The inhibitory effects of allopurinol on the production and cytotoxicity of tumor necrosis factor

Role of allopurinol and febuxostat in the amelioration of dextran-induced colitis in rats

Ulcerative colitis is a chronic auto-inflammatory disorder confined to the colorectal region. It is challenging to find an absolute treatment and current therapy aims to ameliorate symptoms, decrease relapses and prevent prognosis of colorectal cancer. In the present study, we investigated the possible action of xanthine oxidase inhibitors in murine colitis model by measuring different indicative parameters and comparing the results to those of the reference sulfasalazine. Also, we compared the effects of combining sulfasalazine and allopurinol to each drug alone. Dextran Sodium Sulfate (DSS) is used in this study to induce ulcerative colitis in male wistar rats as it is known to be the closest model that mimics human ulcerative colitis. Allopurinol was given prior to colitis induction by four days and febuxostat for six days before induction with DSS (5% w/v) and continue to give them concomitantly during the induction.Il-1β, malondialdehyde, reduced glutathione (GSH), xanthine oxidase, and superoxide dismutase were measured in colonic tissue. We also measured concentrations of IL-1β, Il-6 and uric acid in serum. Allopurinol dose-dependently ameliorated biochemical injuries. Febuxostat has shown better results than allopurinol and sulfasalazine, and this is the first study to demonstrate this.

Revisiting the Role of Thiopurines in Inflammatory Bowel Disease Through Pharmacogenomics and Use of Novel Methods for Therapeutic Drug Monitoring

Azathioprine and 6-mercaptopurine, often referred to as thiopurine compounds, are commonly used in the management of inflammatory bowel disease. However, patients receiving these drugs are prone to developing adverse drug reactions or therapeutic resistance. Achieving predefined levels of two major thiopurine metabolites, 6-thioguanine nucleotides and 6-methylmercaptopurine, is a long-standing clinical practice in ensuring therapeutic efficacy; however, their correlation with treatment response is sometimes unclear. Various genetic markers have also been used to aid the identification of patients who are thiopurine-sensitive or refractory. The recent discovery of novel Asian-specific DNA variants, namely those in the NUDT15 gene, and their link to thiopurine toxicity, have led clinicians and scientists to revisit the utility of Caucasian biomarkers for Asian individuals with inflammatory bowel disease. In this review, we explore the limitations associated with the current methods used for therapeutic monitoring of thiopurine metabolites and how the recent discovery of ethnicity-specific genetic markers can complement thiopurine metabolites measurement in formulating a strategy for more accurate prediction of thiopurine response. We also discuss the challenges in thiopurine therapy, alongside the current strategies used in patients with reduced thiopurine response. The review is concluded with suggestions for future work aiming at using a more comprehensive approach to optimize the efficacy of thiopurine compounds in inflammatory bowel disease.

Allopurinol ameliorates thioacetamide-induced acute liver failure by regulating cellular redox-sensitive transcription factors in rats

Oxidative stress plays important role in the development of acute liver failure. In this study, we investigated effects of allopurinol (AP) upon thioacetamide (TAA)-induced liver injury and the potential mechanisms leading to amelioration in inflammation with AP treatment. Acute liver failure was induced by intraperitoneal administration of TAA (300 mg/kg/day for 2 days). Thirty-five rats were divided into five groups as control (group 1), TAA (group 2), TAA + 25AP (group 3), TAA + 50 AP (group 4), and TAA + 100AP (group 5). The number of animals in each group was seven. At the end of the study, histopathological, biochemical, and western blot analysis were done. TAA treatment significantly increased serum levels of aminotransferases, liver malondialdehyde (MDA), nuclear factor-kappa B (NF-қB ), activator protein-1 (AP-1), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6) levels, and the necro-inflammation scores. Nevertheless, nuclear factor E2-related factor-2 and heme oxygenase-1 (HO-1) expressions in the liver were decreased by TAA. AP treatment significantly lowered the serum levels of aminotransferases (P < 0.01) and liver MDA, NF-κB, AP-1, TNF-α, COX-2, and IL-6 expressions (P < 0.05). Moreover, AP restored the liver Nrf2 and HO-1 expressions and improved the necro-inflammation scores significantly. AP improves oxidative stress-induced liver damage by regulating cellular redox-sensitive transcriptor factors and expression of pro-inflammatory and antioxidant defense mechanisms. AP probably exerts these beneficiary features by its free radical scavenging ability in a dose-dependent manner.

Sequential combined treatment with allopurinol and benznidazole in the chronic phase of Trypanosoma cruzi infection: a pilot study

OBJECTIVES

Even though the use of combined drugs has been proved to be effective in other chronic infections, assessment of combined treatment of antiparasitic drugs in human Chagas' disease has not been performed. Herein, a pilot study was conducted to evaluate the tolerance and side effects of a sequential combined treatment of two antiparasitic drugs, allopurinol and benznidazole, in the chronic phase of Trypanosoma cruzi infection.

PATIENTS AND METHODS

Changes in total and T. cruzi-specific T and B cells were monitored during a median follow-up of 36 months. Allopurinol was administered for 3 months (600 mg/day) followed by 30 days of benznidazole (5 mg/kg/day) in 11 T. cruzi-infected subjects.

RESULTS

The combined sequential treatment of allopurinol and benznidazole was well tolerated. The levels of T. cruzi-specific antibodies significantly decreased after sequential combined treatment, as determined by conventional serology and by a multiplex assay using recombinant proteins. The frequency of T. cruzi-specific interferon-γ-producing T cells significantly increased after allopurinol treatment and decreased to background levels following benznidazole administration in a substantial proportion of subjects evaluated. The levels of total naive (CD45RA + CCR7 + CD62L+) CD4 + and CD8 + T cells were restored after allopurinol administration and maintained after completion of the combined drug protocol, along with a decrease in T cell activation in total peripheral CD4 + and CD8 + T cells.

CONCLUSIONS

This pilot study shows that the combination of allopurinol and benznidazole induces significant modifications in T and B cell responses indicative of a reduction in parasite burden, and sustains the feasibility of administration of two antiparasitic drugs in the chronic phase of Chagas' disease.

Allopurinol reduces antigen-specific and polyclonal activation of human T cells

Allopurinol is the most popular commercially available xanthine oxidase inhibitor and it is widely used for treatment of symptomatic hyperuricaemia, or gout. Although, several anti-inflammatory actions of allopurinol have been demonstrated in vivo and in vitro, there have been few studies on the action of allopurinol on T cells. In the current study, we have assessed the effect of allopurinol on antigen-specific and mitogen-driven activation and cytokine production in human T cells. Allopurinol markedly decreased the frequency of IFN-γ and IL-2-producing T cells, either after polyclonal or antigen-specific stimulation with Herpes Simplex virus 1, Influenza (Flu) virus, tetanus toxoid and Trypanosoma cruzi-derived antigens. Allopurinol attenuated CD69 upregulation after CD3 and CD28 engagement and significantly reduced the levels of spontaneous and mitogen-induced intracellular reactive oxygen species in T cells. The diminished T cell activation and cytokine production in the presence of allopurinol support a direct action of allopurinol on human T cells, offering a potential pharmacological tool for the management of cell-mediated inflammatory diseases.

Optimizing 6-mercaptopurine and azathioprine therapy in the management of inflammatory bowel disease

The thiopurine drugs, 6-mercaptopurine (6-MP) and azathioprine, are efficacious in the arsenal of inflammatory bowel disease (IBD) therapy. Previous reports indicate that 6-thioguanine nucleotide (6-TGN) levels correlate with therapeutic efficacy, whereas high 6-methylmercaptopurine (6-MMP) levels are associated with hepatotoxicity and myelotoxicity. Due to their complex metabolism, there is wide individual variation in patient response therein, both in achieving therapeutic drug levels as well as in developing adverse reactions. Several strategies to optimize 6-TGN while minimizing 6-MMP levels have been adopted to administer the thiopurine class of drugs to patients who otherwise would not tolerate these drugs due to side-effects. In this report, we will review different approaches to administer the thiopurine medications, including the administration of 6-mercaptopurine in those unsuccessfully treated with azathioprine; co-administration of thiopurine with allopurinol; co-administration of thiopurine with anti-tumor necrosis factor α; 6-TGN administration; desensitization trials; and split dosing of 6-MP.

Use of allopurinol with low-dose 6-mercaptopurine in inflammatory bowel disease to achieve optimal active metabolite levels: a review of four cases and the literature

BACKGROUND

At least one-third of patients with inflammatory bowel disease do not respond or are intolerant to therapy with 6-mercaptopurine (6-MP). A subgroup fails to attain optimal levels of 6-thioguanine nucleotide (6-TGN) and instead shunts to 6-methylmercaptopurine nucleotide (6-MMPN).

PATIENTS AND METHODS

A retrospective chart review was conducted, and four patients are described who had been previously unable to achieve optimal 6-TGN metabolite levels until allopurinol was added to their treatment.

RESULTS

All four patients achieved optimal 6-TGN levels and undetectable 6-MMPN with a mean 6-MP dose of 0.49 mg/kg. Three achieved steroid-free clinical remission. Two of those three patients had normalization of liver enzymes; one patient had baseline normal liver enzymes despite an initial 6-MMPN level of 27,369 pmol/8 x 10(8) red blood cells. Two patients experienced reversible leukopenia.

CONCLUSIONS

Combination allopurinol and low-dose 6-MP is an effective means to achieve optimal metabolite levels and steroid-free clinical remission in previously refractory patients. Caution is advised.

Effect of allopurinol on clinical outcomes in inflammatory bowel disease nonresponders to azathioprine or 6-mercaptopurine

BACKGROUND & AIMS

Many IBD patients not responding to azathioprine (AZA) or 6-mercaptopurine (6-MP) preferentially metabolize 6-MP to 6-methylmercaptopurine (6-MMP). We describe the use of allopurinol in AZA/6-MP nonresponders to deliberately shunt metabolism of 6-MP toward 6-thioguanine (6-TGN) and improve clinical responses.

METHODS

Twenty outpatients who were AZA/6-MP nonresponders and had high 6-MMP metabolite levels were included. Subjects were commenced on allopurinol 100 mg daily, and the dose of 6-MP/AZA was reduced to 25%-50% of the original dose.

RESULTS

After allopurinol was started, mean 6-TGN levels increased from 191.3 (+/- standard error of the mean) +/- 17.1 to 400.3 +/- 36.9 pmol/8 x 10(8) red blood cells (P < .001), whereas mean 6-MMP levels decreased from 10,604.7 +/- 1278.2 to 2000.6 +/- 437.1 pmol/8 x 10(8) red blood cells (P < .001). The addition of allopurinol led to a reduction in the mean partial Harvey Bradshaw Index in Crohn's disease patients from 4.9 +/- 1.0 to 1.5 +/- 0.3 points (P = .001), and in ulcerative colitis patients mean Mayo Scores decreased from 4.1 +/- 0.7 to 2.9 +/- 0.7 points (P = .13). The addition of allopurinol enabled a reduction in mean daily prednisone dosage from 17.6 +/- 3.9 to 1.8 +/- 0.7 mg (P < .001) and led to normalization of transaminase levels, with mean AST levels reducing from 42.5 +/- 8.1 to 23.5 +/- 1.6 IU (P = .12) and mean ALT levels reducing from 101.6 +/- 26.9 to 33.9 +/- 5.2 IU (P = .01).

CONCLUSIONS

The addition of allopurinol to thiopurine nonresponders with high 6-MMP metabolite levels is an effective and safe means of optimizing 6-TGN production, leading to improved disease activity scores, reduced corticosteroid requirements, and normalization of liver enzymes.

Allopurinol safely and effectively optimizes tioguanine metabolites in inflammatory bowel disease patients not responding to azathioprine and mercaptopurine

BACKGROUND

Many non-responders to azathioprine or mercaptopurine (6-mercaptopurine) have high normal thiopurine methyltransferase activity and preferentially metabolize mercaptopurine to produce 6-methylmercaptopurine instead of the active 6-tioguanine (6-tioguanine) metabolites.

AIM

To describe the use of allopurinol in mercaptopurine/azathioprine non-responders to deliberately shunt metabolism of mercaptopurine towards 6-tioguanine.

METHODS

Fifteen thiopurine non-responders whose metabolites demonstrated preferential metabolism towards 6-methylmercaptopurine are described. Subjects were commenced on allopurinol 100 mg po daily and mercaptopurine/azathioprine was reduced to 25-50% of the original dose. Patients were followed clinically and with serial 6-tioguanine and 6-methylmercaptopurine metabolite measurements.

RESULTS

After initiating allopurinol, 6-tioguanine levels increased from a mean of 185.73 +/- 17.7 to 385.4 +/- 41.5 pmol/8 x 10(8) red blood cells (P < 0.001), while 6-methylmercaptopurine decreased from a mean of 10 380 +/- 1245 to 1732 +/- 502 pmol/8 x 10(8) RBCs (P < 0.001). Allopurinol led to a decrease in white blood cell from a mean of 8.28 +/- 0.95 to 6.1 +/- 0.82 x 10(8)/L (P = 0.01).

CONCLUSIONS

The addition of allopurinol to thiopurine non-responders with preferential shunting to 6-methylmercaptopurine metabolites appears to be an effective means to shift metabolism towards 6-tioguanine.

Cannabinoids, loratadine and allopurinol as novel additions to the antipsoriatic ammunition

As the current antipsoriatic medications are commonly associated with deleterious side-effects, a determined search for safer agents, which could be used alone or in combination with current antipsoriatic drugs, would be very imperative. Psoriasis is believed to be characterized by a type 1 cytokine pattern; interferon-gamma, interleukin (IL)-2 and tumour necrosis factor (TNF)-alpha are predominantly expressed in this disorder. Nitric oxide, reactive oxygen species, histamine, leukotriene B4, and decreased [corrected] keratinocyte cyclic adenosine monophosphate/cyclic guanosine monophosphate (cAMP/cGMP) ratio are supposed to play roles in the pathogenesis of this disorder. Based on the immunopathogenesis of psoriasis, this paper introduces three novel, potential treatments for this clinical conundrum: (i) cannabinoids, which exert inhibitory effects on antigen processing and macrophage/T-cell interaction and also on the release of IL-2, TNF-alpha and nitric oxide from immune cells; (ii) loratadine, which is an antihistamine capable of increasing [corrected] the cAMP/cGMP ratio and the production of leukotriene B4; and (iii) allopurinol, which scavenges free radicals, inhibits the production of TNF-alpha, and downregulates the expression of intercellular adhesion molecule-1 and P2X7 receptors on monocytes/macrophages, which are involved in antigen presentation and production of the inflammatory response, respectively. Importantly, allopurinol, especially in combination with cyclosporin, has been shown to be effective against experimental autoimmune uveitis, which, like psoriasis, is a cell-mediated autoimmune disorder.

Cetirizine and allopurinol as novel weapons against cellular autoimmune disorders

Type 1, or cellular, immune response is characterized by overproduction of TNF-alpha, IFN-gamma, IL-1, IL-2 and IL-8 and is the underlying immune mechanism of psoriasis, alopecia areata, rheumatoid arthritis, Crohn's disease, multiple sclerosis, insulin-dependent diabetes mellitus and experimental autoimmune uveitis (EAU). Type 2 immune response is seen in antibody-mediated autoimmune diseases. Based on the pharmacokinetic effects of cetirizine and allopurinol, this paper introduces these two safe and inexpensive drugs as novel potential agents against cell-mediated autoimmune disorders. Cetirizine, supposed to inhibit DNA binding activity of NF-kappa B, inhibits the expression of adhesion molecules on immunocytes and endothelial cells and the production of IL-8 and LTB4, two potent chemoattractants, by immune cells. It induces the release of PGE2, a suppressor of antigen presentation and MHC class II expression, from monocyte/macrophages and reduces the number of tryptase positive mast cells in inflammation sites. Tryptase is a chemoattractant, generates kinins from kininogen, activates mast cells, triggers maturation of dendritic cells and stimulates the release of IL-8 from endothelial cells and the production of Th1 lymphokines by mononuclear immunocytes. Allopurinol is a free radical scavenger, suppresses the production of TNF-alpha and downregulates the expression of ICAM-1 and P2X(7) receptors on monocyte/macrophages. ICAM-1 serves as a ligand for LFA-1 (on T lymphocytes), allowing proper antigen presentation. P2X(7) receptors are thought to be involved in IL-1beta release, mitogenic stimulation of T lymphocytes and the probable cytoplasmic communication between macrophages and lymphocytes at inflammation sites. Allopurinol was markedly more effective than prednisolone in treating experimental autoimmune uveitis and in combination with cyclosporine suppressed the inflammatory reaction of this condition more effectively than either agent alone. As allopurinol is a competitive inhibitor of xanthine oxidase and decreases serum levels of uric acid, which is protective against multiple sclerosis, it should preferably be coadministered with uric acid precursors in the treatment of this condition. Cetirizine and allopurinol may prove of benefit in the treatment of various cellular autoimmune disorders.

The effects of allopurinol on immune function in normal BALB/c and SCID mice

To clarify the relationship between purine metabolism and immunity, the in vivo immunosuppressive effects of allopurinol (AL), a xanthinoxidase (XO) inhibitor, were studied using normal BALB/c and severe combined immunodeficient (SCID) mice. Following AL administration for 14 weeks (long term), a decreased immune response to ovalbumin (OVA) in the peripheral blood was observed in normal mice, which might not be only due to direct B cell suppression but also due to suppression of helper T cell function. In the SCID mice, there was a markedly late and reduced recovery of surface immunoglobulin (sIg) positive cells, which are markers for mature B lymphocytes, in the peripheral blood after AL administration. The total immunoglobulin G (IgG) titers in the AL treated group were significantly lower than in the control group 6 weeks after stem cell transfer, but increased until there was no difference in the titers between the two groups at week 14. CD4 positive helper T cells and CD8 positive T cells were slow to recover, though these gradually recovered to reach normal levels in the mature stage. These data suggest that the administration of AL may modulate B cell and T cell responses in OVA-immunized antibody formation. Furthermore, this study showed that AL could influence immune functions during the pre-natal and developmental periods and that its effects might differ according to the stages of maturity of the immune cells.