria, an inherited disease, is clinically diagnosed by detecting cystine in urine. A colorimetric method using sodium cyanide and sodium nitroprusside is a simple qualitative test used to detect cystinuria. Several colorimetric methods have been proposed for quantitative analysis of cystine; however, we found that none of them were satisfactory because the results were not reproducible. The causes of non-reproducible results were: (1) insufficient reduction time for conversion of cystine to cysteine, and (2) the interference of creatinine. In this report, we present a method to quantitate cystine in urine. We also found that ascorbic acid and ferric chloride, but not zinc chloride, interfered with the color reaction. Using this method, 15 normal urine samples (10 males and 5 females) and 12 cystine stone forming patients' (5 males and 7 females) urine were analyzed. The method was compared to commercially available urine controls. Only captopril showed a dose dependent response and color intensity at 521 nm. Thiola and D-penicillamine showed little effect on cystine determination.

[Polymyositis induced by tiopronine]

BACKGROUND

D-penicillamine-induced muscle disorders are well-known, tiopronine-induced disorders are less often reported.

CASE REPORT

A 62-year-old patient, given tiopronine for rheumatoid arthritis, developed severe polymyositis with characteristic clinical and pathology features. The course was favorable after tiopronine withdrawal and substitution with methotrexate.

DISCUSSION

Clinicians should be aware of the side-effects of tiopronine, particularly muscle disorders, and implement careful surveillance to achieve early diagnosis and appropriate therapy.

Cisplatin combined with tiopronin or sodium thiosulfate: cytotoxicity in vitro and antitumor activity in vivo

We have previously reported that the thiol compound tiopronin protects rat kidneys in vitro against the toxic activity of cisplatin. The influence of tiopronin and sodium thiosulfate (STS) on the cytotoxicity of cisplatin has been investigated on P388 leukemic cells in vitro after 3 days. The combination has also been investigated in vivo in BDF1 mice bearing a P388 s.c. tumor. In contrast to STS, tiopronin did not significantly reduce the cytotoxic activity of cisplatin in vitro and nor did it affect the uptake of platinum (cisplatin-derived), binding to DNA or the percentage of interstrand cross-links (%ISCL) formation. The co-administration of cisplatin (4 mg/kg) and tiopronin (150 and 300 mg/kg) to BDF1 female mice bearing a s.c. P388 tumor produced a significant reduction in tumor growth similar to that of a single 6 mg/kg dose of cisplatin. Interestingly, pre-incubation in vitro of either tiopronin or STS for 2 h with the species formed from cisplatin by hydrolysis demonstrated their ability in inhibiting the cytotoxicity of these reactive platinum products. These results indicate that tiopronin does not reduce the cytotoxicity of cisplatin in vitro, as STS does. This may be, at least partly, because of a different effect of the two thiol compounds on the cellular uptake and binding of platinum to DNA. Notably, tiopronin substantially reduced tumor growth in mice treated with a non-toxic dose of cisplatin (p < or = 0.0277), suggesting some positive influence of this thiol compound on the antitumor properties of cisplatin. The ability of tiopronin to protect in vitro against the cytotoxicity of the aquation products of cisplatin may be related to its nephroprotective effect.

Timing of treatment for myocardial reperfusion injury

Early reperfusion of acute myocardial infarctions halts cell death due to ischemia but causes further injury, probably by oxidant mechanisms. We identified the window of opportunity during which antioxidants must be present in therapeutic concentrations to prevent reperfusion injury during 90 min of ischemia and 48 h of reperfusion in 57 dogs. We examined the effect on myocardial infarct size of intravenous infusion of N-2-mercaptopropionyl glycine (MPG), a diffusible antioxidant with a plasma half-time of 7 min, by using a series of protocols with a range of timing. Whereas infusions of MPG for > or =3 h reduced infarct size by approximately 50%, infusions for 1 h only (the first, second or third hours of reperfusion) caused only small reductions. A statistical analysis that focused on identifying components of group membership responsible for differences revealed that duration of treatment was a major determinant of infarct size. If begun any time within the first hour of reperfusion, infusions of > or =3 h markedly diminished infarct size. Because reperfusion injury proceeds for the first 3 h of reperfusion, but decreases thereafter, adequate protection is needed for > or =3 of the first 4 h of reperfusion, but more prolonged protection is not necessary.

[Clinical study on cystinuria in children--the stone management and the prevention of calculi recurrence]

BACKGROUND

Cystinuria is an autosomal recessive disorder, and primary manifestation is the repeated formation of cystine calculi. Little information is available regarding clinical course of pediatric cystinuria having followed into adulthood. We report our experience with the management and the clinical course on cystinuria in children, who have been followed up for relatively long time.

MATERIALS AND METHODS

We retrospectively reviewed the records of all pediatric patients with cystinuria in whom urolithiasis was treated from 1970 to 1996.

RESULTS

A total of 15 pediatric patients with cystine calculi (9 boys, 6 girls) were treated in our hospital. Average age at diagnosis was 3 years 4 months old. Mean follow-up was 104 months. Stone location was upper urinary tract in 11 cases, bladder in 3 cases and both upper urinary tract and bladder in 1 case. Medical treatments including hydration, urine alkalization and dissolution therapy were performed in all patients. In three cases whose urinary cystine level ranged from 138 to 326 mg/gCr, cystine calculi were disappeared by medical therapy alone. In one of 3 cases vesicoureteral reflux was identified. Side effects were noticed in 30.0% of patients with tiopronin and in 85.7% of those with D-penicillamine, especially in 1 case with tiopronin nephrotic syndrome being noticed. Surgical procedures were performed in 13 patients (lithotomy: 17 calculi, endourology: 7 calculi and ESWL: 7 calculi). The stone free rate was 100% with lithotomy, 80 to 100% with endourology and 43% with ESWL at an average of 5.9 procedures. No complications were recognized after the surgical treatments. The stone events of 15 patients ranged from 0 to 1.5 (average 0.55). In all six patients followed up over the age of 20 years, stone recurrences were observed exclusively between 17 and 20 years of age.

CONCLUSION

Dissolution therapy is more effective for cystinuric patients in whom urinary cystine excretion is less than 330 mg/gCr. For those cases with low urinary cystine level it is necessary to evaluate structural abnormalities of the urinary tract to avoid stone recurrence. ESWL and endourology should be tried for pediatric cystinuria except for neonates and infants, considering its safety. The patients and their parents must have adequate knowledge about the disease itself and its management. Prevention of cystine calculi recurrences depends on patient compliance to the therapeutic regimens necessitating close follow up according to the clinical conditions, especially for those in pubertic or postpubertic age.

Prophylaxis of cystine calculi by low dose of alpha-mercapto-propionyl-glycine administered every other day

In a case of typical cystinuria type I with left kidney hypoplasia and bilateral calculosis, calculi were dissolved by means of alpha-mercapto-propionyl-glycine and prophylaxis of the calculosis was performed by the same drug continuously administered in two divided doses (10-4 mg.kg-1.day-1) for 9 years, without urolithiasis. Then, the alpha-mercaptopropionyl-glycine every other day in one dose, 4 mg.kg-1.day-1, for two years was administered without calculosis. The arbitrary discontinuation of the drug by the patient was followed after 6 months from a right ureteral calculosis with transitory renal insufficiency. In our case the administration of a low dose of alpha-mercapto-propionyl-glycine every other day was useful in cystine calculosis prophylaxis.

A comparative study of radioprotection by Ocimum flavonoids and synthetic aminothiol protectors in the mouse

The radioprotective effects of two flavonoids, orientin (Ot) and vicenin (Vc), obtained from the leaves of Ocimum sanctum, and the synthetic compounds WR-2721 and MPG (2-mercaptopropionyl glycine) have been compared by examining chromosome aberration in cells of bone marrow in irradiated mice. Healthy adult Swiss mice were injected intraperitoneally (i.p.) with 50 micrograms kg-1 body weight of Ot or Vc; 20 mg kg-1 of MPG; 150 mg kg-1 of WR-2721 or double distilled water (DDW). They were exposed to whole body irradiation of 2.0 Gy gamma radiation 30 min later. After 24 h, chromosomal aberrations were studied in the bone marrow of the femur by routine metaphase preparation after colchicine treatment. Radiation (2 Gy) increased the number of aberrant cells from less than 1% in controls to almost 20%. Pre-treatment with all the protective compounds resulted in a significant reduction in the percentage of aberrant metaphases as well as in the different types of aberration scored. Vc produced the maximum reduction in percent aberrant cells while MPG was the least effective; Ot and WR-2721 showed an almost similar effect. However, WR-2721 was the most effective against reduction of complex an almost similar effect. However, WR-2721 was the most effective against reduction of complex aberrations, followed by Vc. Neither flavonoids had any systemic toxicity, even at 200 mg kg-1 body weight. Considering the low dose needed for protection and the high margin between the effective and toxic doses, the ocimum flavonoids may be promising for human radiation protection.

Etiological and clinical patterns of urolithiasis in Turkish children

OBJECTIVE

To evaluate the clinical and etiological characteristics of childhood urolithiasis in Turkey.

METHODS

Ninety-two children with urolithiasis were studied retrospectively according to clinical patterns and etiological factors between January 1990 and January 1995.

RESULTS

The age range of the patients was from 2 months to 14 years (mean age 6.9 years), and there was a male/female ratio of 1.6. The onset of the disease was earlier in boys than in girls. The most striking features were the initial admission of 14 (15.2%) children after the development of chronic renal failure and that most of them (64.3%) had infection stones. The stones were localized in the upper urinary system in 68.5% of the patients; bladder stones were rare (10.9%). The recurrence rate at presentation was 15.2% in all patients. As etiological factors, an anatomical defect was found in 30.4% of the patients, infections in 31.5%, and metabolic disorders in 26.1%; 11 (12.0%) of them were classified as idiopathic. The earliest presentation was seen with metabolic and infection stones and the highest recurrence rate (37.5%) in patients with metabolic stones.

CONCLUSION

Childhood urolithiasis is a serious problem in Turkey. In order to prevent the development of end-stage renal failure and to improve the patients' quality of life, more efforts should be made with respect to early diagnosis and management of renal stones and urinary tract infections.

Controlled reperfusion of cardiac grafts from non-heart-beating donors

BACKGROUND

Hearts harvested from non-heart-beating donors sustain severe injury during procurement and implantation, mandating interventions to preserve their function. We tested the hypothesis that limiting oxygen delivery during initial reperfusion of such hearts would reduce free-radical injury.

METHODS

Rabbits sustained hypoxic arrest after ventilatory withdrawal, followed by 20 minutes of in vivo ischemia. Hearts were excised and reperfused with blood under conditions of high arterial oxygen tension (PaO2) (approximately 400 mm Hg), low PaO2 (approximately 60 to 70 mm Hg), high pressure (80 mm Hg), and low pressure (40 mm Hg), with or without free-radical scavenger infusion. Non-heart-beating donor groups were defined by the initial reperfusion conditions: high PaO2/ high pressure (n = 8), low PaO2/high pressure (n = 7), high PaO2/low pressure (n = 8), low PaO2/low pressure (n = 7), and high PaO2/high pressure/free-radical scavenger infusion (n = 7).

RESULTS

After 45 minutes of reperfusion, low PaO2/ high pressure and high PaO2/low pressure had a significantly higher left ventricular developed pressure (63.6 +/- 5.6 and 63.1 +/- 5.6 mm Hg, respectively) than high PaO2/high pressure (40.9 +/- 4.5 mm Hg; p < 0.0000001 versus both). However, high PaO2/high pressure/free-radical scavenger infusion displayed only a trend toward improved ventricular recovery compared with high PaO2/ high pressure.

CONCLUSIONS

Initially reperfusing nonbeating cardiac grafts at low PaO2 or low pressure improves recovery, but may involve mechanisms other than decreased free-radical injury.

Medical treatment of cystinuria: results of contemporary clinical practice

PURPOSE

We determined the efficacy of a contemporary medical regimen for treatment of cystinuria.

MATERIALS AND METHODS

A total of 16 patients with cystinuria was followed for 7 to 141 months (mean 78.1). Standard therapy included hydration and alkalization. D-penicillamine or alpha-mercaptoproprionylglycine was added for failure of hydration and alkalization to prevent new stones or stone growth, or to cause dissolution. Captopril was added for failure of or intolerance to D-penicillamine or alpha-mercaptopropionylglycine. Radiography was performed every 6 to 12 months, at which time stone events were documented.

RESULTS

During hydration and alkalization 46 stone events occurred in 8 of 9 patients (1.6 events per patient-year). With addition of thiol derivatives 7 of 9 patients experienced 24 stone events, all 6 treated with hydration, alkalization and captopril experienced 10 events, and 4 of 5 treated with alkalization, thiols and captopril experienced 8 events (0.52, 0.71 and 0.54 events per patient-year, respectively). During a total treatment time of 104.1 patient-years 88 stone events occurred in 14 of 16 patients (0.84 events per patient-year).

CONCLUSIONS

D-penicillamine and alpha-mercaptopropionylglycine are effective in decreasing the rate of stone formation in patients in whom hydration and alkalization failed. While captopril may also be beneficial in this setting, it does not appear to be as effective as D-penicillamine or alpha-mercaptopropionylglycine, and it does not clearly add clinical benefit to those thiols. Our study demonstrates that patients with cystinuria are at high risk for recurrence when treated with any contemporary medical program. This natural history must be considered when evaluating the long-term efficacy of newer or alternative modes of medical and urological treatment.

Studies of hypoxemic/reoxygenation injury: without aortic clamping. VI. Counteraction of oxidant damage by exogenous antioxidants: N-(2-mercaptopropionyl)-glycine and catalase

This study tests the hypothesis that antioxidants administered before reoxygenation can reduce oxygen-mediated damage and improve myocardial performance. Of 25 Duroc-Yorkshire piglets (2 to 3 weeks, 3 to 5 kg) five underwent 60 minutes of cardiopulmonary bypass without hypoxemia (control group), and five others underwent 30 minutes of hypoxemia on cardiopulmonary bypass with a circuit primed with oxygen tension about 25 mm Hg blood followed by reoxygenation on cardiopulmonary bypass (no treatment). In vitro studies were performed to obtain the optimal dosage of the antioxidants N-(2-mercaptopropionyl)-glycine and and catalase to be used in subsequent in vivo experimental studies; cardiac homogenates were incubated in 0 to 5 mmol/L concentrations of the oxidant t-butylhydroperoxide and malondialdehyde production was measured. Fifteen piglets were made hypoxemic on cardiopulmonary bypass for 30 minutes, and the antioxidants N-(2-mercaptopropionyl)-glycine at either 30 or 80 mg/kg body weight or N-(2-mercaptopropionyl)-glycine, 30 mg/kg body weight, and catalase, 50,000 U/kg body weight, were added to the cardiopulmonary bypass circuit 15 minutes before reoxygenation. Left ventricular contractility, which was expressed as end-systolic elastance, was measured by conductance catheter before hypoxemia and after reoxygenation. Myocardial antioxidant reserve capacity was determined after reoxygenation by incubating cardiac homogenates in the oxidant t-butylhydroperoxide and measuring subsequent malondialdehyde elution. The in vitro bioassay studies showed a dose-dependent reduction of lipid peroxidation with N-(2-mercaptopropionyl)-glycine, with maximal benefits of a 40% decrease and malondialdehyde elaboration occurring with N-(2-mercaptopropionyl)-glycine and catalase compared with untreated cardiac homogenates. Cardiopulmonary bypass (no hypoxemia) caused no oxidant damage or changes in contractile function after cardiopulmonary bypass. Reoxygenation without treatment raised conjugated diene levels 57%,* lowered antioxidant reserve capacity 51%,* and was associated with only 38%* recovery of contractile function (p < 0.05 vs control). In contrast, treatment with antioxidants avoided lipid peroxidation, maintained antioxidant reserve capacity, and resulted in a dose-dependent improvement in left ventricular contractility with complete recovery occurring in N-(2-mercaptopropionyl)-glycine and catalase-treated piglets (*p < 0.05 vs no treatment). This study confirms the occurrence of hypoxemic/reoxygenation injury in immature hearts placed on cardiopulmonary bypass and shows that biochemical and functional damage can be counteracted by adding antioxidants to the cardiopulmonary bypass priming fluid. Contractile function improved in a dose-dependent manner, and oxygen-mediated damage could be avoided by mercaptopropionyl glycine/catalase treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Studies of hypoxemic/reoxygenation injury: with aortic clamping. X. Exogenous antioxidants to avoid nullification of the cardioprotective effects of blood cardioplegia

This study tests the hypothesis that reoxygenation of cyanotic immature hearts when starting cardiopulmonary bypass produces an "unintended" reoxygenation injury that (1) nullifies the cardioprotective effects of blood cardioplegia and (2) is avoidable by adding antioxidants N-(2-mercaptopropionyl)-glycine plus catalase to the cardiopulmonary bypass prime. Twenty immature piglets (2 to 3 weeks) underwent 30 minutes of aortic clamping with a blood cardioplegic solution that was hypocalcemic, alkalotic, hyperosmolar, and enriched with glutamate and aspartate during 1 hour of cardiopulmonary bypass. Of these, six piglets did not undergo hypoxemia (blood cardioplegic control) and 14 others remained hypoxemic (oxygen tension about 25 mm Hg) for up to 2 hours by lowering ventilator fraction of inspired oxygen before reoxygenation on cardiopulmonary bypass. The primary solution of the cardiopulmonary bypass circuit was unchanged in eight piglets (no treatment) and supplemented with the antioxidants N-(2-mercaptopropionyl)-glycine (80 mg/kg) and catalase (5 mg/kg) in six others (N-(2-mercaptopropionyl)-glycine and catalase). Myocardial function (end-systolic elastance), lipid peroxidation (myocardial conjugated diene production), and antioxidant reserve capacity were evaluated. Blood cardioplegic arrest produced no biochemical or functional changes in nonhypoxemic control piglets. Reoxygenation caused an approximate 10-fold increase in conjugated production that persisted throughout cardiopulmonary bypass, lowered antioxidant reserve capacity 86% +/- 12%, and produced profound myocardial dysfunction, because end-systolic elastance recovered only 21% +/- 2%. Supplementation of the cardiopulmonary bypass prime with N-(2-mercaptopropionyl)-glycine and catalase reduced lipid peroxidation, restored antioxidant reserve capacity, and allowed near complete functional recovery (80% +/- 8%).** Lipid peroxidation (conjugated diene) production was lower during warm blood cardioplegic reperfusion than during induction in all reoxygenated hearts, which suggests that blood cardioplegia did not injure reoxygenated myocardium. We conclude that reoxygenation of the hypoxemic immature heart causes cardiac functional and antioxidant damage that nullifies the cardioprotective effects of blood cardioplegia that can be avoided by supplementation of the cardiopulmonary bypass prime with antioxidants (*p < 0.05 vs blood cardioplegic control; **p < 0.05 vs reoxygenation).

Clinical course and cystine stone formation during tiopronin treatment

The formation of stones in patients with cystinuria can be counteracted by reducing the urinary concentration of cystine and by increasing its solubility. Thirty-one patients with homozygous cystinuria and treated with tiopronin (2-mercaptopropionylglycine) were followed for between 0.4 and 12 years (median 8.8). With the aim of avoiding cystine concentrations above 1200 mumol/l, the daily dose varied between 500 and 3000 mg (median 1500). The therapeutic effect was evaluated from the clinical symptoms and repeated radiographic examinations. The rate of stone formation during the treatment period was reduced by 60% in comparison with the pretreatment period (P < 0.001). The frequency of active stone removal was reduced by 72% (P < 0.05). The formation of new stones was associated with a higher cystine concentration than was the case during periods when stone formation and stone growth were excluded (P < 0.05). The probability of new stone formation increased with increasing concentrations of cystine up to 1100 mumol/l, but stone formation was not accentuated above 1200 mumol/l. There was no significant relationship between the 24 h excretion of cystine and stone formation. It is concluded that the formation of cystine stones can be efficiently counteracted during treatment with tiopronin, guided by analysis of the concentration of urinary cystine.

[Myasthenia induced by tiopronin in the treatment of rheumatoid arthritis]

Myasthenia gravis (MG) is a well known side-effect of D-Penicillamine used in the treatment of rheumatoid polyarthritis. Tiopronin is another drug available in France, which can also induce MG. Drug-induced MG are characterized by frequent involvement of facial and oropharyngeal muscles. Moreover, the generalization is scarce and the outcome always quite good. No thymoma is present, anti-acetylcholine receptors antibodies are often highly positive. Furthermore, some HLA phenotypes are most frequently found among patients with drug-induced MG suggesting a genetic predisposition. This observation underlines the interest of careful management of patients treated by tiopronin.

The effect of sodium intake on cystinuria with and without tiopronin treatment

As with many other amino acids the transport of cystine across the tubular epithelium is coupled to a parallel transport of sodium. We have studied the effect of a sodium-restricted diet on the urinary excretion of cystine in 13 patients with cystinuria, 7 of whom were treated with the SH compound tiopronin (2-mercaptopropionylglycine). Five of the patients with tiopronin and 5 without were also given sodium bicarbonate. The patients were instructed to follow a sodium-restricted diet during three periods of 2 weeks each. Four levels of sodium intake were obtained including the preexperimental unrestricted diet. The average 24-hour excretion of free cystine increased by 3.1 mumol (0.75 mg) for each millimole increase in urinary sodium (p < 0.001). There was a greater sodium-related increase in excretion of cystine among patients without tiopronin treatment compared with the group with tiopronin (p < 0.01). Withdrawal of sodium bicarbonate resulted in a decrease in the 24-hour cystine excretion (p < 0.05). In the patients treated with tiopronin the excretion of the mixed disulfide increased with increasing urinary sodium (p < 0.05) suggesting a sodium-dependent active tubular reabsorption of this compound as well. We conclude that in spite of a defective proximal tubular reabsorption of cystine in cystinuria the reabsorption can be increased by restricting the intake of sodium. This effect of sodium may have clinical consequences for some cystinuric patients.

Urinary excretion of free cystine and the tiopronin-cysteine-mixed disulfide during long term tiopronin treatment of cystinuria

We report the results of a biochemical evaluation of long-term treatment of cystinuria with the SH compound tiopronin (2-mercaptopropionylglycine). The effects of tiopronin were studied by monitoring the urinary excretion of free cysteine and the mixed disulfide between tiopronin and cysteine. Thirty-one patients with homozygous cystinuria were treated with tiopronin for 0.4-12 years (mean 7.8 years). The urinary concentration of free cysteine was used to adjust the tiopronin dose. In 28 of the 31 patients a mean urinary cystine concentration of less than 1,200 mumol/1(288 mg/l) was achieved with the final dose. The final daily doses of tiopronin ranged from 250 mg (1.5 mmol) to 3,000 mg (18.4 mmol; mean 1,540 mg; 9.4 mmol). In a majority of the patients the treatment reduced the 24-hour urinary free cystine excretion effectively, on average by 0.61 mumol (0.15 mg)/mg of tiopronin administered. No changes in the efficacy of tiopronin over time were observed, and the frequency of adverse effects was acceptable. To evaluate the effects of tiopronin on the metabolism of cystine we calculated the total urinary excretion of cystine as the sum of free cystine and the amount of cystine corresponding to the cysteine content of the tiopronin-cysteine disulfide. At low doses of tiopronin there was an increase in urinary excretion of the mixed disulfide as well as of total cystine. Monitoring urinary cystine concentration is necessary to achieve adequate individualized doses of tiopronin. Assessment of the mixed tiopronin-cysteine disulfide and the urinary excretion of total cystine shows that tiopronin may interfere with cystine metabolism in a more complex way than through a simple disulfide exchange reaction with urinary cystine.

Contraction band necrosis: its modification by the free radical scavenger N-2-mercaptopropionyl glycine

Contraction band necrosis (CBN) may represent infarct extension from free radical generation during reperfusion. We sought to limit CBN with the free radical scavenger N-2-mercaptopropionyl glycine (MPG, 20 mg/kg). Sixteen chronically instrumented Beagles (8 control, and 8 MPG treated) underwent 90-min left anterior descending coronary artery (LAD) occlusion followed by 6-h reperfusion. Coronary blood flow (CBF) was measured by the radioactive microsphere technique. The dogs were killed, and the hearts were perfused with red and blue dyes to determine area at risk (AAR), stained with nitroblue tetrazolium for infarct localization, and sectioned for histologic analysis and BF measurements. In controls and MPG-treated animals, infarct/risk ratios were 40 +/- 5 and 38 +/- 6%, and epicardial collateral BFs were 0.21 +/- 0.037 and 0.15 +/- 0.034 ml/g/min, respectively (p = NS). Hemodynamic measurements did not differ between the two groups. However, CBN as a percentage of total infarct was reduced in controls (22 +/- 3%) as compared with MPG-treated animals (35 +/- 2%, p = 0.002). Thus, MPG altered the histologic composition of infarcts in this model, surprisingly increasing the amount of CBN without altering overall infarct size (IS). These results raise questions about the role of free radical scavengers in generation of CBN and suggest that a population of cells exists in which treatment with MPG may alter the mechanism of cell death.