Glial expression of the proenkephalin gene in slice cultures of the subventricular zone

Dorsal Striatum Transcriptome Profile Profound Shift in Repeated Aggression Mouse Model Converged to Networks of 12 Transcription Factors after Fighting Deprivation

Both aggressive and aggression-deprived (AD) species represent pathologic cases intensely addressed in psychiatry and substance abuse disciplines. Previously, we reported that AD mice displayed a higher aggressive behavior score than the aggressive group, implying the manifestation of a withdrawal effect. We employed an animal model of chronic social conflicts, curated in our lab for more than 30 years. In the study, we pursued the task of evaluating key events in the dorsal striatum transcriptome of aggression experienced mice and AD species compared to controls using RNA-Seq profiling. Aggressive species were subjected to repeated social conflict encounters (fights) with regular positive (winners) experience in the course of 20 consecutive days (A20 group). This led to a profoundly shifted transcriptome expression profile relative to the control group, outlined by more than 1000 differentially expressed genes (DEGs). RNA-Seq cluster analysis revealed that elevated cyclic AMP (cAMP) signaling cascade and associated genes comprising 170 differentially expressed genes (DEGs) in aggressive (A20) species were accompanied by a downturn in the majority of other metabolic/signaling gene networks (839 DEGs) via the activation of transcriptional repressor DEGs. Fourteen days of a consecutive fighting deprivation period (AD group) featured the basic restoration of the normal (control) transcriptome expression profile yielding only 62 DEGs against the control. Notably, we observed a network of 12 coordinated DEG Transcription Factor (TF) activators from 62 DEGs in total that were distinctly altered in AD compared to control group, underlining the distinct transcription programs featuring AD group, partly retained from the aggressive encounters and not restored to normal in 14 days. We found circadian clock TFs among them, reported previously as a withdrawal effect factor. We conclude that the aggressive phenotype selection with positive reward effect (winning) manifests an addiction model featuring a distinct opioid-related withdrawal effect in AD group. Along with reporting profound transcriptome alteration in A20 group and gaining some insight on its specifics, we outline specific TF activator gene networks associated with transcriptional repression in affected species compared to controls, outlining Nr1d1 as a primary candidate, thus offering putative therapeutic targets in opioid-induced withdrawal treatment.

Cerebellar cortical-layer-specific control of neuronal migration by pituitary adenylate cyclase-activating polypeptide

Migration of immature neurons is essential for forming the cortical layers and nuclei. Impairment of migration results in aberrant neuronal cytoarchitecture, which leads to various neurological disorders. Neurons alter the mode, tempo and rate of migration when they translocate through different cortical layers, but little is known about the mechanisms underlying this process. Here we show that endogenous pituitary adenylate cyclase-activating polypeptide (PACAP) has short-term and cortical-layer-specific effects on granule cell migration in the early postnatal mouse cerebellum. Application of exogenous PACAP significantly slowed the migration of isolated granule cells and shortened the leading process in the microexplant cultures of the postnatal day (P)0-3 cerebella. Interestingly, in the cerebellar slices of P10 mice, application of exogenous PACAP significantly inhibited granule cell migration in the external granular layer (EGL) and molecular layer (ML), but failed to alter the movement in the Purkinje cell layer (PCL) and internal granular layer (IGL). In contrast, application of PACAP antagonist accelerated granule cell migration in the PCL, but did not change the movement in the EGL, ML and IGL. Inhibition of the cAMP signaling and the activity of phospholipase C significantly reduced the effects of exogenous PACAP on granule cell migration. The PACAP action on granule cell migration was transient, and lasted for approximately 2 h. The duration of PACAP action on granule cell migration was determined by the desensitization of its receptors and prolonged by inhibiting the protein kinase C. Endogenous PACAP was present sporadically in the bottom of the ML, intensively in the PCL, and throughout the IGL. Collectively, these results indicated that PACAP acts on granule cell migration as "a brake (stop signal) for cell movement." Furthermore, these results suggest that endogenous PACAP slows granule cell migration when the cells enter the PACAP-rich PCL, and 2 h later the desensitization of PACAP receptors allows the cells to accelerate the rate of migration and to actively move within the PACAP-rich IGL. Therefore, endogenous PACAP may provide a cue that regulates granule cell migration in a cerebellar cortical-layer-specific manner.

Neuroprotection by endogenous and exogenous PACAP following stroke

We investigated the effects of PACAP treatment, and endogenous PACAP deficiency, on infarct volume, neurological function, and the cerebrocortical transcriptional response in a mouse model of stroke, middle cerebral artery occlusion (MCAO). PACAP-38 administered i.v. or i.c.v. 1 h after MCAO significantly reduced infarct volume, and ameliorated functional motor deficits measured 24 h later in wild-type mice. Infarct volumes and neurological deficits (walking faults) were both greater in PACAP-deficient than in wild-type mice, but treatment with PACAP reduced lesion volume and neurological deficits in PACAP-deficient mice to the same level of improvement as in wild-type mice. A 35,546-clone mouse cDNA microarray was used to investigate cortical transcriptional changes associated with cerebral ischemia in wild-type and PACAP-deficient mice, and with PACAP treatment after MCAO in wild-type mice. 229 known (named) transcripts were increased (228) or decreased (1) in abundance at least 50% following cerebral ischemia in wild-type mice. 49 transcripts were significantly up-regulated only at 1 h post-MCAO (acute response transcripts), 142 were up-regulated only at 24 h post-MCAO (delayed response transcripts) and 37 transcripts were up-regulated at both times (sustained response transcripts). More than half of these are transcripts not previously reported to be altered in ischemia. A larger percentage of genes up-regulated at 24 hr than at 1 hr required endogenous PACAP, suggesting a more prominent role for PACAP in later response to injury than in the initial response. This is consistent with a neuroprotective role for PACAP in late response to injury, i.e., even when administered 1 hr or more after MCAO. Putative injury effector transcripts regulated by PACAP include beta-actin, midline 2, and metallothionein 1. Potential neuroprotective transcripts include several demonstrated to be PACAP-regulated in other contexts. Prominent among these were transcripts encoding the PACAP-regulated gene Ier3, and the neuropeptides enkephalin, substance P (tachykinin 1), and neurotensin.

‘Neuro’-peptides in glia: Focus on NPY and galanin

The term neuropeptide was advanced by de Wied and collaborators in the early seventies. At that time, they defined neuropeptides as endogenous substances synthesized in nerve cells and involved in nervous system functions. Since then, several studies have revealed that the very same 'neuropeptides' are also expressed in non-neuronal cells. It is therefore generally accepted that the original definition of these peptides was too limited and, consequently, it has recently been revised. Among the non-neuronal cells that synthesize neuropeptides are several glial cell types.

Evidence for cell specific regulation by PACAP38 of the proenkephalin gene expression in neocortical cells

During the first postnatal week, glial cell production for the neocortex continues in the neocortical subventricular zone. During this time, the proenkephalin gene (PEnk) is expressed in numerous cells of the subventricular zone and of the adjacent neocortex. When neocortical astroglial cells are brought into dissociation culture, they also produce PEnk mRNA. We have investigated the effect of pituitary adenylate cyclase activating peptide-38 (PACAP38) on PEnk gene expression in dissociation cultures as well as in slice cultures, which contained the subventricular zone and the adjacent neocortex. PACAP38 enhanced the levels of PEnk mRNA in both culture systems. In dissociated astroglial cells, inhibition of protein kinase A, of p44,42 mitogen-activated protein kinase as well as of the EGF-receptor tyrosine kinase by H89, PD98059 and AG1478, respectively, reduced the PACAP38-induced expression in a synergistic manner. In the neocortical part of the slice cultures, the effect of PACAP38 on PEnk gene expression was inhibited only by H89 and PD98059. Here, protein kinase A and p44,42 MAP kinases shared a mechanism which increased the gene expression. Surprisingly, the expression of the PEnk gene in the glial progenitors of the subventricular zone as induced by PACAP38 was not affected by any of the three protein kinase inhibitors, but was blocked by the unspecific kinase inhibitor H7. It is concluded that PACAP38 induced the PEnk gene expression in both culture systems in a cell-type specific manner.