Curt D. Wolfgang

Tissue-specific Pattern of Stress Kinase Activation in Ischemic/Reperfused Heart and Kidney

In this report we investigate the molecular mechanisms that contribute to tissue damage following ischemia and ischemia coupled with reperfusion (ischemia/reperfusion) in the rat heart and kidney. We observe the activation of three stress-inducible mitogen-activated protein (MAP) kinases in these tissues: p38 MAP kinase and the 46- and 55-kDa isoforms of Jun N-terminal kinase (JNK46 and JNK55). The heart and kidney show distinct time courses in the activation of p38 MAP kinase during ischemia but no activation of either JNK46 or JNK55. These two tissues also respond differently to ischemia/reperfusion. In the heart we observe activation of JNK55 and p38 MAP kinase, whereas in the kidney all three kinases are active. We also examined the expression pattern of two stress-responsive genes, c-Jun and ATF3. Our results indicate that in the heart both genes are induced by ischemia and ischemia/reperfusion. However, in the kidney c-Jun and ATF3 expression is induced only by ischemia/reperfusion. To correlate these molecular events with tissue damage we examined DNA laddering, a common marker of apoptosis. A significant increase in DNA laddering was evident in both heart and kidney following ischemia/reperfusion and correlated with the pattern of kinase activation, supporting a link between stress kinase activation and apoptotic cell death in these tissues.

Analysis of ATF3, a Transcription Factor Induced by Physiological Stresses and Modulated by gadd153/Chop10

We demonstrate that ATF3, a member of the ATF/CREB family of transcription factors, is induced in a variety of stressed tissues: mechanically injured liver, toxin-injured liver, blood-deprived heart, and postseizure brain. We also demonstrate that an ATF3-interacting protein, gadd153/Chop10, forms a nonfunctional heterodimer with ATF3: the heterodimer, in contrast to the ATF3 homodimer, does not bind to the ATF/cyclic AMP response element consensus site and does not repress transcription. Interestingly, ATF3 and gadd153/Chop10 are expressed in inverse but overlapping manners during the livers response to carbon tetrachloride (CCl4): the level of gadd153/Chop10 mRNA is high in the normal liver and greatly decreases upon CCl4 treatment; the level of ATF3 mRNA, on the other hand, is low in the normal liver and greatly increases upon CCl4 treatment. We hypothesize that in nonstressed liver, gadd153/Chop10 inhibits the limited amount of ATF3 by forming an inactive heterodimer with it, whereas in CCl4-injured liver, the synthesis of gadd153/Chop10 is repressed, allowing the induced ATF3 to function.

ATF3 Gene GENOMIC ORGANIZATION, PROMOTER, AND REGULATION

ATF3 gene, which encodes a member of the activating transcription factor/cAMP responsive element binding protein (ATF/CREB) family of transcription factors, is induced by many physiological stresses. As a step toward understanding the induction mechanisms, we isolated the human ATF3 gene and analyzed its genome organization and 5′-flanking region. We found that the human ATF3 mRNA is derived from four exons distributed over 15 kilobases. Sequence analysis of the 5′-flanking region revealed a consensus TATA box and a number of transcription factor binding sites including the AP-1, ATF/CRE, NF-κB, E2F, and Myc/Max binding sites. As another approach to understanding the mechanisms by which the ATF3 gene is induced by stress signals, we studied the regulation of the ATF3 gene in tissue culture cells by anisomycin, an approach that has been used to study the stress responses in tissue culture cells. We showed that anisomycin at a low concentration activates the ATF3 promoter and stabilizes the ATF3 mRNA. Significantly, co-transfection of DNAs expressing ATF2 and c-Jun activates the ATF3 promoter. A possible mechanism implicating the C-Jun NH-terminal kinase/stress-activated protein kinase (JNK/SAPK) stress-inducible signaling pathway in the induction of the ATF3 gene is discussed.

Activating Transcription Factor 3, a Stress-inducible Gene, Suppresses Ras-stimulated Tumorigenesis *

ATF3 is a stress-inducible gene that encodes a member of the ATF/CREB family of transcription factors. Current literature indicates that ATF3 affects cell death and cell cycle progression. However, controversies exist, because it has been demonstrated to be a negative or positive regulator of these processes. We sought to study the roles of ATF3 in both cell death and cell cycle regulation in the same cell type using mouse fibroblasts. We show that ATF3 promotes apoptosis and cell cycle arrest. Fibroblasts deficient in ATF3 (ATF3-/-) were partially protected from UV-induced apoptosis, and fibroblasts ectopically expressing ATF3-/- under the tet-off system exhibited features characteristic of apoptosis upon ATF3 induction. Furthermore, ATF3-/- fibroblasts transitioned from G2 to S phase more efficiently than the ATF3+/+ fibroblasts, suggesting a growth arrest role of ATF3. Consistent with the growth arrest and pro-apoptotic roles of ATF3, ATF3- fibroblasts upon Ras transformation exhibited higher growth rate, produced more colonies in soft agar, and formed larger tumor upon xenograft injection than the ATF3+/+ counterparts. ATF3-/- cells, either with or without Ras transformation, had increased Rb phosphorylation and higher levels of various cyclins. Significantly, ATF3 bound to the cyclin D1 promoter as shown by chromatin immunoprecipitation (ChIP) assay and repressed its transcription by a transcription assay. Taken together, our results indicate that ATF3 promotes cell death and cell arrest, and suppresses Ras-mediated tumorigenesis. Potential explanations for the controversy about the roles of ATF3 in cell cycle and cell death are discussed.

gadd153/Chop10, a potential target gene of the transcriptional repressor ATF3.

Recently, we demonstrated that the function of ATF3, a stress-inducible transcriptional repressor, is negatively regulated by a bZip protein, gadd153/Chop10. In this report, we present evidence that ATF3 can repress the expression of its own inhibitor, gadd153/Chop10. First, ATF3 represses a chloramphenicol acetyltransferase reporter gene driven by the gadd153/Chop10 promoter when assayed by a transfection assay in vivo and a transcription assay in vitro. Second, the gadd153/Chop10 promoter contains two functionally important binding sites for ATF3: an AP-1 site and a C/EBP-ATF composite site, a previously unidentified binding site for ATF3. The absence of either site reduces the ability of ATF3 to repress the promoter. Third, overexpression of ATF3 by transient transfection results in a reduction of the endogenous gadd153/Chop10 mRNA level. Fourth, as described previously, ATF3 is induced in the liver upon CCl4 treatment. Intriguingly, we show in this report that gadd153/Chop10 mRNA is not present in areas where ATF3 is induced. Taken together, these results strongly suggest that ATF3 represses the expression of gadd153/Chop10. The mutual negative regulation between ATF3 and gadd153/Chop10 is discussed.

Association of the NPAS3 gene and five other loci with response to the antipsychotic iloperidone identified in a whole genome association study.

A whole genome association study was performed in a phase 3 clinical trial conducted to evaluate a novel antipsychotic, iloperidone, administered to treat patients with schizophrenia. Genotypes of 407 patients were analyzed for 334 563 single nucleotide polymorphisms (SNPs). SNPs associated with iloperidone efficacy were identified within the neuronal PAS domain protein 3 gene (NPAS3), close to a translocation breakpoint site previously observed in a family with schizophrenia. Five other loci were identified that include the XK, Kell blood group complex subunit-related family, member 4 gene (XKR4), the tenascin-R gene (TNR), the glutamate receptor, inotropic, AMPA 4 gene (GRIA4), the glial cell line-derived neurotrophic factor receptor-alpha2 gene (GFRA2), and the NUDT9P1 pseudogene located in the chromosomal region of the serotonin receptor 7 gene (HTR7). The study of these polymorphisms and genes may lead to a better understanding of the etiology of schizophrenia and of its treatment. These results provide new insight into response to iloperidone, developed with the ultimate goal of directing therapy to patients with the highest benefit-to-risk ratio.

Whole genome association study identifies polymorphisms associated with QT prolongation during iloperidone treatment of schizophrenia.

Administration of certain drugs (for example, antiarrhythmics, antihistamines, antibiotics, antipsychotics) may occasionally affect myocardial repolarization and cause prolongation of the QT interval. We performed a whole genome association study of drug-induced QT prolongation after 14 days of treatment in a phase 3 clinical trial evaluating the efficacy, safety and tolerability of a novel atypical antipsychotic, iloperidone, in patients with schizophrenia. We identified DNA polymorphisms associated with QT prolongation in six loci, including the CERKL and SLCO3A1 genes. Each single nucleotide polymorphism (SNP) defined two genotype groups associated with a low mean QT change (ranging from −0.69 to 5.67 ms depending on the SNP) or a higher mean QT prolongation (ranging from 14.16 to 17.81 ms). The CERKL protein is thought to be part of the ceramide pathway, which regulates currents conducted by various potassium channels, including the hERG channel. It is well established that inhibition of the hERG channel can prolong the QT interval. SLCO3A1 is thought to play a role in the translocation of prostaglandins, which have known cardioprotective properties, including the prevention of torsades de pointes. Our findings also point to genes involved in myocardial infarction (PALLD), cardiac structure and function (BRUNOL4) and cardiac development (NRG3). Results of this pharmacogenomic study provide new insight into the clinical response to iloperidone, developed with the goal of directing therapy to those patients with the optimal benefit/risk ratio.

Four-week, Double-blind, Placebo- and Ziprasidone-controlled Trial of Iloperidone in Patients With Acute Exacerbations of Schizophrenia

Abstract Iloperidone is a mixed D2/5-HT2 antagonist in development for treatment of schizophrenia. This trial aimed to evaluate the efficacy and safety of a fixed dose of iloperidone in patients with acute exacerbations of schizophrenia. This randomized, placebo-controlled, multicenter study comprised a 1-week titration period and a 3-week double-blind maintenance period. Eligible patients (n = 593) were randomized to iloperidone 24 mg/d, ziprasidone 160 mg/d as an active control, or placebo. Primary efficacy variable was change from baseline in the Positive and Negative Syndrome Scale Total (PANSS-T) score, using a mixed-effects model repeated measures analysis. Iloperidone demonstrated significant reduction versus placebo on the PANSS-T score (P< 0.01). Significant improvement versus placebo was also demonstrated with ziprasidone (P < 0.05). Compared with ziprasidone, iloperidone was associated with lower rates of many adverse events (AEs) that are particularly troublesome with antipsychotics, including sedation, somnolence, extrapyramidal symptoms, akathisia, agitation, and restlessness; iloperidone was associated with higher rates of weight gain, tachycardia, orthostatic hypotension, dizziness, and nasal congestion as reported as an AE. Most AEs were mild to moderate. A similar amount of QT prolongation was observed with both active treatments, although no patient had a treatment-emergent postbaseline corrected QT interval of 500 msec or greater. The incidence of clinically relevant changes in laboratory parameters was comparable between iloperidone and ziprasidone. Iloperidone was associated with a low incidence of extrapyramidal symptoms. Overall, there was improvement in akathisia with iloperidone treatment. Iloperidone treatment was effective, safe, and well tolerated in patients with acute exacerbation of schizophrenia.

Safety profile of iloperidone: a pooled analysis of 6-week acute-phase pivotal trials.

Iloperidone, a mixed D2/5-HT2 antagonist, is currently in clinical development for the treatment of schizophrenia. This article assesses the short-term safety of iloperidone using a pooled analysis of 3 phase 2, short-term acute schizophrenia studies conducted between 1998 and 2002 (N = 1943). Patients exposed to 3 dose ranges of iloperidone, another antipsychotic, or placebo were compared on rates of serious adverse events (SAEs), adverse events (AEs), extrapyramidal symptoms, akathisia, prolactin, weight and metabolic parameters, QTc, and other standard safety parameters. The most common treatment-related AEs observed with iloperidone were dizziness, headache, dry mouth, nausea, and insomnia. Discontinuation due to AEs was 4.8% for iloperidone, 7.6% for haloperidol, 6.2% for risperidone, and 4.8% for placebo. Iloperidone groups showed better overall performance on the Extrapyramidal Symptom Rating Scale and Barnes Akathisia Scale than risperidone or haloperidol groups. Patients taking iloperidone experienced a mild weight increase (range, 1.5-2.1 kg) similar to that of risperidone (1.5 kg), whereas those on haloperidol and placebo showed mean weight loss (−0.1 kg and −0.3 kg, respectively). QTc interval significantly increased across all iloperidone groups (least squares mean change from baseline to end point, 2.9-9.1 msec) and for haloperidol (5.0 msec). No significant QTc changes occurred in the risperidone or placebo groups. Iloperidone was associated with no change from baseline in total cholesterol, mild elevation in serum glucose, and slight decrease in triglycerides. Prolactin levels decreased with iloperidone and increased significantly with risperidone and haloperidol. These short-term trials suggest that iloperidone has a reassuring safety profile in many of the areas that are of potential concern, including relatively low dropout rates because of AEs, low extrapyramidal symptoms, akathisia, and prolactin elevation, and a modest short-term effect on weight gain.

Long-term efficacy and safety of iloperidone: results from 3 clinical trials for the treatment of schizophrenia.

This research compared the long-term efficacy and safety of iloperidone with those of haloperidol in individuals with schizophrenia. Data were pooled from 3 prospective multicenter studies, each with 6-week stabilization followed by 46-week double-blind maintenance phases. Patients were randomized to iloperidone 4 to 16 mg/d or haloperidol 5 to 20 mg/d. Patients included in this analysis completed the initial 6-week phase with at least 20% reduction in Positive and Negative Syndrome Scale (PANSS) total score at weeks 4 and 6, had 7-item Clinical Global Impressions of Change (CGI-C) scores less than 4, received 1 or more doses of long-term phase medication, and had 1 or more efficacy/safety assessments during the long-term phase. The primary efficacy variable was time to relapse, defined as a 25% or more increase in PANSS total score, including at least a 10-point change; discontinuation because of lack of efficacy; aggravated psychosis with hospitalization; or 2-point increase in the 7-item CGI-C after week 6. Of 1644 patients randomized and 1326 completing the 6-week phase, 473 (iloperidone, n = 359; haloperidol, n = 114) were included in the long-term efficacy analysis, and 489 (iloperidone, n = 371; haloperidol, n = 118) in the safety analysis. Iloperidone was equivalent to haloperidol in time to relapse. The most common adverse events were insomnia (18.1%), anxiety (10.8%), and schizophrenia aggravated (8.9%) with iloperidone, and insomnia (16.9%), akathisia (14.4%), tremor (12.7%), and muscle rigidity (12.7%) with haloperidol. The Extrapyramidal Symptoms Rating Scale scores improved with iloperidone and worsened with haloperidol. Metabolic changes were minimal for both groups. Mean changes in Fridericias QT interval correction were 10.3 msec (iloperidone) and 9.4 msec (haloperidol) at end point. Iloperidone demonstrated long-term efficacy equivalent to haloperidol and a favorable long-term safety profile, potentially making this agent a suitable option as maintenance therapy for schizophrenia.