Oxidative damage to ferritin by 5-aminolevulinic acid

Effects of dietary 5-aminolevulinic acid on growth performance and nonspecific immunity of Litopenaeus vannamei, as determined by transcriptomic analysis

5-aminolevulinic acid (5-ALA) is an endogenous non-protein amino acid that is frequently used in modern agriculture. This study set out to determine how dietary 5-ALA affected the nonspecific immunity and growth performance of Litopenaeus vannamei. The shrimp were supplemented with dietary 5-ALA at 0, 15, 30, 45, and 60 mg/kg for three months. Transcriptome data of the control group and the group supplemented with 45 mg/kg dietary 5-ALA were obtained using transcriptome sequencing. 592 DEGs were identified, of which 426 were up-regulated and 166 were down-regulated. The pathways and genes associated with growth performance and nonspecific immunity were confirmed using qRT-PCR. The highest survival rate, body length growth rate, and weight gain values were observed in shrimp fed diets containing 45 mg/kg 5-ALA. L. vannamei in this group had a significantly higher total hemocyte count, phagocytosis rate and respiratory burst value than those in the control group. High doses of dietary 5-ALA (45 mg/kg, 60 mg/kg) significantly increased the activities of catalase, superoxide dismutase, oxidized glutathione, glutathione-peroxidase, phenoloxidase, lysozyme, acid phosphatase, and alkaline phosphatase. At the transcriptional level, dietary 5-ALA significantly up-regulated the expression levels of antioxidant immune-related genes. The optimal concentration of 5-ALA supplementation was 39.43 mg/kg, as indicated by a broken line regression. Our study suggested that dietary 5-ALA positively impacts the growth and nonspecific immunity of L. vannamei, providing a novel theoretical basis for further research into 5-ALA as a dietary supplement.

[Acute hepatic porphyrias: pathophysiology and pathogenesis of acute attacks]

Heme is an iron-containing molecule essential for virtually all living organisms. However, excessive heme is cytotoxic, necessitating tight regulation of intracellular heme concentration. The acute hepatic porphyrias (AHPs) are a group of rare inborn errors of heme biosynthesis that are characterized by episodic acute neurovisceral attacks that are precipitated by various factors. The AHPs are often misdiagnosed, as the acute attack symptom are non-specific and can be attributed to other more common causes. Understanding how heme biosynthesis is dysregulated in AHP patients and the mechanism by which acute attacks are precipitated will aid in accurate and rapid diagnoses, and subsequently, appropriate treatment of these disorders. Therefore, this review article will focus on the biochemical and molecular changes that occur during an acute attack and present what is currently known regarding the underlying pathogenesis of acute attacks.

Iron Metabolism in the Disorders of Heme Biosynthesis

Given its remarkable property to easily switch between different oxidative states, iron is essential in countless cellular functions which involve redox reactions. At the same time, uncontrolled interactions between iron and its surrounding milieu may be damaging to cells and tissues. Heme—the iron-chelated form of protoporphyrin IX—is a macrocyclic tetrapyrrole and a coordination complex for diatomic gases, accurately engineered by evolution to exploit the catalytic, oxygen-binding, and oxidoreductive properties of iron while minimizing its damaging effects on tissues. The majority of the body production of heme is ultimately incorporated into hemoglobin within mature erythrocytes; thus, regulation of heme biosynthesis by iron is central in erythropoiesis. Additionally, heme is a cofactor in several metabolic pathways, which can be modulated by iron-dependent signals as well. Impairment in some steps of the pathway of heme biosynthesis is the main pathogenetic mechanism of two groups of diseases collectively known as porphyrias and congenital sideroblastic anemias. In porphyrias, according to the specific enzyme involved, heme precursors accumulate up to the enzyme stop in disease-specific patterns and organs. Therefore, different porphyrias manifest themselves under strikingly different clinical pictures. In congenital sideroblastic anemias, instead, an altered utilization of mitochondrial iron by erythroid precursors leads to mitochondrial iron overload and an accumulation of ring sideroblasts in the bone marrow. In line with the complexity of the processes involved, the role of iron in these conditions is then multifarious. This review aims to summarise the most important lines of evidence concerning the interplay between iron and heme metabolism, as well as the clinical and experimental aspects of the role of iron in inherited conditions of altered heme biosynthesis.

Kidney Involvement in Acute Hepatic Porphyrias: Pathophysiology and Diagnostic Implications

Porphyrias are a group of rare disorders originating from an enzyme dysfunction in the pathway of heme biosynthesis. Depending on the specific enzyme involved, porphyrias manifest under drastically different clinical pictures. The most dramatic presentation of the four congenital acute hepatic porphyrias (AHPs: acute intermittent porphyria-AIP, ALAD deficiency, hereditary coproporphyria-HCP, and porphyria variegata-VP) consists of potentially life-threatening neurovisceral attacks, for which givosiran, a novel and effective siRNA-based therapeutic, has recently been licensed. Nonetheless, the clinical manifestations of acute porphyrias are multifaceted and do not limit themselves to acute attacks. In particular, porphyria-associated kidney disease (PAKD) is a distinct, long-term degenerating condition with specific pathological and clinical features, for which a satisfactory treatment is not available yet. In PAKD, chronic tubule-interstitial damage has been most commonly reported, though other pathologic features (e.g., chronic fibrous intimal hyperplasia) are consistent findings. Given the relevant role of the kidney in porphyrin metabolism, the mechanisms possibly intervening in causing renal damage in AHPs are different: among others, δ-aminolevulinic acid (ALA)-induced oxidative damage on mitochondria, intracellular toxic aggregation of porphyrins in proximal tubular cells, and derangements in the delicate microcirculatory balances of the kidney might be implicated. The presence of a variant of the human peptide transporter 2 (PEPT2), with a greater affinity to its substrates (including ALA), might confer a greater susceptibility to kidney damage in patients with AHPs. Furthermore, a possible effect of givosiran in worsening kidney function has been observed. In sum, the diagnostic workup of AHPs should always include a baseline evaluation of renal function, and periodic monitoring of the progression of kidney disease in patients with AHPs is strongly recommended. This review outlines the role of the kidney in porphyrin metabolism, the available evidence in support of the current etiologic and pathogenetic hypotheses, and the known clinical features of renal involvement in acute hepatic porphyrias.

Mechanisms of Neuronal Damage in Acute Hepatic Porphyrias

Porphyrias are a group of congenital and acquired diseases caused by an enzymatic impairment in the biosynthesis of heme. Depending on the specific enzyme involved, different types of porphyrias (i.e., chronic vs. acute, cutaneous vs. neurovisceral, hepatic vs. erythropoietic) are described, with different clinical presentations. Acute hepatic porphyrias (AHPs) are characterized by life-threatening acute neuro-visceral crises (acute porphyric attacks, APAs), featuring a wide range of neuropathic (central, peripheral, autonomic) manifestations. APAs are usually unleashed by external "porphyrinogenic" triggers, which are thought to cause an increased metabolic demand for heme. During APAs, the heme precursors δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) accumulate in the bloodstream and urine. Even though several hypotheses have been developed to explain the protean clinical picture of APAs, the exact mechanism of neuronal damage in AHPs is still a matter of debate. In recent decades, a role has been proposed for oxidative damage caused by ALA, mitochondrial and synaptic ALA toxicity, dysfunction induced by relative heme deficiency on cytochromes and other hemeproteins (i.e., nitric oxide synthases), pyridoxal phosphate functional deficiency, derangements in the metabolic pathways of tryptophan, and other factors. Since the pathway leading to the biosynthesis of heme is inscribed into a complex network of interactions, which also includes some fundamental processes of basal metabolism, a disruption in any of the steps of this pathway is likely to have multiple pathogenic effects. Here, we aim to provide a comprehensive review of the current evidence regarding the mechanisms of neuronal damage in AHPs.

Role of 7-chloro-4-(phenylselanyl) quinoline in the treatment of oxaliplatin-induced hepatic toxicity in mice

There is an increasing incidence of hepatotoxicity induced by oxaliplatin (OXA); therefore, researchers' attention has been drawn to therapeutic alternatives that may decrease OXA-induced hepatotoxicity. Studies indicate that oxidative stress plays a major role in OXA-induced liver injury. As several pharmacological effects of 7-chloro-4-(phenylselanyl) quinole (4-PSQ) involve its antioxidant action, the hypothesis that this organoselenium compound could be promising for the treatment or prevention of hepatotoxicity induced by treatment with OXA was investigated. To test this hypothesis, male Swiss mice received OXA (10 mg·kg-1) on days 0 and 2, followed by oral administration of 4-PSQ (1 mg·kg-1) on days 2 to 14. 4-PSQ reduced the plasma aspartate, and alanine aminotransferase activity increased by exposure to OXA. The histopathological examination of the liver showed that 4-PSQ markedly improved OXA-induced hepatic injury. In addition, treatment with 4-PSQ reduced the oxidation of lipids and proteins (thiobarbituric acid reactive species levels and protein carbonyl content) and attenuated the increase of hepatic catalase and glutathione peroxidase activity caused by OXA. The inhibition of hepatic δ-aminolevulinic dehydratase activity induced by OXA was reverted by 4-PSQ. In conclusion, results indicate that 4-PSQ may be a good therapeutic strategy for attenuating OXA-induced liver damage.

Misdistribution of iron and oxidative stress in chronic kidney disease

Chronic kidney disease (CKD) patients have an extremely high risk of developing cardiovascular diseases (CVD) compared to the general population. Systemic inflammation associated with oxidative stress could be an important determinant of morbidity and mortality associated with CVD. We suspected that dysregulation of iron metabolism should be considered in these patients. Anemia is prevalent in CKD patients and is often treated with erythropoiesis-stimulating agents (ESAs) and iron. In addition, iron administration sometimes causes iron overdose. Excessive iron in the cytosol and mitochondria can accelerate the formation of a highly toxic reactive oxygen species, hydroxyl radicals, which damage lipids, proteins, and DNA. In this review, we propose the following four major reasons for oxidative stress in CKD patients: 1) iron is sequestered in cells by proinflammatory cytokines and hepcidin; 2) the reduction in frataxin increases "free" iron in mitochondria; 3) the accumulation of 5-aminolevulinic acid, a heme precursor, has toxic effects on iron and mitochondrial metabolism; and 4) the elevated levels of the metabolic hormone, leptin, promote hepatic hepcidin production. Although an efficient therapy for preventing oxidative stress in these patients has not yet been well defined, we propose that ESAs for renal anemia may ameliorate these causes of oxidative stress. Further clinical trials are necessary to clarify the effectiveness of ESAs on oxidative stress in CKD patients.

Protective effect of rosmarinic acid against oxidative stress biomarkers in liver and kidney of strepotozotocin-induced diabetic rats

In the present study, we investigated the efficiency of rosmarinic acid (RA) in preventing the alteration of oxidative parameters in the liver and kidney of diabetic rats induced by streptozotocin (STZ). The animals were divided into six groups (n = 8): control, ethanol, RA 10 mg/kg, diabetic, diabetic/ethanol, and diabetic/RA 10 mg/kg. After 3 weeks of treatment, we found that TBARS levels in liver and kidney were significantly increased in the diabetic/saline group and the administration of RA prevented this increase in the liver and kidney (P < 0.05). Diabetes caused a significant decrease in the activity of superoxide dismutase (SOD) and catalase (CAT) in the diabetes/saline group (P < 0.05). However, the treatment with 10 mg/kg RA (antioxidant) prevented this alteration in SOD and CAT activity in the diabetic RA group (P < 0.05). In addition, RA reverses the decrease in ascorbic acid and non-protein-thiol (NPSH) levels in diabetic rats. The treatment with RA also prevented the decrease in the Delta-aminolevulinic acid dehydratase (ALA-D) activity in the liver and kidney of diabetic rats. Furthermore, RA did not have any effect on glycemic levels. These results indicate that RA effectively reduced the oxidative stress induced by STZ, suggesting that RA is a potential candidate for the prevention and treatment of pathological conditions in diabetic models.

Chemistry of free radicals produced by oxidation of endogenous α-aminoketones. A study of 5-aminolevulinic acid and α-aminoacetone by fast kinetics spectroscopy

BACKGROUND

Excess 5-aminolevulinic acid (ALA) and α-aminoacetone (AA) are implicated in ketosis, porphyrinpathies and diabetes. Pathologic manifestations involve O₂⁻, H₂O₂, OH, enoyl radicals (ALA and AA) and their oxidation end products.

METHODS

To characterize enoyl radicals resulting from reaction of OH radicals with ALA and AA, micromolar OH concentrations were produced by pulse radiolysis of ALA and AA in aqueous solutions.

RESULTS

ALA and AA react with OH at k=1.5 × 10⁹ M⁻¹s⁻¹. At pH7.4, the ALA absorbance spectrum has a maximum at 330 nm (ε=750 M⁻¹cm⁻¹). This band appears as a shoulder at pH8.3 where two ALA species are present: (NH3)⁺-CH₂-CO-CH₂-CH₂-COO⁻ and NH₂-CH₂-CO-CH₂-CH₂-COO⁻ (pKa=8.3). At pH8.3, ALA reacts with oxygen (k=1.4 × 10⁸ M⁻¹s⁻¹) but not with O₂⁻. At pH8.3, AA oxidation produces two AA species characterized by an absorbance spectrum with maxima at 330 and 450 nm. ALA and AA are repaired by antioxidants (quercetin (QH), catechin, trolox, ascorbate) which are semi-oxidized (k>10(8)M⁻¹s⁻¹). QH bound to HSA or to apoferritin and ferritin repairs ALA and AA. In O₂-saturated apoferritin solutions, Q, O₂⁻, AA and reaction product(s) react with QH.

CONCLUSIONS

The optical absorption properties and the time evolution of ALA and AA were established for the first time. These radicals and their reaction products may be neutralized by antioxidants free in solution or bound to proteins.

GENERAL SIGNIFICANCE

Adjuvant antioxidant administration may be of interest in pathologies related to excess ALA or AA production.

Alterations of the redox state, pentose pathway and glutathione metabolism in an acute porphyria model. Their impact on heme pathway

A classical acute porphyria model in rats consists of combined treatment with 2-allyl-2-isopropylacetamide (AIA) and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). The present work describes the effects of this treatment on the pentose phosphate (PP) pathway, glutahione metabolism and redox state and how they contribute to alter the glucose pool of hepatocytes and modulate porphyria, in Wistar rat livers. Our approach is based on the fact that glucose is a repressor of 5-aminolevulinic synthase (ALA-S), the rate-limiting enzyme of the heme pathway, and treatment with AIA/DCC causes oxidative stress. Different doses of the xenobiotcs were used. The results show that AIA (500 mg/kg body weight [BW])/DDC (50 mg/kg [BW]) treatment increased glutathione peroxidase (GPx) activity by 46%, decreased both glutathione reductase (GR) and glutathione S-transferase (GST) activity by 69% and 52%, respectively, and reduced by 51% reduced glutathione (GSH) and increased by 100% glutathione disulfide (GSSG) concentrations, therefore lowering by four-fold the GSH/GSSG ratio. The activity of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of PP-pathway, was increased by 129% as well as that of 6-phosphogluconate dehydrogenase. NADPH and the NADPH/NADP(+) ratio were increased by 14% and 28%, respectively. These effects could be attributed to the generation of reactive oxygen species (ROS) elicited by the porphyrinogenic treatment, shown by enhanced DNA damage and ROS production. G6PD stimulation would decrease hepatic glucose concentrations and consequently exacerbate the porphyria. A decrease in glucose could stimulate ALA-S and this would add to the effect of drug-induced heme depletion. Since the key role of GST is to inactivate toxic compounds, the drastic fall in its activity together with the accumulation of ALA would account for the symptoms of this hepatic disease model. The present findings show the high metabolic interplay between pathways and constitute a relevant contribution to achieve a better treatment of acute human porphyria.

Hypertension strengthens δ-ALA-D activity inhibition and increases it reactivation index in type 2 diabetic patients

AIMS

To assess the effect of hypertension on δ-aminolevulinate dehydratase (δ-ALA-D) activity of type 2 diabetic patients (T2DM).

METHODS

δ-ALA-D activity and reactivation index, as well as markers of oxidative stress, biochemical and anthropometrics parameters were determined in T2DM (n=23), type 2 diabetic patients with hypertension (T2DM/HT) (n=30) and controls (n=30).

RESULTS

T2DM/HT presented a greater inhibition of δ-ALA-D activity, a higher reactivation index (p<0.05) and a greater depletion of plasma protein thiol groups (P-SH) when compared to T2DM. Moreover, δ-ALA-D activity was positively associated with SH groups and negatively associated with serum protein carbonyl (PC) while its reactivation index was negatively associated with SH groups and positively associated with PC.

CONCLUSIONS

These results point out that there is a possible interference of hypertension on the mechanism of the δ-ALA-D activity suggesting that this condition aggravated the oxidative stress of diabetes mellitus.

Effects of diphenyl diselenide on oxidative stress induced by sepsis in rats

Sepsis is a potentially deadly complication that can be caused by different factors. Actually, it is known that oxidative stress is involved in the pathogenesis of sepsis. Thus, the aim of this study was to evaluate the effect of diphenyl diselenide (PhSe)(2), an emergent compound, on oxidative stress parameters induced by sepsis in rats. Animals were pre-injected with (PhSe)(2) or vehicle. Twenty-four hours later, sepsis was induced by cecal ligation puncture (CLP). After 12 h, liver was taken for thiobarbituric acid reactive species (TBARS) measurement, δ-aminolevunic acid dehydratase (δ-ALA-D), Cu/Zn superoxide dismutase (Cu/Zn SOD) and catalase (CAT) activities assay. The sepsis increased TBARS, inhibited δ-ALA-D, activated Cu/Zn SOD and had a tendency to decrease CAT activity. However, (PhSe)(2) prevented the TBARS formation, but did not prevent the inhibition of δ-ALA-D activity in the animals with damage. Thus, this study showed that (PhSe)(2) partially prevents the oxidative stress induced by sepsis, indicating the potential of this compound as a treatment for this pathology. Nevertheless, more tests should be performed to confirm the hypothesis suggested here.

1,4-Diamino-2-butanone, a wide-spectrum microbicide, yields reactive species by metal-catalyzed oxidation

The α-aminoketone 1,4-diamino-2-butanone (DAB), a putrescine analogue, is highly toxic to various microorganisms, including Trypanosoma cruzi. However, little is known about the molecular mechanisms underlying DAB's cytotoxic properties. We report here that DAB (pK(a) 7.5 and 9.5) undergoes aerobic oxidation in phosphate buffer, pH 7.4, at 37°C, catalyzed by Fe(II) and Cu(II) ions yielding NH(4)(+) ion, H(2)O(2), and 4-amino-2-oxobutanal (oxoDAB). OxoDAB, like methylglyoxal and other α-oxoaldehydes, is expected to cause protein aggregation and nucleobase lesions. Propagation of DAB oxidation by superoxide radical was confirmed by the inhibitory effect of added SOD (50 U ml-1) and stimulatory effect of xanthine/xanthine oxidase, a source of superoxide radical. EPR spin trapping studies with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) revealed an adduct attributable to DMPO-HO(•), and those with α-(4-pyridyl-1-oxide)-N-tert-butylnitrone or 3,5-dibromo-4-nitrosobenzenesulfonic acid, a six-line adduct assignable to a DAB(•) resonant enoyl radical adduct. Added horse spleen ferritin (HoSF) and bovine apo-transferrin underwent oxidative changes in tryptophan residues in the presence of 1.0-10 mM DAB. Iron release from HoSF was observed as well. Assays performed with fluorescein-encapsulated liposomes of cardiolipin and phosphatidylcholine (20:80) incubated with DAB resulted in extensive lipid peroxidation and consequent vesicle permeabilization. DAB (0-10 mM) administration to cultured LLC-MK2 epithelial cells caused a decline in cell viability, which was inhibited by preaddition of either catalase (4.5 μM) or aminoguanidine (25 mM). Our findings support the hypothesis that DAB toxicity to several pathogenic microorganisms previously described may involve not only reported inhibition of polyamine metabolism but also DAB pro-oxidant activity.

Effects of acute and chronic waterborne lead exposure on the swimming performance and aerobic scope of fathead minnows (Pimephales promelas)

Fathead minnows were subjected to an incremental velocity test using swim tunnel respirometry for the analysis of aerobic scope and swimming performance, as critical aerobic swim speed (U(crit)), following chronic exposures (33-57 ) to 0.9±0.4, 157±18 or 689±66 nmol L⁻¹ Pb and an acute exposure (24 h) to 672±35 nmol L⁻¹ Pb (mean±SEM). Assessment of Pb-induced anemia and neurological impairment were evaluated by blood hemoglobin (Hb) concentrations and a cost of transport (COT) analysis, respectively. Fish from the acute 672±35 nmol L⁻¹ Pb (24.4±1.2 BL s⁻¹) and chronic 689±66 nmol L⁻¹ Pb (24.6±0.9 BL s⁻¹) treatments exhibited reduced U(crits) compared to control fish (27.6±0.8 BL s⁻¹). Aerobic scope was reduced by acute Pb exposure (8.6±2.6 μmol O₂ g⁻¹ h⁻¹ vs. 22.6±3.8 μmol O₂ g⁻¹ h⁻¹ from controls) owing to a decrease in maximum oxygen consumption rate (38.8±0.8 μmol O₂ g⁻¹ h⁻¹ vs. 54.0±4.2 μmol O₂ g⁻¹ h⁻¹ from controls). However, no effect on aerobic scope was observed with fish chronically exposed to Pb. Significant differences were not observed for Hb concentrations or COT. These findings suggest that the impaired swimming performances arising from acute and chronic Pb exposures reflect different mechanisms of toxicity.

Heme deficiency in Alzheimer's disease: a possible connection to porphyria

Mechanisms that cause Alzheimer's disease (AD), an invariably fatal neurodegenerative disease, are unknown. Important recent data indicate that neuronal heme deficiency may contribute to AD pathogenesis. If true, factors that contribute to the intracellular heme deficiency could potentially alter the course of AD. The porphyrias are metabolic disorders characterized by enzyme deficiencies in the heme biosynthetic pathway. We hypothesize that AD may differ significantly in individuals possessing the genetic trait for an acute hepatic porphyria. We elaborate on this hypothesis and briefly review the characteristics of the acute hepatic porphyrias that may be relevant to AD. We note the proximity of genes encoding enzymes of the heme biosynthesis pathway to genetic loci linked to sporadic, late-onset AD. In addition, we suggest that identification of individuals carrying the genetic trait for acute porphyria may provide a unique resource for investigating AD pathogenesis and inform treatment and management decisions.

Variegate porphyria induces plasma and neutrophil oxidative stress: effects of dietary supplementation with vitamins E and C

Our aim was to analyse the influence of variegate porphyria (VP) on the antioxidant defenses and markers of oxidative damage and inflammation in plasma and neutrophils and the effects of dietary supplementation with vitamins E and C on these parameters in plasma, neutrophils and erythrocytes. Twelve women affected by VP and twelve pair-matched healthy control women participated in a double-blind crossover study. Each participant took 50 mg/d of vitamin E and 150 mg/d of vitamin C, or a placebo, for 6 months, by consuming an almond-based beverage as the vehicle. Women affected by VP presented higher C-reactive protein and malondialdehyde (MDA) circulating levels. Plasma antioxidant defenses were not different between porphyric and control women. Neutrophils from VP women presented decreased catalase (CAT) and glutathione reductase (GR) activities together with increased protein carbonyl levels. Reactive oxygen species (ROS) production from stimulated neutrophils was also higher in porphyric women than their controls. Dietary supplementation was effective in increasing α-tocopherol levels in neutrophils and in reducing MDA levels in plasma. Erythrocyte CAT and GR activities were enhanced by the enriched beverage only in the control subjects. In conclusion, women affected by VP present a situation of inflammation, plasma oxidative damage and neutrophils more primed to the oxidative burst, with decreased antioxidant activities and increased ROS production capabilities and protein oxidative damage. Dietary supplementation with vitamin E (50 mg/d) and vitamin C (150 mg/d) for 6 months decreased plasma oxidative damage and enhanced the erythrocyte activities of CAT and GR.

Aminoacetone Induces Loss of Ferritin Ferroxidase and Iron Uptake Activities

Aminoacetone (AA) is a threonine and glycine metabolite overproduced and recently implicated as a contributing source of methylglyoxal (MG) in conditions of ketosis. Oxidation of AA to MG, NH4+, and H2O2 has been reported to be catalyzed by a copper-dependent semicarbazide sensitive amine oxidase (SSAO) as well as by copper- and iron ion-catalyzed reactions with oxygen. We previously demonstrated that AA-generated O2*-. and enoyl radical (AA*) induce dose-dependent Fe(II) release from horse spleen ferritin (HoSF); no reaction occurs under nitrogen. In the present study we further explored the mechanism of iron release and the effect of AA on the ferritin apoprotein. Iron chelators such as EDTA, ATP and citrate, and phosphate accelerated AA-promoted iron release from HoSF, which was faster in horse spleen isoferritins containing larger amounts of phosphate in the core. Incubation of apoferritin with AA (2.5-50 mM, after 6 h) changes the apoprotein electrophoretic behavior, suggesting a structural modification of the apoprotein by AA-generated ROS. Superoxide dismutase (SOD) was able to partially protect apoferritin from structural modification whereas catalase, ethanol, and mannitol were ineffective in protection. Incubation of apoferritin with AA (1-10 mM) produced a dose-dependent decrease in tryptophan fluorescence (13-30%, after 5 h), and a partial depletion of protein thiols (29% after 24 h). The AA promoted damage to apoferritin produced a 40% decrease in apoprotein ferroxidase activity and an 80% decrease in its iron uptake ability. The current findings of changes in ferritin and apoferritin may contribute to intracellular iron-induced oxidative stress during AA formation in ketosis and diabetes mellitus.

Delta-ALA-D activity is a reliable marker for oxidative stress in bone marrow transplant patients

Background

Bone marrow transplantation (BMT) is often used in the treatment of various diseases. Before BMT, patients are submitted to a conditioning regimen (CR), which consists of the administration of high doses of chemotherapy. The action of many cytostatic drugs involves the overproduction of reactive oxygen species, which together with inadequate antioxidant protection can lead to oxidative stress and this has been implicated in the etiology of various diseases. The objectives of this study were to look for evidence of oxidative stress and also to analyze δ-Aminolevulinato dehydratase (δ-ALA-D) activity as a possible marker of oxidative stress in autologous and allogeneic BMT patients.

Methods

Lipid peroxidation, vitamin C and thiol group levels as well as catalase, superoxide dismutase and δ-ALA-D activity were determined in 37 healthy controls, 13 patients undergoing autologous peripheral blood stem cell transplantation and 24 patients undergoing allogeneic BMT.

Results

We found that patients presented signs of oxidative stress before they were submitted to BMT, during CR and up to 20 days after BMT. There was a decrease in enzymatic and non enzymatic antioxidant defenses, in δ-ALA-D activity, and an increase in lipoperoxidation in the blood of both patient groups.

Conclusion

This study has indicated that autologous and allogeneic BMT are associated with oxidative stress. Moreover, blood δ-ALA-D activity seems to be an additional biomarker of oxidative stress in BMT patients.

Oxidative stress and delta-ALA-D activity in different conditioning regimens in allogeneic bone marrow transplantation patients

OBJECTIVES

To compare different conditioning regimens (CR), in order to determine whether either of them could be less toxic to allogeneic bone marrow transplantation (BMT) patients in terms of oxidative stress and also analyze delta-ALA-D activity as a possible marker of oxidative stress.

DESIGN AND METHODS

Lipid peroxidation, vitamin C, thiol groups levels and catalase, superoxide dismutase and delta-ALA-D activity were determined in 21 healthy controls, 5 patients with fludarabine+cyclophosphamide (FluCy) CR, 12 with busulfan+cyclophosphamide (BuCy) and 4 with cyclophosphamide+total body irradiation (CyTBI).

RESULTS

There were a decrease in enzymatic and non enzymatic antioxidants, in delta-ALA-D activity, and in all CRs and an increase in lipid peroxidation more pronounced in CyTBI CR.

CONCLUSIONS

All CRs promoted oxidative stress in allogeneic BMT patients, but this was more pronounced with CyTBI and delta-ALA-D activity seemed to be an additional biomarker of oxidative stress in these patients.

TolC-dependent exclusion of porphyrins in Escherichia coli

We found that Escherichia coli tolC mutants showed increased sensitivity to 5-aminolevulinic acid (ALA), a precursor of porphyrins. The tolC mutant cells grown in the presence of ALA showed a reddish brown color under visible light and a strong red fluorescence under near-UV irradiation. Fluorescence spectrometry and high-performance liquid chromatography analysis showed that the tolC mutant cells grown in the presence of ALA accumulated a large amount of coproporphyrin(ogen) intracellularly. In contrast, the wild-type cells produced coproporphyrin extracellularly. The tolC mutant cells grown in the presence of ALA, which were capable of surviving in the dark, were killed by near-UV irradiation, suggesting that the intracellular coproporphyrin(ogen) renders these cells photosensitive. These results suggest that the TolC-dependent efflux system is involved in the exclusion of porphyrin(ogen)s in E. coli.

Toxicogenomics of water chemistry influence on chronic lead exposure to the fathead minnow (Pimephales promelas)

Establishment of water quality criteria (WQC), intended to protect aquatic life, continues to rely principally on water hardness (i.e. Ca(2+)) for lead (Pb) despite growing evidence that other chemical parameters also strongly influence toxicity. To more clearly define the water chemistry parameters mediating Pb toxicity, we evaluated the effects of hardness as CaSO(4) and dissolved organic carbon (DOC) as humic acid during chronic (150 days) exposures to the fathead minnow. Measured Pb concentrations ranged from 157+/-5 nM (33+/-1 microg/L) Pb in base water to 177+/-7 (37+/-1 microg/L) and 187+/-7 nM (39+/-1 microg/L) Pb in CaSO(4)- or HA-supplemented water, respectively. Fish were collected at 2, 4, 10, 30, 63, 90 and 150 days of exposure. Traditional toxicological endpoints were examined alongside gene transcription analyses to help clarify the underlying mechanisms of Pb toxicity and to identify candidate molecular markers that might ultimately serve as robust indicators of exposure and effect. Addition of CaSO(4) did not prevent whole body Pb accumulation whereas DOC afforded strong protection (about half the amount accumulated by fish in base water) suggesting that current, hardness-based WQC are likely inaccurate for predicting chronic Pb effects in aquatic systems. Custom-made microarrays were co-hybridized with base water samples+/-Pb up to the 30 days time point. Quantitative PCR was employed to verify gene transcription responses and to extend analysis to the CaSO(4) and HA treatments and the 150 days time point. Identification of four genes by microarray analysis revealed clear Pb-induced responses over time: glucose-6-phosphate dehydrogenase, glutathione-S-transferase, ferritin and beta-globin. Results obtained by qPCR were in strong agreement with microarray data by regression analysis (r(2)=0.82, slope=1.28). The associated pathways implicated herein for these genes provide further evidence supporting roles for anemia and neurological disorders in chronic Pb toxicity. Effects of water chemistry on Pb accumulation and gene transcription responses were in close parallel, though alterations in ionoregulatory and morphological endpoints were not observed. Whereas DOC was protective against Pb accumulation and mRNA expression changes, Ca(2+) was not. Additionally, several hypothesis-driven genes (ECaC, DMT-1, and ALA-D) were examined by qPCR but revealed either no change or small Pb-induced responses lacking any clear influence attributable to water chemistry. These findings should help pave the way toward development of a new chronic Pb BLM and a Pb-responsive gene transcript profile for fathead minnows, both of which would greatly aid future environmental monitoring and regulatory strategies for Pb.

The dual face of endogenous alpha-aminoketones: pro-oxidizing metabolic weapons

Amino metabolites with potential prooxidant properties, particularly alpha-aminocarbonyls, are the focus of this review. Among them we emphasize 5-aminolevulinic acid (a heme precursor formed from succinyl-CoA and glycine), aminoacetone (a threonine and glycine metabolite), and hexosamines and hexosimines, formed by Schiff condensation of hexoses with basic amino acid residues of proteins. All these metabolites were shown, in vitro, to undergo enolization and subsequent aerobic oxidation, yielding oxyradicals and highly cyto- and genotoxic alpha-oxoaldehydes. Their metabolic roles in health and disease are examined here and compared in humans and experimental animals, including rats, quail, and octopus. In the past two decades, we have concentrated on two endogenous alpha-aminoketones: (i) 5-aminolevulinic acid (ALA), accumulated in acquired (e.g., lead poisoning) and inborn (e.g., intermittent acute porphyria) porphyric disorders, and (ii) aminoacetone (AA), putatively overproduced in diabetes mellitus and cri-du-chat syndrome. ALA and AA have been implicated as contributing sources of oxyradicals and oxidative stress in these diseases. The end product of ALA oxidation, 4,5-dioxovaleric acid (DOVA), is able to alkylate DNA guanine moieties, promote protein cross-linking, and damage GABAergic receptors of rat brain synaptosome preparations. In turn, methylglyoxal (MG), the end product of AA oxidation, is also highly cytotoxic and able to release iron from ferritin and copper from ceruloplasmin, and to aggregate proteins. This review covers chemical and biochemical aspects of these alpha-aminoketones and their putative roles in the oxidative stress associated with porphyrias, tyrosinosis, diabetes, and cri-du-chat. In addition, we comment briefly on a side prooxidant behaviour of hexosamines, that are known to constitute building blocks of several glycoproteins and to be involved in Schiff base-mediated enzymatic reactions.

Acute intermittent porphyria, Rasmussen encephalitis, or both?

A case of a young woman who suffers from refractory epilepsy in the form of Rasmussen encephalitis and acute intermittent porphyria is presented. The patient developed refractory partial seizures with progressive hemispheric atrophy in the first decade. Both her serum and cerebrospinal fluid contained significantly elevated levels of anti-GluR3B antibodies. Her serum also contained anti-NR2A antibodies (directed against the N-methyl-D-aspartate receptor). Seven years later, acute intermittent porphyria was diagnosed as she developed an acute episode of abdominal pain, dark urine, and hyponatremia. For several years, all attempts to discontinue porphyrinogenic antiepileptic drugs such as phenobarbital and valproate resulted in seizure worsening. During a major acute intermittent porphyria crisis, brain edema and coma developed, allowing the discontinuation of phenobarbital. On recovery, atrophy of the right hemisphere ensued. Several etiologic hypotheses are presented. Double insults, porphyria, and an autoimmune process are suggested for the development of Rasmussen encephalitis in this patient. The authors recommend testing for porphyria in cases of Rasmussen encephalitis and other intractable seizures.

CYP1A in TCDD toxicity and in physiology-with particular reference to CYP dependent arachidonic acid metabolism and other endogenous substrates

Toxicologic and physiologic roles of CYP1A enzyme induction, the major biochemical effect of aryl hydrocarbon receptor activation by TCDD and other receptor ligands, are unknown. Evidence is presented that CYP1A exerts biologic effects via metabolism of endogenous substrates (i.e., arachidonic acid, other eicosanoids, estrogens, bilirubin, and melatonin), production of reactive oxygen, and effects on K(+) and Ca(2+) channels. These interrelated pathways may connect CYP1A induction to TCDD toxicities, including cardiotoxicity, vascular dysfunction, and wasting. They may also underlie homeostatic roles for CYP1A, especially when transiently induced by common chemical exposures and environmental conditions (i.e., tryptophan photoproducts, dietary indoles, and changes in oxygen tension).

Involvement of oxidative stress in the pre-malignant and malignant states of cervical cancer in women

OBJECTIVES

To evaluate the potential role of oxidative stress in the evolution of cervical cancer, including its pre-malignant states.

DESIGN AND METHODS

Erythrocytes thiobarbituric acid reactive substances (TBARS) levels, plasma vitamin C and thiol content and total blood delta-ALA-D levels were estimated in 46 untreated cervical cancer and pre-malignant patients and in 46 age-sex-matched controls.

RESULTS

Erythrocytes from patients, regardless of disease state, pre-malignant (low squamous intraepithelial lesion--LSIL and high squamous intraepithelial lesion--HSIL) or cancer, showed a significant 2-3 times increase in TBARS levels (P<0.01). Plasma vitamin C was lower in the carcinoma group (P<0.01). The reactivation index of delta-aminolevulinate dehydratase (delta-ALA-D) was higher in the patient group, when compared to control (P<0.01).

CONCLUSION

LSIL, HSIL or cervical cancer can be associated with changes in 3 indicators of oxidative stress: increase in erythrocyte TBARS, ALA-D reactivation index and a decrease in vitamin C content, that may play an important role in carcinogenesis.

Effect of δ-aminolevulinic acid treatment on N-methyl-d-aspartate receptor at different ages in the rat brain

We report here the effects of the chronic treatment with the oxidant agent delta-aminolevulinic acid (ALA) on the N-methyl-D-aspartate (NMDA) receptors in 4-, 12- and 24-month-old male Wistar rats. ALA was administered daily for 15 days (40 mg/kg i.p). The study was performed by membrane homogenate binding and autoradiography, using tritiated 5-methyl-10, 11-dihydro-5H-dibenzo(a,d)cycloheptan-5,10-imine maleate ([3H]MK-801). [3H]MK-801 binding was significantly decreased in most areas studied (cortex and hippocampus) at all ages in treated rats with respect to their controls. Furthermore, Western blot assays were performed using antibodies against the NMDA receptor NR2A subunit, which is widely distributed in the brain, mainly in cortex and hippocampus. In cortex but not in hippocampus, the ALA treatment induced significant decreases in the amounts of NR2A subunit in 12- and 24-month-old animals. We conclude that chronic treatment with ALA is able to induce NMDA receptor decreases in an age-independent way and that NR2A subunit seems to be involved in these decreases in cerebral cortex, but not in the other structures studied.

Supraphysiological concentrations of 5-aminolevulinic acid dimerize in solution to produce superoxide radical anions via a protonated dihydropyrazine intermediate

5-aminolevulinic acid (ALA) is the committed biological precursor to porphyrins. At supraphysiological concentrations ALA can dimerize to form 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY), which transfers electrons to XTT in a reaction that does not require metal ions and is specifically inhibited by superoxide dismutase. The formation of DHPY from ALA follows dimerization kinetics with a pK of 7.8+/-0.1. At pH 11.2, DHPY is relatively stable, but when the pH is dropped to 6.0 rapid conversion to 2,5-(beta-carboxyethyl)pyrazine occurs via an intermediate with an absorption maximum of 370 nm. Formation of this intermediate is pH-dependent with a pK of 6.0+/-0.1. These data indicate that ALA dimerizes to produce superoxide from a protonated form of DHPY. The significance of these results with respect to the concentrations of ALA used in photodynamic therapy, and the increased incidence of liver cancer in acute intermittent porphyria, is discussed.

Liquid chromatography–tandem mass spectrometry method for the simultaneous determination of δ-ALA, tyrosine and creatinine in biological fluids

BACKGROUND

Several acquired and congenital human disorders perturb the concentrations of delta-aminolevulinate (delta-ALA), creatinine and tyrosine in biological fluids. There is currently no facile, sensitive and specific method to measure these analytes simultaneously.

METHOD

We developed an LC-MS/MS method to quantify delta-ALA, creatinine and tyrosine in urine that requires minimal sample preparation and no derivatization. The method is also applicable to the analysis of tyrosine in plasma.

RESULTS

All calibration plots were linear, with R(2)>or=0.996. Intra- and interday CVs were <10%. The limit of quantitation for delta-ALA was approximately 0.1 micromol/l, and for creatinine and tyrosine it was well below the lowest measured physiological concentrations. The method was applied to analyze urine from 75 healthy volunteers and 43 patients with hereditary tyrosinemia type I (HT I). The mean urinary concentration of delta-ALA in patients (38+/-35 micromol/l, 53+/-30 mg/g creatinine) was higher than that measured in healthy subjects (5.5+/-2.6 micromol/l, 0.9+/-0.2 mg/g creatinine; p<0.001). Treatment with 2-(2-nitro-4-trifluoromethylbenzyl)-1,3-cyclohexanedione (NTBC), an inhibitor of an early step in tyrosine catabolism, decreased urinary delta-ALA (6.4+/-4.8 micromol/l, 13+/-24 mg/g creatinine; p<0.001). The average plasma tyrosine concentration in healthy volunteers (56+/-14 micromol/l) was within normal reference interval used in clinical practice.

CONCLUSIONS

The method is simple, specific and precise and allows simultaneous quantitation of delta-ALA, creatinine and tyrosine at concentrations present under physiological or pathophysiological conditions.

Aminoacetone induces iron-mediated oxidative damage to isolated rat liver mitochondria

Aminoacetone (AA) is a threonine metabolite accumulated in threoninemia, cri-du-chat, and diabetes, where it contributes toward the formation of cytotoxic and genotoxic methylglyoxal (MG). Oxyradicals yielded from iron-catalyzed AA aerobic oxidation to MG are shown here to promote Ca2+ -mediated mitochondrial membrane permeabilization in an AA dose-dependent way. The inhibitory effect of added EGTA, cyclosporin A, Mg2+, and DTT observed in this study suggests the formation of transition pores in the inner mitochondrial membrane by AA, associated with thiol protein aggregation. That the mitochondrial iron pool plays a coadjutant role in the transition of mitochondrial permeability is indicated by the dramatic inhibitory effect of added o-phenanthroline. Iron released from ferritin by AA oxidation products--superoxide anion and AA enolyl radicals--is shown to act as an alternative source of ferrous iron, intensifying the mitochondrial damage. These findings may contribute to clarify the role of accumulated AA and iron overload in the mitochondrial oxidative damage reportedly occurring in diabetes mellitus.

Epilepsy and porphyria: new perspectives

Porphyria is a group of disorders caused by alterations in the enzymatic pathway involved in haem biosynthesis. The clinical picture consists of extraneurological and neurological manifestations, seizures being an important feature. The pathogenesis of seizures is probably related to metabolic imbalance such as hyponatremia and to the intrinsic epileptogenic role of some porphyrins. Many studies report that neural damage can follow a porphyric attack, suggesting that these lesions can be epileptogenic. Several reports also pointed out that porphyria can be precipitated by some antiepileptic drugs (AEDs). More recent AEDs appeared and need assessment in relation to porphyria. An educational program including a registry of patients with porphyria, an intensive study of family history and the genetic background may be useful to obtain better epidemiological data and a clearer understanding of pathogenesis. Application of neuroimaging may detect epileptogenic foci, helping to define the specific risk of seizures for each patient.