Regulation of MARCKS and MARCKS-related protein expression in BV-2 microglial cells in response to lipopolysaccharide

Fokker-Planck diffusion maps of multiple single cell microglial transcriptomes reveals radial differentiation into substates associated with Alzheimer's pathology

The identification of microglia subtypes is important for understanding the role of innate immunity in neurodegenerative diseases. Current methods of unsupervised cell type identification assume a small noise-to-signal ratio of transcriptome measurements that would produce well-separated cell clusters. However, identification of subtypes is obscured by gene expression noise, diminishing the distances in transcriptome space between distinct cell types and blurring boundaries. Here we use Fokker-Planck (FP) diffusion maps to model cellular differentiation as a stochastic process whereby cells settle into local minima, corresponding to cell subtypes, in a potential landscape constructed from transcriptome data using a nearest neighbor graph approach. By applying critical transition fields, we identify individual cells on the verge of transitioning between subtypes, revealing microglial cells in inactivated, homeostatic state before radially transitioning into various specialized subtypes. Specifically, we show that cells from Alzheimer's disease patients are enriched in a microglia subtype associated to antigen presentation and T-cell recruitment.

Secukinumab attenuates neuroinflammation and neurobehavior defect via PKCβ/ERK/NF-κB pathway in a rat model of GMH

AIMS

Germinal matrix hemorrhage (GMH) is a disastrous clinical event for newborns. Neuroinflammation plays an important role in the development of neurological deficits after GMH. The purpose of this study is to investigate the anti-inflammatory role of secukinumab after GMH and its underlying mechanisms involving PKCβ/ERK/NF-κB signaling pathway.

METHODS

A total of 154 Sprague-Dawley P7 rat pups were used. GMH was induced by intraparenchymal injection of bacterial collagenase. Secukinumab was administered intranasally post-GMH. PKCβ activator PMA and p-ERK activator Ceramide C6 were administered intracerebroventricularly at 24 h prior to GMH induction, respectively. Neurobehavioral tests, western blot and immunohistochemistry were used to evaluate the efficacy of Secukinumab in both short-term and long-term studies.

RESULTS

Endogenous IL-17A, IL-17RA, PKCβ and p-ERK were increased after GMH. Secukinumab treatment improved short- and long-term neurological outcomes, reduced the synthesis of MPO and Iba-1 in the perihematoma area, and inhibited the synthesis of proinflammatory factors, such as NF-κB, IL-1β, TNF-α and IL-6. Additionally, PMA and ceramide C6 abolished the beneficial effects of Secukinumab.

CONCLUSION

Secukinumab treatment suppressed neuroinflammation and attenuated neurological deficits after GMH, which was mediated through the downregulation of the PKCβ/ERK/NF-κB pathway. Secukinumab treatment may provide a promising therapeutic strategy for GMH patients.

Plasma proteins, cognitive decline, and 20-year risk of dementia in the Whitehall II and Atherosclerosis Risk in Communities studies

INTRODUCTION

Plasma proteins affect biological processes and are common drug targets but their role in the development of Alzheimer's disease and related dementias remains unclear. We examined associations between 4953 plasma proteins and cognitive decline and risk of dementia in two cohort studies with 20-year follow-ups.

METHODS

In the Whitehall II prospective cohort study proteins were measured using SOMAscan technology. Cognitive performance was tested five times over 20 years. Linkage to electronic health records identified incident dementia. The results were replicated in the Atherosclerosis Risk in Communities (ARIC) study.

RESULTS

Fifteen non-amyloid/non-tau-related proteins were associated with cognitive decline and dementia, were consistently identified in both cohorts, and were not explained by known dementia risk factors. Levels of six of the proteins are modifiable by currently approved medications for other conditions.

DISCUSSION

This study identified several plasma proteins in dementia-free people that are associated with long-term risk of cognitive decline and dementia.

X MARCKS the spot: myristoylated alanine-rich C kinase substrate in neuronal function and disease

Intracellular protein-protein interactions are dynamic events requiring tightly regulated spatial and temporal checkpoints. But how are these spatial and temporal cues integrated to produce highly specific molecular response patterns? A helpful analogy to this process is that of a cellular map, one based on the fleeting localization and activity of various coordinating proteins that direct a wide array of interactions between key molecules. One such protein, myristoylated alanine-rich C-kinase substrate (MARCKS) has recently emerged as an important component of this cellular map, governing a wide variety of protein interactions in every cell type within the brain. In addition to its well-documented interactions with the actin cytoskeleton, MARCKS has been found to interact with a number of other proteins involved in processes ranging from intracellular signaling to process outgrowth. Here, we will explore these diverse interactions and their role in an array of brain-specific functions that have important implications for many neurological conditions.

Migration and Phagocytic Ability of Activated Microglia During Post-natal Development is Mediated by Calcium-Dependent Purinergic Signalling

Microglia play an important role in synaptic pruning and controlled phagocytosis of neuronal cells during developmental stages. However, the mechanisms that regulate these functions are not completely understood. The present study was designed to investigate the role of purinergic signalling in microglial migration and phagocytic activity during post-natal brain development. One-day-old BALB/c mice received lipopolysaccharide (LPS) and/or a purinergic analogue (2-methylthioladenosine-5'-diphosphate; 2MeSADP), intracerebroventrically (i.c.v.). Combined administration of LPS and 2MeSADP resulted in activation of microglia as evident from increased expression of ionised calcium-binding adapter molecule 1 (Iba1). Activated microglia showed increased expression of purinergic receptors (P2Y2, P2Y6 and P2Y12). LPS either alone or in combination with 2MeSADP induced the expression of Na(+)/Ca(2+) exchanger (NCX-1) and P/Q-type Ca(2+) channels along with MARCKS-related protein (MRP), which is an integral component of cell migration machinery. In addition, LPS and 2MeSADP administration induced the expression of microglial CD11b and DAP12 (DNAX-activation protein 12), which are known to be involved in phagocytosis of neurons during development. Interestingly, administration of thapsigargin (TG), a specific Ca(2+)-ATPase inhibitor of endoplasmic reticulum, prevented the LPS/2MeSADP-induced microglial activation and migration by down-regulating the expression of Iba1 and MRP, respectively. Moreover, TG also reduced the LPS/2MeSADP-induced expression of CD11b/DAP12. Taken together, the findings reveal for the first time that Ca(2+)-mediated purinergic receptors regulate the migration and phagocytic ability of microglia during post-natal brain development.

The response of porcine monocyte derived macrophages and dendritic cells to Salmonella Typhimurium and lipopolysaccharide

Background

Following infection and initial multiplication in the gut lumen, Salmonella Typhimurium crosses the intestinal epithelial barrier and comes into contact with cells of the host immune system. Mononuclear phagocytes which comprise macrophages and dendritic cells (DC) are of key importance for the outcome of Salmonella infection. Although macrophages and DC may differentiate from a common precursor, their capacities to process and present antigen differ significantly. In this study, we therefore compared the response of porcine macrophages and DC differentiated from peripheral blood monocytes to S. Typhimurium and one of the most potent bacterial pathogen associated molecular patterns, bacterial lipopolysaccharide. To avoid any bias, the expression was determined by protein LC-MS/MS and verified at the level of transcription by quantitative RT-PCR.

Results

Within 4 days of culture, peripheral blood monocytes differentiated into two populations with distinct morphology and expression of MHC II. Mass spectrometry identified 446 proteins in macrophages and 672 in DC. Out of these, 433 proteins were inducible in macrophages either after infection with S. Typhimurium or LPS exposure and 144 proteins were inducible in DC. The expression of the 46 most inducible proteins was verified at the level of transcription and the differential expression was confirmed in 22 of them. Out of these, 16 genes were induced in both cell types, 3 genes (VCAM1, HMOX1 and Serglycin) were significantly induced in macrophages only and OLDLR1 and CDC42 were induced exclusively in DC. Thirteen out of 22 up-regulated genes contained the NF-kappaB binding site in their promoters and could be considered as either part of the NF-kappaB feedback loop (IkappaBalpha and ISG15) or as NF-kappaB targets (IL1beta, IL1alpha, AMCF2, IL8, SOD2, CD14, CD48, OPN, OLDLR1, HMOX1 and VCAM1).

Conclusions

The difference in the response of monocyte derived macrophages and DC was quantitative rather than qualitative. Despite the similarity of the responses, compared to DC, the macrophages responded in a more pro-inflammatory fashion.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-014-0244-1) contains supplementary material, which is available to authorized users.

Development and validation of a gene expression score that predicts response to fulvestrant in breast cancer patients

Fulvestrant is a selective estrogen receptor antagonist. Based on the measured growth inhibition of 60 human cancer cell lines (NCI60) in the presence of fulvestrant, as well as the baseline gene expression of the 60 cell lines, a gene expression score that predicts response to fulvestrant was developed. The score is based on 414 genes, 103 of which show increased expression in sensitive cell lines, while 311 show increased expression in the non-responding cell lines. The sensitivity genes primarily sense signaling through estrogen receptor alpha, whereas the resistance genes modulate the PI3K signaling pathway. The latter genes suggest that resistance to fulvestrant can be overcome by drugs targeting the PI3K pathway. The level of this gene expression score and its correlation with fulvestrant response was measured in a panel of 20 breast cancer cell lines. The predicted sensitivity matched the measured sensitivity well (CC = -0.63, P = 0.003). The predictor was applied to tumor biopsies obtained from a Phase II clinical trial. The sensitivity of each patient to treatment with fulvestrant was predicted based on the RNA profile of the biopsy taken before neoadjuvant treatment and without knowledge of the subsequent response. The prediction was then compared to clinical response to show that the responders had a significantly higher sensitivity prediction than the non-responders (P = 0.01). When clinical covariates, tumor grade and estrogen receptor H-score, were included in the prediction, the difference in predicted senstivity between responders and non-responders improved (P = 0.003). Using a pre-defined cutoff to separate patients into predicted sensitive and predicted resistant yielded a positive predictive value of 88% and a negative predictive value of 100% when compared to clinical data. We conclude that pre-screening patients with the new gene expression predictor has the potential to identify those postmenopausal women with locally advanced, estrogen-receptor-positive breast cancer most likely to respond to fulvestrant.

The role of Src kinase in macrophage-mediated inflammatory responses

Src kinase (Src) is a tyrosine protein kinase that regulates cellular metabolism, survival, and proliferation. Many studies have shown that Src plays multiple roles in macrophage-mediated innate immunity, such as phagocytosis, the production of inflammatory cytokines/mediators, and the induction of cellular migration, which strongly implies that Src plays a pivotal role in the functional activation of macrophages. Macrophages are involved in a variety of immune responses and in inflammatory diseases including rheumatoid arthritis, atherosclerosis, diabetes, obesity, cancer, and osteoporosis. Previous studies have suggested roles for Src in macrophage-mediated inflammatory responses; however, recently, new functions for Src have been reported, implying that Src functions in macrophage-mediated inflammatory responses that have not been described. In this paper, we discuss recent studies regarding a number of these newly defined functions of Src in macrophage-mediated inflammatory responses. Moreover, we discuss the feasibility of Src as a target for the development of new pharmaceutical drugs to treat macrophage-mediated inflammatory diseases. We provide insights into recent reports regarding new functions for Src that are related to macrophage-related inflammatory responses and the development of novel Src inhibitors with strong immunosuppressive and anti-inflammatory properties, which could be applied to various macrophage-mediated inflammatory diseases.

MARCKS as a negative regulator of lipopolysaccharide signaling

Myristoylated alanine-rich C kinase substrate (MARCKS) is an intrinsically unfolded protein with a conserved cationic effector domain, which mediates the cross-talk between several signal transduction pathways. Transcription of MARCKS is increased by stimulation with bacterial LPS. We determined that MARCKS and MARCKS-related protein specifically bind to LPS and that the addition of the MARCKS effector peptide inhibited LPS-induced production of TNF-α in mononuclear cells. The LPS binding site within the effector domain of MARCKS was narrowed down to a heptapeptide that binds to LPS in an extended conformation as determined by nuclear magnetic resonance spectroscopy. After LPS stimulation, MARCKS moved from the plasma membrane to FYVE-positive endosomes, where it colocalized with LPS. MARCKS-deficient mouse embryonic fibroblasts (MEFs) responded to LPS with increased IL-6 production compared with the matched wild-type MEFs. Similarly, small interfering RNA knockdown of MARCKS also increased LPS signaling, whereas overexpression of MARCKS inhibited LPS signaling. TLR4 signaling was enhanced by the ablation of MARCKS, which had no effect on stimulation by TLR2, TLR3, and TLR5 agonists. These findings demonstrate that MARCKS contributes to the negative regulation of the cellular response to LPS.

Opisthorchis viverrini-antigen induces expression of MARCKS during inflammation-associated cholangiocarcinogenesis

Myristoylated alanine rich C kinase substrate (MARCKS) has been implicated in PKC-mediated membrane-cytoskeleton alterations that underlie lipopolysaccharide (LPS)-induced macrophage responses. MARCKS is postulated to be involved in inflammation-associated CCA based on its overexpression in cholangiocarcinoma (CCA) and inflammatory cells. The aims of this study were to investigate localization patterns of MARCKS in hamster and human tissue during cholangiocarcinogenesis and to examine the involvement of MARCKS in inflammation. MARCKS protein expression was found prominently in inflammatory cells of Opisthorchis viverrini-treated as well as O. viverrini plus N-nitrosodimethylamine (NDMA)-treated hamsters from week 2 to week 3 of treatment. The positive signal decreased during week 4 to week 12, then increased again at week 26 when CCA developed. At the last time point the expression of MARCKS was observed in both cancer and inflammatory cells. MARCKS protein expression was also found in inflammatory cells, including macrophages in human CCA tissues. O. viverrini excretory/secretory products or worm antigen induced MARCKS mRNA and protein expression in a dose- and time-dependent manner in the human U937 macrophage cell line. The relative mRNA expression of MARCKS in white blood cells of O. viverrini-infected patients was significantly higher than in healthy subjects (P = 0.02). Thus, MARCKS is significantly expressed in macrophages and plays a role in inflammation-related CCA induced by O. viverrini.

Alternation of gene expression in trigeminal ganglion neurons following complete Freund's adjuvant or capsaicin injection into the rat face

The hyperexcitability of trigeminal ganglion (TG) neurons following inflammation or C-fiber stimulation is known to be involved in a variety of changes in gene expression in TG neurons, resulting in pain abnormalities in orofacial regions. We analyzed nocifensive behavior following complete Freund's adjuvant (CFA) or capsaicin injection into the maxillary whisker pad, and gene expression in the TG neurons using microarray analysis. The head-withdrawal latency to capsaicin injection or the head-withdrawal threshold to mechanical stimulation of the whisker pad skin in CFA-treated rats was significantly decreased compared to vehicle-treated rats. Many up-regulated and down-regulated genes in the TG neurons of each model were reported. Genes which have not been linked to peripheral inflammation or C-fiber activation were detected. Moreover, microarray chip containing a number of non-coding sequences was also up-regulated by C-fiber activation. These findings suggest that the diverse gene expressions in TG neurons are differentially involved in the inflammatory chronic pain and the acute pain induced by C-fiber activation, and the hyperexcitation of C-fibers are associated with the activation of certain non-coding RNAs.

Angiotensin type 1 receptor antagonist inhibits lipopolysaccharide-induced stimulation of rat microglial cells by suppressing nuclear factor kappaB and activator protein-1 activation

We investigated whether angiotensin (ANG) II and its receptors contribute to lipopolysaccharide (LPS)-induced microglial activation through activation of the proinflammatory transcription factors nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1). Using primary microglial cell cultures, we examined whether losartan [ANG type 1 receptor (AT(1)) antagonist] alters the effects of LPS on: the production of interleukin-1 (IL-1) and nitric oxide, cell morphology, and NF-kappaB and AP-1 activities. Reverse transcription-polymerase chain reaction revealed that LPS-stimulated microglial cells exhibited marked mRNA expression for AT(1), ANG type 2 receptor (AT(2)) and the ANG II precursor angiotensinogen, whereas non-stimulated microglial cells expressed only those for AT(2) and angiotensinogen. We further demonstrated marked peptide/protein expression for AT(1) and ANG II in LPS-activated microglial cells. LPS (100 ng/mL)-stimulated microglial cells showed increased concentrations of IL-1 and nitrite (a relatively stable metabolite of nitric oxide), and increased expression of IL-1 mRNA as well as a morphological change from an amoeboid shape to a multipolar (mostly bipolar but sometimes tripolar) rod shape. These effects were all significantly inhibited by losartan treatment (10(-5) M or less). NF-kappaB and AP-1 activities were enhanced in LPS-stimulated microglial cells, effects that were significantly suppressed by losartan (10(-5) M). ANG II application enhanced the LPS-induced increases in IL-1 and nitrite concentrations, as well as the LPS-induced morphological changes and AP-1 activation, and these enhancements were inhibited by losartan (10(-5) M). These results suggest that endogenous ANG II enhances LPS-induced microglial activities through stimulation of the microglial AT(1), which itself evokes activation of the transcription factors NF-kappaB and AP-1.

The regulation of MacMARCKS expression by integrin β3

Integrin-mediated adhesion regulates multiple signaling pathways. Our group previously showed that ectopic expression of different integrin beta-subunits in the neuroepithelial cell line GE11, has distinct effects on cell morphology, actin cytoskeletal organization, and on focal contact distribution. In this report we have investigated changes in gene transcription levels resulting from overexpression of the integrin beta3 subunit. We found that beta3 overexpression leads to the transcriptional downregulation of MARCKS related protein (MRP) resulting in a decreased expression of the MRP protein. Furthermore, we show that the Ras/MAPK pathway controls the basal level of MRP expression but beta3 overexpression bypasses this pathway downstream of ERK to downregulate MRP. Further studies indicate that a region of the cytoplasmic tail of beta3 containing part of the NITY motif is responsible for increased cell spreading and MRP downregulation. However, MRP overexpression failed to inhibit the beta3-induced increase in cell spreading while the knock down of MRP expression in GE11 cells did not increase cell spreading. We suggest that the downregulation of MRP by beta3 is not required for increased cell spreading but instead that MRP downregulation is a secondary effect of increased cell spreading.

ANP inhibits LPS-induced stimulation of rat microglial cells by suppressing NF-kappaB and AP-1 activations

Atrial natriuretic peptide (ANP) contributes to the inhibition of such causes of inflammation as the lipopolysaccharide (LPS)-induced productions of nitric oxide (NO) and proinflammatory cytokines [including interleukin-1 (IL-1)] in macrophages. In the present study we used primary cultures of rat brain macrophage-like cells (i.e., microglial cells) to investigate whether ANP binding to its receptors inhibits LPS-induced microglial activation via effects on the activation of the proinflammatory transcription factors NF-kappaB and AP-1. The productions of NO and IL-1, as well as morphological changes, were examined to assess LPS-induced activation of microglial cells. Our RT-PCR study revealed that rat microglial cells express the mRNAs for ANP receptors (types A, B, and C) and that for the ANP molecule. LPS (100 ng/ml)-stimulated microglial cells showed increases in nitrite (a relatively stable metabolite of NO) and IL-1 concentrations, and in the expression of IL-1 mRNA, as well as a morphological change from an amoeboid shape to a multipolar (mostly bipolar, but sometimes tripolar) rod shape. These effects were all significantly inhibited by treatment with ANP (at 10(-6)M or less). The inhibition by ANP of the LPS-induced nitrite response was abrogated by a NP-receptor antagonist, HS-142-1 (100 ng/ml). NF-kappaB and AP-1 activities were enhanced in LPS-stimulated microglial cells, and these enhancements were significantly suppressed by ANP (10(-6)M). These results suggest that ANP inhibits LPS-stimulated activities in microglial cells through activation of microglial ANP receptors, leading to inhibitions of NF-kappaB and AP-1.

Src family kinases play multiple roles in differentiation of trophoblasts from human term placenta

Tyrosine phosphorylation plays a major role in controlling many biological processes in different cell types. Src family kinases (SFKs) are one of the most studied groups of tyrosine kinases and can mediate a variety of signalling pathways. However, little is known about the expression of SFKs in human term placenta and their implication in trophoblast differentiation. Therefore, we examined the expression profile of SFK members over time in culture and their implication in differentiation. In vitro, freshly isolated cytotrophoblast cells, cultured in 10% fetal bovine serum (FBS), spontaneously aggregate and fuse to form multinucleated cells that resemble phenotypically mature syncytiotrophoblasts, that concomitantly produce human chorionic gonadotropin (hCG) and human placental lactogen (hPL). In this study, we showed that trophoblasts expressed all SFK members and some of them are expressed as different splice variants. Moreover, using real-time PCR, this study showed two different expression profiles of SFKs in human trophoblasts during culture. In addition, the protein level and phosphorylation status of Src were evaluated using specific antibodies. Src was rapidly phosphorylated at Tyr-416 and dephosphorylated at Tyr-527 after FBS addition. Surprisingly, inhibition of SFKs by 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo[3,4-d] pyrimidine (PP2) or herbimycin A had different effects on trophoblast differentiation. While herbimycin A inhibited morphological and hormonal differentiation, PP2 stimulated hormonal differentiation and inhibited cell adhesion and spreading with no effect on cell fusion. In summary, this study showed that SFKs play different roles in trophoblast differentiation, probably depending on SFK members activated. Thus, this study increases our knowledge and understanding of pathology related to impaired trophoblast differentiation such as pre-eclampsia and trophoblast neoplasm.

Adenosine A2A receptor stimulation potentiates nitric oxide release by activated microglia

The absence of adenosine A2A receptors, or its pharmacological inhibition, has neuroprotective effects. Experimental data suggest that glial A2A receptors participate in neurodegeneration induced by A2A receptor stimulation. In this study we have investigated the effects of A2A receptor stimulation on control and activated glial cells. Mouse cortical mixed glial cultures (75% astrocytes, 25% microglia) were treated with the A2A receptor agonist CGS21680 alone or in combination with lipopolysaccharide (LPS). CGS21680 potentiated lipopolysaccharide-induced NO release and NO synthase-II expression in a time- and concentration-dependent manner. CGS21680 potentiation of lipopolysaccharide-induced NO release was suppressed by the A2A receptor antagonist ZM-241385 and did not occur on mixed glial cultures from A2A receptor-deficient mice. In mixed glial cultures treated with LPS + CGS21680, the NO synthase-II inhibitor 1400W abolished NO production, and NO synthase-II immunoreactivity was observed only in microglia. Binding experiments demonstrated the presence of A2A receptors on microglial but not on astroglial cultures. However, the presence of astrocytes was necessary for CGS21680 potentiating effect. In light of the reported neurotoxicity of microglial NO synthase-II and the neuroprotection of A2A receptor inhibition, these data suggest that attenuation of microglial NO production could contribute to the neuroprotection afforded by A2A receptor antagonists.

Effect of rottlerin, a PKC-δ inhibitor, on TLR-4-dependent activation of murine microglia

In microglia, Toll-like receptors have been shown to recognize pathogen-associated molecular patterns and initiate innate immune responses upon interaction with infectious agents. The effect of rottlerin, a PKC-delta specific inhibitor, on TLR-4-mediated signaling was investigated in murine microglia stimulated with lipopolysaccharide and taxol. Pretreatment of microglia cells with rottlerin decreased LPS- and taxol-induced nitric oxide production in a concentration-dependent manner (IC50 = 99.1+/-1.5 nM). Through MTT and FACS analysis, we found that the inhibition effect of rottlerin was not due to microglial cell death. Rottlerin pretreatment also attenuated LPS-induced phosphorylation of IkappaB-alpha, nuclear translocation of NF-kappaB, and expression of type II nitric oxide synthase. In addition, microglial phagocytosis in response to TLR-4 activation was diminished in which rottlerin was pretreated. Together, these data raise the possibility that certain PKC-delta specific inhibitors can modulate TLR-4-derived signaling and inflammatory target gene expression, and can alter susceptibility to microbial infection and chronic inflammatory diseases in central nervous system.

Signal transduction pathways of nitric oxide release in primary microglial culture challenged with gram-positive bacterial constituent, lipoteichoic acid

Between one-third and one-half of all cases of sepsis are known to be caused by gram-positive microorganisms through the cell wall component, e.g. lipoteichoic acid (LTA). Gram-positive bacteria are also known to induce encephalomyelitis and meningeal inflammation, and enhance the production of nitric oxide (NO) via expression of inducible nitric oxide synthase (iNOS) in murine tissue macrophages. It remains to be explored if LTA could activate microglia considered to be resident brain macrophages. We report here that LTA derived from gram-positive bacteria (Staphylococcus aureus) significantly induces NO release and iNOS expression in primary microglia. LTA-induced NO accumulation was detected at 2 h in microglial culture and was significantly attenuated by pretreatment with anti-CD14, complement receptor type 3 (CR3) or scavenger receptor (SR) antibodies. LTA activated mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase, p38 MAPK or c-Jun N-terminal kinase in cultured microglia. LTA-elicited microglial NO production was also drastically suppressed by SB203580 (p38 MAPK inhibitor) or pyrrolidine dithiocarbamate (an inhibitor of nuclear factor kappaB), indicating that p38 MAPK and nuclear factor kappaB were involved in microglial NO release after LTA challenge. These results suggest that gram-positive bacterial product such as LTA can activate microglia to release NO via the signal transduction pathway involving multiple LTA receptors (e.g. CD14, CR3 or SR), p38 MAPK and nuclear factor kappaB. The in vivo study further confirmed that administered intracerebrally LTA induced considerable noticeable iNOS, phospho-IkappaB and phospho-p38 MAPK expression in microglia/macrophages.

The MARCKS family of phospholipid binding proteins: regulation of phospholipase D and other cellular components

Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) are essential proteins that are implicated in coordination of membrane-cytoskeletal signalling events, such as cell adhesion, migration, secretion, and phagocytosis in a variety of cell types. The most prominent structural feature of MARCKS and MRP is a central basic effector domain (ED) that binds F-actin, Ca2+-calmodulin, and acidic phospholipids; phosphorylation of key serine residues within the ED by protein kinase C (PKC) prevents the above interactions. While the precise roles of MARCKS and MRP have not been established, recent attention has focussed on the high affinity of the MARCKS ED for phosphatidylinositol 4,5-bisphosphate (PIP2), and a model has emerged in which calmodulin- or PKC-mediated regulation of these proteins at specific membrane sites could in turn control spatial availability of PIP2. The present review summarizes recent progress in this area and discusses how the above model might explain a role for MARCKS and MRP in activation of phospholipase D and other PIP2-dependent cellular processes.

Biolistic expression of the macrophage colony stimulating factor receptor in organotypic cultures induces an inflammatory response

The receptor for macrophage colony-stimulating factor (M-CSFR; c-fms) is expressed at increased levels by microglia in Alzheimer's disease (AD) and in mouse models for AD. Increased expression of M-CSFR on cultured microglia results in a strong proinflammatory response, but the relevance of this cell culture finding to intact brain is unknown. To determine the effects of increased microglial expression of M-CSFR in a complex organotypic environment, we developed a system for biolistic transfection of microglia in hippocampal slice cultures. The promoter for the Mac-1 integrin alpha subunit CD11b is active in cells of myeloid origin. In the brain, CD11b expression is restricted to microglia. Constructs consisting of the promoter for CD11b and a c-fms cDNA or an enhanced green fluorescent protein (EGFP) cDNA were introduced into monotypic cultures of microglia, neurons, and astrocytes. Strong CD11b promoter activity was observed in microglia, whereas little activity was observed in other cell types. Biolistic transfection of organotypic hippocampal cultures with the CD11b/c-fms construct resulted in expression of the c-fms mRNA and protein that was localized to microglia. Furthermore, biolistic overexpression of M-CSFR on microglia resulted in significantly increased production by the hippocampal cultures of the proinflammatory cytokines interleukin (IL)-1alpha macrophage inflammatory protein (MIP-1alpha), and trends toward increased production of IL-6 and M-CSF. These findings demonstrate that microglial overexpression of M-CSFR in an organotypic environment induces an inflammatory response, and suggest that increased microglial expression of M-CSFR could contribute to the inflammatory response observed in AD brain.

Product diversity and regulation of type II fatty acid synthases

Fatty acid biosynthesis is catalyzed in most bacteria by a group of highly conserved proteins known as the type II fatty acid synthase (FAS II) system. FAS II has been extensively studied in the Escherichia coli model system, and the recent explosion of bioinformatic information has accelerated the investigation of the pathway in other organisms, mostly important human pathogens. All FAS II systems possess a basic set of enzymes for the initiation and elongation of acyl chains. This review focuses on the variations on this basic theme that give rise to the diversity of products produced by the pathway. These include multiple mechanisms to generate unsaturated fatty acids and the accessory components required for branched-chain fatty acid synthesis in Gram-positive bacteria. Most of the known mechanisms that regulate product distribution of the pathway arise from the fundamental biochemical properties of the expressed enzymes. However, newly identified transcriptional factors in bacterial fatty acid biosynthetic pathways are a fertile field for new investigation into the genetic control of the FAS II system. Much more work is needed to define the role of these factors and the mechanisms that regulate their DNA binding capability, but there appear to be fundamental differences in how the expression of the pathway genes is controlled in Gram-negative and in Gram-positive bacteria.Key words: fatty acid synthase, bacteria.

Pyrazolo Pyrimidine-Type Inhibitors of Src Family Tyrosine Kinases Promote Ovarian Steroid-Induced Differentiation of Human Endometrial Stromal Cells In Vitro1

Reversible protein tyrosine phosphorylation, coordinately controlled by protein tyrosine kinases and phosphatases, is a critical element in signal transduction pathways regulating a wide variety of biological processes, including cell growth, differentiation, and tumorigenesis. We have previously reported that c-Src belonging to the Src family tyrosine kinase (SFK) becomes dephosphorylated at tyrosine 530 (Y530) and thereby activated during progestin-induced differentiation of human endometrial stromal cells (i.e., decidualization). In this study, to elucidate the role of decidual c-Src activation, we examined whether 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP1) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), both potent and selective SFK inhibitors, affected the ovarian steroid-induced decidualization in vitro. Unexpectedly, PP1 paradoxically increased the kinase activity of decidual c-Src together with dephosphorylation of Y530 in the presence of ovarian steroids. Concomitantly, PP1 enhanced morphological and functional decidualization, as determined by induction of decidualization markers, such as insulin-like growth factor binding protein-1 and prolactin. PP2 also advanced decidualization along with up-regulation of the active form of c-Src whose Y-530 was dephosphorylated. In contrast to PP1 and PP2, herbimycin A, a tyrosine kinase inhibitor with less specificity for SFKs, showed little enhancing effect on the expression of both IGFBP-1 and active c-Src. These results suggest that SFKs, including c-Src, may play a significant role in stromal cell differentiation, providing a clue for a possible therapeutic strategy to modulate endometrial function by targeting signaling pathway(s) involving SFKs.

Induction of protein kinase C substrates, Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP), by amyloid beta-protein in mouse BV-2 microglial cells

Microglial activation by amyloid beta-protein in senile plaques contributes to neurodegeneration in Alzheimer disease. In BV-2 microglial cells, amyloid beta-protein 1-40 (Abeta 1-40) elicited a dose-dependent increase (3-4 fold) of Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP), two protein kinase C substrates implicated in membrane-cytoskeletal alterations underlying microglial adhesion, migration, secretion, and phagocytosis. Neither MARCKS nor MRP was induced by the amyloid fragment Abeta 25-35, although both Abeta 1-40 and Abeta 25-35 caused extensive aggregation of BV-2 cells. Interferon-gamma synergistically enhanced the induction by Abeta 1-40 of inducible nitric oxide synthase, but not MARCKS or MRP. Our results suggest that MARCKS and MRP may play important roles in microglia activated by amyloid peptides.

Regulating factors for microglial activation

Microglia, residential macrophages in the central nervous system, can release a variety of factors including cytokines, chemokines, etc. to regulate the communication among neuronal and other types of glial cells. Microglia play immunological roles in mechanisms underlying the phagocytosis of invading microorganisms and removal of dead or damaged cells. When microglia are hyperactivated due to a certain pathological imbalance, they may cause neuronal degeneration. Pathological activation of microglia has been reported in a wide range of conditions such as cerebral ischemia, Alzheimer's disease, prion diseases, multiple sclerosis, AIDS dementia, and others. Nearly 5000 papers on microglia can be retrieved on the Web site PubMed at present (November 2001) and half of them were published within the past 5 years. Although it is not possible to read each paper in detail, as many factors as possible affecting microglial functions in in vitro culture systems are presented in this review. The factors are separated into "activators" and "inhibitors," although it is difficult to classify many of them. An overview on these factors may help in the development of a new strategy for the treatment of various neurodegenerative diseases.