Dapsone-induced hemolytic anemia

Ocular-Surface Regeneration Therapies for Eye Disorders: The State of the Art

The ocular surface is a complex structure that includes cornea, conjunctiva, limbus, and tear film, and is critical for maintaining visual function. When the ocular-surface integrity is altered by a disease, conventional therapies usually rely on topical drops or tissue replacement with more invasive procedures, such as corneal transplants. However, in the last years, regeneration therapies have emerged as a promising approach to repair the damaged ocular surface by stimulating cell proliferation and restoring the eye homeostasis and function. This article reviews the different strategies employed in ocular-surface regeneration, including cell-based therapies, growth-factor-based therapies, and tissue-engineering approaches. Dry eye and neurotrophic keratopathy diseases can be treated with nerve-growth factors to stimulate the limbal stem-cell proliferation and the corneal nerve regeneration, whereas conjunctival autograft or amniotic membrane are used in subjects with corneal limbus dysfunction, such as limbal stem-cell deficiency or pterygium. Further, new therapies are available for patients with corneal endothelium diseases to promote the expansion and migration of cells without the need of corneal keratoplasty. Finally, gene therapy is a promising new frontier of regeneration medicine that can modify the gene expression and, potentially, restore the corneal transparency by reducing fibrosis and neovascularization, as well as by stimulating stem-cell proliferation and tissue regeneration.

The medication for pneumocystis pneumonia with glucose-6-phosphate dehydrogenase deficiency patients

Pneumocystis pneumonia (PCP) is an opportunity acquired infection, which is usually easy to occur in patients with AIDS, organ transplantation, and immunosuppressive drugs. The prevention and treatment must be necessary for PCP patients with immunocompromise. And the oxidants are currently a typical regimen, including sulfanilamide, dapsone, primaquine, etc. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked gene-disease that affects about 400 million people worldwide. The lack of G6PD in this population results in a decrease in intracellular glutathione synthesis and a weakening of the detoxification ability of the oxidants. As a result, oxidants can directly damage haemoglobin in red blood cells, inducing methemoglobin and hemolysis. When patients with G6PD deficiency have low immunity, they are prone to PCP infection, so choosing drugs that do not induce hemolysis is essential. There are no clear guidelines to recommend the drug choice of this kind of population at home and abroad. This paper aims to demonstrate the drug choice for PCP patients with G6PD deficiency through theoretical research combined with clinical cases.

Anemia in Pediatric Kidney Transplant Recipients-Etiologies and Management

Posttransplant anemia (PTA) is a common complication of pediatric kidney transplantation, with a prevalence ranging from 22 to 85%. PTA is categorized as early (within 6 months posttransplant) and late (>6 months posttransplant). Early PTA is typically associated with surgical blood losses and iron deficiency. Late PTA primarily results from graft dysfunction; however, iron deficiency, drug toxicity, and posttransplant inflammation also play a role. PTA is more severe compared with the anemia in glomerular-filtration-rate matched patients with native chronic kidney disease. Treatment of PTA is directed toward the underlying cause. Erythropoiesis stimulating agents (ESA) are effective; however, their use is limited in the transplant setting. Timely diagnosis and treatment of PTA are vital to prevent long-term adverse outcomes in pediatric transplant recipients.

Autoimmune bullous diseases in pregnancy: clinical and epidemiological characteristics and therapeutic approach

Autoimmune bullous dermatoses are a heterogeneous group of diseases with autoantibodies against structural skin proteins. Although the occurrence of autoimmune bullous dermatoses during pregnancy is low, this topic deserves attention, since the immunological and hormonal alterations that occur during this period can produce alterations during the expected course of these dermatoses. The authors review the several aspects of autoimmune bullous dermatoses that affect pregnant women, including the therapeutic approach during pregnancy and breastfeeding. Gestational pemphigoid, a pregnancy-specific bullous disease, was not studied in this review.

A Study on the Relevance of Glucose-6-Phosphate Dehydrogenase Level Screening in Patients with Rheumatic Diseases Prior to Initiating Treatment With Hydroxychloroquine

Objective

Drug-induced hemolytic anemia can occur in patients with glucose-6-phosphate-dehydrogenase (G6PD) deficiency. The practice of G6PD-deficiency screening in the rheumatology field has been inconsistent. This study aimed to determine the utility of screening prior to the initiation of hydroxychloroquine and/or sulfasalazine in rheumatology patients in the ambulatory clinics at Stony Brook University Hospital, New York.

Methods

We conducted a retrospective chart review of cases of rheumatic diseases that were screened for G6PD deficiency at Stony Brook University Hospital ambulatory clinics. Demographic details and relevant clinical and laboratory data of the patients were collected. The data from similar studies in the literature were searched for and reviewed.

Results

This study consisted of 228 patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjögren’s syndrome. Among those patients, 94.7% received hydroxychloroquine, sulfasalazine, or dapsone; 41% (89/228) of patients were screened for G6PD deficiency, and the majority of them were on treatment with hydroxychloroquine. Of those patients, 7.9% (five Caucasians and two African Americans) were found to have G6PD deficiency, and two of the G6PD-deficient patients received hydroxychloroquine. There was no incidence of hemolytic anemia documented in any of the seven patients with G6PD deficiency. We reviewed the literature and found three similar studies of patients receiving hydroxychloroquine with no reported hemolytic anemia from different medical centers in the US, and the frequency of G6PD deficiency reported in these studies was 1.4%, 4.0%, and 4.2%, respectively.

Conclusions

Our study suggests that the frequency of G6PD deficiency in our rheumatic population is similar to that of the general population, and the risk of hemolytic anemia in G6PD deficiency associated with hydroxychloroquine is extremely rare. Hence, G6PD screening may not be recommended prior to starting treatment with hydroxychloroquine.

Managing Pemphigoid Gestationis

Pemphigoid gestationis (PG) is important to diagnose and treat because it carries considerable morbidity for the pregnant woman and can also constitute a risk to the fetus. Herein, the treatment options for PG and a proposed treatment algorithm for PG during pregnancy, breastfeeding, and late postpartum are reviewed.

Causes of Death among Persons Affected by Leprosy in Korea, 2010-2013

In addition to the complications of leprosy, people affected by leprosy (PALs) can suffer from chronic diseases. We evaluated the recent pattern of deaths among Korean PALs and compared it with that in the general population. We analyzed the death certificate data of 1,359 PALs from 2010 through 2013. The all-cause and cause-specific standardized mortality ratio (SMR) and standardized mortality with 95% CI were calculated. Malignancy had the highest standardized mortality, with 130.9 deaths per 100,000 persons, followed by cardiovascular diseases (CVDs; 85.5 deaths) and respiratory diseases (38.2 deaths). Of malignancies, liver cancer caused the greatest number of cancer deaths (40.0 deaths). The all-cause mortality of PALs was significantly lower than that in the general population, corresponding to an SMR of 0.84 (95% CI 0.79-0.88). Deaths from malignancy and CVDs were significantly lower, corresponding to SMRs (95% CIs) of 0.88 (0.79-0.98) and 0.75 (0.67-0.84), respectively. The death rates for lung and stomach cancers were lower, whereas mortality due to liver cancer was higher, with an SMR of 1.79 (95% CI 1.43-2.22). Except for liver cancer and infection, the causes of mortality of PALs tend to be lower than that in the general population. The most common underlying cause of death in PALs was stroke, followed by ischemic heart disease, liver cancer, and pneumonia.

Recovery of Dementia Syndrome following Treatment of Brain Inflammation

Aim/Background

This research aims to prevent progression from mild cognitive impairment (MCI) to Alzheimer's disease. A Japanese study of leprosy patients revealed that the incidence of dementia in leprosy patients was lower than that in patients taking dapsone who had never been treated. But a similar study the following year refuted the finding of less dementia in leprosy patients taking dapsone. According to conflicting reports, Mycobacterium leprae was a factor in reducing the incidence of Alzheimer's disease. Thus, we formed a hypothesis that if dapsone is administered to patients without leprosy but with MCI and the prophylactic effect of dementia syndrome is observed over a long period of time, we can determine whether dapsone can prevent the progression of MCI to dementia syndrome. If dementia does not occur after treating inflammation in brain cells while dementia develops after a certain long-term period (usually within 2–3 years), brain cell inflammation can be demonstrated as the cause of dementia.

Methods

This is a prospective cohort research. We report on an elderly patient diagnosed with MCI from February 2008 to January 2019. The patient took dapsone 100 mg once a day from 2010 to 2015 for the treatment of MCI. Since 2016, the production of dapsone has ceased in Korea. In June 2018, the patient was diagnosed with Alzheimer's disease. The patient took Aricept for the treatment of Alzheimer's disease but complained of serious side effects. And dapsone was re-administered to the patient from November 2018.

Results

The patient recovered to MCI and improved her daily life owing to the treatment with dapsone. The drug controls the inflammatory response in the brain, irrespective of whether proteins are deposited in neurons.

Conclusions

This finding means that dementia syndrome is an inflammatory disease. This research suggests that diagnostic criteria for Alzheimer's disease should be based on the presence or absence of inflammation in neurons. Because inflammation in neurons can occur in middle age due to various causes, we can treat inflammation in neurons and prevent and treat dementia syndrome, including Alzheimer's disease.

Hematological alterations in lepromatous leprosy: A cross-sectional observational study

BACKGROUND

Dapsone has been the mainstay for the treatment of leprosy since its discovery in the 1940s. However, hematological disturbances are not uncommon in leprosy patients on daily dapsone therapy. Hence, the present study was conducted to document the hematologic alterations observed in lepromatous leprosy patients treated with Dapsone 100 mg daily.

METHODOLOGY

A cross-sectional observational study was conducted amongst 32 lepromatous leprosy patients treated with Dapsone 100 mg daily. A complete hemogram was conducted for all the study recruits. The test results were compared against the standard average values for adults for the given variables. The one sample t-test was employed to compare the difference between the study values and the standard normal values for adults. The statistical significance was considered at p < 0.05.

RESULTS

The study reveals a marked decrease in hemoglobin concentration in patients on dapsone, 100 mg daily. Other hematological alterations found were reduced platelet count, reduced mean platelet volume, reduced Hematocrit, reduced Mean Corpuscular hemoglobin, reduced Mean Corpuscular hemoglobin concentration. (p < 0.05).

CONCLUSION

Treatment of lepromatous leprosy with 100 mg daily Dapsone therapy may lead to hematological alterations. These findings are suggestive of dapsone-induced hemolysis.

Treatment of Autoimmune Bullous Disorders in Pregnancy

Autoimmune bullous diseases (AIBD), including pemphigus, bullous pemphigoid, epidermolysis bullosa acquisita, mucous membrane pemphigoid, and pemphigoid gestationis, pose significant therapeutic challenges, especially in pregnant and post-partum breastfeeding patients or those planning to conceive. Data on the safety and efficacy of therapeutic interventions during the perinatal period are lacking because randomized controlled trials are typically not performed in this setting. However, many of the treatments for AIBD are also used in other diseases, so data can be extrapolated from studies or case reports in these other patient populations. It appears that many of the treatments for AIBD can adversely affect the fetus or neonate, and alterations in immune status caused by pregnancy-associated hormonal changes can negatively impact disease control. This article summarizes and weighs the risks and benefits of the various agents used to treat AIBD during pregnancy. We also present the available information on lactation as well as effects on male fertility.

Acute visual loss following dapsone-induced methemoglobinemia and hemolysis

OBJECTIVE

While methemoglobinemia is a possible complication of chronic dapsone therapy or of acute overdose, serious adverse manifestations related to methemoglobin formation remain rare. We present an unusual case with severe ischemic retinal injury.

CASE REPORT

A 30-year-old African woman presented with a sudden decrease of visual acuity secondary to retinal ischemia. She was chronically treated with dapsone (50 mg/day) for a dermatologic disease and denied any drug overdose. However, the determination of serum dapsone level on admission revealed a largely supratherapeutic concentration (20,044 μg/ml compared with 1-3.5 ± 0.5 μg/ml for therapeutic levels). The methemoglobin level at admission was 32% (sulfhemoglobin 1.2%), with hemoglobin level, 7.4 g/dl, schistocytes count, 2-5%, lactate dehydrogenase level, 580 IU/l, and haptoglobin level, < 10 mg/dl. The patient had both alpha-thalassemia and sickle cell trait. She was treated with methylene blue, vitamin C, and exchange transfusion. There was no improvement in visual symptoms over time.

CONCLUSIONS

In a patient with supratherapeutic serum levels of dapsone, the severity of visual injury was associated with dapsone-induced methemoglobinemia and hemolysis, and perhaps also with some hematologic predisposing factors.

Hemolytic anemia in two patients with glioblastoma multiforme: A possible interaction between vorinostat and dapsone

Patients undergoing treatment for glioblastoma multiforme are routinely placed on prophylactic treatment for Pneumocystis jirovecii pneumonia because of significant therapy-induced lymphopenia. In patients with sulfa allergies, dapsone prophylaxis is often used due to its efficacy, long half-life, cost effectiveness, and general safety at low doses. However, dapsone may uncommonly induce a hemolytic anemia, particularly in patients deficient of glucose-6-phosphate dehydrogenase. This hemolysis is thought to be a result of oxidative stress on red blood cells induced by dapsone metabolites which produce reactive oxygen species that disrupt the red blood cell membrane and promote splenic sequestration. A single case report of dapsone-induced hemolytic anemia in a patient with glioblastoma multiforme has been reported. We present two patients with glioblastoma multiforme who developed severe hemolytic anemia shortly after initiating therapy with vorinostat, a pan-active histone deacetylase inhibitor, while on prophylactic dapsone. There are several potential mechanisms by which histone deacetylase inhibition may alter dapsone metabolism including changes in hepatic acetylation or N-glucuronidation leading to an increase in the bioavailability of dapsone’s hematotoxic metabolites. In addition, vorinostat may lead to increased hemolysis through inhibition of heat shock protein-90, a chaperone protein that maintains the integrity of the red blood cell membrane cytoskeleton. The potential interaction between dapsone and vorinostat may have important clinical implications as more than 10 clinical trials evaluating drug combinations with vorinostat in patients with malignant glioma are either ongoing or planned in North America.

Repeated Topical Application of para-Phenylenediamine Induces Renal Histopathological Changes in Rats

Hemolytic anemia and rhabdomyolysis have been often reported to be an adverse effect of drug- and chemical-induced toxicity both in experimental and real-life scenario. para-Phenylenediamine (PPD) is a derivative of para-nitroaniline and has been found as an ingredient of almost all hair dye formulations in varying concentrations from 2% to 4% w/v. Earlier studies have reported that the accidental oral ingestion of PPD in humans can lead to acute renal failure because of rhabdomyolysis. In the present investigation, we have tested the chronic topical application of PPD and its effect on the renal histology of Sprague-Dawley rats. The experiment provides clear evidence that topically applied PPD induces hemolytic anemia as evident from the decrease in the total RBC count, packed cell volume, and hemoglobin content apart from rhabdomyolysis which subsequently causes acute renal failure in rats.

High prevalence of Dapsone-induced oxidant hemolysis in North American SCT recipients without glucose-6-phosphate-dehydrogenase deficiency

Dapsone (4-4'-diaminodiphenylsulfone) is commonly used for Pneumocystis jirovecii pneumonia (PCP) prophylaxis in immunocompromised patients. Oxidant hemolysis is a known complication of dapsone, but its frequency in adult patients who have undergone a SCT for hematological malignancies is not well established. We studied the presence of oxidant hemolysis, by combining examination of RBC morphology and laboratory data, in 30 patients who underwent a SCT and received dapsone for PCP prophylaxis, and compared this group with 26 patients who underwent a SCT and received trimethoprim-sulfamethoxazole (TMP-SMX) for PCP prophylaxis. All patients had normal glucose-6-phosphate dehydrogenase (G6PDH) enzymatic activity. In SCT patients, dapsone compared with TMP-SMX for PCP prophylaxis was associated with a high incidence of oxidant hemolysis (87 vs 0%, P<0.001), and the morphological evaluation of oxidant hemolysis correlated well with laboratory evidence of hemolysis. Dapsone-induced oxidant hemolysis in SCT patients is 20-fold higher than the reported rate in the population of HIV-infected patients, and thus much higher than the prevalence of G6PDH variants in the general population. In our patients, it manifested clinically as a lower Hb that was not significant enough to result in increased packed RBC transfusions.

DDS, 4,4'-diaminodiphenylsulfone, extends organismic lifespan

DDS, 4,4'-diaminodiphenylsulfone, is the most common drug prescribed to treat Hansen disease patients. In addition to its antibacterial activity, DDS has been reported to be involved in other cellular processes that occur in eukaryotic cells. Because DDS treatment significantly enhances the antioxidant activity in humans, we examined its effect on lifespan extension. Here we show that DDS extends organismic lifespan using Caenorhabditis elegans as a model system. DDS treatment caused a delay in aging and decreased the levels of a mitochondrial complex. The oxygen consumption rate was also significantly lowered. Consistent with these data, paraquat treatment evoked less reactive oxygen species in DDS-treated worms, and these worms were less sensitive to paraquat. Interestingly enough, all of the molecular events caused by DDS treatment were consistently reproduced in mice treated with DDS for 3 mo and in the C2C12 muscle cell line. Structural prediction identified pyruvate kinase (PK) as a protein target of DDS. Indeed, DDS bound and inhibited PK in vitro and inhibited it in vivo, and a PK mutation conferred extended lifespan of C. elegans. Supplement of pyruvate to the media protected C2C12 cells from apoptosis caused by paraquat. Our findings establish the significance of DDS in lowering reactive oxygen species generation and extending the lifespan, which renders the rationale to examining the possible effect of DDS on human lifespan extension.

Mechanistic study on aniline-induced erythrocyte toxicity

Strategies for the use of bio-indicators in the prediction of environmental damage should include mechanistic research. This study involves the relationship between the chemical structure and hemotoxic markers of aniline and its halogenated analogs. Aniline-induced methemoglobinemia, loss of circulating blood cells, blood stability, glutathione depletion and membrane cytoskeletal changes were assessed following exposure to phenylhydroxylamine (PHA), para-fluoro-, para-bromo-, and para-iodo in male Sprague-Dawley rats. Methemoglobin was determined spectrophotometrically at 635 nm. Erythrocyte depletion was investigated by loss of radioactivity in chromium-labeled red blood cells in vivo. Membrane proteins were analyzed by SDS-PAGE using red blood ghost cells treated with various aniline analogs. Results showed dose- and time-dependent changes in the induction of methemoglobin of up to 78% with para-bromo PHA and 75% with para-iodo PHA compared to 3% to 5% in control. Treated animals lost up to three times more blood from circulation compared to control within 14 days after treatment. Erythrocytes were more stable in buffer solution than in para-iodo-treated cells. Depletion of reduced glutathione in PHA and para-iodo-PHA treated red cells was also observed. Analysis of red cell skeletal membrane treated with para-iodo-PHA showed that protein band 2.1 became broader and band 2.2 diminished completely in some treatments. Dose- and time-dependent changes suggested the use of hemotoxic endpoints as potential biomarkers for assessing chemical and drug safety.

Complications related to dapsone use for Pneumocystis jirovecii pneumonia prophylaxis in solid organ transplant recipients

Dapsone, used for prevention of Pneumocystis jirovecii infections, has been reported to cause hemolytic anemia and methemoglobinemia; its tolerability in solid organ transplant recipients is not well described. We investigated dapsone-related adverse events in patients undergoing solid organ transplantation from 1999 to 2004. Transplant providers identified patients for the investigators who then reviewed the patients' hospital and outpatient records. Sixteen solid organ transplant recipients fit case definitions for dapsone-related hemolytic anemia (n = 11) or methemoglobinemia (n = 5). Median time from event to dapsone discontinuation was 15 days; all patients improved after drug discontinuation. G6PD enzyme activity was normal in all patients whose test results were available. Dapsone may be associated with hemolytic anemia or methemoglobinemia, even with normal G6PD levels. These events are often not promptly recognized, and drug discontinuation is delayed. Dapsone-related hemolytic anemia or methemoglobinemia should be considered in solid organ transplant recipients with unexplained anemia or hypoxia.

Protective role of vitamin E on the oxidative stress in Hansen's disease (Leprosy) patients

BACKGROUND

A constellation of reactive oxygen species (ROS) capable of damaging cellular constituents generated in excess during the chronic, inflammatory, neurodegenerative disease process of leprosy. The consequences of this leads to enhanced oxidative stress and lower antioxidant status. Enzymatic antioxidants provide first line defense against ROS. We have measured the levels of oxidative stress indices like lipid peroxidation (LPO), protein carbonyls together with enzymatic antioxidants in the blood samples of control and leprosy patients. Nutritional rehabilitation by way of exogenous supplementation of functionally efficient antioxidants like vitamin E reactivates the enzymatic antioxidant system and guards against the insult caused by ROS during the pathogenesis of the disease and antileprosy chemotherapy.

DESIGN

Untreated leprosy patients were selected on the basis of clinical examination and skin smear. All diagnosed untreated leprosy patients received multi drug therapy (MDT) consisting of rifampicin, dapsone and clofazimine as recommended by World Health Organization. A small number of untreated cases were selected for co-supplementation of vitamin E along with MDT. Oxidative stress indices, enzymatic and nonenzymatic antioxidant status were assayed in untreated, MDT treated and those supplemented vitamin E along with MDT.

STATISTICAL METHODS

We have compared the significance in the mean+/-s.d. values of the oxidative stress indices and the levels of antioxidants using one way analysis of variance (ANOVA) between control, untreated, MDT treated and those supplemented vitamin E with MDT and the results were significant at P < 0.05. Statistical analysis of the results suggests that oral administration of vitamin E lowers oxidative stress and augments antioxidant status in affected individuals.

RESULTS

Enhanced oxidative stress as evidenced by increased LPO and protein carbonyl in leprosy cases lowers the antioxidant status. Treatment with MDT has a limited impact on increased oxidative stress and decreased antioxidant status. Coadministration of vitamin E along with MDT decreases oxidative stress and activate the antioxidant status.

DISCUSSION

The excess production of ROS as seen in leprosy cases could lead to degeneration of tissues and derangement of internal organs. The possible reason for the decreased antioxidant status in leprosy cases may be increased production of ROS, deranged liver function, and the free radical producing ability of drugs used in MDT of leprosy. Intervention with antioxidant supplementation like vitamin E prevents oxidative stress mediated through ROS and activates the net antioxidant status during the chronic course of the disease and antileprosy chemotherapy.

Oxidant stress and haemolysis of the human erythrocyte

The erythrocyte is a highly specialised cell with a limited metabolic repertoire. As an oxygen shuttle, it must continue to perform this essential task while exposed to a wide range of environments on each vascular circuit, and to a variety of xenobiotics across its lifetime. During this time, it must continuously ward off oxidant stress on the haeme iron, the globin chain and on other essential cellular molecules. Haemolysis, the acceleration of the normal turnover of senescent erythrocytes, follows severe and irreversible oxidant injury. A detailed understanding of the molecular mechanisms underlying oxidant injury and its reversal, and of the clinical and laboratory features of haemolysis is important to the medical toxicologist. This review will also briefly review glucose-6-phosphate deficiency, a common but heterogeneous range of enzyme-deficient states, which impairs the ability of the erythrocyte to respond to oxidant injury.

Disulone

For 60 years, dapsone has been used as a both antibacterial and anti-inflammatory agent. Dapsone (4,4'-diaminodiphenylsulfone, DDS) continues to be used successfully to treat a wide range of dermatologic disorders, notably those characterized by abnormal neutrophil and eosinophil polynuclear accumulation. A considerable number of other inflammatory as well as bullous dermatoses, of which dermatitis herpetiformis is the best known, have been shown to respond in varying degrees to dapsone, although the indication for the molecule has not been demonstrated in of them all. This article reviews current knowledge on the pharmacokinetics, mechanism of action and side effects of dapsone in dermatology. Despite the lack of controlled studies, the aim of this study is to specify and classify the pathological states in which disulone could be indicated.

Primaquine-induced hemolytic anemia: effect of 6-methoxy-8-hydroxylaminoquinoline on rat erythrocyte sulfhydryl status, membrane lipids, cytoskeletal proteins, and morphology

Previous studies have shown that 6-methoxy-8-hydroxylaminoquinoline (MAQ-NOH), an N-hydroxy metabolite of the antimalarial drug, primaquine, is a direct-acting hemolytic agent in rats. To investigate the mechanism underlying this hemolytic activity, the effects of hemotoxic concentrations of MAQ-NOH on rat erythrocyte sulfhydryl status, membrane lipids, skeletal proteins, and morphology have been examined. Treatment of rat erythrocytes with a TC(50) concentration of MAQ-NOH (350 microM) caused only a modest and transient depletion of reduced glutathione (GSH) (~30%), which was matched by modest increases in the levels of glutathione disulfide and glutathione-protein mixed disulfides. Lipid peroxidation, as measured by thiobarbituric acid-reactive substances and F(2)-isoprostane formation, was induced in a concentration-dependent manner by MAQ-NOH. However, the formation of disulfide-linked hemoglobin adducts on membrane skeletal proteins and changes in erythrocyte morphology were not observed. These data suggest that hemolytic activity results from peroxidative damage to the lipid of the red cell membrane and is not dependent on skeletal protein thiol oxidation. However, when red cell GSH was depleted (>90%) by titration with diethyl maleate, hemolytic activity of MAQ-NOH was markedly enhanced. Of interest, exacerbation of hemotoxicity was not matched by increases in lipid peroxidation, but by the appearance of hemoglobin-skeletal protein adducts. Collectively, the data are consistent with the concept that MAQ-NOH may operate by more than one mechanism; one that involves lipid peroxidation in the presence of normal amounts of erythrocytic GSH, and one that involves protein oxidation in red cells with low levels of GSH, such as are seen in individuals with glucose-6-phosphate dehydrogenase deficiency.

Arylamine N-acetyltransferases and drug response

Arylamine N-acetyltransferases (NATs) play an important role in the interaction of competing metabolic pathways determining the fate of and response to xenobiotics as therapeutic drugs, occupational chemicals and carcinogenic substances. Individual susceptibility for drug response and possible adverse drug reactions are modulated by the genetic predisposition (manifested for example, by polymorphisms) and the phenotype of these enzymes. For all drugs metabolized by NATs, the impact of different in vivo enzyme activities is reviewed with regard to therapeutic use, prevention of side effects and possible indications for risk assessment by phenotyping and/or genotyping. As genes of NATs are susceptibility genes for multifactorial adverse effects and xenobiotic-related diseases, risk prediction can only be made possible by taking the complexity of events into consideration.

Dapsone-induced cholestasis and impairment of bile salt output in the rat

To evaluate the effect of dapsone (4,4'-diaminodiphenylsulfone, DDS) on biliary bile salt secretion, we administered the drug to male and female Wistar rats at a dose of 30 mg/kg body wt, twice a day, for 4 days. DDS decreased basal bile flow by about 20% in both male and female rats. In addition, basal biliary bile salt secretion was decreased by the drug in animals from both sexes (about 30% decrease). Bile salt maximum secretory rate, as evaluated by infusing tauroursodeoxycholate at stepwise-increasing rates, was not affected by DDS in either male or female rats, suggesting that the density of canalicular bile salt transporters is preserved. The size of the bile salt pool and the rate of de novo synthesis of bile salts, measured in bile salt-depleted animals, were decreased by about 33 and 35%, respectively; there was no difference in response between males and females. The ability of the ileum to reabsorb bile salts, as estimated by analysis of the expression of the ileal apical sodium-dependent bile salt transporter and of sodium taurocholate transport activity in brush border membrane vesicles, was not affected by DDS in either males or females. Overall, our findings suggest that an impairment of de novo synthesis mediated by a direct inhibition of CYP3A metabolism, rather than a decreased intestinal reabsorption of bile salts, accounts for the decrease in bile salt pool size. The dissociation between alteration of bile secretory function and the oxidative stress induced by DDS, which is known to be relevant only in male rats, is discussed.

Dapsone and sulfones in dermatology: overview and update

In their 60-year history, dapsone and the sulfones have been used as both antibacterial and anti-inflammatory agents. Dapsone has been used successfully to treat a range of dermatologic disorders, most successfully those characterized by abnormal neutrophil and eosinophil accumulation. This article reviews and updates the chemistry, pharmacokinetics, clinical application, mechanism of action, adverse effects, and drug interactions of dapsone and the sulfones in dermatology.

Hemolytic drugs aniline and dapsone induce iron release in erythrocytes and increase the free iron pool in spleen and liver

Incubation of rat erythrocytes with the hydroxylated metabolites of aniline and dapsone (4-4'-diaminodiphenylsulfone), phenylhydroxylamine and dapsone hydroxylamine, respectively, induced marked release of iron and methemoglobin formation. On the contrary, no release of iron nor methemoglobin formation was seen when the erythrocytes were incubated with the parent compounds (aniline and dapsone). The acute intoxication of rats with aniline or dapsone induced a marked increase in the erythrocyte content of free iron and methemoglobin, indicating that the xenobiotics are effective only after biotransformation to toxic metabolites in vivo. Prolonged administration of aniline or dapsone to rats produced continuous release of iron from erythrocytes. Marked iron overload was seen in the spleen and in the liver Kupffer cells, as detected histochemically. The spleen weight in these subchronically treated animals was significantly increased. The free iron pool was markedly increased in the spleen and to a lower extent in the liver. The possible relationships between iron release in erythrocytes, oxidative damage seen in senescent cells, hemolysis, overwhelmed capacity of spleen and liver to keep iron in storage forms and subsequent increase in low molecular weight, catalitically active iron is discussed.

Formation of free radicals and protein mixed disulfides in rat red cells exposed to dapsone hydroxylamine

The hemolytic activity of dapsone is well known to reside in its N-hydroxylamine metabolites. Addition of dapsone hydroxylamine (DDS-NOH) to red cell suspensions causes damage such that when reintroduced into the circulation of isologous rats, the injured cells are rapidly removed by the spleen. Hemolytic activity is associated with the extensive formation of disulfide-linked hemoglobin adducts on red cell membrane skeletal proteins. To determine if free radicals could be involved in this process, rat red cells were incubated with DDS-NOH in the presence of the spin trap, 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) and subjected to EPR analysis. Addition of DDS-NOH (25-50 microM) to a red cell suspension gave rise to a four-line (1:2:2:1) EPR spectrum with coupling constants identical to those of a DMPO-hydroxyl radical adduct (DMPO-OH) standard. No other radicals were detected; however, preincubation of red cells with cysteamine caused the DDS-NOH-generated DMPO-OH signal to be replaced by a cysteamine thiyl radical adduct signal. DDS-NOH-treated red cells were also found to contain ferrylhemoglobin, indicating the presence of hydrogen peroxide. Furthermore, DDS-NOH was found to stimulate salicylate hydroxylation in red cell suspensions, confirming the presence of oxygen radicals. These data support the hypothesis that oxygen radicals are involved in the mechanism underlying dapsone-induced hemolytic anemia.