Increase in Bcl-2 phosphorylation and reduced levels of BH3-only Bcl-2 family proteins in kainic acid-mediated neuronal death in the rat brain

TMT-based proteomics profile reveals changes of the entorhinal cortex in a kainic acid model of epilepsy in mice

Experimental modeling and clinical neuroimaging of patients has shown that certain seizures are capable of causing neuronal death. Research into cell death after seizures has identified the induction of the molecular machinery of apoptosis. Temporal lobe epilepsy (TLE) is the most common type of epilepsy in adults, which is characterized by substantial pathological abnormalities in the temporal lobe, including the hippocampus and entorhinal cortex (EC). Although decades of studies have revealed numerous molecular abnormalities in the hippocampus that are linked to TLE, the biochemical mechanisms associated with TLE in EC remain unclear. In this study, we explored these early phenotypical alterations in the EC 5 days after mice were given a systemic injection of kainic acid (KA) to induce status epilepticus (KA-SE). we used the Tandem Mass Tag (TMT) combined with LC-MS/MS approach to identify distinct proteins in the EC in a mouse model of KA-SE model. According to the findings, 355 differentially abundant proteins including 199 upregulated and 156 downregulated differentially abundant proteins were discovered. The first-ranked biological process according to Gene Ontology (GO) analysis was "negative control of extrinsic apoptotic signaling". "Apoptosis" was the most significantly enriched Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway. Compared with those in control mice, BCL2L1, NTRK2 and MAPK10 abundance levels were reduced in KA mice. MAPK10 and NTRK2 act as upstream regulators to regulate BCL2L1, and BCL2L1 Inhibits cell death by blocking the voltage- dependent anion channel (VDAC) and preventing the release of the caspase activator, CYC1, from the mitochondrial membrane. However, ITPR1 was increased at the mRNA and protein levels in KA mice. Furthermore, there was no significant difference in ACTB, TUBA1A and TUBA4A levels between the two groups. Our results offer clues to help identify biomarkers for the development of pharmacological therapies targeted at epilepsy.

Apoptosis in the Dentate Nucleus Following Kindling-induced Seizures in Rats

BACKGROUND

Epilepsy is a common neurological disorder characterized by abnormal and recurrent neuronal discharges that result in epileptic seizures. The dentate nuclei of the cerebellum receive excitatory input from different brain regions. Purkinje cell loss due to chronic seizures could lead to decreased inhibition of these excitatory neurons, resulting in the activation of apoptotic cascades in the dentate nucleus.

OBJECTIVE

The present study was designed to determine whether there is a presence of apoptosis (either intrinsic or extrinsic) in the dentate nucleus, the final relay of the cerebellar circuit, following kindling-induced seizures.

METHODS

In order to determine this, seizures were triggered via the amygdaloid kindling model. Following 0, 15, or 45 stimuli, rats were sacrificed, and the cerebellum was extracted. It was posteriorly prepared for the immunohistochemical analysis with cell death biomarkers: TUNEL, Bcl-2, truncated Bid (tBid), Bax, cytochrome C, and cleaved caspase 3 (active form). Our findings reproduce results obtained in other parts of the cerebellum.

RESULTS

We found a decrease of Bcl-2 expression, an anti-apoptotic protein, in the dentate nucleus of kindled rats. We also determined the presence of TUNEL-positive neurons, which confirms the presence of apoptosis in the dentate nucleus. We observed the expression of tBid, Bax, as well as cytochrome C and cleaved caspase-3, the main executor caspase of apoptosis.

CONCLUSION

There is a clear activation of both the intrinsic and extrinsic apoptotic pathways in the cells of the dentate nucleus of the cerebellum of rats subjected to amygdaloid kindling.

Peroxisome Proliferator-Activated Receptor γ Coactivator 1α Activates Vascular Endothelial Growth Factor That Protects Against Neuronal Cell Death Following Status Epilepticus through PI3K/AKT and MEK/ERK Signaling

Status epilepticus may cause molecular and cellular events, leading to hippocampal neuronal cell death. Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) is an important regulator of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2), also known as fetal liver kinase receptor 1 (Flk-1). Resveratrol is an activator of PGC-1α. It has been suggested to provide neuroprotective effects in epilepsy, stroke, and neurodegenerative diseases. In the present study, we used microinjection of kainic acid into the left hippocampal CA3 region in Sprague Dawley rats to induce bilateral prolonged seizure activity. Upregulating the PGC-1α pathway will increase VEGF/VEGFR2 (Flk-1) signaling and further activate some survival signaling that includes the mitogen activated protein kinase kinase (MEK)/mitogen activated protein kinase (ERK) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways and offer neuroprotection as a consequence of apoptosis in the hippocampal neurons following status epilepticus. Otherwise, downregulation of PGC-1α by siRNA against pgc-1α will inhibit VEGF/VEGFR2 (Flk-1) signaling and suppress pro-survival PI3K/AKT and MEK/ERK pathways that are also accompanied by hippocampal CA3 neuronal cell apoptosis. These results may indicate that the PGC-1α induced VEGF/VEGFR2 pathway may trigger the neuronal survival signaling, and the PI3K/AKT and MEK/ERK signaling pathways. Thus, the axis of PGC-1α/VEGF/VEGFR2 (Flk-1) and the triggering of downstream PI3K/AKT and MEK/ERK signaling could be considered an endogenous neuroprotective effect against apoptosis in the hippocampus following status epilepticus.

Evidence for additionally increased apoptosis in the peripheral blood mononuclear cells of major depressive patients with a high risk for suicide

Several studies have suggested a pathophysiological role of blood cell apoptosis in major depressive disorder (MDD). The aim of this study was to evaluate mRNA expression levels of Bcl-2, Bax, and Fas in peripheral blood mononuclear cells (PBMCs) of MDD patients with a high risk for suicide relative to those without a high risk for suicide as well as healthy subjects. The mRNA expression of Bcl-2, Bax, and Fas as well as the Bcl-2/Bax ratio was examined in the PBMCs of 30 MDD patients with a high risk for suicide, 30 MDD patients without a high risk for suicide, and 30 healthy controls. The mRNA expression of target genes was measured using real-time quantitative Polymerase Chain Reaction (PCR). FAS mRNA expression was significantly increased, and Bcl-2 mRNA expression and the Bcl-2/Bax expression ratio were significantly decreased, in the PBMCs of MDD patients with or without a high risk for suicide attempts compared to healthy controls (p < .001). However, Bax mRNA expression was significantly increased only in MDD patients with a high risk for suicide. Moreover, MDD patients with a high risk for suicide had increased Bax and FAS mRNA expression and decreased Bcl-2 and Bcl-2/Bax ratio when compared to patients without risk for suicide (p < .001). Our findings may support the role of both internal and external apoptotic pathways in the interplay between the immune system and depressive symptoms, especially in patients with a high risk for suicide.

Peroxisome proliferator-activated receptor-γ coactivator-1α mediates neuroprotection against excitotoxic brain injury in transgenic mice: role of mitochondria and X-linked inhibitor of apoptosis protein

Peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is a transcriptional coactivator involved in the regulation of mitochondrial biogenesis and cell defense. The functions of PGC-1α in physiology of brain mitochondria are, however, not fully understood. To address this we have studied wild-type and transgenic mice with a two-fold overexpression of PGC-1α in brain neurons. Data showed that the relative number and basal respiration of brain mitochondria were increased in PGC-1α transgenic mice compared with wild-type mitochondria. These changes occurred concomitantly with altered levels of proteins involved in oxidative phosphorylation (OXPHOS) as studied by proteomic analyses and immunoblottings. Cultured hippocampal neurons from PGC-1α transgenic mice were more resistant to cell degeneration induced by the glutamate receptor agonist kainic acid. In vivo kainic acid induced excitotoxic cell death in the hippocampus at 48 h in wild-type mice but significantly less so in PGC-1α transgenic mice. However, at later time points cell degeneration was also evident in the transgenic mouse hippocampus, indicating that PGC-1α overexpression can induce a delay in cell death. Immunoblotting showed that X-linked inhibitor of apoptosis protein (XIAP) was increased in PGC-1α transgenic hippocampus with no significant changes in Bcl-2 or Bcl-X. Collectively, these results show that PGC-1α overexpression contributes to enhanced neuronal viability by stimulating mitochondria number and respiration and increasing levels of OXPHOS proteins and the anti-apoptotic protein XIAP.

Expression and localisation of brain-type organic cation transporter (BOCT/24p3R/LCN2R) in the normal rat hippocampus and after kainate-induced excitotoxicity

The iron siderophore binding protein lipocalin 2 (LCN2, also known as 24p3, NGAL and siderocalin) may be involved in iron homeostasis, but to date, little is known about expression of its putative receptor, brain-type organic cation transporter (BOCT, also known as BOCT1, 24p3R, NGALR and LCN2R), in the brain during neurodegeneration. The present study was carried out to elucidate the expression of LCN2 and BOCT in hippocampus after excitotoxicity induced by the glutamate analog, kainate (KA) and a possible role of LCN2 in neuronal injury. As reported previously, a rapid and sustained induction in expression of LCN2 was found in the hippocampus after intracerebroventicular injection of KA. BOCT was expressed in neurons of the saline-injected control hippocampus, and immunolabel for BOCT protein was preserved in pyramidal neurons of CA1 at 1 day post-KA injection, likely due to the delayed onset of neurodegeneration after KA injection. At 3 days and 2 weeks after KA injections, loss of immunolabel was observed due to degenerated neurons, although remaining neurons continued to express BOCT, and induction of BOCT was found in OX-42 positive microglia. This resulted in an overall decrease in BOCT mRNA and protein expression after KA treatment. Increased expression of the pro-apoptotic marker, Bim, was found in both neurons and microglia after KA injection, but TUNEL staining indicating apoptosis was found primarily in Bim-expressing neurons, but not microglia. Interaction between LCN2 and BOCT was found by DuoLink assay in cultured hippocampal neurons. Apo-LCN2 without iron caused no significant differences in neuronal Bim expression or cell survival, whereas holo-LCN2 consisting of LCN2:iron:enterochelin complex increased Bim mRNA expression and decreased neuronal survival. Together, results suggest that LCN2 and BOCT may have a role in neuronal injury.

EGF reverses multi-drug resistance via the p-ERK pathway in HepG2/ADM and SMMC7721/ADM hepatocellular carcinoma models

AIM

To investigate signaling pathways for reversal of EGF-mediated multi-drug resistance (MDR) in hepatocellular carcinoma (HCC) models.

MATERIALS AND METHODS

HCC MDR cell strain HepG2/adriamycin (ADM) and SMMC7721/ADM models were established using a method of exposure to medium with ADM between low and high concentration with gradually increasing concentration. Drug sensitivity and reversal of multi-drug resistance by EGF were determined and the cell cycle distribution and apoptosis were analyzed by flow cytometry. Phosphorylation of ERK1, ERK2, ERK5 and expression of Bim were detected by Western blotting.

RESULTS

The results showed that HepG2/ADM and SMMC7721/ADM cells were resistant not only to ADM, but also to multiple anticancer drugs. When used alone, EGF had no anti-tumor activity in HepG2/ADM and SMMC7721/ADM cells in vitro, while it increased the cytotoxicity of ADM. EGF induced cell apoptosis and G0/G1 phase cell cycle arrest in HepG2/ADM And SMMC7721/ADM cells, while enhancing activity of p-ERKs and up-regulated expression of BimEL.

CONCLUSIONS

EGF might enhance the chemosensitivity of HepG2/ADM and SMMC7721/ADM cells via up-regulating p-ERKs and BimEL protein.

Salubrinal, ER stress inhibitor, attenuates kainic acid-induced hippocampal cell death

Kainic acid (KA)-induced neuronal death is closely linked to endoplasmic reticulum (ER) and mitochondrial dysfunction. Parkin is an ubiquitin E3 ligase that mediates the ubiquitination of the Bcl-2 family of proteins and its mutations are associated with neuronal apoptosis in neurodegenerative diseases. We investigated the effect of salubrinal, an ER stress inhibitor, on the regulation of ER stress and mitochondrial apoptosis induced by KA, in particular, by controlling parkin expression. We showed that salubrinal significantly reduced seizure activity and increased survival rates of mice with KA-induced seizures. We found that salubrinal protected neurons against apoptotic death by reducing expression of mitochondrial apoptotic factors and elF2α-ATF4-CHOP signaling proteins. Interestingly, we showed that salubrinal decreased the KA-induced parkin expression and inhibited parkin translocation to mitochondria, which suggests that parkin may regulate a cross-talk between ER and mitochondria. Collectively, inhibition of ER stress attenuates mitochondrial apoptotic and ER stress pathways and controls parkin-mediated neuronal death following KA-induced seizures.

The roles of cyclic AMP-ERK-Bad signaling pathways on 6-hydroxydopamine-induced cell survival and death in PC12 cells

The roles of cyclic AMP (cAMP)-ERK1/2-Bad signaling pathways in 6-hydroxydopamine (6-OHDA)-induced cell survival and death were investigated. In PC12 cells, 6-OHDA (10-100μM) concentration-dependently increased the intracellular levels of cAMP mediated by the Ca(2+)-CaMKII-adenylyl cyclase system. 6-OHDA at the non-toxic level (10μM) induced transient ERK1/2 phosphorylation and BadSer112 phosphorylation, which maintained cell survival. In contrast, the high levels of cAMP induced by toxic levels (50 and 100μM) of 6-OHDA induced sustained ERK1/2 phosphorylaton and BadSer155 phosphorylation. The cells then moved to cell death process through Bcl2 phosphorylation and caspase-3 activation. BadSer155 phosphorylation by 6-OHDA was inhibited by PKA (H89) and MEK (U0126) inhibitors, indicating that it was mediated via the cAMP-PKA-sustained ERK1/2 system. In SK-N-BE(2)C cells, the non-toxic level of 6-OHDA also showed transient ERK1/2 phosphorylation and BadSer112 phosphorylation, and toxic levels of 6-OHDA exhibited sustained ERK1/2 phosphorylation and BadSer155 phosphorylation. These results suggest that ERK1/2 phosphorylation by 6-OHDA shows biphasic functions on cell survival and death in PC12 cells. It is, therefore, proposed that the cAMP-ERK1/2-Bad signaling pathways incurred by toxic levels of 6-OHDA play a role in dopamine neuron death of animal models of Parkinson's disease.

Endoplasmic reticulum stress contributes to CRH-induced hippocampal neuron apoptosis

The hypothalamic-pituitary-adrenal (HPA) axis is critical to mediating the body's response to stress. Corticotropin releasing hormone (CRH) plays a central role in controlling the stress response and regulating the HPA axis. Recent findings support CRH participates in the stress-induced hippocampal neuron apoptosis, but the underlying mechanisms are not fully understood. Our present study demonstrates that CRH can independently decrease hippocampal neuron cell viability in vitro in a concentration- and time-dependent manner. CRH receptor 1 (CRHR1) is involved in CRH-induced neuron apoptosis. Endoplasmic reticulum (ER) stress response marker, glucose-regulated protein 78 (GRP78), either protein or mRNA, is significantly elevated after treatment of CRH, and decreased when co-treated with salubrinal, ER stress inhibitor. The ER stress associated proapoptotic transcription factor C/EBP homologous protein (CHOP) and cleavage of caspase-12 protein expression are also increased following CRH treatment. Furthermore, we investigate which ER stress cascades are affected by CRH. CRH activates inositol-requiring enzyme 1 (IRE1), apoptosis signal regulating kinase 1 (ASK1), and c-jun kinase (JNK). Neuron apoptotic rate, examined by flow cytometry, is increased when CRH treatment and attenuated by salubrinal, thioredoxin (ASK1 inhibitor) and SP600125 (JNK inhibitor). Therefore, current data indicate that ER stress, through activating the IRE1/ASK1/JNK cascade, plays an important role in CRH-induced neuron apoptosis.

The JNK inhibitor D-JNKI-1 blocks apoptotic JNK signaling in brain mitochondria

Kainic acid (KA) induced seizures provokes an extensive neuronal degeneration initiated by c-Jun N-terminal kinases (JNK) as central mediators of excitotoxicity. However, the actions of their individual isoforms in cellular organelles including mitochondria remain to be elucidated. Here, we have studied the activation of JNK1, JNK2 and JNK3 and their activators, mitogen-activated protein kinase kinase (MKK) 4/7, in brain mitochondria, cytosolic and nuclear fractions after KA seizures. In the mitochondrial fraction, KA significantly increased the presence of JNK1, JNK3 and MKK4 and stimulated their phosphorylation i.e. activation. The pro-apoptotic proteins, Bim and Bax were induced and, consequently, the ratio Bcl-2-Bax decreased. These changes were paralleled by the release of cytochrome c and cleavage of poly(ADP-ribose)-polymerase (PARP). The JNK peptide inhibitor, D-JNKI-1 (XG-102) reversed these pathological events in the mitochondria and almost completely abolished cytochrome c release and PARP cleavage. Importantly, JNK3, but not JNK1 or JNK2, was associated with Bim in mitochondria and D-JNKI-1 prevented the formation of this apoptotic complex. Apart from of the attenuation of c-Jun phosphorylation in the nucleus, D-JNKI-1 did not affect the level of JNK3 isoform in the nuclear and cytosolic fractions. These findings provide novel insights into the mode of action of individual JNK isoforms in cell organelles and points to the JNK3 pool in mitochondria as a target of the JNK inhibitor D-JNKI-1 to confer neuroprotection.

Cell signaling underlying epileptic behavior

Epilepsy is a complex disease, characterized by the repeated occurrence of bursts of electrical activity (seizures) in specific brain areas. The behavioral outcome of seizure events strongly depends on the brain regions that are affected by overactivity. Here we review the intracellular signaling pathways involved in the generation of seizures in epileptogenic areas. Pathways activated by modulatory neurotransmitters (dopamine, norepinephrine, and serotonin), involving the activation of extracellular-regulated kinases and the induction of immediate early genes (IEGs) will be first discussed in relation to the occurrence of acute seizure events. Activation of IEGs has been proposed to lead to long-term molecular and behavioral responses induced by acute seizures. We also review deleterious consequences of seizure activity, focusing on the contribution of apoptosis-associated signaling pathways to the progression of the disease. A deep understanding of signaling pathways involved in both acute- and long-term responses to seizures continues to be crucial to unravel the origins of epileptic behaviors and ultimately identify novel therapeutic targets for the cure of epilepsy.

In vivo contributions of BH3-only proteins to neuronal death following seizures, ischemia, and traumatic brain injury

The Bcl-2 homology (BH) domain 3-only proteins are a proapoptotic subgroup of the Bcl-2 gene family, which regulate cell death via effects on mitochondria. The BH3-only proteins react to various cell stressors and promote cell death by binding and inactivating antiapoptotic Bcl-2 family members and direct activation of proapoptotic multi-BH domain proteins such as Bax. Here, we review the in vivo evidence for their involvement in the pathophysiology of status epilepticus and contrast it to ischemia and traumatic brain injury. Seizures in rodents activate three potent proapoptotic BH3-only proteins: Bid, Bim, and Puma. Analysis of damage after seizures in mice singly deficient for each BH3-only protein supports a causal role for Puma and to a lesser extent Bim but, surprisingly, not Bid. In ischemia and trauma, where core aspects of the pathophysiology of cell death overlap, multiple BH3-only proteins are also activated and Bid has been shown to be required for neuronal death. The findings suggest that while each neurologic insult activates multiple BH3-only proteins, there may be specificity in their functional contribution. Future challenges include evaluating the remaining BH3-only proteins, explaining different causal contributions, and, if possible, exploring neurologic outcomes in mouse models deficient for multiple BH3-only proteins.

Effect of maternal immunopotentiation on apoptosis-associated molecules expression in teratogen-treated embryos

PROBLEM

Potentiation of the maternal immune system was shown by us to affect the embryonic response to teratogenic insults. In order to understand better the mechanisms underlying that phenomenon, we explored the effect of maternal immunopotentiation by rat splenocytes on the early stages of the embryonic response to cyclophosphamide (CP).

METHOD OF STUDY

Immunopotentiated CP-treated embryos were analysed for cell cycle changes by flow cytometry, while cell proliferation and apoptosis were assessed by 5'-bromo-2'-deoxyuridine (BrdU) incorporation and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL) respectively. The expression of the p65 subunit of NF-kappaB, IkappaBalpha, Bax, bcl-2 and p53 was assessed by flow cytometry.

RESULTS

Exposure to CP resulted in significant growth retardation and in the appearance of cellular damage, a reduction in cell proliferation and the appearance of apoptotic cells, which were all found to be delayed in immunopotentiated embryos. In parallel, CP-treated embryos demonstrated a reduction in the percentage of p65- or IkappaBalpha-positive cells, while the percentage of bcl-2- or p53-positive cells increased initially and decreased later. Those changes were normalized by maternal immunopotentiation when tested at 24 hrs after exposure to the teratogen.

CONCLUSION

Our data implicate maternal immunopotentiation to protect the embryo against teratogenic insults, possibly through its effect on the expression of p65, bcl-2 or p53.

Endoplasmic reticulum stress, inflammation, and perinatal brain damage

Inflammation seems to play a role in the pathogenesis of perinatal brain damage in fetuses/infants born much before term. We raise the possibility that noninflammatory phenomena induce endoplasmic reticulum stress, which, in turn, leads to the unfolded protein response, which is followed by apoptosis-promoting processes and inflammation. Perhaps by these events, noninflammatory stimuli lead to perinatal brain damage.

Contrasting patterns of Bim induction and neuroprotection in Bim-deficient mice between hippocampus and neocortex after status epilepticus

Prolonged seizures (status epilepticus) are associated with brain region-specific regulation of apoptosis-associated signaling pathways. Bcl-2 homology domain 3-only (BH3) members of the Bcl-2 gene family are of interest as possible initiators of mitochondrial dysfunction and release of apoptogenic molecules after seizures. Previously, we showed that expression of the BH3-only protein, Bcl-2 interacting mediator of cell death (Bim), increased in the rat hippocampus but not in the neocortex after focal-onset status epilepticus. In this study, we examined Bim expression in mice and compared seizure damage between wild-type and Bim-deficient animals. Status epilepticus induced by intra-amygdala kainic acid (KA) caused extensive neuronal death within the ipsilateral hippocampal CA3 region. Hippocampal activation of factors associated with transcriptional and posttranslational activation of Bim, such as CHOP and c-Jun NH(2)-terminal kinases, was significant within 1 h. Upregulation of bim mRNA was evident after 2 h and Bim protein increased between 4 and 24 h. Hippocampal CA3 neurodegeneration was reduced in Bim-deficient mice compared with wild-type animals after seizures in vivo, and short interfering RNA molecules targeting bim reduced cell death after KA treatment of hippocampal organotypic cultures. In contrast, neocortical Bim expression declined after status epilepticus, and neocortex damage in Bim-deficient mice was comparable with that in wild-type animals. These results show region-specific differential contributions of Bim to seizure-induced neuronal death.

Bax-associated mechanisms underlying the response of embryonic cells to methotrexate

Bax was shown previously to regulate apoptotic cell death in various experimental systems, however, its involvement in teratogen-induced apoptosis is not clear yet. Therefore, we explored the involvement of Bax in the response of mouse embryonic fibroblasts (MEFs) to the anti cancer drug methotrexate (MTX), using Bax wild type (WT) and knockout (Bax(-/-)) MEFs. Our results demonstrated a significant teratogen-induced dose- and time-dependant decrease in the survival and culture density of both cell lines, which were found to be somewhat more prominent in WT cells. Exposure to MTX resulted also in decreased cell proliferation of WT but not Bax(-/-) cells and accordingly, we observed an accumulation of cells in the S phase and an increased percentage of cells in the Sub-G(1) phase of the cell cycle and the appearance of condensed nuclei, which were found to be somewhat more prominent in WT MEFs. In parallel, WT MEFs demonstrated a MTX-induced increase in the percentage of Bax-positive cells and a significant decrease in the percentage of bcl-2-, p65- or IkappaBalpha-positive cells, which were not detected in Bax(-/-) MEFs. Altogether, the differential sensitivity of WT or Bax(-/-) MEFs to MTX suggests a possible involvement of this molecule in the response of embryonic cells to teratogens.

The Bcl-2 family in autoimmune and degenerative disorders

Members of the Bcl-2 family are essential regulators of programmed cell death and thus play a major role in the development and function of many tissues. The balance between pro-survival and pro-apoptotic members of the family decides whether a cell will live or die. This mechanism allows organisms to get rid of cells that are no longer needed or have become dangerous. Deregulation of apoptosis is a major contributing factor in the development of many diseases. A deeper understanding of how the Bcl-2 family proteins orchestrate death in normal and pathologic conditions is thus relevant not only for disease etiology, but also to try to prevent these various disorders. Experiments with transgenic and gene-ablated mice have helped elucidate the function of the different members of the Bcl-2 family and their physiological roles. The present review highlights the role of Bcl-2 family members in autoimmune and degenerative disorders, with a particular focus on the mouse models that have been used to study their function.

Repeated unpredictable stress and antidepressants differentially regulate expression of the bcl-2 family of apoptotic genes in rat cortical, hippocampal, and limbic brain structures

Apoptosis has been proposed as a contributing cellular mechanism to the structural alterations that have been observed in stress-related mood disorders. Antidepressants, on the other hand, are hypothesized to exert trophic and/or neuroprotective actions. The present study examined the regulation of the major antiapoptotic (Bcl-2, Bcl-xl) and proapoptotic (Bax) genes by repeated unpredictable stress (an animal model of depression) and antidepressant treatments (ADT). In adult rats, exposure to unpredictable stress reduced Bcl-2 mRNA levels in the central nucleus of the amygdala (CeA), cingulate (Cg), and frontal (Fr) cortices. Bcl-xl mRNA was significantly decreased in hippocampal subfields. In contrast, chronic administration of clinically effective antidepressants from four different classes, ie fluoxetine, reboxetine, tranylcypromine, and electroconvulsive seizures (ECS) upregulated Bcl-2 mRNA expression in the Cg, Fr, and CeA. Reboxetine, tranylcypromine, and ECS selectively increased Bcl-xl, but not Bcl-2 mRNA expression in the hippocampus. Chemical ADT but not ECS, robustly enhanced Bcl-2 expression in the medial amygdaloid nucleus and ventromedial hypothalamus. Fluoxetine did not influence Bcl-xl expression in the hippocampus, but it was the only ADT that decreased Bax expression in this region. In the CeA, again in direct contrast to the stress effects, exposure to all classes of ADTs significantly increased Bcl-2 mRNA. The selective regulation of Bcl-xl and Bax in hippocampal subfields and of Bcl-2 in the Cg cortex, amygdala, and hypothalamus suggests that these cellular adaptations contribute to the long-term neural plastic adaptations to stress and ADTs in cortical, hypothalamic, and limbic brain structures.

Bcl2 enhances induced hematopoietic differentiation of murine embryonic stem cells

Bcl2 is a potent antiapoptotic gene that can increase resistance of adult bone marrow hematopoietic progenitor cells to lethal irradiation, and thereby preserve their ability to differentiate. However, the effect of Bcl2 on murine embryonic stem (ES) cells induced to undergo hematopoietic differentiation in the absence of a toxic stress is not known. To test this, murine CCE-ES cells that can be induced to undergo hematopoietic differentiation in a two-step process that results in upregulation of Bcl2 were used. Upregulation of Bcl2 precedes formation of hematopoietic embryoid bodies (EB) and their further differentiation into hematopoietic colony-forming units, when plated as single cells in methylcellulose. ES cells stably expressing a Bcl2 siRNA plasmid to "knock-down" endogenous expression or cells expressing wild-type (WT) Bcl2 or phosphomimetic Bcl2 mutants were examined. ES cells expressing the Bcl2 siRNA or those expressing a dominant-negative, nonphosphorylatable Bcl2 display a strikingly reduced capacity to form hematopoietic EBs and colony-forming units compared to cells expressing WT or phosphomimetic Bcl2 that demonstrate an increased capacity. Bcl2's effect on induced-hematopoietic differentiation of ES cells does not result from either decreased apoptosis or a reduced number of cells. Rather, Bcl2-enhances hematopoietic differentiation of ES cells by upregulating p27, which results in retardation of the cell cycle at G1/G 0. Thus siRNA silencing of p27 reverts Bcl2's enhancement phenotype in a manner similar to that of Bcl2 "silencing" or expression of a nonphosphorylable Bcl2. In addition to Bcl2's well-described antiapoptotic and cell-cycle retardant effect on somatic cells, Bcl2 may also function to enhance induced hematopoietic cell differentiation of murine ES cells. These findings may have potential relevance for expanding hematopoietic stem/progenitor cell numbers from an ES cell source for stem cell transplantation applications.

Neuroprotective strategies to avert seizure-induced neurodegeneration in epilepsy

Neurodegeneration in limbic circuits is a hallmark feature of chronic temporal lobe epilepsy (TLE). Studies in experimental animal models and human patients indicate that seizure-induced neuronal injury involves some active, as well as passive cell death processes. Experimental approaches that inhibit active steps in cell death programs have been shown to reduce neuronal cell death and sclerosis, but not to prevent epileptogenesis in animal models of TLE. These findings suggest that we need additional research using both animal models and brain slices from human patients to understand the pathological mechanisms underlying seizure generation. Such comparative studies will also aid in evaluating the potential therapeutic value of inhibiting cell death in seizure disorders.

Endoplasmic reticulum stress inhibition protects against excitotoxic neuronal injury in the rat brain

Elevated brain glutamate with activation of neuronal glutamate receptors accompanies neurological disorders, such as epilepsy and brain trauma. However, the mechanisms by which excitotoxicity triggers neuronal injury are not fully understood. We have studied the glutamate receptor agonist kainic acid (KA) inducing seizures and excitotoxic cell death. KA caused the disintegration of the endoplasmic reticulum (ER) membrane in hippocampal neurons and ER stress with the activation of the ER proteins Bip, Chop, and caspase-12. Salubrinal, inhibiting eIF2alpha (eukaryotic translation initiation factor 2 subunit alpha) dephosphorylation, significantly reduced KA-induced ER stress and neuronal death in vivo and in vitro. KA-induced rise in intracellular calcium was not affected by Salubrinal. The results show that ER responses are essential parts of excitotoxicity mediated by glutamate receptor activation and that Salubrinal decreases neuronal death in vivo. Inhibition of ER stress by small molecular compounds may be beneficial for treatment of various neuronal injuries and brain disorders.

Impairment of GABAergic neurotransmitter system in the amygdala of young rats after 4-week zinc deprivation

On the basis of the evidence that the excitability of hippocampal glutamatergic neurotransmitter system is enhanced by dietary zinc deficiency, the response of amygdalar neurotransmitter system was checked in young rats fed a zinc-deficient diet for 4 weeks. Extracellular zinc concentration in the amygdala, which was measured by the in vivo microdialysis, was almost the same as that in the hippocampus and decreased by zinc deficiency. Extracellular zinc concentration in the amygdala was increased both in the control and zinc-deficient rats by stimulation with 100mM KCl, suggesting that the increase in extracellular zinc in the amygdala, as well as that in the hippocampus, is linked with neuronal depolarization. In amygdalar extracellular fluid, the basal glutamate concentration was not significantly different between the control and zinc-deficient rats and was increased to almost the same extent between them by stimulation with 100mM KCl, unlike more increase in extracellular glutamate concentration in the hippocampus in zinc deficiency. On the other hand, the basal GABA concentration in the amygdalar extracellular fluid was significantly lower in zinc-deficient rats and was not increased both in the control and zinc-deficient rats by stimulation with 100mM KCl. These results suggest that GABAergic neurotransmitter system is critically impaired in the amygdala of young rats after 4-week zinc deprivation.

Involvement of NF-κB in the response of embryonic cells to Methotrexate

The involvement of NF-kappaB in the regulation of the apoptotic process was demonstrated previously, however, its exact role has not been established yet. In order to unravel mechanisms underlying teratogen-induced cell death, we tried in our present study to assess the involvement of the p65 subunit of NF-kappaB in the response of mouse embryonic fibroblasts (MEFs) to the anti-cancer drug methotrexate (MTX), using p65 knockout MEFs (p65(-/-)). Indeed, this cell line was found to be more susceptible to the exposure to MTX, demonstrated by more profound changes in cell survival, cell cycle, proliferation and the percentage of apoptotic or necrotic cells, as compared to wild type (WT) MEFs. Also, a different pattern of intracellular localization of p65 in WT cells as well as IkappaBalpha and Bax in both cell lines was detected in response to MTX. Altogether, our results implicate the p65 subunit of NF-kappaB to play an important role in the response of embryonic cells to MTX.

Expression of apoptosis-associated molecules in the fetoplacental unit of cyclophosphamide-treated mice

The mechanisms underlying the teratogen-induced apoptotic process leading to anomaly formation are not as yet understood. Therefore, we tried to evaluate possible changes in the expression of molecules regulating the apoptotic process induced in the embryo and placenta by exposure to cyclophosphamide (CP). Exposure to CP resulted in clear growth retardation that was accompanied by a time-dependent increase in cellular damage and an appearance of apoptotic cells in the embryonic brain and limbs as well as a decrease in cell proliferation. Western blot analysis demonstrated an increase in the level of Bax and a decrease in the expression of the p65 subunit of NF-kappaB and IkappaB alpha in the embryo and placenta. Immunohistochemical analysis localized cells expressing those molecules to the areas that exhibited CP-induced cellular damage, while in the placenta they were revealed mainly in the luminal and glandular epithelium. Our results suggest a possible involvement of Bax, p65 and IkappaB alpha in the response of the embryo and the placenta to teratogenic insults.

Modulation of apoptosis in the mouse brain after morphine treatments and morphine withdrawal

We have examined the effects of acute or chronic morphine and naltrexone-precipitated withdrawal on mouse brain apoptotic cell death. The associated changes in the expression of apoptosis regulatory proteins were also analyzed. After a single dose of morphine, no apoptotic cells were detected by TUNEL or active caspase-3 immunocytochemistry. Concurrently, a down-regulation of the proapoptotic proteins FasL and Bad was detected in cortical lysates. On the other hand, the brains of chronic-morphine-treated mice and abstinent mice exhibited scattered apoptotic neurons and astrocytes throughout the brain. This neurotoxic effect was accompanied by up-regulation of the proapoptotic proteins FasL, Fas, and Bad and the active fragments of caspases-8 and -3 in cortical and hippocampal lysates. Abstinent mice also displayed a reduced expression of the antiapoptotic protein Bcl-2. No changes on t-Bid expression were detected under any experimental condition. These results suggest a neurotoxic effect exerted by chronic, but not acute, morphine and its withdrawal by activating both the intrinsic and the extrinsic apoptotic pathways. The possible clinical implications of our findings are discussed.

Induction of Bcl-2 and Bax was related to hyperphosphorylation of tau and neuronal death induced by okadaic acid in rat brain

Abnormal hyperphosphorylation of the cytoskeletal protein tau is a characteristic feature of neurodegeneration in Alzheimer's disease (AD) brain. Okadaic acid (OA), a protein phosphatase inhibitor, induces neuronal death and hyperphosphorylation of tau. In the present study using a model of microinjection of OA into rat frontal cortex, we aimed to investigate if OA-induced hyperphosphorylation of tau and neuronal death are related to the expression of Bcl-2, an apoptosis inhibitor, or Bax, an apoptosis inducer. Immunohistochemistry and Western blot analysis showed that OA injection dose- and time-dependently induced the expression of Bcl-2 and Bax protein in the surrounding of OA injection areas, which were similar with that of AT8 immunostaining, a marker of hyperphosphorylated tau. However, the ratios of Bcl-2 over Bax had a negative relationship to the expression of AT8. Furthermore, double fluorescent staining showed that AT8-positive neurons mainly costained with terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick-end labeling, a marker of DNA damage, indicating that tau hyperphosphorylation may be associated with DNA damage in the neurons of rat brain. In the areas more adjacent to the OA injection site, most neurons with AT8-positive staining showed vulnerability to OA toxicity and could be triple-stained with Bcl-2 and Bax or double-stained with Bcl-2. However, in the areas further from the OA injection site, neurons with few AT8-positive staining showed resistance to OA toxicity and only stained with Bcl-2, but not Bax. The results suggest that the ratios of Bcl-2 over Bax expression may have an effect on tau hyperphosphorylation and neuronal death following OA injection.

Bcl-2 phosphorylation in the BH4 domain precedes caspase-3 activation and cell death after neonatal cerebral hypoxic–ischemic injury

To date, there are very few in vivo studies addressing the role of Bcl-2 phosphorylation. In a model of neonatal hypoxic-ischemic (HI) brain injury, we characterized the spatial and temporal phosphorylation of Bcl-2 at serine-24 (PS24-Bcl-2), using a site-specific antibody. Very few cells positive for PS24-Bcl-2 were found in control animals, but the number increased during reperfusion in all investigated brain areas in the ipsilateral hemisphere after HI, particularly in the border region between intact and damaged tissue. The highest numbers were encountered 24 h post-HI. Phosphorylation of Bcl-2 at serine-24 coincided with cytochrome c release after hypoxia-ischemia and preceded caspase-3 activation. Injured neurons displayed a predominantly nuclear, but also mitochondrial, localization of PS24-Bcl-2 immunoreactivity. In conclusion, phosphorylation of Bcl-2 at serine 24 was induced by hypoxia-ischemia, presumably resulting in loss of its anti-apoptotic function.

Loss of neurons from laminas I-III of the spinal dorsal horn is not required for development of tactile allodynia in the spared nerve injury model of neuropathic pain

It has been proposed that death of inhibitory interneurons in the dorsal horn contributes to the neuropathic pain that follows partial nerve injury. In this study, we have used two approaches to test whether there is neuronal death in the dorsal horn in the spared nerve injury (SNI) model. We performed a stereological analysis of the packing density of neurons in laminas I-III 4 weeks after operation and found no reduction on the ipsilateral side compared with that seen on the contralateral side or in sham-operated or naive rats. In addition, we used two markers of apoptosis, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) staining and immunocytochemical detection of cleaved (activated) caspase-3. Neither of these methods demonstrated apoptotic neurons in the dorsal spinal cord 1 week after operation. Although TUNEL-positive cells were present throughout the gray and white matter at this stage, they were virtually all labeled with antibody against ionized calcium-binding adapter molecule 1, a marker for microglia. All animals that underwent SNI showed clear signs of tactile allodynia affecting the ipsilateral hindpaw. These results suggest that a significant loss of neurons from the dorsal horn is not necessary for the development of tactile allodynia in the SNI model.

Live cell detection of caspase-3 activation by a Discosoma-red-fluorescent-protein-based fluorescence resonance energy transfer construct

A probe consisting of Discosoma red fluorescent protein (DsRed) and enhanced yellow fluorescent protein (EYFP) linked by a 19-amino-acid chain containing the caspase-3 cleavage site Asp-Glu-Val-Asp was developed to monitor caspase-3 activation in living cells. The expression of the tandem construct in mammalian cells yielded a strong red fluorescence when excited with 450- to 490-nm light or with a 488-nm argon ion laser line as a result of fluorescence resonance energy transfer (FRET) from donor EYFP to acceptor DsRed. The advantage over previous constructs using cyan fluorescent protein is that our construct can be used when excitation wavelengths lower than 488nm are not available. To validate the construct, murine HT-22 hippocampal neuronal cells were triggered to undergo CD95-induced neuronal death. An increase in caspase-3 activity was demonstrated by a reduction of FRET in cells transfected with the construct. This was manifested by a dequenching of EYFP fluorescence leading to an increase in EYFP emission and a corresponding decrease in DsRed fluorescence, which correlated with an increase in pro-caspase-3 processing. We conclude that CD95-induced caspase-3 activation in HT-22 cells was readily detected at the single-cell level using the DsRed-EYFP-based FRET construct, making this a useful technology to monitor caspase-3 activity in living cells.

Mutually exclusive subsets of BH3-only proteins are activated by the p53 and c-Jun N-terminal kinase/c-Jun signaling pathways during cortical neuron apoptosis induced by arsenite

The c-Jun N-terminal protein kinase (JNK)/c-Jun and p53 pathways form distinct death-signaling modules in neurons that culminate in Bax-dependent apoptosis. To investigate whether this signaling autonomy is due to recruitment of particular BH3-only proteins, we searched for a toxic signal that would activate both pathways in the same set of neurons. We show that arsenite activates both the JNK/c-Jun and p53 pathways in cortical neurons, which together account for >95% of apoptosis, as determined by using the mixed-lineage kinase (JNK/c-Jun) pathway inhibitor CEP11004 and p53-null mice. Despite the coexistence of both pathways in at least 30% of the population, Bim mRNA and protein expression was increased only by the JNK/c-Jun signaling pathway, whereas Noxa and Puma mRNA and Puma protein expression was entirely JNK/c-Jun independent. About 50% of Puma/Noxa expression was p53 dependent, with the remaining signal being independent of both pathways and possibly facilitated by arsenite-induced reduction in P-Akt. However, functionally, Puma was predominant in mediating Bax-dependent apoptosis, as evidenced by the fact that more than 90% of apoptosis was prevented in Puma-null neurons, although Bim was still upregulated, while Bim- and Noxa-null neurons died similarly to wild-type neurons. Thus, the p53 and JNK/c-Jun pathways can activate mutually exclusive subclasses of BH3-only proteins in the same set of neurons. However, other factors besides expression may determine which BH3-only proteins mediate apoptosis.

Epilepsy and apoptosis pathways

Epilepsy is a common, chronic neurologic disorder characterized by recurrent unprovoked seizures. Experimental modeling and clinical neuroimaging of patients has shown that certain seizures are capable of causing neuronal death. Such brain injury may contribute to epileptogenesis, impairments in cognitive function or the epilepsy phenotype. Research into cell death after seizures has identified the induction of the molecular machinery of apoptosis. Here, the authors review the clinical and experimental evidence for apoptotic cell death pathway function in the wake of seizure activity. We summarize work showing intrinsic (mitochondrial) and extrinsic (death receptor) apoptotic pathway function after seizures, activation of the caspase and Bcl-2 families of cell death modulators and the acute and chronic neuropathologic impact of intervening in these molecular cascades. Finally, we describe evolving data on nonlethal roles for these proteins in neuronal restructuring and cell excitability that have implications for shaping the epilepsy phenotype. This review highlights the work to date on apoptosis pathway signaling during seizure-induced neuronal death and epileptogenesis, and speculates on how emerging roles in brain remodeling and excitability have enriched the number of therapeutic strategies for protection against seizure-damage and epileptogenesis.

Bruce/apollon promotes hippocampal neuron survival and is downregulated by kainic acid

Prolonged or excess stimulation of excitatory amino acid receptors leads to seizures and the induction of excitotoxic nerve cell injury. Kainic acid acting on glutamate receptors produces degeneration of vulnerable neurons in parts of the hippocampus and amygdala, but the exact mechanisms are not fully understood. We have here investigated whether the anti-apoptotic protein Bruce is involved in kainic acid-induced neurodegeneration. In the rat hippocampus and cortex, Bruce was exclusively expressed by neurons. The levels of Bruce were rapidly downregulated by kainic acid in hippocampal neurons as shown both in vivo and in cell culture. Caspase-3 was activated in neurons exhibiting low levels of Bruce causing cell death. Likewise, downregulation of Bruce using antisense oligonucleotides decreased viability and enhanced the effect of kainic acid in the hippocampal neurons. The results show that Bruce is involved in neurodegeneration caused by kainic acid and the downregulation of the protein promotes neuronal death.

19-Nortestosterone influences neural stem cell proliferation and neurogenesis in the rat brain

Abuse of androgenic anabolic steroids can affect brain function leading to behavioural changes. In this study, the effects of the testosterone analogue, 19-nortestosterone, on rat neural stem cells was examined. The androgen receptor is expressed by cultured embryonic and adult neural stem cells, and is also present in the ventricular epithelium during development and in the adult brain in, among others, dentate gyrus. In neural stem cells stimulated with epidermal growth factor, nandrolone reduced cell proliferation, especially in adult ones. The decrease was abolished by flutamide, a receptor antagonist. Nandrolone also decreased the BrdU labelling of neural stem cells in the dentate gyrus, demonstrating an effect of the hormone on cell proliferation in vivo. The effect of nandrolone was observed with both female and male rats but it was more pronounced in pregnant rats, indicating an involvement of oestrogen in nandrolone action. Nandrolone also decreased the number of newly born neuronal cells in the dentate gyrus of male rats. The results show that nandrolone has important effects on the proliferation and differentiation of neural stem cells expressing the cognate androgen receptor. The data show that the use of nandrolone may severely affect the formation of neural stem cells and could therefore have long-term negative consequences in the brain.

Transcriptional mechanisms of hippocampal aging

Aging related cognitive decline is an increasing health problem but affects only a subset of elderly humans. This research uses outbred young (Y) and aged rats. Behavioral characterization distinguishes aged rats with impaired spatial learning (AI) and aged rats with unimpaired learning ability (AU), mimicking the varied susceptibility of the human population to age-associated learning impairment. Studies are testing a hypothesis that hippocampal transcriptional mechanisms and gene expression profiles linked to activator protein-1 (AP-1) and glucocorticoid receptor (GR), mineralocorticoid receptor (MR) or cyclic AMP response element binding protein (CREB) families of transcription factors distinguish successful or unsuccessful aging and cognition. Results from mRNA assays, in situ hybridization, electromobility shift assays and western immunoblot indicate changes in GR and CREB in AI rats. State of the art future approaches to define downstream transcription targets are described.

VEGF-induced phosphorylation of Bcl-2 influences B lineage leukemic cell response to apoptotic stimuli

Post-translational modification of Bcl-2 protein has been described in a variety of cell models with effects varying from enhanced to abrogated function. In this study, we demonstrated that Bcl-2 was constitutively phosphorylated in several hematopoietic tumor cell lines and in primary ALL cells. Increased phosphorylation of Bcl-2 protein in the JM1 ALL cell line, achieved by expression of the phosphomimetic Bcl-2 construct S70E, enhanced JM1 cell chemoresistance. In contrast, initiation of JM1 cell apoptosis was coincident with dephosphorylation of Bcl-2 and elevated protein phosphatase 2A activity. S70E expression also diminished tBid-mediated cytochrome c release and blunted chemotherapy-induced activation of caspases-9 and -3 in JM1 cells. To determine whether soluble factors produced by stromal cells in the bone marrow influence phosphorylation of Bcl-2 protein, a panel of recombinant cytokines was evaluated. Of those tested, vascular endothelial growth factor (VEGF) induced phosphorylation of Bcl-2 protein and blunted cytochrome c release during chemotherapy or tBid treatment of ALL cells. In contrast, JM1 cells transfected with S70A, resulting in expression of Bcl-2 protein that cannot be phosphorylated, were not efficiently rescued from apoptosis by VEGF. These observations suggest that optimal protection of leukemic cells by VEGF may require activation of a pathway that includes Bcl-2 phosphorylation.

Hippocalcin protects against caspase-12-induced and age-dependent neuronal degeneration

Hippocalcin is a neuronal calcium binding protein, but its physiological function in brain is unknown. We show here that hippocampal neurons from hippocalcin-deficient mice are more vulnerable to degeneration, particularly using thapsigargin, elevating intracellular calcium. Caspase-12 was activated in neurons lacking hippocalcin, while calpain was unchanged. Neuronal viability was accompanied by endoplasmic reticulum (ER) stress and a change in the relative induction of the ER chaperone, BiP/GRP78. Neuronal apoptosis inhibitor protein (NAIP), known to interact with hippocalcin, was not altered, but hippocampal neurons from gene-deleted mice were more sensitive to excitotoxicity caused by kainic acid. In addition, an age-dependent increase in neurodegeneration occurred in the gene-deleted mice, showing that hippocalcin contributes to neuronal viability during aging.

Bim, Bad, and Bax: a deadly combination in epileptic seizures

Several Bcl-2 family members, including Bim, may contribute to programmed cell death by inducing mitochondrial cytochrome c release, which activates caspase-9 and then caspase-3, the "executioner" of the cell. In this issue of the JCI, Shinoda and collaborators show the key role of Bim in epileptic seizure-induced neuronal injury and identify the contribution of transcription factors responsible for seizure-induced Bim upregulation.

Bcl-2 family regulation of neuronal development and neurodegeneration

Neuronal cell death is a key feature of both normal nervous system development and neuropathological conditions. The Bcl-2 family, via its regulation of both caspase-dependent and caspase-independent cell death pathways, is uniquely positioned to critically control neuronal cell survival. Targeted gene disruptions of specific bcl-2 family members and the generation of transgenic mice overexpressing anti- or pro-apoptotic Bcl-2 family members have confirmed the importance of the Bcl-2 family in the nervous system. Data from studies of human brain tissue and experimental animal models of neuropathological conditions support the hypothesis that the Bcl-2 family regulates cell death in the mature nervous system and suggest that pharmacological manipulation of Bcl-2 family action could prove beneficial in the treatment of human neurological conditions such as stroke and neurodegenerative diseases.