Metabolic and neurobehavioral disturbances induced by purine recycling deficiency in Drosophila

Adenine phosphoribosyltransferase (APRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT) are two structurally related enzymes involved in purine recycling in humans. Inherited mutations that suppress HGPRT activity are associated with Lesch-Nyhan disease (LND), a rare X-linked metabolic and neurological disorder in children, characterized by hyperuricemia, dystonia, and compulsive self-injury. To date, no treatment is available for these neurological defects and no animal model recapitulates all symptoms of LND patients. Here, we studied LND-related mechanisms in the fruit fly. By combining enzymatic assays and phylogenetic analysis, we confirm that no HGPRT activity is expressed in Drosophila melanogaster, making the APRT homolog (Aprt) the only purine-recycling enzyme in this organism. Whereas APRT deficiency does not trigger neurological defects in humans, we observed that Drosophila Aprt mutants show both metabolic and neurobehavioral disturbances, including increased uric acid levels, locomotor impairments, sleep alterations, seizure-like behavior, reduced lifespan, and reduction of adenosine signaling and content. Locomotor defects could be rescued by Aprt re-expression in neurons and reproduced by knocking down Aprt selectively in the protocerebral anterior medial (PAM) dopaminergic neurons, the mushroom bodies, or glia subsets. Ingestion of allopurinol rescued uric acid levels in Aprt-deficient mutants but not neurological defects, as is the case in LND patients, while feeding adenosine or N6-methyladenosine (m6A) during development fully rescued the epileptic behavior. Intriguingly, pan-neuronal expression of an LND-associated mutant form of human HGPRT (I42T), but not the wild-type enzyme, resulted in early locomotor defects and seizure in flies, similar to Aprt deficiency. Overall, our results suggest that Drosophila could be used in different ways to better understand LND and seek a cure for this dramatic disease.

Structural basis for substrate selectivity and nucleophilic substitution mechanisms in human adenine phosphoribosyltransferase catalyzed reaction

The reversible adenine phosphoribosyltransferase enzyme (APRT) is essential for purine homeostasis in prokaryotes and eukaryotes. In humans, APRT (hAPRT) is the only enzyme known to produce AMP in cells from dietary adenine. APRT can also process adenine analogs, which are involved in plant development or neuronal homeostasis. However, the molecular mechanism underlying substrate specificity of APRT and catalysis in both directions of the reaction remains poorly understood. Here we present the crystal structures of hAPRT complexed to three cellular nucleotide analogs (hypoxanthine, IMP, and GMP) that we compare with the phosphate-bound enzyme. We established that binding to hAPRT is substrate shape-specific in the forward reaction, whereas it is base-specific in the reverse reaction. Furthermore, a quantum mechanics/molecular mechanics (QM/MM) analysis suggests that the forward reaction is mainly a nucleophilic substitution of type 2 (S_N2) with a mix of S_N1-type molecular mechanism. Based on our structural analysis, a magnesium-assisted S_N2-type mechanism would be involved in the reverse reaction. These results provide a framework for understanding the molecular mechanism and substrate discrimination in both directions by APRTs. This knowledge can play an instrumental role in the design of inhibitors, such as antiparasitic agents, or adenine-based substrates.

Clinical, biochemical and genetic characteristics of a cohort of 101 French and Italian patients with HPRT deficiency

BACKGROUND

HPRT deficiency is a rare disorder of purine metabolism whose natural history is not fully understood. No optimal management recommendations exist. The objective of the present study is to characterize a large cohort of patients with HPRT deficiency, comparing Lesch-Nyhan Disease (LND) and its attenuated variants, with the purpose of helping clinicians in disease management and prognostic definition.

METHODS

Genetic and clinical features of French and Italian patients with a confirmed diagnosis of HPRT deficiency were collected.

RESULTS

A hundred and one patients were studied, including 66 LND, 22 HND (HPRT-related Neurological Dysfunction) and 13 HRH (HPRT-Related Hyperuricemia) patients. The clinical manifestations at onset were not specific, but associated with an orange coloration of diapers in 22% of patients. The overall neurological involvement was more severe in LND than in HND patients. Behavioural disturbances were not limited to self-injuries and were not exclusive of LND. Median age of involuntary movements and self-injuries appearance in LND was 1.0 and 3 years, respectively. Renal manifestations (66.3% of patients) occurred at any age with a median onset age of 1.1 years, while gout (25.7% of patients) appeared later in disease course (median onset age 18 years) and was more frequent in attenuated variants than in LND. HPRT activity and genotype showed a significant correlation with the severity of the neurological disease. On the contrary, there were no significant differences in the development of nephropathy or gout. For the treatment of neurological aspects, botulinum toxin injections, oral or intrathecal baclofen and gabapentin were partially efficacious and well tolerated, while deep brain stimulation was associated to a worsening of patients' condition.

CONCLUSIONS

The present study improves the knowledge of the natural history of HPRT deficiency and could represent a starting point for the development of future management guidelines.

Structural Insights into the Forward and Reverse Enzymatic Reactions in Human Adenine Phosphoribosyltransferase

Phosphoribosyltransferases catalyze the displacement of a PRPP α-1'-pyrophosphate to a nitrogen-containing nucleobase. How they control the balance of substrates/products binding and activities is poorly understood. Here, we investigated the human adenine phosphoribosyltransferase (hAPRT) that produces AMP in the purine salvage pathway. We show that a single oxygen atom from the Tyr105 side chain is responsible for selecting the active conformation of the 12 amino acid long catalytic loop. Using in vitro, cellular, and in crystallo approaches, we demonstrated that Tyr105 is key for the fine-tuning of the kinetic activity efficiencies of the forward and reverse reactions. Together, our results reveal an evolutionary pressure on the strictly conserved Tyr105 and on the dynamic motion of the flexible loop in phosphoribosyltransferases that is essential for purine biosynthesis in cells. These data also provide the framework for designing novel adenine derivatives that could modulate, through hAPRT, diseases-involved cellular pathways.

A comprehensive characterization of the impact of mycophenolic acid on the metabolism of Jurkat T cells

Metabolic reprogramming is critical for T cell fate and polarization and is regulated by metabolic checkpoints, including Myc, HIF-1α, AMPK and mTORC1. Our objective was to determine the impact of mycophenolic acid (MPA) in comparison with rapamycin (Rapa), an inhibitor of mTORC1, on the metabolism of Jurkat T cells. We identified a drug-specific transcriptome signature consisting of the key enzymes and transporters involved in glycolysis, glutaminolysis or nucleotide synthesis. MPA produced an early and transient drop in the intracellular ATP content related to the inhibition of de novo synthesis of purines, leading to the activation of the energy sensor AMPK. MPA decreases glycolytic flux, consistent with a reduction in glucose uptake, but also in the oxidation of glutamine. Additionally, both drugs reduce aerobic glycolysis. The expression of HIF-1α and Myc, promoting the activation of glycolysis and glutaminolysis, was inhibited by MPA and Rapa. In conclusion, we report that MPA profoundly impacts the cellular metabolism of Jurkat T cells by generating an energetic distress, decreasing the glycolytic and glutaminolytic fluxes and by targeting HIF-1α and Myc. These findings open interesting perspectives for novel combinatorial therapeutic strategies targeting metabolic checkpoints to block the proliferation of T cells.

Molecular insight into thiopurine resistance: transcriptomic signature in lymphoblastoid cell lines

Background

There has been considerable progress in the management of acute lymphoblastic leukemia (ALL) but further improvement is needed to increase long-term survival. The thiopurine agent 6-mercaptopurine (6-MP) used for ALL maintenance therapy has a key influence on clinical outcomes and relapse prevention. Genetic inheritance in thiopurine metabolism plays a major role in interindividual clinical response variability to thiopurines; however, most cases of thiopurine resistance remain unexplained.

Methods

We used lymphoblastoid cell lines (LCLs) from healthy donors, selected for their extreme thiopurine susceptibility. Thiopurine metabolism was characterized by the determination of TPMT and HPRT activity. We performed genome-wide expression profiling in resistant and sensitive cell lines with the goal of elucidating the mechanisms of thiopurine resistance.

Results

We determined a higher TPMT activity (+44%; P = 0.024) in resistant compared to sensitive cell lines, although there was no difference in HPRT activity. We identified a 32-gene transcriptomic signature that predicts thiopurine resistance. This signature includes the GTPBP4 gene coding for a GTP-binding protein that interacts with p53. A comprehensive pathway analysis of the genes differentially expressed between resistant and sensitive cell lines indicated a role for cell cycle and DNA mismatch repair system in thiopurine resistance. It also revealed overexpression of the ATM/p53/p21 pathway, which is activated in response to DNA damage and induces cell cycle arrest in thiopurine resistant LCLs. Furthermore, overexpression of the p53 target gene TNFRSF10D or the negative cell cycle regulator CCNG2 induces cell cycle arrest and may also contribute to thiopurine resistance. ARHGDIA under-expression in resistant cell lines may constitute a novel molecular mechanism contributing to thiopurine resistance based on Rac1 inhibition induced apoptosis and in relation with thiopurine pharmacodynamics.

Conclusion

Our study provides new insights into the molecular mechanisms underlying thiopurine resistance and suggests a potential research focus for developing tailored medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-015-0150-6) contains supplementary material, which is available to authorized users.

2,8-Dihydroxyadenine urolithiasis: a not so rare inborn error of purine metabolism

Adenine phosphoribosyltransferase (APRT) deficiency is a rare inherited metabolic disorder that leads to the formation and hyperexcretion of 2,8-dihydroxyadenine (DHA) into urine. The low solubility of DHA results in precipitation and formation of urinary crystals and kidney stones. The disease can be present as recurrent urolithiasis or nephropathy secondary to crystal precipitation into renal parenchyma (DHA nephropathy). The diagnostic tools available, including stone analysis, crystalluria, and APRT activity in red blood cells, make the diagnosis easy to confirm when APRT deficiency is suspected. However, the lack of recognition of this metabolic disorder frequently resulted in a delay in diagnosis and treatment with grave consequences. The early recognition and treatment of APRT deficiency are of crucial importance to prevent irreversible loss of renal function. This review summarizes the genetic and metabolic mechanisms underlying DHA stones formation and chronic kidney disease, along with the issues of diagnosis and management of APRT deficiency. Moreover, we report the mutations in the APRT gene responsible for APRT deficiency in 51 French patients (43 families) including 22 pediatric cases (18 families) among the 64 patients identified in the biochemistry laboratories of Necker Hospital, Paris (1978-2013).

Transcriptomic approach to Lesch-Nyhan disease

Lesch-Nyhan disease (LND) is an X-linked metabolic disease caused by various mutations in the gene HPRT1 encoding an enzyme of purine metabolism, hypoxanthine guanine phosphoribosyltransferase (HPRT). In its most severe form, LND patients suffer from overproduction of uric acid along with neurological or behavioural difficulties including self-injurious behaviours. To gain more insight into pathogenesis, we compared the transcriptome from human LND fibroblasts to normal human fibroblasts using a microarray with 60,000 probes corresponding to the entire human genome. Using stringent criteria, we identified 25 transcripts whose expression was significantly different between LND and control cells. These genes were confirmed by quantitative RT-PCR to be dysregulated in LND cells. Moreover, bioinformatic analysis of microarray data using gene ontology (GO) highlighted clusters of genes displaying biological processes most significantly affected in LND cells. These affected genes belonged to specific processes such as cell cycle and cell-division processes, metabolic and nucleic acid processes, demonstrating the specific nature of the changes and providing new insights into LND pathogenesis.

New biomarkers for early diagnosis of Lesch-Nyhan disease revealed by metabolic analysis on a large cohort of patients

BACKGROUND

Lesch-Nyhan disease is a rare X-linked neurodevelopemental metabolic disorder caused by a wide variety of mutations in the HPRT1 gene leading to a deficiency of the purine recycling enzyme hypoxanthine-guanine phosphoribosyltransferase (HGprt). The residual HGprt activity correlates with the various phenotypes of Lesch-Nyhan (LN) patients and in particular with the different degree of neurobehavioral disturbances. The prevalence of this disease is considered to be underestimated due to large heterogeneity of its clinical symptoms and the difficulty of diagnosing of the less severe forms of the disease. We therefore searched for metabolic changes that would facilitate an early diagnosis and give potential clues on the disease pathogenesis and potential therapeutic approaches.

METHODS

Lesch-Nyhan patients were diagnosed using HGprt enzymatic assay in red blood cells and identification of the causal HPRT1 gene mutations. These patients were subsequently classified into the three main phenotypic subgroups ranging from patients with only hyperuricemia to individuals presenting motor dysfunction, cognitive disability and self-injurious behavior. Metabolites from the three classes of patients were analyzed and quantified by High Performance Ionic Chromatography and biomarkers of HGprt deficiency were then validated by statistical analyses.

RESULTS

A cohort of 139 patients, from 112 families, diagnosed using HGprt enzymatic assay in red blood cells, was studied. 98 displayed LN full phenotype (86 families) and 41 (26 families) had attenuated clinical phenotypes. Genotype/phenotype correlations show that LN full phenotype was correlated to genetic alterations resulting in null enzyme function, while variant phenotypes are often associated with missense mutations allowing some residual HGprt activity. Analysis of metabolites extracted from red blood cells from 56 LN patients revealed strong variations specific to HGprt deficiency for six metabolites (AICAR mono- and tri-phosphate, nicotinamide, nicotinic acid, ATP and Succinyl-AMP) as compared to controls including hyperuricemic patients without HGprt deficiency.

CONCLUSIONS

A highly significant correlation between six metabolites and the HGprt deficiency was established, each of them providing an easily measurable marker of the disease. Their combination strongly increases the probability of an early and reliable diagnosis for HGprt deficiency.

Lesch Nyhan syndrome: a novel complex mutation in a Tunisian child

Lesch Nyhan syndrome (LNS) is an X-linked recessive disorder due to complete deficiency of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) enzyme. Defect of the enzymatic activity is related to mutations of the HPRT1 gene. The disorder severity is due to neurological features and renal complications. Up to now, more than 300 mutations have been reported. We report on a Tunisian child with a severe phenotype due to a novel identified complex mutation.

Recurrent 2,8-dihydroxyadenine nephropathy: a rare but preventable cause of renal allograft failure

Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive enzyme defect of purine metabolism that usually manifests as 2,8-dihydroxyadenine (2,8-DHA) nephrolithiasis and more rarely chronic kidney disease. The disease is most often misdiagnosed and can recur in the renal allograft. We analyzed nine patients with recurrent 2,8-DHA crystalline nephropathy, in all of whom the diagnosis had been missed prior to renal transplantation. The diagnosis was established at a median of 5 (range 1.5-312) weeks following the transplant procedure. Patients had delayed graft function (n=2), acute-on-chronic (n=5) or acute (n=1) allograft dysfunction, whereas one patient had normal graft function at the time of diagnosis. Analysis of allograft biopsies showed birefringent 2,8-DHA crystals in renal tubular lumens, within tubular epithelial cells and interstitium. Fourier transformed infrared microscopy confirmed the diagnosis in all cases, which was further supported by 2,8-DHA crystalluria, undetectable erythrocyte APRT enzyme activity, and genetic testing. With allopurinol therapy, the allograft function improved (n=7), remained stable (n=1) or worsened (n=1). At last follow-up, two patients had experienced allograft loss and five had persistent chronic allograft dysfunction. 2,8-DHA nephropathy is a rare but underdiagnosed and preventable disorder that can recur in the renal allograft and may lead to allograft loss.

Phenotypic variation among seven members of one family with deficiency of hypoxanthine-guanine phosphoribosyltransferase

We describe a family of seven boys affected by Lesch-Nyhan disease with various phenotypes. Further investigations revealed a mutation c.203T>C in the gene encoding HGprt of all members, with substitution of leucine to proline at residue 68 (p.Leu68Pro). Thus patients from this family display a wide variety of symptoms although sharing the same mutation. Mutant HGprt enzyme was prepared by site-directed mutagenesis and the kinetics of the enzyme revealed that the catalytic activity of the mutant was reduced, in association with marked reductions in the affinity towards phosphoribosylpyrophosphate (PRPP). Its Km for PRPP was increased 215-fold with hypoxanthine as substrate and 40-fold with guanine as substrate with associated reduced catalytic potential. Molecular modeling confirmed that the most prominent defect was the dramatically reduced affinity towards PRPP. Our studies suggest that the p.Leu68Pro mutation has a strong impact on PRPP binding and on stability of the active conformation. This suggests that factors other than HGprt activity per se may influence the phenotype of Lesch-Nyhan patients.

Adenine phosphoribosyltransferase deficiency

Complete adenine phosphoribosyltransferase (APRT) deficiency is a rare inherited metabolic disorder that leads to the formation and hyperexcretion of 2,8-dihydroxyadenine (DHA) into urine. The low solubility of DHA results in precipitation of this compound and the formation of urinary crystals and stones. The disease can present as recurrent urolithiasis or nephropathy secondary to crystal precipitation into renal parenchyma (DHA nephropathy). The diagnostic tools available-including stone analysis, crystalluria, and APRT activity measurement-make the diagnosis easy to confirm when APRT deficiency is suspected. However, the disease can present at any age, and the variability of symptoms can present a diagnostic challenge to many physicians. The early recognition and treatment of APRT deficiency are of crucial importance for preventing irreversible loss of renal function, which still occurs in a non-negligible proportion of cases. This review summarizes the genetic and metabolic mechanisms underlying stone formation and renal disease, along with the diagnosis and management of APRT deficiency.

Adenine phosphoribosyltransferase deficiency in children

Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive disorder characterized by 2,8-dihydroxyadenine (2,8-DHA) crystalluria that can cause nephrolithiasis and chronic kidney disease. The aim of our study was to assess the clinical presentation, diagnosis, and outcome of APRT deficiency in a large pediatric cohort. All pediatric cases of APRT deficiency confirmed at the same French reference laboratories between 1978 and 2010 were retrospectively reviewed. Twenty-one patients from 18 families were identified. The median age at diagnosis was 3 years. Diagnosis was made after one or more episodes of nephrolithiasis (17 patients), after urinary tract infection (1 patient), and by family screening (3 patients). The diagnosis was based on stone analysis and microscopic examination of urine and/or enzymatic determination of APRT on red blood cells. All children had null APRT enzyme activity in erythrocytes. APRT gene sequencing was performed on 18 patients, revealing six homozygous and 12 compound heterozygous mutations. At diagnosis, half of the patients had decreased kidney function, and two children presented with acute renal failure. Allopurinol treatment was given to all patients at a median dose of 9 mg/kg/day. After a median follow-up of 5 years, all patients showed stabilization or improvement of kidney function, normal growth and development, and six patients had recurrence of nephrolithiasis. Based on these results, we conclude that an excellent outcome can be achieved in children with APRT deficiency who receive the proper treatment.

Decreased kidney function and crystal deposition in the tubules after kidney transplant

Adenine phosphoribosyltransferase (APRT) deficiency is an autosomal recessive purine enzyme defect that results in the inability to utilize adenine, which consequently is oxidized by xanthine dehydrogenase to 2,8-dihydroxyadenine (2,8-DHA), an extremely insoluble substance eventually leading to crystalluria, nephrolithiasis, and kidney injury. We describe a case of APRT deficiency not diagnosed until the evaluation of a poorly functioning kidney transplant in a 67-year-old white woman. After the transplant, there was delayed transplant function, urine specimens showed crystals with unusual appearance, and the transplant biopsy specimen showed intratubular obstruction by crystals identified as 2,8-DHA using infrared spectroscopy. APRT enzymatic activity was undetectable in red blood cell lysates, and analysis of the APRT gene showed 1 heterozygous sequence variant, a duplication of T at position 1832. The patient was treated with allopurinol, 300 mg/d, and transplant function progressively normalized. Because patients with undiagnosed APRT deficiency who undergo kidney transplant may risk losing the transplant because of an otherwise treatable disease, increased physician awareness may hasten the diagnosis and limit the morbidity associated with this disease.

Phenotype and genotype characterization of adenine phosphoribosyltransferase deficiency

Adenine phosphoribosyltransferase (APRT) deficiency is a rare autosomal recessive disorder causing 2,8-dihydroxyadenine stones and renal failure secondary to intratubular crystalline precipitation. Little is known regarding the clinical presentation of APRT deficiency, especially in the white population. We retrospectively reviewed all 53 cases of APRT deficiency (from 43 families) identified at a single institution between 1978 and 2009. The median age at diagnosis was 36.3 years (range 0.5 to 78.0 years). In many patients, a several-year delay separated the onset of symptoms and diagnosis. Of the 40 patients from 33 families with full clinical data available, 14 (35%) had decreased renal function at diagnosis. Diagnosis occurred in six (15%) patients after reaching ESRD, with five diagnoses made at the time of disease recurrence in a renal allograft. Eight (20%) patients reached ESRD during a median follow-up of 74 months. Thirty-one families underwent APRT sequencing, which identified 54 (87%) mutant alleles on the 62 chromosomes analyzed. We identified 18 distinct mutations. A single T insertion in a splice donor site in intron 4 (IVS4 + 2insT), which produces a truncated protein, accounted for 40.3% of the mutations. We detected the IVS4 + 2insT mutation in two (0.98%) of 204 chromosomes of healthy newborns. This report, which is the largest published series of APRT deficiency to date, highlights the underdiagnosis and potential severity of this disease. Early diagnosis is crucial for initiation of effective treatment with allopurinol and for prevention of renal complications.

Severe gouty arthritis and mild neurologic symptoms due to F199C, a newly identified variant of the hypoxanthine guanine phosphoribosyltransferase

A deficiency in hypoxanthine guanine phosphoribosyltransferase (HPRT) activity leads to overproduction of uric acid. According to the degree of enzymatic deficiency, a large spectrum of neurologic features can also be observed, ranging from mild or no neurologic involvement to complete Lesch-Nyhan disease. Herein, we describe a patient with hyperuricemia, juvenile-onset gouty arthritis, nephrolithiasis, and mild neurologic symptoms, attributed to a newly identified variant of the hprt gene, c.596T>G, resulting in the amino acid change p.F199C. Residual HPRT activity (8%) protected against severe neurologic involvement in this patient. Modeling of the mutated protein was used to predict the mechanisms that led to partial enzymatic activity. Careful neurologic examination is warranted in juvenile and middle-aged patients with gout, in order to detect mild symptoms that may lead to a diagnosis of HPRT deficiency.

Consequences of impaired purine recycling in dopaminergic neurons

A unique sensitivity to specific biochemical processes is responsible for selective vulnerability of midbrain dopamine neurons in several diseases. Prior studies have shown these neurons are susceptible to energy failure and mitochondrial dysfunction, oxidative stress, and impaired disposal of misfolded proteins. These neurons also are especially vulnerable to the loss of purine recycling. In the brains of humans or mice with inherited defects of the purine recycling enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT), the most prominent defect is loss of basal ganglia dopamine. To investigate the nature of the relationship between HPRT deficiency and dopamine, the mouse MN9D dopaminergic neuronal cell line was used to prepare 10 sublines lacking HPRT. The mutant sublines grew more slowly than the parent line, but without morphological signs of impaired viability. As a group, the mutant sublines had significantly lower dopamine than the parent line. The loss of dopamine in the mutants did not reflect impaired energy status, as judged by ATP levels or vulnerability to inhibitors of energy production. Indeed, the mutant lines as a group appeared energetically more robust than the parent line. The loss of dopamine also was not accompanied by enhanced susceptibility to oxidative stress or proteasome inhibitors. Instead, the loss of dopamine reflected only one aspect of a broad change in the molecular phenotype of the cells affecting mRNAs encoding tyrosine hydroxylase, the dopamine transporter, the vesicular monoamine transporter, monoamine oxidase B, catechol-O-methyltransferase, and GTP-cyclohydrolase. These changes were selective for the dopamine phenotype, since multiple control mRNAs were normal. These studies suggest purine recycling is an intrinsic metabolic process of particular importance to the molecular phenotype of dopaminergic neurons independent of previously established mechanisms involving energy failure, oxidative stress, or proteasome dysfunction.

Reconsideration of the proposed luteotropic and luteoprotective actions of ovine placental lactogen in sheep: in vivo and in vitro studies

Ovine placental lactogen (oPL) is produced by the conceptus trophectoderm and is secreted into both the maternal and fetal circulations. The present study was designed to examine in vivo the luteotropic effect of recombinant oPL (roPL), as determined by monitoring progesterone concentration and cycle length (experiment 1), and the antioxidative and antiapoptotic effects of roPL, as determined respectively by monitoring antioxidant enzymatic activity and apoptosis in the corpus luteum (CL) of cyclic ewes (experiment 2). We also studied whether roPL is capable of stimulating progesterone secretion in vitro by cultured luteal tissue of functionally active CL obtained from day-10 cyclic ewes (experiment 3) and day-60 pregnant ewes (experiment 4). Circulating concentrations of progesterone and cycle length were not affected by treatment of ewes with 80 microg/kg body weight per day of roPL (n = 4 ewes) for 10 days beginning on day 11 post-estrus, as compared with saline-treated ewes (n = 4 ewes). Luteolysis occurred between days 15 and 16 post-estrus in the four saline-treated ewes and in 3/4 roPL-treated ewes. The activities of the key antioxidant enzymes copper-zinc superoxide dismutase (Cu,Zn-SOD), manganese SOD (Mn-SOD), glutathione peroxidase (GPX), glutathione reductase (GSR) and glutathione S-transferase (GST) were unaffected by treatment of ewes with 80 microg/kg per day of roPL (n = 4 ewes) for 3 days, between days 11 and 14 post-estrus, as compared with saline-treated ewes (n = 4 ewes). In situ TUNEL method revealed that the number of apoptotic cells was not different between the two groups of ewes. There was no significant change in progesterone secretion by explants from day-10 estrous cycle (n = 3 ewes) or day-60 pregnancy (n = 3 ewes) CL cultured with different concentrations (10, 100 and 1000 ng/ml) of roPL, whereas treatment with oLH at the concentration of 100 or 1000 ng/ml caused a significant increase in progesterone secretion by explants from day-10 estrous cycle CL (P < 0.05) and by explants from day-60 pregnancy CL (P < 0.01). In conclusion, our results demonstrate that oPL has no luteotropic and/or luteoprotective actions in sheep, either in vivo or in vitro.

Changes in activities of superoxide dismutase, nitric oxide synthase, glutathione-dependent enzymes and the incidence of apoptosis in sheep corpus luteum during the estrous cycle

Anti-oxidative enzymes play a role in protecting cells from oxidative stress-induced cell death. The present study was conducted to evaluate whether the anti-oxidant and pro-oxidant enzymatic capacities of the sheep corpus luteum (CL) are correlated with steroidogenic and structural status of the gland during the estrous cycle. Steroidogenic activity, apoptosis and superoxide dismutase (SOD1 and SOD2), nitric oxide synthase (NOS), glutathione peroxidase (GPX), glutathione reductase (GSR) and glutathione S-transferase (GST) activities were determined in the CL at specific developmental stages of the luteal phase. The intensity of apoptotic DNA fragmentation, characteristic of physiological cell death, was much greater in CL at late luteal phase than at early and mid-luteal phase, concomitantly with the diminution in the plasma progesterone concentrations from mid-to late luteal phase. SOD1 and GPX activities increased from early to mid-luteal phase, and increased further at late luteal phase. SOD2 and GST activities were not different between early and mid-luteal phase, but increased at late luteal phase. GSR activity was not different between any luteal phase examined. NOS activity decreased from early to mid- and late luteal phase. These results show that the activities of SOD1, SOD2, NOS, GPX, GSR and GST in the sheep CL are subject to major changes during the estrous cycle, and that the anti-oxidant and pro-oxidant enzymatic capacities of luteal cells are not correlated with cell steroidogenic status and integrity during the late luteal phase.

Antioxidant enzymatic defence systems in sheep corpus luteum throughout pregnancy

The activities of copper, zinc-superoxide dismutase (SOD1), manganese SOD (SOD2), glutathione peroxidase (GPX), glutathione reductase (GSSG-R) and glutathione S-transferase (GST) were studied in sheep corpora lutea (CL) obtained on days 15, 40, 60, 80 and 128 of pregnancy. Maintained enzymatic activity of SOD1, SOD2, GPX, GSSG-R and GST were found in the sheep CL throughout pregnancy. Enzymatic activity of SOD1, GPX and GST increased significantly from day 15 to day 40 of pregnancy, and thereafter remained constant until day 128. SOD2 and GSSG-R activities were not different between any days of pregnancy examined. Apoptotic luteal cells identified by the terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick-end labelling were very rarely observed, and their incidence (less than 0.5%) was not different between days of pregnancy. These results showed that the activities of antioxidant enzymes in the sheep CL are subject to major changes during early pregnancy, suggesting that the CL of early pregnancy may be rescued from luteolysis through increasing activities of key antioxidant enzymes and inhibition of apoptosis. Maintained levels of antioxidant enzymes in the CL throughout pregnancy may be linked to reactive oxygen species continuously generated in the steroidogenically active luteal cells, and may be involved in the maintenance of luteal steroidogenic activity and cellular integrity.

Examination of stress-related genes in human temporal versus occipital cortex in the course of neurodegeneration: involvement of 14-3-3 zeta in this dynamic process

The progressive invasion of the brain by neurofibrillary tangles characterized by paired helical filaments (PHF) along a precise network is stereotypical and hierarchical from normal aging to severe Alzheimer's disease. We describe here the differential expression of genes in the temporal area with PHF compared with the occipital area non-affected by PHF in cases with cognitive impairment versus the same cortical regions of control human brains without PHF. A stronger overexpression for 14-3-3 zeta gene is demonstrated in the affected temporal cortex of cases with cognitive impairment than in cases with normal mental status. This data obtained directly from human brains confirmed a 14-3-3 zeta implication in the Alzheimer's neuropathology.

Expression and activity of cyclin-dependent kinases and glycogen synthase kinase-3 during NT2 neuronal differentiation

In the presence of retinoic acid undifferentiated NT2 cells turn into terminally differentiated hNT (or NT2N) neurons within 5 weeks. We have used this in vitro cellular model to investigate the changes in expression and activity of cyclin-dependent kinases (CDKs) and glycogen synthase kinase-3 (GSK-3) during this neuronal differentiation process. We here show that CDK1/2 protein level and kinase activity sharply decrease during the NT2-->hNT transition. In contrast, the activity of CDK5/p35 dramatically increases, probably as a result of an enhanced expression of p35 in a stable CDK5 level background. GSK-3 activity increases modestly during the differentiation of hNT cells, and this event correlates with enhanced expression of each of the three GSK-3 isoforms. Pharmacological inhibitors of CDKs and GSK-3 lead to a dose-dependent decrease in cell viability.

Kelley-Seegmiller syndrome due to a new variant of the hypoxanthine-guanine phosphoribosyltransferase (I136T) encoding gene (HPRT Marseille)

A patient with hyperuricaemia and gouty arthritis due to a new variant of hypoxanthine-guanine phosphoribosyltransferase is described. The mutation (I136T, HPRT Marseille) is in the phosphoribosylpyrophosphate-binding region of the gene and leads to almost total loss of enzyme activity in erythrocytes, with 5% in lymphocytes. Nevertheless, the patient showed no neurological abnormality.

Intrafamilial variability in the phenotypic expression of adenylosuccinate lyase deficiency: a report on three patients

We report on the striking variable expression of adenylosuccinate lyase (ADSL) deficiency in three patients belonging to a family which originates from Portugal. ADSL deficiency is a rare autosomal recessive disorder of the de novo purine synthesis which results in accumulation of succinylpurines in body fluids. As a result, patients may have variable combinations of psychomotor retardation and/or regression, seizures, autistic features and cerebellar vermis hypoplasia. However, intrafamilial variable expression of the phenotype has not been documented to date in this disease and is not commonly observed in metabolic disorders. Here, while the proband had marked psychomotor regression and progressive cerebellar vermis atrophy, the other two affected patients presented mainly autistic features. Mutation analysis of the ADSL gene revealed the presence of a homozygous R426H mutation in this family. Finally, although ADSL deficiency is a rare disorder, this diagnosis should be considered and assessed using a simple urinary screening method for the presence of succinylpurines in any patient with mental retardation of unexplained origin.

Aloisines, a new family of CDK/GSK-3 inhibitors. SAR study, crystal structure in complex with CDK2, enzyme selectivity, and cellular effects

Cyclin-dependent kinases (CDKs) regulate the cell cycle, apoptosis, neuronal functions, transcription, and exocytosis. The observation of CDK deregulations in various pathological situations suggests that CDK inhibitors may have a therapeutic value. In this article, we report on the identification of 6-phenyl[5H]pyrrolo[2,3-b]pyrazines (aloisines) as a novel potent CDK inhibitory scaffold. A selectivity study performed on 26 kinases shows that aloisine A is highly selective for CDK1/cyclin B, CDK2/cyclin A-E, CDK5/p25, and GSK-3 alpha/beta; the two latter enzymes have been implicated in Alzheimer's disease. Kinetic studies, as well as the resolution of a CDK2-aloisine cocrystal structure, demonstrate that aloisines act by competitive inhibition of ATP binding to the catalytic subunit of the kinase. As observed with all inhibitors reported so far, aloisine interacts with the ATP-binding pocket through two hydrogen bonds with backbone nitrogen and oxygen atoms of Leu 83. Aloisine inhibits cell proliferation by arresting cells in both G1 and G2.

The Ginkgo biloba extract EGb 761 increases viability of hnt human neurons in culture and affectsthe expression of genes implicated in the stress response

There are numerous studies describing the neuroprotective effects of Ginkgo biloba extract EGb 761 on patients with disturbances of vigilance, memory and cognitive functions associated with aging and senility. Describing the pattern of gene expression in EGb 761-treated human hNT neurons may elucidate the molecular pathways leading to the neuroprotection. We used cDNA macroarrays including genes implicated in the antioxidant and stress responses to define the transcriptional effects of EGb 761 (250 microg/ml, 24 hr) on human hNT neurons. Seven genes were identified whose expression was strongly modified by the EGb 761 treatment. Three groups are distinguished: genes encoding transcription factors (increase of NF-kappaB p65 subunit and zinc finger protein 91 mRNAs, and decrease of c-myc transcripts), genes involved in antioxidant defenses (increase of the CuZn SOD mRNAs, and decrease of glutathione reductase and glutathione S-transferase pi mRNAs) and genes involved in stress responses (up-regulation of HSP70 transcripts). Consistent with the modulation of mRNAs by EGb 761, the enzymatic activities of glutathione reductase and glutathione S-transferase were decreased. Surprisingly, CuZn SOD activity was decreased despite increased abundance of the mRNAs; furthermore MnSOD activity was unmodified, and thus the effect of EGb 761 was specific to CuZn SOD. These results support the idea that modulation of target genes and transcription factors may be involved in the neuroprotective action of EGb 761.

The amyloid peptide induces early genotoxic damage in human preneuron NT2

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the extracellular deposition of amyloid beta-peptide (Abeta) in the brain. Abeta is involved in the pathogenesis of AD but the molecular mechanisms of its neurotoxicity are unknown. Here, we report that Abeta exposure on human preneuronal NT2 cells provoked a strong and early up-regulation of growth arrest and DNA damage inducible gene (Gadd45 mRNA), an indicator of DNA damage and DNA excision-repair processes, strongly suggesting that Abeta causes an early DNA strand breakage leading to a cellular DNA repair response. Comet assay clearly demonstrated that both full-length Abeta (1-42), and its minimal cytotoxic fragment Abeta (25-35), caused DNA breakage as early as 3h after the start of Abeta exposure. This extensive DNA damage provoked by Abeta constitutes an early event in the pathogenic cascade leading to neuronal death which could contribute to the neuropathogenesis of AD.

Human cultured skin fibroblasts survive profound inherited ubiquinone depletion

Beside its role in electron transfer in the mitochondrial respiratory chain, ubiquinone is known to prevent lipid peroxidation and DNA damage by trapping cellular free radicals. Thanks to its antioxidant properties, ubiquinone may represent an important factor controlling both necrotic and apoptotic processes. We have investigated the consequences of a profound inherited ubiquinone depletion on cultured skin fibroblasts of a patient presenting with encephalomyopathy. Interestingly, cell respiration, mitochondrial oxidation of various substrates, and cell growth of ubiquinone-deficient fibroblasts were only partially decreased. Moreover, these cells did not apparently overproduce superoxide anions or lipoperoxides. Finally, apoptosis did not increase as compared to control, even after serum deprivation. These observations suggest that ubiquinone may not play a major role in the antioxidant defenses of cultured fibroblasts and that its role in controlling oxidative stress and apoptosis may greatly vary across cell types, especially as not all tissues were equally affected in the patient despite the widespread ubiquinone depletion in vivo.

Synaptic sprouting increases the uptake capacities of motoneurons in amyotrophic lateral sclerosis mice

Using adenoviruses encoding reporter genes as retrograde tracers, we assessed the capacity of motoneurons to take up and retrogradely transport adenoviral particles injected into the muscles of transgenic mice expressing the G93A human superoxide dismutase mutation, a model of amyotrophic lateral sclerosis. Surprisingly, transgene expression in the motoneurons was significantly higher in symptomatic mice than in control or presymptomatic mice. Using botulinum toxin to induce nerve sprouting at neuromuscular junctions, we showed that the unexpectedly high level of motoneurons retrograde transduction results, at least in part, from newly acquired uptake properties of the sprouts. These findings demonstrate the remarkable uptake properties of amyotrophic lateral sclerosis motoneurons in response to denervation and the rationale of using intramuscular injections of adenoviruses to overexpress therapeutic proteins in motor neuron diseases.

Overproduction of Cu/Zn-superoxide dismutase or Bcl-2 prevents the brain mitochondrial respiratory dysfunction induced by glutathione depletion

Recent work has focused attention on the role of oxidative stress in various acute and chronic neurodegenerative diseases. Low concentrations of the powerful antioxidant glutathione (GSH) and impaired brain energy metabolism, particularly in the substantia nigra, are key features of Parkinson's disease (PD). The main goal of this study was to better characterize the deleterious effects of brain GSH depletion on mitochondrial function. We depleted GSH in the brains of newborn wild-type (WT) and transgenic (Tg) mice overproducing either human Cu/Zn-superoxide dismutase (h-CuZnSOD) or human Bcl2 (h-Bcl-2), by subcutaneous injection of l-buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase. GSH was 97% depleted in brain homogenates and 90% depleted in brain mitochondria for both WT and Tg mice. This depletion of brain GSH led to a decrease in the activity of the GSH-dependent antioxidant enzyme glutathione peroxidase, both in WT and in Tg animals. BSO treatment decreased the activities of respiratory complexes I, II, and IV in the brain homogenates of WT mice. BSO-treated h-CuZnSOD or h-Bcl-2 Tg mice had no respiratory chain deficiencies. Thus, brain GSH depletion leads to the impairment of mitochondrial respiratory chain activity. The protection of mitochondrial respiratory function by overproduction of Bcl-2 may result from a decrease in the generation of reactive oxygen species (ROS) or lipid peroxidation. The protection of mitochondria by overproduction of CuZnSOD is consistent with the involvement of superoxide or superoxide-derived ROS in the mitochondrial dysfunction caused by brain GSH depletion. This study demonstrates that the antioxidant balance is critical for maintenance of brain mitochondrial function, and its disruption may contribute to the pathogenesis of PD.

Transgenic murine cortical neurons expressing human Bcl-2 exhibit increased resistance to amyloid beta-peptide neurotoxicity

The generation of reactive oxygen species has been implicated in the neurotoxicity of amyloid beta-peptide, the main constituent of the senile plaques that accumulates in the brain of Alzheimer's disease victims. In this study, we have compared the toxicity of amyloid beta-peptide on cultured cortical neurons from control mice and transgenic mice expressing either human copper-zinc superoxide dismutase or human Bcl-2, two proteins that protect cells against oxidative damage. Copper-zinc superoxide dismutase overexpression failed to protect cortical neurons against the toxicity of amyloid beta-peptide(25-35) [the minimal cytotoxic fragment of amyloid beta-peptide(1-42)] as assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction and an enzyme-linked immunoabsorbent assay using an antibody directed against microtubule-associated protein-2 (a specific neuronal protein), ruling out a role for superoxide anion and peroxynitrite in amyloid beta-peptide-evoked neurotoxicity. On the contrary, cortical neurons expressing human copper-zinc superoxide dismutase exhibited increased apoptotic nuclei in both untreated and amyloid beta-peptide(25-35)-exposed neurons. Transgenic neurons expressing human Bcl-2 were partially protected against amyloid beta-peptide-induced neuronal death. This neuroprotection appears to be related to the complete inhibition of apoptosis induced by both amyloid beta-peptide(25-35) and amyloid beta-peptide(1-42). This study may be relevant for developing neuroprotective gene therapy to inhibit neuronal apoptosis in Alzheimer's disease.

Identification of beta-amyloid-responsive genes by RNA differential display: early induction of a DNA damage-inducible gene, gadd45

Alzheimer's disease is a neurodegenerative disorder characterized by the extracellular deposition in the brain of amyloid beta-peptide (A beta), presumed to play a pathogenic role. However, the precise molecular mechanisms of its neurotoxicity are not fully understood. Recent studies have suggested that it may exert its toxic effect via activation of transcription factors. We investigated A beta-responsive genes in human preneuron NT2 cells, at early stages of A beta (25-35) exposure, by RNA differential display. A beta induced the expression of (i) the growth arrest and DNA damage-inducible gene (gadd45) implicated in the DNA excision-repair process; (ii) a stress-signaling kinase gene encoding the mitogen-activated protein kinase/Erk kinase kinase-1 (MEKK1); (iii) a new growth factor-inducible immediate-early gene, CYR61, the product of which functions as an extracellular matrix signaling molecule; (iv) other immediate-early genes, such as c-jun and c-fos; (v) the gene encoding the basic fibroblast growth factor (bFGF); (vi) a gene encoding a constituent of the mitochondrial pyruvate dehydrogenase complex, the dihydrolipoamide dehydrogenase-binding protein (E3-BP); and (vii) an unidentified human gene (KIAA0099). A beta not only activates but also respresses genes: (i) the gene encoding "hinge" protein, a subunit of the mitochondrial cytochrome-c reductase and (ii) the SRp55 gene encoding a splicing factor involved in constitutive pre-mRNA splicing and alternative splice site selection. Our results underscored A beta-responsive genes that play key roles in the response (damage/recovery) of neuron cells to A beta exposure. In particular, the strong upregulation of gadd45, indicating DNA damage, was detected early in A beta cytotoxicity. This suggests that DNA strand breaks occurred rapidly in cells exposed to A beta, which may be a critical event in A beta neurotoxicity.

Reduction of ischemic damage in NGF-transgenic mice: correlation with enhancement of antioxidant enzyme activities

If permanent focal ischemia is induced by middle cerebral artery occlusion (MCAO), neurons within the infarcted territory die by necrosis and apoptosis (or programmed cell death). We have previously shown, using a mouse strain transgenic (tg) for the nerve growth factor (NGF) gene, that tg mice have consistently smaller infarcted areas than wild-type (wt) animals, correlated with upregulated NGF synthesis and impaired apoptotic cell death. We studied, in wt and tg mice subjected to MCAO, the activities of several antioxidant enzymes and the synthesis of the proteins of the Bcl-2 family. Our results show that the antiapoptotic Bcl-2 protein and glutathione peroxidase are recruited after MCAO. NGF-tg mice also had an intrinsic resistance to oxidative stress because their basal copper zinc superoxide dismutase (SOD) and glutathione transferase activities were high. Additionally, manganese SOD activity increased in NGF-tg mice after MCAO, correlating strongly with the resistance of these mice to apoptosis.

Direct evidence for glutathione as mediator of apoptosis in neuronal cells

Recent evidence has focused attention on the role of oxidative stress in various acute and chronic neurodegenerative diseases. Particularly, a decrease in the level of the powerful antioxidant glutathione (GSH) and death of dopaminergic neurons in substantia nigra are prominent features in Parkinson's disease. The mode of neuronal death is uncertain; however, apoptosis has been hypothesized to be mediated through the induction of free radicals via oxidative pathways. An approach to determine the role of GSH depletion in neurodegeneration and apoptosis was to create a selective modulation of this antioxidant by metabolic manipulations in a clonal cell line of neuronal origin (mouse neuroblastoma NS20Y). Intracellular GSH levels was lowered by inhibiting its biosynthesis with L-buthionine-(S,R)-sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase. This treatment led to a GSH depletion of 50% after 1 h and 98% after 24 h. A direct cause/effect relationship between GSH depletion and apoptosis was evidenced in this neuronal cell type. GSH depletion induced the death of NS20Y and promoted nuclear alterations of apoptosis as demonstrated by the in situ staining of DNA fragmentation after 5 days of BSO treatment (by terminal-deoxynucleotide transferase-mediated dUTP-nick end labeling), and the appearance of DNA laddering on agarose gel. These results suggested that redox desequilibrium induced by GSH depletion may serve as a general trigger for apoptosis in neuronal cells, and are consistent with the hypothesis that GSH depletion contribute to neuronal death in Parkinson's disease.

Recruitment of several neuroprotective pathways after permanent focal ischemia in mice

After an ischemic episode induced by the electrocoagulation of the left middle cerebral artery (MCA) in mouse, neurons within the damaged territory die either by an apoptotic or by a necrotic process. Most of the cortical neurons within the ischemic area display both morphological and biochemical signs of programmed cell death: nuclear condensation, DNA degradation, formation of apoptotic bodies, and glutathione depletion. In fact, apoptosis essentially contributes to the expansion of the ischemic lesion and the maximum of damaged territory is reached 24 h postocclusion. Several potentially neuroprotective pathways have been evidenced in different experimental models of ischemia including the activation of antioxidant enzyme activities and/or the recruitment of neurotrophic as well as antiapoptotic factors. In our model of permanent focal ischemia induced by MCA occlusion, we measured the temporal synthesis of nerve growth factor (NGF) and examined the status of antioxidant enzymes as well as Bcl-2 antiapoptotic product. We detected in both cortices a transient increase of NGF which peaks at 6 h. Moreover, we reported that glutathione peroxidase is recruited with a time course which parallels NGF synthesis. Finally, we observed the induction of Bcl-2 in safe neurons; this may represent a self-protective response against ischemia-induced apoptosis. We provide evidence that in a model of permanent focal ischemia, several neuroprotective pathways could be coactivated.

Mitochondrial impairment as an early event in the process of apoptosis induced by glutathione depletion in neuronal cells: relevance to Parkinson's disease

In Parkinson's disease (PD), dopaminergic cell death in the substantia nigra was associated with a profound glutathione (GSH) decrease and a mitochondrial dysfunction. The fall in GSH concentration seemed to appear before the mitochondrial impairment and the cellular death, suggesting that a link may exist between these events. The relationships between GSH depletion, reactive oxygen species (ROS) production, mitochondrial dysfunction and the mode of cell death in neuronal cells remain to be resolved and will provide important insights into the etiology of Parkinson's disease. An approach to determine the role of GSH in the mitochondrial function and in neurodegeneration was to create a selective depletion of GSH in a neuronal cell line in culture (NS20Y) by inhibiting its biosynthesis with L-buthionine-(S,R)-sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase. This treatment led to a nearly complete GSH depletion after 24 hr and induced cellular death via an apoptotic pathway after 5 days of BSO treatment. By using the reactive oxygen species-sensitive probe 2',7'-dichlorofluorescin, we observed that the rapid GSH depletion was accompanied, early in the process, by a strong and transient intracellular increase in reactive oxygen species evidenced after 1 hr with BSO, culminating after 3 hr when the GSH level decreased to 30% of normal. GSH depletion induced a loss of mitochondrial function after 48 hr of BSO treatment. In particular, the activities of complexes I, II and IV of the respiratory chain were decreased by 32, 70 and 65%, respectively as compared to controls. These results showed the crucial role of GSH for maintaining the integrity of mitochondrial function in neuronal cells. Oxidative stress and mitochondrial impairment, preceding DNA fragmentation, could be early events in the apoptotic process induced by GSH depletion. Our data are consistent with the hypothesis that GSH depletion could contribute to neuronal apoptosis in Parkinson's disease through oxidative stress and mitochondrial dysfunction.

Reduction of cortical infarction and impairment of apoptosis in NGF-transgenic mice subjected to permanent focal ischemia

The neuroprotective potential of the nerve growth factor (NGF) against permanent ischemic brain damage has been investigated in vivo using NGF-transgenic (tg) mice. The expression of the transgene is driven by part of the promoter of the proto-oncogene c-fos, which belongs to the first set of genes activated after brain ischemic insult. Wild-type (wt) mice and tg mice were subjected to permanent focal ischemia induced by electrocoagulation of the middle cerebral artery. Twenty four hours (h) after the ischemic shock, when compared to wt, tg mice displayed a 40% reduction of the infarcted area, which lasted up to 1 week. However, infarcted brain areas were similar in wt and tg mice within the first hours post-occlusion, indicating that NGF acted to block the progression of neuronal damage. Kinetics of NGF synthesis assessed by ELISA was in good agreement with the observed neuroprotective effect, since NGF content peaked 6 h post-ischemia. This was further correlated with the time-course of c-Fos immunoreactivity, detectable only from 6 h post-ischemia. The neuroprotective effect of NGF involved the impairment of apoptotic cell death, as evidenced by a marked decrease of the number of apoptotic profiles inside the ischemic zone in tg mice. These results underline the potential of c-fos-NGF-tg mice to study in vivo the molecular and cellular mechanisms of the NGF-induced neuroprotective effect against ischemic damage.