Recent progress in animal modeling of immune inflammatory processes in schizophrenia: implication of specific cytokines

A review of the fetal brain cytokine imbalance hypothesis of schizophrenia

Maternal infection during pregnancy increases the risk of schizophrenia and other brain disorders of neurodevelopmental origin in the offspring. A multitude of infectious agents seem to be involved in this association. Therefore, it has been proposed that factors common to the immune response to a wide variety of bacterial and viral pathogens may be the critical link between prenatal infection and postnatal brain and behavioral pathology. More specifically, it has been suggested that the maternal induction of pro-inflammatory cytokines may mediate the neurodevelopmental effects of maternal infections. Here, we review recent findings from in vitro and in vivo investigations supporting this hypothesis and further emphasize the influence of enhanced anti-inflammatory cytokine signaling on early brain development. Disruption of the fetal brain balance between pro- and anti-inflammatory cytokine signaling may thus represent a key mechanism involved in the precipitation of schizophrenia-related pathology following prenatal maternal infection and innate immune imbalances.

Early-life programming of later-life brain and behavior: a critical role for the immune system

The immune system is well characterized for its critical role in host defense. Far beyond this limited role however, there is mounting evidence for the vital role the immune system plays within the brain, in both normal, “homeostatic” processes (e.g., sleep, metabolism, memory), as well as in pathology, when the dysregulation of immune molecules may occur. This recognition is especially critical in the area of brain development. Microglia and astrocytes, the primary immunocompetent cells of the CNS, are involved in every major aspect of brain development and function, including synaptogenesis, apoptosis, and angiogenesis. Cytokines such as tumor necrosis factor (TNF)α, interleukin [IL]-1β, and IL-6 are produced by glia within the CNS, and are implicated in synaptic formation and scaling, long-term potentiation, and neurogenesis. Importantly, cytokines are involved in both injury and repair, and the conditions underlying these distinct outcomes are under intense investigation and debate. Evidence from both animal and human studies implicates the immune system in a number of disorders with known or suspected developmental origins, including schizophrenia, anxiety/depression, and cognitive dysfunction. We review the evidence that infection during the perinatal period of life acts as a vulnerability factor for later-life alterations in cytokine production, and marked changes in cognitive and affective behaviors throughout the remainder of the lifespan. We also discuss the hypothesis that long-term changes in brain glial cell function underlie this vulnerability.

Cytokines and schizophrenia: Microglia hypothesis of schizophrenia

The etiology of schizophrenia remains unclear, while there has been a growing amount of evidence for the neuroinflammation and immunogenetics, which are characterized by an increased serum concentration of several pro-inflammatory cytokines. Despite the fact that microglia comprise only <10% of the total brain cells, microglia respond rapidly to even minor pathological changes in the brain and may contribute directly to the neuronal degeneration by producing various pro-inflammatory cytokines and free radicals. In many aspects, the neuropathology of schizophrenia has recently been reported to be closely associatedwith microglial activation. Previous studies have shown the inhibitory effects of some typical/atypical antipsychotics on the release of inflammatory cytokines and free radicals from activated microglia, both of which have recently been known to cause a decrease in neurogenesis as well as white matter abnormalities in the brains of patients with schizophrenia. The microglia hypothesis of schizophrenia may shed new light on the therapeutic strategy for schizophrenia.

Prenatal immune activation leads to multiple changes in basal neurotransmitter levels in the adult brain: implications for brain disorders of neurodevelopmental origin such as schizophrenia

Maternal infection during pregnancy enhances the offspring's risk for severe neuropsychiatric disorders in later life, including schizophrenia. Recent attempts to model this association in animals provided further experimental evidence for a causal relationship between in-utero immune challenge and the postnatal emergence of a wide spectrum of behavioural, pharmacological and neuroanatomical dysfunctions implicated in schizophrenia. However, it still remains unknown whether the prenatal infection-induced changes in brain and behavioural functions may be associated with multiple changes at the neurochemical level. Here, we tested this hypothesis in a recently established mouse model of viral-like infection. Pregnant dams on gestation day 9 were exposed to viral mimetic polyriboinosinic-polyribocytidilic acid (PolyI:C, 5 mg/kg i.v.) or vehicle treatment, and basal neurotransmitter levels were then compared in the adult brains of animals born to PolyI:C- or vehicle-treated mothers by high-performance liquid chromatography on post-mortem tissue. We found that prenatal immune activation significantly increased the levels of dopamine and its major metabolites in the lateral globus pallidus and prefrontal cortex, whilst at the same time it decreased serotonin and its metabolite in the hippocampus, nucleus accumbens and lateral globus pallidus. In addition, a specific reduction of the inhibitory amino acid taurine in the hippocampus was noted in prenatally PolyI:C-exposed offspring relative to controls, whereas central glutamate and gamma-aminobutyric acid (GABA) content was largely unaffected by prenatal immune activation. Our results thus confirm that maternal immunological stimulation during early/middle pregnancy is sufficient to induce long-term changes in multiple neurotransmitter levels in the brains of adult offspring. This further supports the possibility that infection-mediated interference with early fetal brain development may predispose the developing organism to the emergence of neurochemical imbalances in adulthood, which may be critically involved in the precipitation of adult behavioural and pharmacological abnormalities after prenatal immune challenge.

Neonatal polyI:C treatment in mice results in schizophrenia-like behavioral and neurochemical abnormalities in adulthood

It has been reported that viral infection in the first and second trimesters of pregnancy in humans increases the risk of subsequently developing schizophrenia. To develop a mouse model of immune activation during the early postnatal period, neonatal ICR mice were repeatedly injected with polyriboinosinic-polyribocytidilic acid (polyI:C; an inducer of strong innate immune responses) for 5 days (postnatal day 2-6) which may correspond, in terms of brain development, to the early second trimester in human. Cognitive and emotional behavior as well as the extracellular level of glutamate in the hippocampus were analyzed at the age of 10-12 weeks old. PolyI:C-treated mice showed anxiety-like behavior, impairment of object recognition memory and social behavior, and sensorimotor gating deficits, as compared to the saline-treated control group. Depolarization-evoked glutamate release in the hippocampus was impaired in polyI:C-treated mice compared to saline-treated control mice. Furthermore, to investigate the effect of neonatal immune activation on the expression levels of schizophrenia-related genes, we analyzed mRNA levels in the hippocampus 2 and 24h after polyI:C treatment. No significant differences or only transient and marginal changes were observed between polyI:C-treated and saline-treated control mice in the expression levels of schizophrenia-related genes in the hippocampus.

Evidence for disruption of sphingolipid metabolism in schizophrenia

As the field of glycobiology grows, important roles for glycolipids and glycoproteins in neurological disorders are being increasingly appreciated. However, few studies have explored the involvement of these molecules in the pathology of psychiatric illnesses. We investigated molecular differences related to glycobiology in subjects with schizophrenia by analyzing gene expression profiles using a focused glycogene chip, a custom-designed oligonucleotide array containing genes encoding proteins related to glycobiology, including glycosyltransferases, carbohydrate-binding proteins, proteoglycans, and adhesion molecules. We measured expression profiles in prefrontal cortical (BA46) samples from schizophrenic subjects and matched controls. We find differential expression of genes particularly related to glycosphingolipid/sphingolipid metabolism and N- and O-linked glycan biosynthesis in subjects with schizophrenia. Expression decreases of seven genes associated with these pathways, UGT8, SGPP1, GALC, B4GALT6, SPTLC2, ASAH1, and GAL3ST1, were validated by quantitative PCR in schizophrenic subjects with short-term illness. Only one of these genes, SPTLC2, showed differential expression in chronic schizophrenic subjects, although an increase in expression was observed. Covariate analysis showed that the expression of five of these genes was significantly positively correlated with age in schizophrenic, but not control, subjects. These changing patterns of expression could represent an adaptive response to pathology with disease progression or a compensatory effect of antipsychotic medication, although no significant correlations between gene expression levels and drug doses were observed. Disruption of sphingolipid metabolism early in illness could result in widespread downstream effects encompassing diverse pathological deficits already described in schizophrenia, especially those involving myelination and oligodendrocyte function; hence, this system may represent an important link in schizophrenia pathology.

Atypical antipsychotics suppress production of proinflammatory cytokines and up-regulate interleukin-10 in lipopolysaccharide-treated mice

There is considerable evidence that schizophrenia is associated with immune system dysregulation. For example, blood and cerebrospinal fluid (CSF) levels of proinflammatory cytokines are significantly increased in schizophrenic patients, and their normalization correlates with improvement in psychotic symptoms. In fact, typical and atypical antipsychotics are reported to modulate immune function in in vitro and in vivo studies. In the present study, we examined the anti-inflammatory effect of antipsychotics, clozapine, olanzapine, risperidone and haloperidol, on serum cytokine levels in lipopolysaccharide (LPS)-treated mice. Atypical antipsychotics, such as clozapine, olanzapine and risperidone, but not haloperidol, suppressed tumor necrosis factor (TNF)-alpha and interleukin (IL)-6, and up-regulated IL-10. Moreover, only clozapine, robustly increased the serum levels of IL-10. Clozapine reproduced its anti-inflammatory feature in polyinsinic-polycytidylic acid sodium salt (Poly[I:C])-induced inflammation. Thus, the anti-inflammatory effect of clozapine would adapt to inflammation induced by some varieties of antigens. Several receptor ligands, such as 8-OH-DPAT, ketanserin, prazosin and scopolamine, were also examined as to their anti-inflammatory effects on serum cytokine levels in LPS-treated mice. Ketanserin and prazosin, but not 8-OH-DPAT nor scopolamine, behaved similarly to atypical antipsychotics. However, the remarkable increase of serum IL-10 level observed in clozapine was not detected in ketanserin and prazosin. These results suggest the unique efficacy of atypical antipsychotics in the suppression of proinflammatory cytokines, and the increase of anti-inflammatory cytokine, IL-10.

Deficient maternal care resulting from immunological stress during pregnancy is associated with a sex-dependent enhancement of conditioned fear in the offspring

Activation of maternal stress response systems during pregnancy has been associated with altered postpartum maternal care and subsequent abnormalities in the offspring’s brain and behavioral development. It remains unknown, however, whether similar effects may be induced by exposure to immunological stress during pregnancy. The present study was designed to address this issue in a mouse model of prenatal immune activation by the viral mimic polyriboinosinic–polyribocytidilic acid (PolyI:C). Pregnant mice were exposed to PolyI:C-induced immune challenge or sham treatment, and offspring born to PolyI:C- and sham-treated dams were simultaneously cross-fostered to surrogate rearing mothers, which had either experienced inflammatory or vehicle treatment during pregnancy. We evaluated the effects of the maternal immunological manipulation on postpartum maternal behavior, and we assessed the prenatal and postnatal maternal influences on anxiety- and fear-related behavior in the offspring at the peri-adolescent and adult stage of development. We found that PolyI:C treatment during pregnancy led to changes in postpartum maternal behavior in the form of reduced pup licking/grooming and increased nest building activity. Furthermore, the adoption of neonates by surrogate rearing mothers, which had experienced PolyI:C-induced immunological stress during pregnancy, led to enhanced conditioned fear in the peri-adolescent and adult offspring, an effect that was exclusively seen in female but not male subjects. Unconditioned (innate) anxiety-related behavior as assessed in the elevated plus maze and open field explorations tests were not affected by the prenatal and postnatal manipulations. Our results thus highlight that being raised by gestationally immune-challenged surrogate mothers increases the vulnerability for specific forms of fear-related behavioral pathology in later life, and that this association may be mediated by deficits in postpartum maternal care. This may have important implications for the identification and characterization of early-life risk factors involved in the developmental etiology of fear-related neuropsychiatric disorders.

Association study of interleukin 2 (IL2) and IL4 with schizophrenia in a Japanese population

Interleukin 2 (IL-2) and IL-4 are pleiotropic cytokines regulating Th1/Th2 balance and have a regulatory activity in brain function. Thus these cytokines have been implicated in the pathophysiology of schizophrenia. The latest studies provided controversial results regarding the genetic associations of these cytokines. The functional polymorphisms, IL2-330T/G and IL4-590C/T, were associated with schizophrenia in a German population, although contradictory findings were also reported in a Korean population. To ascertain whether IL2 and IL4 contribute to vulnerability to schizophrenia, we conducted a moderate-scale case-control (536 patients and 510 controls) association study for seven polymorphisms in Japanese subjects. There were no significant associations of these genes with schizophrenia using either single marker or haplotype analyses. The present study suggests that IL2 and IL4 do not contribute to vulnerability to schizophrenia in the Japanese population.

Serum levels of P-selectin in men with high-functioning autism

Immune dysfunction has been proposed as a mechanism for the pathophysiology of autistic-spectrum disorders. The selectin family of adhesion molecules plays a prominent role in immune/inflammatory responses. We determined the serum levels of three types of soluble-form selectin (sP, sL and sE) in 15 men with high-functioning autism and 22 age-matched healthy controls by enzyme-linked immunosorbent assay. Levels of sP-selectin and sL-selectin were significantly lower in patients than in controls. Furthermore, sP-selectin levels were negatively correlated with impaired social development during early childhood.

Common behavioral influences of the ErbB1 ligands transforming growth factor alpha and epiregulin administered to mouse neonates

Ligands for epidermal growth factor (EGF) receptor (ErbB1), such as EGF, transforming growth factor alpha (TGFalpha), and epiregulin, are enriched in body fluids and blood and regulate development of various peripheral organs. It remains however how such circulating polypeptide growth factors influence brain development and function. Here, we performed peripheral injections of TGFalpha and epiregulin to mouse neonates and evaluated immediate physical and neurochemical development and later behavioral consequences. Subcutaneous administration of TGFalpha and epiregulin increased phosphorylation of brain ErbB1, suggesting their effects on brain development. Repeated their injections similarly enhanced physical development of eyelid opening and tooth eruption during early postnatal stage and resulted in abnormal behavioral traits in the adult stage. Acoustic startle responses of mice treated with these growth factors as neonates were enhanced and prepulse inhibition was decreased without an apparent correlation between prepulse inhibition level and startle intensity. Locomotor activity and fear-learning performance with tone and context cues were not altered, however. These results suggest that circulating ErbB1 ligands in the periphery of neonates have some common influences on later behavioral traits. Abnormal ErbB1 ligand production at neonatal and potentially prenatal stages might therefore associate with neurodevelopmental disorders such as schizophrenia.

Up-regulation of ADM and SEPX1 in the lymphoblastoid cells of patients in monozygotic twins discordant for schizophrenia

The contribution of genetic factors to schizophrenia is well established and recent studies have indicated several strong candidate genes. However, the pathophysiology of schizophrenia has not been totally elucidated yet. To date, studies of monozygotic twins discordant for schizophrenia have provided insight into the pathophysiology of this illness; this type of study can exclude inter-individual variability and confounding factors such as effects of drugs. In this study we used DNA microarray analysis to examine the mRNA expression patterns in the lymphoblastoid (LB) cells derived from two pairs of monozygotic twins discordant for schizophrenia. From five independent replicates for each pair of twins, we selected five genes, which included adrenomedullin (ADM) and selenoprotein X1 (SEPX1), as significantly changed in both twins with schizophrenia. Interestingly, ADM was previously reported to be up-regulated in both the LB cells and plasma of schizophrenic patients, and SEPX1 was included in the list of genes up-regulated in the peripheral blood cells of schizophrenia patients by microarray analysis. Then, we performed a genetic association study of schizophrenia in the Japanese population and examined the copy number variations, but observed no association. These findings suggest the possible role of ADM and SEPX1 as biomarkers of schizophrenia. The results also support the usefulness of gene expression analysis in LB cells of monozygotic twins discordant for an illness.

Obsessive-compulsive disorder and immunology: a review

Interest in the possibility of an immune-mediated pathophysiology of obsessive-compulsive disorder and related disorders has increased. In the late 1980s, the National Institute of Mental Health reported an increase in obsessive-compulsive symptoms (OCS) in patients with Sydenham chorea (SC). Subsequently, a precipitating streptococcal infection in children with sudden onset of OCS but no chorea led to the coining of PANDAS (Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection). This association has furthered interest in biological measures for immune and genetic susceptibility in non-PANDAS obsessive-compulsive disorder patients (OCD). Furthermore, some studies are trying to demonstrate alterations of immune parameters in OCD patients, with few positive results. In this narrative review, our objective was to describe the immunologic findings in OCD, PANDAS, and their association with SC.

Adult brain and behavioral pathological markers of prenatal immune challenge during early/middle and late fetal development in mice

Maternal infection during pregnancy increases the risk for neurodevelopmental disorders such as schizophrenia and autism in the offspring. This association appears to be critically dependent on the precise prenatal timing. However, the extent to which distinct adult psychopathological and neuropathological traits may be sensitive to the precise times of prenatal immune activation remains to be further characterized. Here, we evaluated in a mouse model of prenatal immune challenge by the viral mimic, polyriboinosinic-polyribocytidilic acid (PolyIC), whether prenatal immune activation in early/middle and late gestation may influence the susceptibility to some of the critical cognitive, pharmacological, and neuroanatomical dysfunctions implicated in schizophrenia and autism. We revealed that PolyIC-induced prenatal immune challenge on gestation day (GD) 9 but not GD17 significantly impaired sensorimotor gating and reduced prefrontal dopamine D1 receptors in adulthood, whereas prenatal immune activation specifically in late gestation impaired working memory, potentiated the locomotor reaction to the NMDA-receptor antagonist dizocilpine, and reduced hippocampal NMDA-receptor subunit 1 expression. On the other hand, potentiation of the locomotor reaction to the dopamine-receptor agonist amphetamine and reduction in Reelin- and Parvalbumin-expressing prefrontal neurons emerged independently of the precise times of prenatal immune challenge. Our findings thus highlight that prenatal immune challenge during early/middle and late fetal development in mice leads to distinct brain and behavioral pathological symptom clusters in adulthood. Further examination and evaluation of in utero immune challenge at different times of gestation may provide important new insight into the neuroimmunological and neuropathological mechanisms underlying the segregation of different symptom clusters in heterogeneous neuropsychiatric disorders such as schizophrenia and autism.

Low serum levels of brain-derived neurotrophic factor and epidermal growth factor in patients with chronic schizophrenia

Neurotrophic factors (NFs) play a pivotal role in the development of the central nervous system. They are thus also suspected of being involved in the etiology of schizophrenia. Previous studies reported a decreased level of serum brain-derived neurotrophic factor (BDNF) in schizophrenia, whereas the association of epidermal growth factor (EGF) with this illness remains controversial. Using a two-site enzyme immunoassay, we conducted the simultaneous measurement of serum BDNF and EGF levels in a group of patients with chronic schizophrenia (N=74) and a group of normal controls matched in age, body mass index, smoking habit and sex (N=87). We found that, compared to normal controls, patients with chronic schizophrenia exhibited lower serum levels of both BDNF and EGF across all ages examined (21-59 years). The serum levels of BDNF and EGF were negatively correlated in the controls (r=-0.387, P=0.0002) but not in the patients. Clinical parameters such as duration of illness and psychiatric rating scale also showed no robust correlations with the NF levels. Collectively, these results suggest that pervasive, abnormal signaling of NFs underlies the pathophysiology of chronic schizophrenia.

Association study in the 5q31-32 linkage region for schizophrenia using pooled DNA genotyping

BACKGROUND

Several linkage studies suggest that chromosome 5q31-32 might contain risk loci for schizophrenia (SZ). We wanted to identify susceptibility genes for schizophrenia within this region.

METHODS

We saturated the interval between markers D5S666 and D5S436 with 90 polymorphic microsatellite markers and genotyped two sets of DNA pools consisting of 300 SZ patients of Bulgarian origin and their 600 parents. Positive associations were followed-up with SNP genotyping.

RESULTS

Nominally significant evidence for association (p < 0.05) was found for seven markers (D5S0023i, IL9, RH60252, 5Q3133_33, D5S2017, D5S1481, D5S0711i) which were then individually genotyped in the trios. The predicted associations were confirmed for two of the markers: D5S2017, localised in the SPRY4-FGF1 locus (p = 0.004) and IL9, localized within the IL9 gene (p = 0.014). Fine mapping was performed using single nucleotide polymorphisms (SNPs) around D5S2017 and IL9. In each region four SNPs were chosen and individually genotyped in our full sample of 615 SZ trios. Two SNPs showed significant evidence for association: rs7715300 (p = 0.001) and rs6897690 (p = 0.032). Rs7715300 is localised between the TGFBI and SMAD5 genes and rs6897690 is within the SPRY4 gene.

CONCLUSION

Our screening of 5q31-32 implicates three potential candidate genes for SZ: SMAD5, TGFBI and SPRY4.

Immune activation during mid-gestation disrupts sensorimotor gating in rat offspring

Maternal immune activation (MIA) is a newly developed animal model of schizophrenia. It has recently been reported that when MIA is induced with the cytokine inducer polyinosinic-polycytidilic acid (poly I:C) rats do not show deficits in prepulse inhibition (PPI), a test that is often considered a validity benchmark. The aim of the current experiment was to determine whether doses of poly I:C that have previously been shown to induce the behavioural features of schizophrenia can disrupt PPI in rats. Pregnant rat dams were given a single injection of poly I:C (4.0 mg/kg) or a saline injection equivalent on gestational day 15. Acoustic startle reactivity, habituation of the startle response and PPI were assessed in juvenile (34-35 day) and adult (>56 day) offspring. Prenatal immune activation did not alter startle reactivity on startle-only or prepulse-only trials. Furthermore, there was no effect of MIA on habituation of the startle response. MIA does however disrupt PPI, as PPI was reduced significantly in adult MIA offspring, and a trend was observed in the juvenile animals. Our finding that prenatal poly I:C can disrupt PPI in MIA rats further validates this procedure as an animal model.

Adult behavioral and pharmacological dysfunctions following disruption of the fetal brain balance between pro-inflammatory and IL-10-mediated anti-inflammatory signaling

Maternal infections during pregnancy increase the risk for schizophrenia and related disorders of putative neurodevelopmental origin in the offspring. This association has been attributed to enhanced expression of pro-inflammatory cytokines in the fetal environment in response to maternal immunological stimulation. In contrast, the specific roles of anti-inflammatory cytokines are virtually unknown in this context. Here, we demonstrate that genetically enforced expression of the anti-inflammatory cytokine interleukin (IL)-10 by macrophages attenuates the long-term behavioral and pharmacological consequences of prenatal immune activation in a mouse model of prenatal viral-like infection by polyriboinosinic-polyribocytidilic acid (PolyI:C; 2 mg/kg, intravenously). In the absence of a discrete prenatal inflammatory stimulus, however, enhanced levels of IL-10 at the maternal-fetal interface by itself also precipitates specific behavioral abnormalities in the grown offspring. This highlights that in addition to the disruptive effects of excess pro-inflammatory molecules, a shift toward enhanced anti-inflammatory signaling in prenatal life can similarly affect cognitive and behavioral development. Hence, shifts of the balance between pro- and anti-inflammatory cytokine classes may be a critical determinant of the final impact on neurodevelopment following early life infection or innate immune imbalances.

Relative prenatal and postnatal maternal contributions to schizophrenia-related neurochemical dysfunction after in utero immune challenge

Prenatal exposure to infections represents a risk factor for the emergence of neuropsychiatric disorders in later life, including schizophrenia and autism. However, it remains essentially unknown whether this association is primarily attributable to prenatal and/or postnatal maternal effects on the offspring. Here, we addressed this issue by dissecting the relative contributions of prenatal inflammatory events and postnatal maternal factors in an animal model of prenatal viral-like infection. Pregnant mice were exposed to the inflammatory agent polyriboinosinic-polyribocytidilic acid (PolyI:C; 5 mg/kg, i.v.) or vehicle treatment on gestation day 9, and offspring born to PolyI:C- and vehicle-treated dams were cross fostered to surrogate rearing mothers that had either experienced inflammatory or sham treatment during pregnancy. We demonstrate that a variety of dopamine- and glutamate-related pharmacological and neuroanatomical disturbances emerge after prenatal immune challenge regardless of whether neonates were raised by vehicle- or PolyI:C-exposed surrogate mothers. However, the adoption of prenatal control animals to immune-challenged surrogate mothers was also sufficient to induce specific pharmacological and neuroanatomical abnormalities in the fostered offspring. Multiple schizophrenia-related dysfunctions emerging after prenatal immune challenge are thus mediated by prenatal but not postnatal maternal effects on the offspring, but immunological stress during pregnancy may affect postpartum maternal factors in such a way that being reared by an immune-challenged surrogate mother can confer risk for distinct forms of psychopathology in adult life.

Herceptin

The biology of the human epidermal growth factor (EGF) receptor-2 (HER2) has been reviewed numerous times and provides an excellent example for developing a targeted cancer therapeutic. Herceptin, the FDA-approved therapeutic monoclonal antibody against HER2, has been used to treat over 150,000 women with breast cancer. However, the developmental history of Herceptin, the key events within the program that created pivotal decision points, and the reasons why decisions were made to pursue the monoclonal antibody approach have never been adequately described. The history of Herceptin is reviewed in a way which allows the experience to be shared for the purposes of understanding the drug discovery and development process. It is the objective of this review to describe the pivotal events and explain why critical decisions were made that resulted in the first therapeutic to successfully target tyrosine kinases in cancer. New approaches and future prospects for therapeutics targeting the HER family are also discussed.

A cyclooxygenase-2 inhibitor ameliorates behavioral impairments induced by striatal administration of epidermal growth factor

Consistent with the hypothesis that neuroinflammatory processes contribute to the neuropathology of schizophrenia, the protein levels of epidermal growth factor (EGF) and its receptor ErbB1 are abnormal in patients with schizophrenia. To evaluate neuropathological significance of this abnormality, we established an animal model for behavioral deficits by administering EGF into the striatum and evaluated the effects of cyclooxygenase-2 (Cox-2) inhibitor celecoxib. Intracranial infusion of EGF into the striatum of adult male rats activated ErbB1 and induced neurobehavioral impairments observed in several schizophrenia models. Unilateral EGF infusion to the striatum lowered prepulse inhibition (PPI) in a dose-dependent manner and impaired latent learning of active shock avoidance without affecting basal learning ability. Bilateral EGF infusion similarly affected PPI. In contrast, EGF infusion to the nucleus accumbens did not induce a behavioral deficit. Intrastriatal EGF infusion also increased Cox-2 expression, elevated tyrosine hydroxylase activity, and upregulated the levels of dopamine and its metabolites. Subchronic administration of celecoxib (10 mg/kg, p.o.) ameliorated the abnormalities in PPI and latent learning as well as normalized dopamine metabolism. We conclude that this EGF-triggered neuroinflammatory process is mediated in part by Cox-2 activity and perturbs dopamine metabolism to generate neurobehavioral abnormalities.

Molecular evidence for increased expression of genes related to immune and chaperone function in the prefrontal cortex in schizophrenia

BACKGROUND

Schizophrenia is characterized by complex gene expression changes. The transcriptome alterations in the prefrontal cortex have been the subject of several recent postmortem studies that yielded both convergent and divergent findings.

METHODS

To increase measurement precision, we used a custom-designed DNA microarray platform with long oligonucleotides and multiple probes with replicates. The platform was designed to assess the expression of > 1800 genes specifically chosen because of their hypothesized roles in the pathophysiology of schizophrenia. The gene expression differences in dorsolateral prefrontal cortex samples from 14 matched pairs of schizophrenia and control subjects were analyzed with two technical replicates and four data mining approaches.

RESULTS

In addition to replicating many expression changes in synaptic, oligodendrocyte, and signal transduction genes, we uncovered and validated a robust immune/chaperone transcript upregulation in the schizophrenia samples.

CONCLUSIONS

We speculate that the overexpression of SERPINA3, IFITM1, IFITM2, IFITM3, CHI3L1, MT2A, CD14, HSPB1, HSPA1B, and HSPA1A in schizophrenia subjects represents a long-lasting and correlated signature of an early environmental insult during development that actively contributes to the pathophysiology of prefrontal dysfunction.

The cellular and behavioral consequences of interleukin-1 alpha penetration through the blood-brain barrier of neonatal rats: a critical period for efficacy

Proinflammatory cytokines circulating in the periphery of early postnatal animals exert marked influences on their subsequent cognitive and behavioral traits and are therefore implicated in developmental psychiatric diseases such as schizophrenia. Here we examined the relationship between the permeability of the blood-brain barrier to interleukin-1 alpha (IL-1 alpha) in neonatal and juvenile rats and their later behavioral performance. Following s.c. injection of IL-1 alpha into rat neonates, IL-1 alpha immunoreactivity was first detected in the choroid plexus, brain microvessels, and olfactory cortex, and later diffused to many brain regions such as neocortex and hippocampus. In agreement, IL-1 alpha administration to the periphery resulted in a marked increase in brain IL-1 alpha content of neonates. Repeatedly injecting IL-1 alpha to neonates triggered astrocyte proliferation and microglial activation, followed by behavioral abnormalities in startle response and putative prepulse inhibition at the adult stage. Analysis of covariance with a covariate of startle amplitude suggested that IL-1 alpha administration may influence prepulse inhibition. However, adult rats treated with IL-1 alpha as neonates exhibited normal learning ability as measured by contextual fear conditioning, two-way passive shock avoidance, and a radial maze task and had no apparent sign of structural abnormality in the brain. In comparison, when IL-1 alpha was administered to juveniles, the blood-brain barrier permeation was limited. The increases in brain IL-1 alpha content and immunoreactivity were less pronounced following IL-1 alpha administration and behavioral abnormalities were not manifested at the adult stage. During early development, therefore, circulating IL-1 alpha efficiently crosses the blood-brain barrier to induce inflammatory reactions in the brain and influences later behavioral traits.

Neurobehavioral and immunological consequences of prenatal immune activation in rats. Influence of antipsychotics

Increasing evidence suggests that pre- or perinatal events that influence the immune system contribute to the development of behavioral or neuropsychiatric disorders. For instance, exposure of pregnant rats to the bacterial endotoxin lipopolysaccharide (LPS) disrupts sensorimotor information processing, as assessed by the prepulse inhibition test (PPI), and also the immune function in adult offspring, which might be of particular relevance as regards schizophrenia. However, the consequences of maternal LPS exposure during pregnancy on synaptic functioning in adult offspring and, more importantly, the therapeutic opportunity to re-establish PPI and immune function have still to be demonstrated. In this work, we analyzed the consequences of prenatal LPS exposure on dopaminergic neurotransmission and presynaptic markers in adult brain areas related to PPI circuitry. In addition, we tested whether oral treatment with the typical antipsychotic drug haloperidol (HAL) could reinstate PPI performances and cytokine serum levels in six-month-old male rats with prenatal LPS exposure. Both sensory information processing deficits and immune anomalies induced by prenatal exposure to LPS were accompanied by changes in dopaminergic neurotransmission and synaptophysin expression. It is important to note that PPI disruption and serum increases in cytokines induced by prenatal LPS exposure were both reversed by HAL. Taken together, these results demonstrate the critical influence of prenatal immune events on the functioning of adult nervous and immune systems, in association with the putative role of the immune system in the development of behavior relevant to schizophrenia.

No association between the ERBB3 gene and schizophrenia in a Japanese population

There is cumulative evidence that neuregulin 1 (NRG1) is a susceptibility gene for schizophrenia. Postmortem studies on brains from schizophrenia patients have revealed changes in the mRNA expression levels of v-erb-b2 erythroblastic leukemia viral oncogene homolog 3 (ERBB3), one of the NRG1 receptor genes. These observations suggest that NRG1-ERBB signaling is involved in the pathogenesis of schizophrenia. To assess whether the ERBB3 gene could be implicated in vulnerability to schizophrenia, we conducted a case-control (399 patients and 438 controls) association study in Japanese subjects. There were no significant association between the polymorphisms or haplotypes of ERBB3 and schizophrenia. The present study shows that ERBB3 does not play a major role in conferring susceptibility to schizophrenia in the Japanese population.

Therapeutic possibilities of cysteamine in the treatment of schizophrenia

Schizophrenia has complicated pathogeneses that is not able to be explained by any one supposed hypothesis, although alterations in dopamine neurotransmission have been widely accepted as the most plausible mechanism. A transition from traditional typical antipsychotics to contemporary atypical antipsychotics which have significantly improved tolerability and enhanced specific efficacy has been also made based on this dopamine hypothesis. Cysteamine is a natural product of mammalian cells and found to be useful pharmacological alternative. A number of evidence suggests that cysteamine may control directly or indirectly dopamine neurotransmission in nucleus accumbens and other schizophrenia-related brain regions. Systemic cysteamine injection mitigated the apomorphine-induced stereotypy as well as decreasing motor stimulant effects of amphetamine, which favor cysteamine over animal models of schizophrenia relative to hyperactivity of dopaminergic pathway. In addition, cysteamine showed neuroprotective effects by way of enhancing central and serum brain derived neurotrophic factor (BDNF) that has been proved to be altered in patients with schizophrenia. Antipsychotic drugs exert their effect partly by modifying the synthesis and distribution of BDNF in selected brain region. Cysteamine was effective to reverse a disruption in prepulse inhibition, an endophenotypic marker of schizophrenia. Cysteamine can also stimulate the release of cortical dopamine, which is interesting in that decreased dopaminergic function in the cerebral cortex has been repeatedly demonstrated in patients with schizophrenia and associated with prominent depressive and negative symptoms. Cysteamine can also increase an important antioxidant, glutathione. Finally, cysteamine treatment was found to decrease weight gain, cataleptic behavior, and serum prolactin levels, which are the major beneficial properties of contemporary atypical antipsychotics. Hence, further explorations of therapeutic implication of cysteamine for schizophrenia in preclinical studies should be warranted in future.