Mohammed Emamussalehin Choudhury

A cytokine mixture of GM‐CSF and IL‐3 that induces a neuroprotective phenotype of microglia leading to amelioration of (6‐OHDA)‐induced Parkinsonism of rats

Dopamine (DA) agonists are widely used as primary treatments for Parkinsons disease. However, they do not prevent progressive degeneration of dopaminergic neurons, the central pathology of the disease. In this study, we found that subcutaneous injection of a cytokine mixture containing granulocyte macrophage colony‐stimulating factor and interleukin‐3 (IL‐3) markedly suppressed dopaminergic neurodegeneration in 6‐hydroxydopamine‐lesioned rats, an animal model of Parkinsons disease. The cytokine mixture suppressed the decrease of DA content in the striatum, and ameliorated motor function in the lesioned rats. In response to the cytokine injection, dopaminergic neurons in the substantia nigra pars compacta increased expression of the antiapoptotic protein Bcl‐xL. Microglial activation in the pars compacta was evident in both the saline‐ and cytokine‐injected rats. However, the cytokine mixture suppressed expression of the proinflammatory cytokines IL‐1β and tumor necrosis factors α, and upregulated the neuroprotective factors insulin‐like growth factor‐1 and hepatocyte growth factor. Similar responses were observed in cultured microglia. Detailed morphometric analyses revealed that NG2 proteoglycan‐expressing glial cells increased in the cytokine‐injected rats, while astrocytic activation with increased expression of antioxidative factors was evident only in the saline‐injected rats. Thus, the present findings show that the cytokine mixture was markedly effective in suppressing neurodegeneration. Its neuroprotective effects may be mediated by increased expression of Bcl‐xL in dopaminergic neurons, and the activation of beneficial actions of microglia that promote neuronal survival. Furthermore, this cytokine mixture may have indirect actions on NG2 proteoglycan‐expressing glia, whose role may be implicated in neuronal survival.

Zonisamide-induced long-lasting recovery of dopaminergic neurons from MPTP-toxicity

Zonisamide is an antiepileptic drug that also improves the cardinal symptoms of Parkinsons disease. This study investigated the effects of zonisamide on dopaminergic neuronal degeneration in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. Six groups of mice were treated as follows: 1) normal saline; 2) MPTP, 15 mg/kg×4 every 2h; 3) MPTP and zonisamide, 40 mg/kg×1, 1h after the last MPTP dose; 4) MPTP and zonisamide, 1 day after the last dose of MPTP; 5) MPTP and zonisamide, 1h before the first MPTP dose; and 6) zonisamide, 40 mg/kg. MPTP-treatment decreased the contents of dopamine as well as the number and area of tyrosine hydroxylase (TH)-positive neurons. Concurrent treatment of mice with zonisamide and MPTP did not show any inhibition of the toxic effect of MPTP towards dopamine contents at 1 week after treatment but it increased the number and area of TH-positive neurons compared to the MPTP-treated group. Surviving TH-positive neurons had recovery of dopamine production after several weeks. Moreover, zonisamide increased the number of S100β-positive and glial fibrillary acidic protein (GFAP)-positive astrocytes and dopamine turnover. These results suggest that zonisamide acts as a neuro-protectant against MPTP-induced dopaminergic neuronal degeneration as shown by an increase of TH-positive neurons and this may be mediated by increased S100β secretion.

Zonisamide up-regulated the mRNAs encoding astrocytic anti-oxidative and neurotrophic factors

Zonisamide has been proven as an effective drug for the recovery of degenerating dopaminergic neurons in the animal models of Parkinsons disease. However, several lines of evidence have questioned the neuroprotective capacity of zonisamide in animal models of Parkinsons disease. Although it suppresses dopaminergic neurodegeneration in animal models, the cellular and molecular mechanisms underlying the effectiveness of zonisamide are not fully understood. The current study demonstrates the effects of zonisamide on astrocyte cultures and two 6-hydroxydopamine-induced models of Parkinsons disease. Using primary astrocyte cultures, we showed that zonisamide up-regulated the expression of mRNA encoding mesencephalic astrocyte-derived neurotrophic factor, vascular endothelial growth factor, proliferating cell nuclear antigen, metallothionein-2, copper/zinc superoxide dismutase, and manganese superoxide dismutase. Similar responses to zonisamide were found in substantia nigra where the rats were pre-treated with 6-hydroxydopamine. Notably, pharmacological inhibition of 6-hydroxydopamine-induced toxicity by zonisamide pre-treatment was also confirmed using rat mesencephalic organotypic slice cultures of substantia nigra. In addition to this, zonisamide post-treatment also attenuated the nigral tyrosine hydroxylase-positive neuronal loss induced by 6-hydroxydopamine. Taken together, these studies demonstrate that zonisamide protected dopamine neurons in two Parkinsons disease models through a novel mechanism, namely increasing the expression of some important astrocyte-mediated neurotrophic and anti-oxidative factors.

Anti-inflammatory effects of noradrenaline on LPS-treated microglial cells: Suppression of NFκB nuclear translocation and subsequent STAT1 phosphorylation.

Noradrenaline (NA) has marked anti-inflammatory effects on activated microglial cells. The present study was conducted to elucidate the mechanisms underlying the NA effects using rat primary cultured microglial cells. NA, an α1 agonist, phenylephrine (Phe) and a β2 agonist, terbutaline (Ter) suppressed lipopolysaccharide (LPS)-induced nitric oxide (NO) release by microglia and prevented neuronal degeneration in LPS-treated neuron-microglia coculture. The agents suppressed expression of mRNA encoding proinflammatory mediators. Both an α1-selective blocker terazocine and a β2-selective blocker butoxamine overcame the suppressive effects of NA. cAMP-dependent kinase (PKA) inhibitors did not abolish the suppressive NA effects. LPS decreased IκB leading to NFκB translocation into nuclei, then induced phosphorylation of signal transducer and activator of transcription 1 (STAT1) and expression of interferon regulatory factor 1 (IRF1). NA inhibited LPS-induced these changes. When NFκB expression was knocked down with siRNA, LPS-induced STAT1 phosphorylation and IRF1 expression was abolished. NA did not suppress IL-6 induced STAT1 phosphorylation and IRF1 expression. These results suggest that one of the critical mechanisms underlying the anti-inflammatory effects of NA is the inhibition of NFκB translocation. Although inhibitory effects of NA on STAT1 phosphorylation and IRF1 expression may contribute to the overall suppressive effects of NA, these may be the downstream events of inhibitory effects on NFκB. Since NA, Phe and Ter exerted almost the same effects and PKA inhibitors did not show significant antagonistic effects, the suppression by NA might not be dependent on specific adrenergic receptors and cAMP-dependent signaling pathway.

The hypnotic bromovalerylurea ameliorates 6-hydroxydopamine-induced dopaminergic neuron loss while suppressing expression of interferon regulatory factors by microglia

The low molecular weight organic compound bromovalerylurea (BU) has long been used as a hypnotic/sedative. In the present study, we found that BU suppressed mRNA expression of proinflammatory factors and nitric oxide release in lipopolysaccharide (LPS)-treated rat primary microglial cell cultures. BU prevented neuronal degeneration in LPS-treated neuron-microglia cocultures. The anti-inflammatory effects of BU were as strong as those of a synthetic glucocorticoid, dexamethasone. A rat hemi-Parkinsonian model was prepared by injecting 6-hydroxydopamine into the right striatum. BU was orally administered to these rats for 7 days, which ameliorated the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and alleviated motor deficits. BU suppressed the expression of mRNAs for interferon regulatory factors (IRFs) 1, 7 and 8 in the right (lesioned) ventral midbrain as well as those for proinflammatory mediators. BU increased mRNA expression of various neuroprotective factors, including platelet-derived growth factor and hepatocyte growth factor, but it did not increase expression of alternative activation (M2) markers. In microglial culture, BU suppressed the LPS-induced increase in expression of IRFs 1 and 8, and it reduced LPS-induced phosphorylation of JAK1 and STATs 1 and 3. Knockdown of IRFs 1 and 8 suppressed LPS-induced NO release by microglial cells. These results suggest that suppression of microglial IRF expression by BU prevents neuronal cell death in the injured brain region, where microglial activation occurs. Because many Parkinsonian patients suffer from sleep disorders, BU administration before sleep may effectively ameliorate neurological symptoms and alleviate sleep dysfunction.

Treadmill exercise ameliorates ischemia-induced brain edema while suppressing Na+/H+ exchanger 1 expression

Exercise may be one of the most effective and sound therapies for stroke; however, the mechanisms underlying the curative effects remain unclear. In this study, the effects of forced treadmill exercise with electric shock on ischemic brain edema were investigated. Wistar rats were subjected to transient (90 min) middle cerebral artery occlusion (tMCAO). Eighty nine rats with substantially large ischemic lesions were evaluated using magnetic resonance imaging (MRI) and were randomly assigned to exercise and non-exercise groups. The rats were forced to run at 4-6m/s for 10 min/day on days 2, 3 and 4. Brain edema was measured on day 5 by MRI, histochemical staining of brain sections and tissue water content determination (n=7, each experiment). Motor function in some rats was examined on day 30 (n=6). Exercise reduced brain edema (P<0.05-0.001, varied by the methods) and ameliorated motor function (P<0.05). The anti-glucocorticoid mifepristone or the anti-mineralocorticoid spironolactone abolished these effects, but orally administered corticosterone mimicked the ameliorating effects of exercise. Exercise prevented the ischemia-induced expression of mRNA encoding aquaporin 4 (AQP4) and Na(+)/H(+) exchangers (NHEs) (n=5 or 7, P<0.01). Microglia and NG2 glia expressed NHE1 in the peri-ischemic region of rat brains and also in mixed glial cultures. Corticosterone at ~10nM reduced NHE1 and AQP4 expression in mixed glial and pure microglial cultures. Dexamethasone and aldosterone at 10nM did not significantly alter NHE1 and AQP4 expression. Exposure to a NHE inhibitor caused shrinkage of microglial cells. These results suggest that the stressful short-period and slow-paced treadmill exercise suppressed NHE1 and AQP4 expression resulting in the amelioration of brain edema at least partly via the moderate increase in plasma corticosterone levels.

The ameliorative effects of a hypnotic bromvalerylurea in sepsis

Sepsis is a severe pathologic event, frequently causing death in critically ill patients. However, there are no approved drugs to treat sepsis, despite clinical trials of many agents that have distinct targets. Therefore, a novel effective treatment should be developed based on the pathogenesis of sepsis. We recently observed that an old hypnotic drug, bromvalerylurea (BU) suppressed expression of many kinds of pro- and anti-inflammatory mediators in LPS- or interferon-γ activated alveolar and peritoneal macrophages (AMs and PMs). Taken the anti-inflammatory effects of BU on macrophages, we challenged it to septic rats that had been subjected to cecum-ligation and puncture (CLP). BU was subcutaneously administered to septic rats twice per day. Seven days after CLP treatment, 85% of septic rats administrated vehicle had died, whereas administration of BU reduce the rate to 50%. Septic rats showed symptoms of multi-organ failure; respiratory, circulatory and renal system failures as revealed by histopathological analyses, blood gas test and others. BU ameliorated these symptoms. BU also prevented elevated serum-IL-6 level as well as IL-6 mRNA expression in septic rats. Collectively, BU might be a novel agent to ameliorate sepsis by preventing the onset of MOF.

Effects of hypnotic bromovalerylurea on microglial BV2 cells

An old sedative and hypnotic bromovalerylurea (BU) has anti-inflammatory effects. BU suppressed nitric oxide (NO) release and proinflammatory cytokine expression by lipopolysaccharide (LPS)-treated BV2 cells, a murine microglial cell line. However, BU did not inhibit LPS-induced nuclear translocation of nuclear factor-κB and subsequent transcription. BU suppressed LPS-induced phosphorylation of signal transducer and activator of transcription 1 (STAT1) and expression of interferon regulatory factor 1 (IRF1). The Janus kinase 1 (JAK1) inhibitor filgotinib suppressed the NO release much more weakly than that of BU, although filgotinib almost completely prevented LPS-induced STAT1 phosphorylation. Knockdown of JAK1, STAT1, or IRF1 did not affect the suppressive effects of BU on LPS-induced NO release by BV2 cells. A combination of BU and filgotinib synergistically suppressed the NO release. The mitochondrial complex I inhibitor rotenone, which did not prevent STAT1 phosphorylation or IRF1 expression, suppressed proinflammatory mediator expression less significantly than BU. BU and rotenone reduced intracellular ATP (iATP) levels to a similar extent. A combination of rotenone and filgotinib suppressed NO release by LPS-treated BV2 cells as strongly as BU. These results suggest that anti-inflammatory actions of BU may be attributable to the synergism of inhibition of JAK1/STAT1-dependent pathways and reduction in iATP level.

Sustained anti-inflammatory effects of TGF-β1 on microglia/macrophages

Ischemic brain injuries caused release of damage-associated molecular patterns (DAMPs) that activate microglia/macrophages (MG/MPs) by binding to Toll-like receptors. Using middle cerebral artery transiently occluded rats, we confirmed that MG/MPs expressed inducible nitric oxide synthase (iNOS) on 3days after reperfusion (dpr) in ischemic rat brain. iNOS expression almost disappeared on 7dpr when transforming growth factor-β1 (TGF-β1) expression was robustly increased. After transient incubation with TGF-β1 for 24h, rat primary microglial cells were incubated with lipopolysaccharide (LPS) and released NO level was measured. The NO release was persistently suppressed even 72h after removal of TGF-β1. The sustained TGF-β1 effects were not attributable to microglia-derived endogenous TGF-β1, as revealed by TGF-β1 knockdown and in vitro quantification studies. Then, boiled supernatants prepared from ischemic brain tissues showed the similar sustained inhibitory effects on LPS-treated microglial cells that were prevented by the TGF-β1 receptor-selective blocker SB525334. After incubation with TGF-β1 for 24h and its subsequent removal, LPS-induced phosphorylation of IκB kinases (IKKs), IκB degradation, and NFκB nuclear translocation were inhibited in a sustained manner. SB525334 abolished all these effects of TGF-β1. In consistent with the in vitro results, phosphorylated IKK-immunoreactivity was abundant in MG/MPs in ischemic brain lesion on 3dpr, whereas it was almost disappeared on 7dpr. The findings suggest that abundantly produced TGF-β1 in ischemic brain displays sustained anti-inflammatory effects on microglial cells by persistently inhibiting endogenous Toll-like receptor ligand-induced IκB degradation.

Truncated CD200 stimulates tumor immunity leading to fewer lung metastases in a novel Wistar rat metastasis model

CD200 mediates immunosuppression in immune cells that express its receptor, CD200R. There are two CD200 variants; truncated CD200 that lacks the part of N-terminal sequence necessary for CD200R binding (CD200S) and full-length CD200 (CD200L). We established a novel lung metastasis model by subcutaneously transplanting C6 glioma cells into the backs of neonatal Wistar rats. All transplanted rats developed large back tumors, nearly 90% of which bore lung metastases. To compare the effects of CD200S and CD200L on tumor immunity, CD200L (C6-L)- or CD200S (C6-S)-expressing C6 cells were similarly transplanted. The results showed that 100% of rats with C6-L tumors developed lung metastases, while metastases were found in only 44% of rats with C6-S tumors (n = 25). Tumors disappeared in approximately 20% of the C6-S-bearing rats, and these animals evaded death 180 d after transplantation, while all C6-L tumor-bearing rats died after 45 d. Next generation sequencing revealed that C6-S tumors expressed chemokines and granzyme B at much higher levels than C6-L tumors. Flow cytometry revealed that C6-S tumors contained more dead cells and more CD45+ cells, including natural killer cells and CD8+ lymphocytes. In particular, multiple subsets of dendritic cells expressing CD11c, MHC class II, CD8, and/or CD103 were more abundant in C6-S than in C6-L tumors. These results suggested that CD200S induced the accumulation of multiple dendritic cell subsets that activated cytotoxic T lymphocytes, leading to the elimination of metastasizing tumor cells.