IL‐1β enhances the antibacterial activity of astrocytes by activation of NF‐κB

Astrocytes have important immune functions in CNS, and astrocytes stimulated by interferon‐γ were showed to have direct antimicrobial function. However whether astrocytes without the stimulation of cytokines have antibacterial function, and how this function is regulated are still largely unknown. In this study, we found that primary cultured astrocytes inhibited the growth of both gram‐negative and gram‐positive bacteria. Further more, we showed that interleukin‐1β (IL‐1β) enhanced the antibacterial effect in a dose‐dependent manner, and the antibacterial effect of astrocytes from IL‐1β receptor‐deficient mice failed to be enhanced by IL‐1β. IL‐1β stimulated IκBα degradation, NF‐κB nuclear translocation, and transactivation in astrocytes. NF‐κB inhibitors blocked NF‐κB activation and the enhanced antibacterial effect induced by IL‐1β. In addition, overexpression of dominant negative IκBα in astrocytes inhibited IκBα degradation and NF‐κB transactivation, and also inhibited the enhanced antibacterial effect induced by IL‐1β. All these data demonstrated that IL‐1β enhanced the antibacterial activity of astrocytes by activation of NF‐κB. © 2009 Wiley‐Liss, Inc.     

The effect of P2X7 receptor activation on nuclear factor‐kappa B phosphorylation induced by status epilepticus in the rat hippocampus

Nuclear factor‐kappa B (NFκB) signal is essential for neuronal survival and its activation may protect neuron against various stimuli. Since purinergic signals activate NFκB through the P2X7 receptor, we investigated the distinct pattern of NF‐κB phosphorylation in neurons by P2X7 receptor activation following status epilepticus (SE) in an effort to understand the role of P2X7 receptor in epileptogenic insult. In non‐SE animals, 2′(3′)‐O‐(4‐benzoyl)benzoyl adenosine 5′‐triphosphate (BzATP, a P2X7R agonist) treatment increased only p52‐Ser869 NF‐κB phosphorylation in neuron. Following SE, p52‐Ser865, p52‐Ser869, p65‐Ser276, p65‐Ser311, p65‐Ser468, and p65‐Ser529 NF‐κB phosphorylation was significantly decreased in CA1 and CA3 neurons. However, BzATP treatment prevented reductions in p65‐Ser276, p65‐Ser311, p65‐Ser529, and p52‐Ser869 NF‐κB phosphorylations in CA1 and/or CA3 neurons induced by SE. Furthermore, BzATP treatment reduced SE‐induced p65‐Ser311, p65‐Ser468, p65‐Ser536, and p52‐Ser869 NF‐κB phosphorylations in astrocytes. These findings indicate that P2X7 functions may be involved in the regulation of SE‐induced reactive astrocytes and neuronal degeneration via NF‐κB phosphorylations in response to pilocarpine‐induced SE in the rat hippocampus. © 2013 Wiley Periodicals, Inc.     

IL‐12 p40 homodimer,the so‐called biologically inactive molecule,induces nitric oxide synthase in microglia via IL‐12Rβ1

Earlier we have demonstrated that IL‐12 p40 homodimer (p40₂) induces the expression of inducible nitric oxide synthase (iNOS) in microglia. This study was undertaken to investigate underlying mechanisms required for IL‐12 p40₂‐ and IL‐12 p70‐induced expression of iNOS in microglia. IL‐12 p40₂ alone induced the activation of both extracellular signal‐regulated kinase (ERK) and p38 mitogen‐activated protein kinase (MAPK). Interestingly, the ERK pathway coupled p40₂ to iNOS expression via C/EBPβ, but not NF‐κB, whereas the p38 pathway relayed the signal from p40₂ to iNOS expression via both NF‐κB and C/EBPβ. Furthermore, by using microglia from IL‐12Rβ1 (?/?) and IL‐12Rβ2 (?/?) mice or siRNA against IL‐12Rβ1 and IL‐12Rβ2, we demonstrate that p40₂ induced the expression of iNOS in microglia via IL‐12Rβ1–(ERK+p38)–(NF‐κB +C/EBPβ) pathway. In contrast, both IL‐12Rβ1 and IL‐12Rβ2 were involved for IL‐12 p70‐induced microglial expression of iNOS. Although IL‐12Rβ1 coupled p70 to NF‐κB and C/EBPβ, IL‐12Rβ2 was responsible for p70‐mediated activation of GAS. This study delineates a new role of IL‐12Rβ1 and IL‐12Rβ2 for the expression of iNOS and production of NO in microglia that may participate in the pathogenesis of neuroinflammatory diseases. © 2009 Wiley‐Liss, Inc.     

PPARγ Agonist Pioglitazone Reverses Memory Impairment and Biochemical Changes in a Mouse Model of Type 2 Diabetes Mellitus

Aims: Pioglitazone, known as a peroxisome proliferator‐activated receptor γ (PPARγ) agonist, is used to treat type 2 diabetes mellitus (T2DM). T2DM has been associated with reduced performance on numerous domains of cognitive function. Here, we investigated the effects of pioglitazone on memory impairment in a mouse model with defects in insulin sensitivity and secretion, namely high‐fat diet (HFD) streptozotocin (STZ)‐induced diabetic mice. Methods: ICR mice were fed with HFD for 4 weeks and then injected with a single low dose of STZ followed by continued HFD feeding for an additional 4 weeks. Pioglitazone (18 mg/kg, 9 mg/kg body weight) was orally administered for 6 weeks once daily. Y‐maze test and Morris water maze test (MWM) were employed for testing learning and memory. Serum glucose, serum insulin, serum triglyceride, brain β‐amyloid peptide (Aβ), brain β‐site amyloid precursor protein cleaving enzyme (BACE1), brain nuclear factor κB (NF‐κB), and brain receptor for advanced glycation end products (RAGE) were also tested. Results: The STZ/HFD diabetic mice, characterized by hyperglycemia, hyperlipemia and hypoinsulinemia, performed poorly on Y‐maze and MWM hence reflecting impairment of learning and memory behavior with increases of Aβ40/Aβ42, BACE1, NF‐κB, and RAGE in brain. Treatment of PPARγ agonist, pioglitazone (18 or 9 mg/kg body weight), significantly reversed diabetes‐induced impairment of learning and memory behavior, which is involved in decreases of Aβ40/Aβ42 via inhibition of NF‐κB, BACE1 and RAGE in brain as well as attenuation of hyperglycemia, hyperlipemia, and hypoinsulinemia. Conclusions: It is concluded that PPARγ agonist pioglitazone may be considered as potential pharmacological agents for the management of cognitive dysfunction in T2DM.     

Differential contributions of microglial and neuronal IKKβ to synaptic plasticity and associative learning in alert behaving mice

Microglia are CNS resident immune cells and a rich source of neuroactive mediators, but their contribution to physiological brain processes such as synaptic plasticity, learning, and memory is not fully understood. In this study, we used mice with partial depletion of IκB kinase β, the main activating kinase in the inducible NF‐κB pathway, selectively in myeloid lineage cells (mIKKβKO) or excitatory neurons (nIKKβKO) to measure synaptic strength at hippocampal Schaffer collaterals during long‐term potentiation (LTP) and instrumental conditioning in alert behaving individuals. Resting microglial cells in mIKKβKO mice showed less Iba1‐immunoreactivity, and brain IL‐1β mRNA levels were selectively reduced compared with controls. Measurement of field excitatory postsynaptic potentials (fEPSPs) evoked by stimulation of the CA3‐CA1 synapse in mIKKβKO mice showed higher facilitation in response to paired pulses and enhanced LTP following high frequency stimulation. In contrast, nIKKβKO mice showed normal basic synaptic transmission and LTP induction but impairments in late LTP. To understand the consequences of such impairments in synaptic plasticity for learning and memory, we measured CA1 fEPSPs in behaving mice during instrumental conditioning. IKKβ was not necessary in either microglia or neurons for mice to learn lever‐pressing (appetitive behavior) to obtain food (consummatory behavior) but was required in both for modification of their hippocampus‐dependent appetitive, not consummatory behavior. Our results show that microglia, through IKKβ and therefore NF‐κB activity, regulate hippocampal synaptic plasticity and that both microglia and neurons, through IKKβ, are necessary for animals to modify hippocampus‐driven behavior during associative learning. GLIA 2015;63:549–566     

Protein‐bound crotonaldehyde accumulates in the spinal cord of superoxide dismutase‐1 mutation‐associated familial amyotrophic lateral sclerosis and its transgenic mouse model

Growing evidence documents oxidative stress involvement in ALS. We previously demonstrated accumulation of a protein‐bound form of the highly toxic lipid peroxidation product crotonaldehyde (CRA) in the spinal cord of sporadic ALS patients. In the present study, to the determine the role for CRA in the disease processes of superoxide dismutase‐1 (SOD1) mutation‐associated familial ALS (FALS), we performed immunohistochemical and semiquantitative cell count analyses of protein‐bound CRA (P‐CRA) in the spinal cord of SOD1‐mutated FALS and its transgenic mouse model. Immunohistochemical analysis revealed increased P‐CRA immunoreactivity in the spinal cord of the FALS patients and the transgenic mice compared to their respective controls. In the FALS patients, P‐CRA immunoreactivity was localized in almost all of the chromatolytic motor neurons, neurofilamentous conglomerates, spheroids, cordlike swollen axons, reactive astrocytes and microglia, and the surrounding neuropil in the affected areas represented by the anterior horns. In the transgenic mice, P‐CRA immunoreactivity was localized in only a few ventral horn glia in the presymptomatic stage, in almost all of the vacuolated motor neurons and cordlike swollen axons and some of the ventral horn reactive astrocytes and microglia in the onset stage, and in many of the ventral horn reactive astrocytes and microglia in the advanced stage. Cell count analysis on mouse spinal cord sections disclosed a statistically significant increase in the density of P‐CRA‐immunoreactive glia in the ventral horns of the young to old G93A mice compared to the age‐matched control mice. The present results indicate that enhanced CRA formation occurs in motor neurons and reactive glia in the spinal cord of SOD1‐mutated FALS and its transgenic mouse model as well as sporadic ALS, suggesting implications for CRA in the pathomechanism common to these forms of ALS.     

Minocycline and fluorocitrate suppress spinal nociceptive signaling in intrathecal IL‐1β–induced thermal hyperalgesic rats

We previously demonstrated that intrathecal IL‐1β caused thermal hyperalgesia in rats. This study was conducted to examine the effects and cellular mechanisms of glial inhibitors on IL‐1β–induced nociception in rats. The effects of minocycline (20 μg), fluorocitrate (1 nmol), and SB203580 (5 μg) on IL‐1β (100 ng) treatment in rats were measured by nociceptive behaviors, western blotting of p38 mitogen‐activated protein kinase (MAPK) and inducible nitric oxide synthase (iNOS) expression, cerebrospinal fluid nitric oxide (NO) levels, and immunohistochemical analyses. The results demonstrated that intrathecal IL‐1β activated microglia and astrocytes, but not neurons, in the dorsal horn of the lumbar spinal cord, as evidenced by morphological changes and increased immunoreactivity, phosphorylated p38 (P‐p38) MAPK, and iNOS expression; the activation of microglia and astrocytes peaked at 30 min and lasted for 6 h. The immunoreactivities of microglia and astrocytes were significantly increased at 30 min (6.6‐ and 2.7‐fold, respectively) and 6 h (3.3‐ and 4.0‐fold, respectively) following IL‐1β injection, as compared with saline controls at 30 min (all P < 0.01). IL‐1β induced P‐p38 MAPK and iNOS expression predominantly in microglia and less in astrocytes. Minocycline, fluorocitrate, or SB203580 pretreatment suppressed this IL‐1β–upregulated P‐p38 MAPK mainly in microglia and iNOS mainly in astrocytes; minocycline exhibited the most potent effect. Minocycline and fluorocitrate pretreatment abrogated IL‐1β–induced NO release and thermal hyperalgesia in rats. In conclusion, minocycline, fluorocitrate, and SB203580 effectively suppressed the IL‐1β–induced central sensitization and hyperalgesia in rats. © 2012 Wiley Periodicals, Inc.     

Redox regulation of NF‐κB p50 and M1 polarization in microglia

Redox‐signaling is implicated in deleterious microglial activation underlying CNS disease, but how ROS program aberrant microglial function is unknown. Here, the oxidation of NF‐κB p50 to a free radical intermediate is identified as a marker of dysfunctional M1 (pro‐inflammatory) polarization in microglia. Microglia exposed to steady fluxes of H₂O₂ showed altered NF‐κB p50 protein–protein interactions, decreased NF‐κB p50 DNA binding, and augmented late‐stage TNFα expression, indicating that H₂O₂ impairs NF‐κB p50 function and prolongs amplified M1 activation. NF‐κB p50^?/? mice and cultures exhibited a disrupted M2 (alternative) response and impaired resolution of the M1 response. Persistent neuroinflammation continued 1 week after LPS (1 mg/kg, IP) administration in the NF‐κB p50^?/? mice. However, peripheral inflammation had already resolved in both strains of mice. Treatment with the spin‐trap DMPO mildly reduced LPS‐induced 22 h TNFα in the brain in NF‐κB p50^+/+ mice. Interestingly, DMPO failed to reduce and strongly augmented brain TNFα production in NF‐κB p50^?/? mice, implicating a fundamental role for NF‐κB p50 in the regulation of chronic neuroinflammation by free radicals. These data identify NF‐κB p50 as a key redox‐signaling mechanism regulating the M1/M2 balance in microglia, where loss of function leads to a CNS‐specific vulnerability to chronic inflammation. GLIA 2015;63:423–440     

Tripchlorolide protects neuronal cells from microglia‐mediated β‐amyloid neurotoxicity through inhibiting NF‐κB and JNK signaling

Recent research has focused on soluble oligomeric assemblies of β‐amyloid peptides (Aβ) as the proximate cause of neuroinflammation, synaptic loss, and the eventual dementia associated with Alzheimer's disease (AD). In this study, tripchlorolide (T₄), an extract of Tripterygium wilfordii Hook. F (TWHF), was studied as a novel agent to suppress neuroinflammatory process in microglial cells and to protect neuronal cells against microglia‐mediated oligomeric Aβ toxicity. T₄ significantly attenuated oligomeric Aβ(1‐42)‐induced release of inflammatory productions such as tumor necrosis factor‐α, interleukin‐1β, nitric oxide (NO), and prostaglandin E₂. It also downregulated the protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase‐2 (COX‐2) in microglial cells. Further molecular mechanism study demonstrated that T₄ inhibited the nuclear translocation of nuclear factor‐κB (NF‐κB) without affecting I‐κBα phosphorylation. It repressed Aβ‐induced JNK phosphorylation but not ERK or p38 MAPK. The inhibition of NF‐κB and JNK by T₄ is correlated with the suppression of inflammatory mediators in Aβ‐stimulated microglial cells. These results suggest that T₄ protects neuronal cells by blocking inflammatory responses of microglial cells to oligomeric Aβ(1‐42) and that T₄ acts on the signaling of NF‐κB and JNK, which are involved in the modulation of inflammatory response. Therefore, T₄ may be an effective agent in modulating neuroinflammatory process in AD. © 2009 Wiley‐Liss, Inc.     

Tumor necrosis factor‐alpha mediates activation of NF‐κB and JNK signaling cascades in retinal ganglion cells and astrocytes in opposite ways

Tumor necrosis factor‐alpha (TNF) is an important mediator of the innate immune response in the retina. TNF can activate various signaling cascades, including NF‐κB, nuclear factor kappa B (NF‐κB) and c‐Jun N‐terminal kinase (JNK) pathways. The harmful role of these pathways, as well as of TNF, has previously been shown in several retinal neurodegenerative conditions including glaucoma and retinal ischemia. However, TNF and TNF‐regulated signaling cascades are capable not only of mediating neurotoxicity, but of being protective. We performed this study to delineate the beneficial and detrimental effects of TNF signaling in the retina. To this end, we used TNF‐treated primary retinal ganglion cell (RGC) and astrocyte cultures. Levels of expression of NF‐κB subunits in RGCs and astrocytes were evaluated by quantitative RT‐PCR (qRT‐PCR) and Western blot (WB) analysis. NF‐κB and JNK activity in TNF‐treated cells was determined in a time‐dependent manner using ELISA and WB. Gene expression in TNF‐treated astrocytes was measured by qRT‐PCR. We found that NF‐κB family members were present in RGCs and astrocytes at the mRNA and protein levels. RGCs failed to activate NF‐κB in the presence of TNF, a phenomenon that was associated with sustained JNK activation and RGC death. However, TNF initiated the activation of NF‐κB and mediated transient JNK activation in astrocytes. These events were associated with glial survival and increased expression of neurotoxic pro‐inflammatory factors. Our findings suggest that, in the presence of TNF, NF‐κB and JNK signaling cascades are activated in opposite ways in RGCs and astrocytes. These events can directly and indirectly facilitate RGC death.     

Astrocytes drive upregulation of the multidrug resistance transporter ABCB1 (P‐Glycoprotein) in endothelial cells of the blood–brain barrier in mutant superoxide dismutase 1‐linked amyotrophic lateral sclerosis

The efficacy of drugs targeting the CNS is influenced by their limited brain access, which can lead to complete pharmacoresistance. Recently a tissue‐specific and selective upregulation of the multidrug efflux transporter ABCB1 or P‐glycoprotein (P‐gp) in the spinal cord of both patients and the mutant SOD1‐G93A mouse model of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease that prevalently kills motor neurons has been reported. Here, we extended the analysis of P‐gp expression in the SOD1‐G93A ALS mouse model and found that P‐gp upregulation was restricted to endothelial cells of the capillaries, while P‐gp expression was not detected in other cells of the spinal cord parenchyma such as astrocytes, oligodendrocytes, and neurons. Using both in vitro human and mouse models of the blood–brain barrier (BBB), we found that mutant SOD1 astrocytes were driving P‐gp upregulation in endothelial cells. In addition, a significant increase in reactive oxygen species production, Nrf2 and NFκB activation in endothelial cells exposed to mutant SOD1 astrocytes in both human and murine BBB models were observed. Most interestingly, astrocytes expressing FUS‐H517Q, a different familial ALS‐linked mutated gene, also drove NFκB‐dependent upregulation of P‐gp. However, the pathway was not dependent on oxidative stress but rather involved TNF‐α release. Overall, these findings indicated that nuclear translocation of NFκB was a converging mechanism used by endothelial cells of the BBB to upregulate P‐gp expression in mutant SOD1‐linked ALS and possibly other forms of familial ALS. GLIA 2016 GLIA 2016;64:1298–1313     

Impairment of nuclear factor‐κB activation increased glutamate excitotoxicity in a motoneuron–neuroblastoma hybrid cell line expressing mutant (G93A) Cu/Zn‐superoxide dismutase

Mutations in the superoxide dismutase 1 (SOD1) gene are linked to glutamate excitotoxicity in familial amyotrophic lateral sclerosis (fALS), but the underlying mechanism remains unclear. We investigated whether nuclear factor‐κB (NF‐κB) activation is involved in glutamate excitotoxicity by using motor neuron–neuroblastoma hybrid cells that expressed a mutant (G93A) SOD1 (mtSOD1) or wild‐type SOD1 (wtSOD1). MtSOD1 cells were more vulnerable to glutamate excitotoxicity than wtSOD1 cells and showed higher NF‐κB activity, higher nuclear cRel expression, and lower nuclear RelA expression under basal conditions. Glutamate treatment increased NF‐κB activation along with nuclear expressions of RelA and cRel in wtSOD1 cells but induced only weak nuclear RelA expression in mtSOD1 cells. Suppression of NF‐κB activation using transfection of the superrepressive mutant form of IκBα (mIκBα) inhibited nuclear RelA expression in both types of SOD1 cells, which increased glutamate excitotoxicity in wtSOD1 cells but not in mtSOD1 cells. Furthermore, immunohistochemistry confirmed stronger RelA immunoreactivity in the nuclei of motor neurons of spinal cord in wild‐type SOD1 transgenic mice than in those in SOD1 G93A transgenic mice. In addition, we found that glutamate treatment decreased XIAP expression and increased caspase‐3 activity in mtSOD1 cells and mIκBα‐overexpressing wtSOD1 cells. Our results suggest that glutamate excitotoxicity in motor neurons of SOD1‐linked fALS is attributable, at least in part, to the impairment of IκBα‐dependent RelA activation and subsequent apoptosis mediated by XIAP inhibition and caspase‐3 activation. © 2010 Wiley‐Liss, Inc.     

Glial activation in the periaqueductal gray promotes descending facilitation of neuropathic pain through the p38 MAPK signaling pathway

The midbrain ventrolateral periaqueductal gray (VL‐PAG) is a key component that mediates pain modulation. Although spinal cord glial cells appear to play an important role in chronic pain development, the precise mechanisms involving descending facilitation pathways from the PAG following nerve injury are poorly understood. This study shows that cellular events that occur during glial activation in the VL‐PAG may promote descending facilitation from the PAG during neuropathic pain. Chronic constriction nerve injury (CCI) was induced by ligature construction of the sciatic nerve in male Sprague‐Dawley rats. Behavioral responses to noxious mechanical (paw withdrawal threshold; PWT) and thermal (paw withdrawal latency; PWL) stimuli were evaluated. After CCI, immunohistochemical and Western blot analysis of microglia and astrocytes in the VL‐PAG showed morphological and quantitative changes indicative of activation in microglia and astrocytes. Intra‐VL‐PAG injection of microglial or astrocytic inhibitors attenuated PWT and PWL at days 7 and 14, respectively, following CCI. We also evaluated the effects of intra‐VL‐PAG administration of the phosphorylated p38 mitogen‐activated protein kinase (p‐p38 MAPK) inhibitor SB 203580 at day 7 after CCI. This treatment abolished microglial activation and produced a significant time‐dependent attenuation of PWT and PWL. Western blot analysis showed localized expression of p‐p38 in the VL‐PAG after CCI. P‐p38 was expressed in labeled microglia of the VL‐PAG but was not present in astrocytes and neurons on day 7 after CCI. These results demonstrate that CCI‐induced neuropathic pain is associated with glial activation in the VL‐PAG, which likely participates in descending pain facilitation through the p38 MAPK signaling pathway. © 2015 Wiley Periodicals, Inc.     

Expression of insulin‐like growth factor‐II and leukemia inhibitory factor antibody immunostaining on the ionized calcium‐binding adaptor molecule 1‐positive microglias in the spinal cord of amyotrophic lateral sclerosis patients

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease involving the upper and lower motor neuron systems. Activated microglia are reported to enhance motor neuron death by secreting neurotoxic cytokines in SOD1‐transgenic mice. Recent studies have provided evidence that chronic stimulation leads microglia to acquire an anti‐inflammatory phenotype, characterized by activated morphology and induction of neuroprotective and immunoregulatory molecules. However, little information is available on the protective functions of microglia in the ALS spinal cord. To investigate the roles of microglia in ALS, we examined the appearance of ionized calcium‐binding adaptor molecule 1‐positive (Iba1‐positive) microglia as correlated to the disease duration and immunohistochemical expression of neurogrowth factors in the ALS spinal cord. In this study, the number of Iba1‐positive rod‐like microglia significantly increased in the ALS spinal cord compared to controls. The number of ramified microglia was positively correlated with the number of normal‐looking neurons and clinical duration of ALS patients; however, the number of rod‐like microglia was not correlated with that of abnormal neurons, nor with the clinical duration of the disease. Some rod‐like microglia were positive for anti‐insulin‐like growth factor‐II (IGF II) and anti‐leukemia inhibitory factor (LIF) immunostaining. Motor neurons in the ALS spinal cords also showed immunoreactivity for IGF‐II, LIF and the receptors of IGF‐II and LIF. Taken together, these findings suggest that at least some microglia might have a protective effect on motor neurons in the ALS spinal cord. Neuroprotective and/or neurotoxic effects of microglia on motor neurons should be further studied.     

Systemic and local anti‐nociceptive effects of simvastatin in the rat formalin assay: Role of peroxisome proliferator‐activated receptor γ and nitric oxide

This study aimed to determine the potential systemic and local anti‐nociceptive effects of simvastatin (SIM) and the possible role of peroxisome proliferator‐activated receptor gamma (PPARγ) and nitric oxide (NO) pathways using a formalin assay in rats. After allocation, rats were intraplantarly (i.pl.) treated with formalin solution (2.5%) and the flinching behaviors were recorded for 5 min (phase 1) and 15‐60 min (phase 2). SIM was given intraperitoneally (i.p.) and i.pl. 30 and 20 min before test, respectively. Intraperitoneal administration of SIM attenuated the flinching number during both phases of the test. This effect of i.p. SIM was significantly reduced by _L‐NAME (NO synthase blocker, i.p.), but was augmented by _L‐arginine (NO precursor, i.p.) during both phases of the formalin assay. Moreover, the antinociception caused by i.p. SIM was blocked by GW‐9662 (PPARγ antagonist) at dose 2 mg/kg (i.p.). In another experiment, concurrent ip administration of non‐effective dose of simvastatin (5 mg/kg) with pioglitazone (PPARγ agonist; 10, 20 mg/kg) produced antinociception. However, pre‐treatment with i.p. GW‐9662 inhibited the enhanced antinociceptive effect of pioglitazone on SIM during the phase 2 of formalin assay. Results also showed that i.pl. SIM alone had no anti‐nociceptive effects. However, significant anti‐nociception was observed when SIM (i.pl.) co‐administered with non‐effective dose of pioglitazone. Moreover, the enhanced effect was antagonized by pre‐treatment with i.pl. GW‐9662. Our data suggest that SIM produced antinociception through systemic but not local route of administration in rats. Moreover, the antinociceptive effect of SIM is partly mediated through PPARγ receptors and NO pathway. © 2017 Wiley Periodicals, Inc.     

Nuclear factor‐κB/p65 responds to changes in the Notch signaling pathway in murine BV‐2 cells and in amoeboid microglia in postnatal rats treated with the γ‐secretase complex blocker DAPT

Microglial cells constitutively express Notch‐1 and nuclear factor‐κB/p65 (NF‐κB/p65), and both pathways modulate production of inflammatory mediators. This study sought to determine whether a functional relationship exists between them and, if so, to investigate whether they synergistically regulate common microglial cell functions. By immunofluorescence labeling, real‐time polymerase chain reaction (RT‐PCR), flow cytometry, and Western blot, BV‐2 cells exhibited Notch‐1 and NF‐κB/p65 expression, which was significantly up‐regulated in cells challenged with lipopolysaccharide (LPS). This was coupled with an increase in expression of Hes‐1, tumor necrosis factor‐α (TNF‐α), and interleukin‐1β (IL‐1β). In BV‐2 cells pretreated with N‐[N‐(3,5‐difluorophenacetyl)‐1‐alany1]‐S‐phenyglycine t‐butyl ester (DAPT), a γ‐secretase inhibitor, followed by LPS stimulation, Notch‐1 expression level was enhanced but that of all other markers was suppressed. Additionally, Hes‐1 expression and NF‐κB nuclear translocation decreased as shown by flow cytometry. Notch‐1's modulation of NF‐κB/p65 was also evidenced in amoeboid microglial cells (AMC) in vivo. In 5‐day‐old rats given intraperitoneal injections of LPS, Notch‐1, NF‐κB/p65, TNF‐α, and IL‐1β immunofluorescence in AMC was markedly enhanced. However, in rats given an intraperitoneal injection of DAPT prior to LPS, Notch‐1 labeling was augmented, but that of TNF‐α and IL‐1β was reduced. The results suggest that blocking of Notch‐1 activation with DAPT would reduce the level of its downstream end product Hes‐1 along with suppression of NF‐κB/p65 translocation, resulting in suppressed production of proinflammatory cytokines. It is concluded that Notch‐1 signaling can trans‐activate NF‐κB/p65 by amplifying NF‐κB/p65‐dependent proinflammatory functions in activated microglia. © 2010 Wiley‐Liss, Inc.