Adipose stem cell secretome markedly improves rodent heart and human induced pluripotent stem cell-derived cardiomyocyte recovery from cardioplegic transport solution exposure.

Heart transplantation is a life-saving therapy for end-stage organ failure. Organ deterioration during transportation limits storage to 4 hours, limiting hearts available. Approaches ameliorating organ damage could increase the number of hearts acceptable for transplantation. Prior studies show that adipose-derived stem/stromal cell secretome (ASC-S) rescues tissues from postischemic damage in vivo. This study tested whether ASC-S preserved the function of mouse hearts and human induced pluripotent stem cell-derived cardiomyocytes (iCM) exposed to organ transportation and transplantation conditions. Hearts were subjected to cold University of Wisconsin (UW) cardioplegic solution ± ASC-S for 6 hours followed by analysis using the Langendorff technique. In parallel, the effects of ASC-S on the recovery of iCM from UW solution were examined when provided either during or after cold cardioplegia. Exposure of hearts and iCM to UW deteriorated contractile activity and caused cell apoptosis, worsening in iCM as a function of exposure time; these were ameliorated by augmenting with ASC-S. Silencing of superoxide dismutase 3 and catalase expression prior to secretome generation compromised the ASC-S cardiomyocyte-protective effects. In this study, a novel in vitro iCM model was developed to complement a rodent heart model in assessing efficacy of approaches to improve cardiac preservation. ASC-S displays strong cardioprotective activity on iCM either with or following cold cardioplegia. This effect is associated with ASC-S-mediated cellular clearance of reactive oxygen species. The effect of ASC-S on the temporal recovery of iCM function supports the possibility of lengthening heart storage by augmenting cardioplegic transport solution with ASC-S, expanding the pool of hearts for transplantation.

Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Recent data suggested a causative role of uric acid (UA) in the development of renal disease, in which endothelial dysfunction is regarded as the key mechanism. Endothelial-to-mesenchymal transition (EndoMT) and shedding of the glycocalyx are early changes of endothelial dysfunction. We investigated whether UA induced EndoMT in HUVECs and an animal model of hyperuricemia fed with 2% oxonic acid for 4 wk. UA induced EndoMT in HUVECs with a generation of reactive oxygen species via the activation of membranous NADPH oxidase (from 15 min) and mitochondria (from 6 h) along with glycocalyx shedding (from 6 h), which were blocked by probenecid. GM6001, an inhibitor of matrix metalloproteinase, alleviated UA-induced glycocalyx shedding and EndoMT. Antioxidants including N-acetyl cysteine, apocynin, and mitotempo ameliorated EndoMT; however, they did not change glycocalyx shedding in HUVECs. In the kidney of hyperuricemic rats, endothelial staining in peritubular capillaries (PTCs) was substantially decreased with a de novo expression of α-smooth muscle actin in PTCs. Plasma level of syndecan-1 was increased in hyperuricemic rats, which was ameliorated by allopurinol. UA caused a phenotypic transition of endothelial cells via induction of oxidative stress with glycocalyx shedding, which could be one of the mechanisms of UA-induced endothelial dysfunction and kidney disease.-Ko, J., Kang, H.-J., Kim, D.-A., Kim, M.-J., Ryu, E.-S., Lee, S., Ryu, J.-H., Roncal, C., Johnson, R. J., Kang, D.-H. Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Allopurinol suppresses expression of the regulatory T-cell migration factors TARC/CCL17 and MDC/CCL22 in HaCaT keratinocytes via restriction of nuclear factor-κB activation.

Recent studies have shown that sparse distribution of regulatory T cells (Tregs) in the skin might be involved in the onset of severe cutaneous adverse drug reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis. Treg migration toward epithelial cells is regulated by certain chemokines, including TARC/CCL17 and MDC/CCL22. In this study, we analyzed the effect of allopurinol (APN), a drug known to cause severe adverse reactions, on the expression of factors affecting Treg migration and the mechanisms involved. APN inhibited the tumor necrosis factor (TNF)-α- and interferon (IFN)-γ-associated expression of TARC/CCL17 and MDC/CCL22 mRNA in HaCaT cells in a dose-dependent manner. Consistent with this, APN also suppressed TNF-α- and IFN-γ-induced production of TARC/CCL17 and MDC/CCL22 proteins and the migration of C-C chemokine receptor type 4-positive cells. Activity of the transcription factors NF-κB and STAT1, which are involved in TARC/CCL17 and MDC/CCL22 expression, was also investigated. APN inhibited activation of NF-κB, but not that of STAT1. Furthermore, it restricted p38 MAPK phosphorylation. These results suggest that APN inhibits TNF-α- and IFN-γ-induced TARC/CCL17 and MDC/CCL22 production through downregulation of p38 MAPK and NF-κB signaling, resulting in the sparse distribution of Tregs in the skin of patients with APN-associated Stevens-Johnson syndrome/toxic epidermal necrolysis.

Allopurinol induces innate immune responses through mitogen-activated protein kinase signaling pathways in HL-60 cells.

Allopurinol, an inhibitor of xanthine oxidase, is a frequent cause of severe cutaneous adverse reactions (SCARs) in humans, including drug rash with eosinophilia and systemic symptoms, Stevens-Johnson syndrome and toxic epidermal necrolysis. Although SCARs have been suspected to be immune-mediated, the mechanisms of allopurinol-induced SCARs remain unclear. In this study, we examined whether allopurinol has the ability to induce innate immune responses in vitro using human dendritic cell (DC)-like cell lines, including HL-60, THP-1 and K562, and a human keratinocyte cell line, HaCaT. In this study, we demonstrate that treatment of HL-60 cells with allopurinol significantly increased the mRNA expression levels of interleukin-8, monocyte chemotactic protein-1 and tumor necrosis factor α in a time- and concentration-dependent manner. Furthermore, allopurinol induced the phosphorylation of mitogen-activated protein kinases (MAPK), such as c-Jun N-terminal kinase and extracellular signal-regulated kinase, which regulate cytokine production in DC. In addition, allopurinol-induced increases in cytokine expression were inhibited by co-treatment with the MAPK inhibitors. Collectively, these results suggest that allopurinol has the ability to induce innate immune responses in a DC-like cell line through activation of the MAPK signaling pathways. These results indicate that innate immune responses induced by allopurinol might be involved in the development of allopurinol-induced SCARs. Copyright © 2015 John Wiley & Sons, Ltd.

Febuxostat Increases Ventricular Arrhythmogenesis Through Calcium Handling Dysregulation in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Febuxostat is a xanthine oxidase inhibitor used to reduce the formation of uric acid and prevent gout attacks. Previous studies have suggested that febuxostat was associated with a higher risk of cardiovascular events, including atrial fibrillation, compared with allopurinol, another anti-hyperuricemia drug. Whereas in our clinical practice, we identified 2 cases of febuxostat-associated ventricular tachycardia (VT) events. The proarrhythmogenic effects of febuxostat on human cardiomyocytes and underlined mechanisms remain poorly understood. In this study, we employed real-time cell analysis and calcium transient to investigate the effects of febuxostat on the cytotoxicity and electrophysiology properties of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Up to 10 µM febuxostat treatment did not show toxicity to cell viability. However, 48-h febuxostat exposure generated dose-dependent increased irregular calcium transients and decreased calcium transient amplitude. Furthermore, RNA-seq analysis indicated that the MAPK signaling pathway was enriched in the febuxostat-treated group, especially the protein kinases c-Jun N-terminal kinase (JNK). Western blotting of 3 main protein kinases demonstrated that JNK activation is related to febuxostat-induced arrhythmia rather than extracellular signal regulated kinases (ERK) or p38. The dysfunctional calcium dynamics of febuxostat-treated hiPSC-CMs could be ameliorated by SP600125, the inhibitor of JNK. In conclusion, our study demonstrated that febuxostat increases the predisposition to ventricular arrhythmia by dysregulating calcium dynamics.

Basic measures and systemic medical treatment of patients with toxic epidermal necrolysis.

BACKGROUND: With an incidence of 1.5-1.8/1 million inhabitants per year, toxic epidermal necrolysis is a rare but life threatening disease. It is almost always drug-induced and its lethality is pronounced with up to 50 %. Several therapeutic options are described in literature; however, there is still lack of a universally accepted and specific therapy of toxic epidermal necrolysis. METHODS: This survey considers 8 cases of toxic epidermal necrolysis diagnosed and treated in our clinic from 2003 to 2007. The epidermal sloughing was > 30 % of the body surface in each case. RESULTS: After immediately discontinuing the drug suspected of being responsible for toxic epidermal necrolysis, we treated with systemic corticosteroids in an initial dose of up to 1.5 mg/kg. Moreover, special emphasis was put on basic measures such as control of vital parameters. With this treatment we reached good results; none of the patients died. conclusions: Immediate beginning of therapy is essential for a successful treatment of toxic epidermal necrolysis. Besides systemic therapy with corticosteroids, certain basic measures such as isolation of patients at adequate room temperature to prevent hypothermia, strict control of circulation, temperature and laboratory parameters, daily smears of skin and mucous membranes and a diet rich in calories due to the catabolic metabolic status are very important for successful outcome.

Allopurinol-induced toxic epidermal necrolysis featuring almost 60% skin detachment.

RATIONALE: Toxic epidermal necrolysis (TEN) is a life-threatening, immunologically mediated, and usually drug-induced disease. Rarely, clinical pharmacists participating in finding the etiology have been reported. PATIENTS CONCERNS: A 33-year-old male presented to the emergency department with a 1-day history of fever and rash. The patient, being newly diagnosed with gout 10 days ago, received allopurinol at a dose of 250 mg by mouth daily. After 10 days' exposure to allopurinol, the patient manifested with an "influenza-like" prodromal phase (fever of 38°C, throat pains), which was treated with amoxicillin and nonsteroidal anti-inflammatory drugs of the oxicam type. The next day, he developed a worsening fever of 39.5°C, accompanied by a pruriginous rash all over his body. DIAGNOSIS: On physical examination, we observed coalescing dusky red macules over >60% of his body surface area, with blisters and detachment of large sheets of necrolytic epidermis all over his chest and face. The diagnosis of TEN was confirmed. INTERVENTIONS: The patient recovered following treatment with short-term high-dose methylprednisolone sodium succinate, immunoglobulin therapy, topical medication, and supportive therapy. OUTCOMES: He showed a slow but progressive improvement both in symptoms and cutaneous manifestations. Reepithelization of the skin was achieved after 3 weeks. LESSONS: Drug-induced-TEN is potentially fatal. This case underlines the necessity of asking medication history in detail and detecting related drug gene to correctly identify the cause of TEN.

Inherent toxicity of organ preservation solutions to cultured hepatocytes.

Organ preservation solutions have been designed to protect grafts against the injury inflicted by cold ischemia. However, toxicity of University of Wisconsin (UW) solution during rewarming has been reported. Therefore, we here assessed the toxicity of UW, histidine-tryptophan-ketoglutarate (HTK), Euro-Collins, histidine-lactobionate (HL), sodium-lactobionate-sucrose and Celsior solutions in cultured hepatocytes under hypothermic (4 degrees C), intermediate (21 degrees C) and physiological (37 degrees C) conditions. Marked toxicity of UW, HTK, HL and Euro-Collins solutions was observed at both 37 and 21 degrees C. With the exception of UW solution, these solutions also increased cell injury during cold incubation (LDH release after 18 h at 4 degrees C: HTK 76+/-2%, Euro-Collins 78+/-17%, HL 81+/-15%; control: Krebs-Henseleit buffer 20+/-6%). Testing of individual components using modified Krebs-Henseleit buffers suggested that histidine and phosphate are responsible for (part of) this toxicity. These potential toxicities should be taken into account in the development of future preservation solutions.

The teratogenicity of allopurinol: A comprehensive review of animal and human studies.

Allopurinol is widely used in the management of multiple disorders including gout, kidney stones and inflammatory bowel disease. Despite of long-term experience, its safety in pregnancy has been debated due to reports on possible teratogenicity. We aimed to review the literature on the safety of allopurinol in pregnancy and offspring. In animals, allopurinol induced species-specific reproductive toxicity. In humans, a total of 53 allopurinol exposed infants were reported in the literature. Major congenital malformations were reported in two cases with a comparable pattern of multiple abnormalities. Five other infants had minor birth defects. In conclusion, the association between allopurinol and teratogenicity appears to be weak and limited to two reports with uncertain causality. However, the available data are insufficient to make a certain judgement, and as allopurinol treatment evolves, report and prospective follow-up of all exposed infants (i.e. deviant and normal cases) should be encouraged.

Xanthine oxidase inhibitors and sepsis.

Xanthine oxidase activation occurs in sepsis and results in the generation of uric acid (UrAc) and reactive oxygen species (ROS). We aimed to evaluate the effect of xanthine oxidase inhibitors (XOis) in rats stimulated with lipopolysaccharide (LPS). LPS (10 mg/kg) was administered intraperitoneally (i.p.) immediately after allopurinol (Alo, 2 mg/kg) or febuxostat (Feb, 1 mg/kg) every 24 h for 3 days. To increase UrAc levels, oxonic acid (Oxo) was administered by gavage (750 mg/kg per day) for 5 days. Animals were divided into the following 10 groups (n = 6 each): (1) Control, (2) Alo, (3) Feb, (4) LPS, (5) LPSAlo, (6) LPSFeb, (7) Oxo, (8) OxoLPS, (9) OxoLPSAlo, and (10) OxoLPSFeb. Feb with or without Oxo did not aggravate sepsis. LPS administration (with or without Oxo) significantly decreased the creatinine clearance (ClCr) in LPSAlo (60%, P < 0.01) versus LPS (44%, P < 0.05) and LPSFeb (35%, P < 0.05). Furthermore, a significant increase in mortality was observed with LPSAlo (28/34, 82%) compared to LPS treatment alone (10/16, 63%) and LPSFeb (11/17, 65%, P < 0.05). In addition, increased levels of thiobarbituric acid reactive substances (TBARS), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 were observed at 72 h compared to the groups that received LPS and LPSFeb with or without Oxo. In this study, coadministration of Alo in LPS-induced experimental sepsis aggravated septic shock, leading to mortality, renal function impairment, and high ROS and proinflammatory IL levels. In contrast, administration of Feb did not potentiate sepsis, probably because it did not interfere with other metabolic events.

A novel parasite-derived suicide gene for cancer gene therapy with specificity for lung cancer cells.

The enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) expressed by the parasite Trypanosoma brucei (Tb) can convert allopurinol, a purine analogue, to corresponding nucleotides with greater efficiency than its human homologue. We have developed a retroviral system that expresses the parasitic enzyme and tested its capacity to activate the prodrug allopurinol to a cytotoxic metabolite. Cytotoxicity assays demonstrated that five non-small cell lung carcinoma cell lines transduced with the construct were sensitized to the prodrug by 2.1- to 7.6-fold compared with control values. This selectivity was not observed in seven other cell lines also expressing the construct, such as breast carcinoma. Assays indicated that enhanced cytotoxicity to allopurinol correlated with induction of apoptosis in lung cancer cells. The selectivity of this suicide gene was not explained either by the TbHGPRT expression or by the allopurinol accumulation. Our study shows that this novel system may represent a therapeutic tool for gene prodrug targeting of lung cancer, considering the fact that allopurinol is well tolerated in humans.

Severe allopurinol toxicity. Description and guidelines for prevention in patients with renal insufficiency.

A life-threatening toxicity syndrome consisting of an erythematous, desquamative skin rash, fever, hepatitis, eosinophilia, and worsening renal function in 78 patients receiving allopurinol is described. In a majority of cases, the development of this syndrome was associated with the use of standard (200 to 400 mg per day) doses of allopurinol in patients with renal insufficiency. In pharmacologic studies, it was demonstrated that the renal clearance of the major metabolite of allopurinol, oxipurinol, is directly proportional to the renal clearance of creatinine (oxipurinol clearance = 0.22 X creatinine clearance -2.87). An inverse linear relation was noted between the serum oxipurinol half-life and the renal creatinine clearance [( serum oxipurinol half-life in hours]-1 = 0.00034 X creatinine clearance in milliliters per minute + 0.0045). Long-term use of 300 mg per day of allopurinol was found to result in elevated steady-state serum oxipurinol concentrations in patients with renal insufficiency (serum oxipurinol concentration in micromoles per liter = -2.5 X creatinine clearance in milliliters per minute + 326). Avoidance of allopurinol or use of reduced doses in patients with renal insufficiency according to proposed guidelines should be adequate to inhibit uric acid production in most patients and may reduce the incidence of life-threatening allopurinol toxicity.

Involvement of superoxide and xanthine oxidase in neutrophil-independent rat gastric damage induced by NO donors.

1. Nitric oxide (NO) and the superoxide anion can interact to form the cytotoxic moiety, peroxynitrite. The involvement and potential source of superoxide in the gastric mucosal damage induced by local infusion of NO donors, has now been investigated in the pentobarbitone-anaesthetized rat. 2. Local intra-arterial infusion of the NO donor, sodium nitroprusside (40 micrograms kg-1 min-1) for 10 min induced macroscopically apparent gastric mucosal injury. 3. This mucosal damage was dose-dependently reduced by prior administration of a systemically acting form of superoxide dismutase conjugated with polyethylene glycol (500-2000 iu kg-1, i.v.). 4. Likewise, the mucosal damage induced by nitroprusside was dose-dependently reduced by prior administration of the xanthine oxidase inhibitor, allopurinol (20-100 mg kg-1, i.p. or 100 mg kg-1, p.o.). 5. Pretreatment with allopurinol (100 mg kg-1, i.p.) also reduced the mucosal injury induced by local intra-arterial infusion of the nitrosothiol, S-nitroso-N-acetyl-penicillamine (40 micrograms kg-1 min-1), but not that induced by local infusion of endothelin-1 (5 pmol kg-1 min-1), indicating specificity of action. 6. Prior administration (4h) of rabbit anti-rat neutrophil serum (0.4 ml kg-1, i.p.), which reduced circulating neutrophils by 90%, did not significantly protect against mucosal injury induced by nitroprusside. 7. Intravenous administration of the platelet-activating factor receptor antagonists, WEB 2086 (1 mg kg-1) or BN 52021 (10 mg kg-1), or the thromboxane synthase inhibitor, OKY 15181 (25 mg kg-1), did not modify mucosal damage induced by nitroprusside, showing lack of involvement of these neutrophil-derived mediators. 8. These findings indicate the involvement of superoxide in the injurious actions of the NO donors, implicating a cytotoxic role of peroxynitrite. Xanthine oxidase, but not neutrophils, appears to be a source of the superoxide.

Promoting effects of various agents in rat urinary bladder carcinogenesis initiated by N-butyl-N-(4-hydroxybutyl)nitrosamine.

The effects of various chemicals on the development of neoplastic lesions in the urinary bladder were investigated in male F344 rats given 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) as an initiator in their drinking water for 4 weeks. The compounds tested, indomethacin, acemetacin, epsilon-aminocaproic acid (EACA), diphenyl, allopurinol and acetaminophen (AAP), were added to the diet or drinking water for 32 weeks, and all animals were killed at the end of week 36. Of the chemicals tested, only diphenyl significantly increased the incidences and average numbers (per 10 cm basement membrane) of papillary or nodular hyperplasias (PN hyperplasia), papillomas and carcinomas of the urinary bladder over those in animals treated with BBN alone. These findings show that diphenyl is a promoter of urinary bladder carcinogenesis in male F344 rats.

Loss of endothelium-dependent vasodilatation and nitric oxide release after myocardial protection with University of Wisconsin solution.

University of Wisconsin solution has proved to be a superior form of cardioplegia for cardiac transplantation, demonstrating better functional recovery than that provided by extracellular crystalloid solutions. Furthermore, experimental data have suggested a role for University of Wisconsin solution in protection of the neonatal heart during operations for congenital heart defects. However, significant concerns have been raised regarding potential endothelial injury from the high potassium concentration contained in University of Wisconsin solution that could affect its safety and thus its clinical application. Fourteen neonatal (aged 1 to 3 days) piglet hearts were harvested and supported on an isolated, blood-perfused circuit. Endothelium-dependent vasodilatation was measured by bradykinin (10(-6) mol/L) infusion and nitric oxide release was determined. Endothelium-independent vasodilatation was then induced by sodium nitroprusside (10(-6) mol/L) infusion. A 2-hour period of cold cardioplegic arrest was instituted with multidose University of Wisconsin solution (group 1, n = 7) or blood cardioplegia (group 2, n = 7). After reperfusion and stabilization, another stimulation with bradykinin and nitroprusside was carried out and nitric oxide was again measured. After 2 hours of arrest with University of Wisconsin solution, there was a near-complete loss of vasodilatation in response to bradykinin infusion; coronary blood flow reached 245% of baseline before arrest versus only 117% of baseline after arrest (p = 0.0011). This correlated with an inability of the endothelium to release nitric oxide (96 +/- 30 nmol/min before arrest versus -32 +/- 9 nmol/min after arrest, p = 0.0039. In group 2, the vasodilatory response to bradykinin was preserved after arrest and reperfusion; 265% of baseline before arrest versus 222% of baseline after arrest. These results demonstrate a loss of endothelium-dependent vasodilatation after multidose University of Wisconsin cardioplegia caused by the inability of the endothelium to release nitric oxide. In contrast, blood cardioplegia does not result in impaired endothelial function.

Attenuation of reperfusion injury with probucol in the heterotopic rat cardiac isograft.

BACKGROUND: We tested the hypothesis that pretreatment with the antioxidant probucol attenuates reperfusion-induced diastolic abnormalities in the heterotopic rat cardiac isograft. METHODS: American Cancer Institute rats (n = 48) were divided into 6 groups. Hearts were arrested by coronary perfusion with 3 ml 4 degrees C University of Wisconsin solution at 60 mmHg. Eighteen donor hearts were divided into 3 groups of 6 and arrested either 1 hour after intraperitoneal injection of 3 ml oil with (Prob Tx) or without (Oil Tx) probucol (300 mg/kg) or without injection (Ctrl Tx). After a 90 minute storage period, abdominal isografting was performed with a total ischemic time of 2 hours. Following 15 minutes of blood reperfusion, donor hearts were rearrested and excised. Recipients' native hearts (NH, n = 18) were also arrested. Two additional groups with (Prob NR, n = 6) and without (Ctrl NR, n = 6) probucol pretreatment were arrested and subjected to 2 hours of ischemia without reperfusion. Postmortem LV pressure-volume curves and myocardial water content (MWC) were measured. RESULTS: At each pressure interval normalized LV volume (LVV) was significantly greater for Prob Tx than Oil Tx or Ctrl Tx. All isograft groups had significantly lower LVV at all pressure intervals and higher MWC than non-transplanted hearts. CONCLUSIONS: Pretreatment with probucol attenuates reperfusion-induced decreases in LVV in the heterotopic rat heart isograft model. Probucol, which is orally active in humans, merits further study for its potential to improve myocardial protection during cardiac surgery.

Allopurinol, indomethacin and riboflavin enhance radiation lethality in mice.

Two widely used drugs, allopurinol and indomethacin, and the vitamin riboflavin increased the response of mice to ionizing radiation. In mice a dose of 10.5 Gy of gamma rays from a 60Co source resulted in a dose-dependent shortening of survival times after pretreatment with the three agents, applied at doses which were well tolerated alone. When the dose dependency of these drugs on the influence on survival was tested, two response patterns emerged. Indomethacin (25 mg/kg) shifted the survival curve to the left and reduced the LD50 from approximately 6.5 Gy to approximately 4.5 Gy. Allopurinol (100 mg/kg) diminished the survival rate to approximately 50% irrespective of the radiation dose (ranging from 0.75 to 6.0 Gy). A similar though less striking trend was seen with riboflavin (120 mg/kg), which reduced the survival rate to approximately 65% in the dose range from 3 to 6 Gy. Mortality in mice treated with allopurinol or riboflavin and irradiated with nonlethal exposures (from radiation alone) occurred within the first few days after irradiation, suggesting a different type of injury than is usually associated with radiation death. Although doses of the three drugs used clinically are clearly lower than those providing enhanced radioresponse in our experiments, subtle and nonovert injury caused by combined exposure to the drugs and radiation cannot be completely excluded.

Action of allopurinol and aspirin on rat whole-embryo cultures.

The effects of allopurinol (HPP) at concentrations ranging from 0.33-1.83 mM and of aspirin (ASA) from 0.28-2.22 mM, were studied on the rat whole-embryo culture system. Embryos were explanted at day 10 of gestation and cultured for 48 h, either in the absence or in the presence of rat and human S9. HPP proved to be potentially embryolethal and teratogenic without any S9, while it was embryolethal with rat S9 and dysmorphogenic with human S9. ASA showed an embryolethal and teratogenic potency without any S9 samples. These responses were increased in the presence of rat S9, while ASA embryolethality was predominant with human S9. These results obtained on rat embryos in culture suggest a correlation between the species origin of the biotransforming system and the known teratogenicity of HPP in sensitive animal models. However, ASA elicited responses not in agreement with the known teratogenic response in rodents.

Allopurinol induces renal toxicity by impairing pyrimidine metabolism in mice.

We investigated the relationship between the toxic effect of allopurinol and pyrimidine metabolism in mice. Allopurinol-induced increases in plasma transaminase levels in dinitrofluorobenzene (DNFB)-sensitized mice were not affected by uridine. In contrast, plasma creatinine and BUN tended to decrease 18 hr after the last injection of uridine. Both plasma and urinary orotidine (OD) were detected in DNFB-sensitized mice after administration of a single dose of allopurinol. In contrast, TEI-6720, a newly synthesized xanthine oxidase/xanthine dehydrogenase inhibitor, caused neither pyrimidine metabolism abnormality nor renal impairment in DNFB-sensitized mice. Also, normal mice administered high doses of allopurinol showed abnormal pyrimidine metabolism together with renal toxicity which could be ameliorated by uridine, indicating that allopurinol essentially causes pyrimidine metabolism abnormality leading to renal impairment. In DNFB-sensitized mice, allopurinol increased urinary OD excretion to an extent similar to that in normal mice administered the same dose of allopurinol. However, renal impairment by allopurinol was more striking in DNFB-sensitized mice than in normal mice. Histopathological observations showed that allopurinol induced calculus formation in the collecting tubules and papillary duct. Calculus formation was increased by DNFB and decreased by uridine. These observations indicate that the enhancement of the renal toxicity of allopurinol by DNFB-sensitization may be due to some biological interactions between DNFB and allopurinol. In humans, it is possible that there are some biological interactions which serve to enhance the toxicity of allopurinol, resulting in the development of allopurinol hypersensitivity syndrome (AHS). In contrast, TEI-6720, had no effect on pyrimidine metabolism and showed no toxic effect.

Evaluation of a thiazide-allopurinol drug interaction.

Allopurinol toxicity has been associated with the use of this drug in patients with renal insufficiency, a situation where the half-life of oxipurinol, the major metabolite of allopurinol, is prolonged. Allopurinol toxicity has also been associated with the concomitant use of allopurinol and thiazide diuretics. In the present study, the effect of hydrochlorothiazide administration on the renal clearance and serum half-life of oxipurinol has been studied in eight normal volunteers to determine if thiazides delay the clearance of oxipurinol. Oxipurinol's renal clearance and serum half-life were measured in each volunteer during a control period and again while the volunteer was receiving 50 mg/day hydrochlorothiazide for 1 week. No change in renal oxipurinol clearance (21.1 +/- 5.9 vs. 20.4 +/- 8.7 ml/min) or serum oxipurinol half-life (23.7 +/- 4.2 vs. 23.4 +/- 4.4 hours) was noted with the addition of thiazides. The association previously noted between the use of thiazide diuretics and the development of allopurinol toxicity cannot be explained by alterations in oxipurinol pharmacokinetics.