Met-RANTES preserves the blood-brain barrier through inhibiting CCR1/SRC/Rac1 pathway after intracerebral hemorrhage in mice.

BACKGROUND: C-C chemokine receptor type 1 (CCR1) and its endogenous ligand, CCL5, participate in the pathogenesis of neuroinflammatory diseases. However, much remains unknown regarding CCL5/CCR1 signaling in blood-brain barrier (BBB) permeability after intracerebral hemorrhage (ICH). METHODS: A total of 250 CD1 male mice were used and ICH was induced via autologous whole blood injection. Either Met-RANTES, a selective CCR1 antagonist, or Met-RANTES combined with a Rac1 CRISPR activator was administered to the mice 1 h after ICH. Post-ICH assessments included neurobehavioral tests, brain water content, BBB integrity, hematoma volume, Western blot, and immunofluorescence staining. The CCR1 ligand, rCCL5, and SRC CRISPR knockout in naïve mice were used to further elucidate detrimental CCL5/CCR1/SRC signaling. RESULTS: Brain endogenous CCR1 and CCL5 were upregulated after ICH in mice with a peak at 24 h, and CCR1 was expressed in endothelial cells, astrocytes, and neurons. Met-R treatment reduced brain edema and neurobehavioral impairment, as well as preserved BBB integrity and tight junction protein expression in ICH mice. Met-R treatment decreased expression of p-SRC, Rac1, albumin, and MMP9, but increased claudin-5, occludin, and ZO-1 tight junction proteins after ICH. These effects were regressed using the Rac1 CRISPR activator. Administration of rCCL5 in naïve mice increased expression of p-SRC, Rac1, albumin, and MMP9, but decreased levels of claudin-5, occludin, and ZO-1 tight junction proteins. These effects in naïve mice were reversed with SRC CRISPR (KO). CONCLUSIONS: Our findings demonstrate that CCR5 inhibition by Met-R improves neurological deficits after ICH by preserving BBB integrity through inhibiting CCR1/SRC/Rac1 signaling pathway in mice. Thus, Met-R has therapeutic potential in the management of ICH patients.

Association between thiopurine exposure and depression in patients with inflammatory bowel disease and rheumatoid arthritis.

BACKGROUND: Ras-related C3 botulinum substrate 1 (Rac1) is a member of the small molecule family Rho guanosine triphosphate (GTP)ases. Recent findings reveal epigenetic downregulation of Rac1 is a mechanism of depression. AIMS: The purpose of this study was to evaluate Rac1 as a therapeutic target for depression we examine the association between thiopurines, which inhibit Rac1, and the risk of depression among US veterans. METHODS: This study uses data spanning January 2000-May 2019, comparing thiopurine exposure (no exposure, less than one year, 1-2.9 years, 3-5 years, and greater than five years) in two separate cohorts, a rheumatoid arthritis cohort and inflammatory bowel disease cohort. We estimate the hazard of depression using a time dependent cox proportional hazards model. RESULTS: A total of 76,763 rheumatoid arthritis and 46,787 inflammatory bowel disease patients met all inclusion criteria. Patients exposed to thiopurines less than one year have a 27% (hazard ratio=1.272; 95% confidence interval=(1.038-1.559)) and 67% (hazard ratio=1.667 95% confidence interval=(1.501-1.850)) higher risk of depression in the rheumatoid arthritis and inflammatory bowel disease cohorts, respectively. In the inflammatory bowel disease cohort, we find the risk of depression is increased for up to five years of thiopurine exposure. CONCLUSION: These results provide evidence that Rac1 regulation is a viable therapeutic target for depression. Further research into therapeutics targeting Rac1 for the treatment of depression is warranted.

PTPσ inhibitors promote hematopoietic stem cell regeneration.

Receptor type protein tyrosine phosphatase-sigma (PTPσ) is primarily expressed by adult neurons and regulates neural regeneration. We recently discovered that PTPσ is also expressed by hematopoietic stem cells (HSCs). Here, we describe small molecule inhibitors of PTPσ that promote HSC regeneration in vivo. Systemic administration of the PTPσ inhibitor, DJ001, or its analog, to irradiated mice promotes HSC regeneration, accelerates hematologic recovery, and improves survival. Similarly, DJ001 administration accelerates hematologic recovery in mice treated with 5-fluorouracil chemotherapy. DJ001 displays high specificity for PTPσ and antagonizes PTPσ via unique non-competitive, allosteric binding. Mechanistically, DJ001 suppresses radiation-induced HSC apoptosis via activation of the RhoGTPase, RAC1, and induction of BCL-XL. Furthermore, treatment of irradiated human HSCs with DJ001 promotes the regeneration of human HSCs capable of multilineage in vivo repopulation. These studies demonstrate the therapeutic potential of selective, small-molecule PTPσ inhibitors for human hematopoietic regeneration.

Atorvastatin inhibits pro-inflammatory actions of aldosterone in vascular smooth muscle cells by reducing oxidative stress.

Vascular inflammatory responses play an important role in several cardiovascular diseases. Of the many pro-inflammatory vasoactive factors implicated in this process, is aldosterone, an important mediator of vascular oxidative stress. Statins, such as atorvastatin, are cholesterol-lowering drugs that have pleiotropic actions, including anti-oxidant properties independently of their cholesterol-lowering effect. This study investigated whether atorvastatin prevents aldosterone-induced VSMC inflammation by reducing reactive oxygen species (ROS) production. Vascular smooth muscle cells (VSMC) from WKY rats were treated with 1 µM atorvastatin for 60 min or for 72 h prior to aldosterone (10-7 mol/L) stimulation. Atorvastatin inhibited Rac1/2 and p47phox translocation from the cytosol to the membrane, as well as reduced aldosterone-induced ROS production. Atorvastatin also attenuated aldosterone-induced vascular inflammation and macrophage adhesion to VSMC. Similarly EHT1864, a Rac1/2 inhibitor, and tiron, ROS scavenger, reduced macrophage adhesion. Through its inhibitory effects on Rac1/2 activation and ROS production, atorvastatin reduces vascular ROS generation and inhibits VSMC inflammation. Our data suggest that in conditions associated with aldosterone-induced vascular damage, statins may have vasoprotective effects by inhibiting oxidative stress and inflammation.

CB1R regulates CDK5 signaling and epigenetically controls Rac1 expression contributing to neurobehavioral abnormalities in mice postnatally exposed to ethanol.

Fetal alcohol spectrum disorders (FASD) represent a wide array of defects that arise from ethanol exposure during development. However, the underlying molecular mechanisms are limited. In the current report, we aimed to further evaluate the cannabinoid receptor type 1 (CB1R)-mediated mechanisms in a postnatal ethanol-exposed animal model. We report that the exposure of postnatal day 7 (P7) mice to ethanol generates p25, a CDK5-activating peptide, in a time- and CB1R-dependent manner in the hippocampus and neocortex brain regions. Pharmacological inhibition of CDK5 activity before ethanol exposure prevented accumulation of cleaved caspase-3 (CC3) and hyperphosphorylated tau (PHF1) (a marker for neurodegeneration) in neonatal mice and reversed cAMP response element-binding protein (CREB) activation and activity-regulated cytoskeleton-associated protein (Arc) expression. We also found that postnatal ethanol exposure caused a loss of RhoGTPase-related, Rac1, gene expression in a CB1R and CDK5 activity-dependent manner, which persisted to adulthood. Our epigenetic analysis of the Rac1 gene promoter suggested that persistent suppression of Rac1 expression is mediated by enhanced histone H3 lysine 9 dimethylation (H3K9me2), a repressive chromatin state, via G9a recruitment. The inhibition of CDK5/p25 activity before postnatal ethanol exposure rescued CREB activation, Arc, chromatin remodeling and Rac1 expression, spatial memory, and long-term potentiation (LTP) abnormalities in adult mice. Together, these findings propose that the postnatal ethanol-induced CB1R-mediated activation of CDK5 suppresses Arc and Rac1 expression in the mouse brain and is responsible for persistent synaptic plasticity and learning and memory defects in adult mice. This CB1R-mediated activation of CDK5 signaling during active synaptic development may slow down the maturation of synaptic circuits and may cause neurobehavioral defects, as found in this FASD animal model.

Rac1 Modulates Endothelial Function and Platelet Aggregation in Diabetes Mellitus.

BACKGROUND: Vascular complications and abnormal platelet function contribute to morbidity and mortality in diabetes mellitus. We hypothesized that the Rho-related GTPase protein, Rac1, can influence both endothelial and platelet function and might represent a potential novel therapeutic target in diabetes mellitus. METHODS AND RESULTS: We used both in vitro and ex vivo approaches to test the effects of pharmacological inhibition of Rac1 during hyperglycemic condition. We evaluated the effect of NSC23766, a pharmacological inhibitor of Rac1, on vascular function in diabetic mice and platelet aggregation in diabetic subjects. We demonstrated that the administration of NSC23766 protects from hyperglycemia-induced endothelial dysfunction, restoring NO levels, and reduces oxidative stress generated by nicotinamide adenine dinucleotide phosphate oxidase. Mechanistically, we identified Rho-associated coiled-coil serine/threonine kinase-1 as a downstream target of Rac1. Moreover, we reported that during hyperglycemic conditions, human platelets showed hyperactivation of Rac1 and impaired NO release, which were both partially restored after NSC23766 treatment. Finally, we characterized the antiplatelet effect of NSC23766 during hyperglycemic conditions, demonstrating the additional role of Rac1 inhibition in reducing platelet aggregation in diabetic patients treated with common antiplatelet drugs. CONCLUSIONS: Our data suggest that the pharmacological inhibition of Rac1 could represent a novel therapeutic strategy to reduce endothelial dysfunction and platelet hyperaggregation in diabetes mellitus.

Semaphorin 4D inhibits neutrophil activation and is involved in the pathogenesis of neutrophil-mediated autoimmune vasculitis.

OBJECTIVES: Inappropriate activation of neutrophils plays a pathological role in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The aim of this study was to investigate the functions of semaphorin 4D (SEMA4D) in regulation of neutrophil activation, and its involvement in AAV pathogenesis. METHODS: Serum levels of soluble SEMA4D were evaluated by ELISA. Blood cell-surface expression of membrane SEMA4D was evaluated by flow cytometry. To determine the functional interactions between neutrophil membrane SEMA4D and endothelial plexin B2, wild-type and SEMA4D-/- mice neutrophils were cultured with an endothelial cell line (MS1) stained with SYTOX green, and subjected to neutrophil extracellular trap (NET) formation assays. The efficacy of treating human neutrophils with recombinant plexin B2 was assessed by measuring the kinetic oxidative burst and NET formation assays. RESULTS: Serum levels of soluble SEMA4D were elevated in patients with AAV and correlated with disease activity scores. Cell-surface expression of SEMA4D was downregulated in neutrophils from patients with AAV, a consequence of proteolytic cleavage of membrane SEMA4D. Soluble SEMA4D exerted pro-inflammatory effects on endothelial cells. Membranous SEMA4D on neutrophils bound to plexin B2 on endothelial cells, and this interaction decreased NET formation. Recombinant plexin B2 suppressed neutrophil Rac1 activation through SEMA4D's intracellular domain, and inhibited pathogen-induced or ANCA-induced oxidative burst and NET formation. CONCLUSIONS: Neutrophil surface SEMA4D functions as a negative regulator of neutrophil activation. Proteolytic cleavage of SEMA4D as observed in patients with AAV may amplify neutrophil-mediated inflammatory responses. SEMA4D is a promising biomarker and potential therapeutic target for AAV.

Recombinant Osteopontin Stabilizes Smooth Muscle Cell Phenotype via Integrin Receptor/Integrin-Linked Kinase/Rac-1 Pathway After Subarachnoid Hemorrhage in Rats.

BACKGROUND AND PURPOSE: Recombinant osteopontin (rOPN) has been reported to be neuroprotective in stroke animal models. The purpose of this study is to investigate a potential role and mechanism of nasal administration of rOPN on preserving the vascular smooth muscle phenotype in early brain injury after subarachnoid hemorrhage (SAH). METHODS: One hundred and ninety-two male adult Sprague-Dawley rats were used. The SAH model was induced by endovascular perforation. Integrin-linked kinase small interfering RNA was intracerebroventricularly injected 48 hours before SAH. The integrin receptor antagonist fibronectin-derived peptide Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), focal adhesion kinase inhibitor Fib-14, and Rac-1 inhibitor NSC23766 were administered 1 hour before SAH induction. rOPN was administered via the intracerebroventricular and nasal route after SAH. SAH grade, neurological scores, brain water content, brain swelling, hematoxylin and eosin staining, India ink angiography, Western blots, and immunofluorescence were used to study the mechanisms of rOPN on the vascular smooth muscle phenotypic transformation. RESULTS: The marker proteins of vascular smooth muscle phenotypic transformation α-smooth muscle actin decreased and embryonic smooth muscle myosin heavy chain (SMemb) increased significantly at 24 and 72 hours in the cerebral arteries after SAH. rOPN prevented the changes of α-smooth muscle actin and SMemb and significantly alleviated neurobehavioral dysfunction, increased the cross-sectional area and the lumen diameter of the cerebral arteries, reduced the brain water content and brain swelling, and improved the wall thickness of cerebral arteries. These effects of rOPN were abolished by GRGDSP, integrin-linked kinase small interfering RNA, and NSC23766. Intranasal application of rOPN at 3 hours after SAH also reduced neurological deficits. CONCLUSIONS: rOPN prevented the vascular smooth muscle phenotypic transformation and improved the neurological outcome, which was possibly mediated by the integrin receptor/integrin-linked kinase/Rac-1 pathway.

Botulinum Toxin A Upregulates Rac1, Cdc42, and RhoA Gene Expression in a Dose-Dependent Manner: In Vivo and in Vitro Study.

UNLABELLED: Angiogenesis is the development of new capillaries from existing blood vessels and is a prerequisite for the wound-healing process. Many lines of scientific evidences have shown that complicated roles of small guanosine triphosphatases (GTPases) (ras-related C3 botulinum toxin substrate 1 [Rac1], cell division control protein 42 [Cdc42], and ras homolog gene family, member A [RhoA]) in regulation of signal transduction pathways exist to transmit distinct cellular effects on the modulation of actin cytoskeleton remodeling such as cell cycle progression, cell survival, and cell motility. In addition, these small GTPases activate mitogen-activated protein kinase kinase kinases (MAP3Ks) leading to activated mitogen-activated protein kinase kinases (MAPKK), mitogen-activated protein kinase (MAPK), and various transcription factors such as vascular endothelial growth factor with involvement of MAPK signaling pathways.In this study, the authors hypothesized that botulinum toxin A increases angiogenesis via the expression of small GTPases in vivo and in vitro studies.In vivo experiment, 24 Sprague-Dawley rats were randomly divided into 2 groups: a control group and a botulinum toxin A group. Five days prior to superiorly based transverse rectus abdominis myocutaneous flap elevation, the botulinum toxin A (BoTA) group was pretreated with BoTA, while the control group was pretreated with normal saline. quantitative real-time polymerase chain reaction was performed to evaluate the expression of Rac1, RhoA, and Cdc42.The angiogenic effects of botulinum toxin A on human dermal fibroblasts were measured in vitro experiment. To understand the mechanism of botulinum toxin A on small GTPases production of fibroblasts, Rac1, Cdc42, and RhoA were measured using qRT-PCR.The relative messenger ribonucleic acid expression of Rac1, RhoA, and Cdc42 was significantly higher in the BoTA group than in the control group, in every zone and pedicle muscle, on postoperative days 1, 3, and 5. Levels of these molecules increased significantly in human dermal fibroblasts grown in the presence of BoTA compared with control group over 5 IU.Our in vivo and in vitro studies suggest that administration of BoTA upregulates the expression of RhoA, Rac1, and Cdc42 in a dose-dependent manner. MAPK signaling pathway might be involved in BoTA-induced angiogenesis mechanism. LEVEL OF EVIDENCE: N/A.

Involvement of renin-angiotensin-aldosterone system in calcium oxalate crystal induced activation of NADPH oxidase and renal cell injury.

INTRODUCTION AND OBJECTIVES: Reactive oxygen species (ROS) are produced during the interaction between oxalate/calcium oxalate monohydrate (COM) crystals and renal epithelial cells and are responsible for the various cellular responses through the activation of NADPH oxidase (Nox). Ox and COM also activate the renin-angiotensin-aldosterone system (RAAS). Aldosterone stimulates ROS production through activation of Nox with the involvement of mineralocorticoid receptor (MR), Rac1 and mitogen-activated protein kinases (MAPK). We investigated RAAS pathways in vivo in an animal model of hyperoxaluria and in vitro by exposing renal epithelial cells to COM crystals. METHODS: Hyperoxaluria was induced in male SD rats by administering ethylene glycol. One group of rats was additionally given spironolactone. Total RNA was extracted and subjected to genomic microarrays to obtain global transcriptome data. Normal rat kidney cell line (NRK-52E) was incubated with aldosterone(10(-7) M) and COM(67 µg/cm(2)) with or without spironolactone(10(-5) M), a selective inhibitor of SRC family of kinases; protein phosphatase 2(pp2) (10(-5) M) and Nox inhibitor; diphenylene iodonium (DPI) (10(-5) M). RESULTS: Relative expression of genes encoding for AGT, angiotensin receptors 1b and 2, Renin 1, Cyp11b, HSD11B2, Nr3c2, NOx4 and Rac1 was upregulated in the kidneys of rats with hyperoxaluria. Treatment with spironolactone reversed the effect of hyperoxaluria. Both aldosterone and COM crystals activated Nox and Rac1 expression in NRK52E, while spironolactone inhibited Nox and Rac1 expression. Increased Rac1 expression was significantly attenuated by treatment with PP2 and spironolactone. CONCLUSIONS: Results indicate that hyperoxaluria-induced production of ROS, injury and inflammation are in part associated with the activation of Nox through renin-angiotensin-aldosterone pathway.

Osteopontin-Rac1 on Blood-Brain Barrier Stability Following Rodent Neonatal Hypoxia-Ischemia.

Osteopontin (OPN) is a neuroprotective molecule that is upregulated following rodent neonatal hypoxic-ischemic (nHI) brain injury. Because Rac1 is a regulator of blood-brain barrier (BBB) stability, we hypothesized a role for this in OPN signaling. nHI was induced by unilateral ligation of the right carotid artery followed by hypoxia (8 % oxygen for 2 h) in P10 Sprague-Dawley rat pups. Intranasal (iN) OPN was administered at 1 h post-nHI. Groups consisted of: (1) Sham, (2) Vehicle, (3) OPN, and (4) OPN + Rac1 inhibitor (NSC23766). Evans blue dye extravasation (BBB permeability) was quantified 24 h post-nHI, and brain edema at 48 h. Increased BBB permeability and brain edema following nHI was ameliorated in the OPN treatment group. However, those rat pups receiving OPN co-treatment with the Rac1 inhibitor experienced no improvement compared with vehicle. OPN protects the BBB following nHI, and this was reversed by Rac1 inhibitor (NSC23766).

Cell-to-cell propagation of the bacterial toxin CNF1 via extracellular vesicles: potential impact on the therapeutic use of the toxin.

Eukaryotic cells secrete extracellular vesicles (EVs), either constitutively or in a regulated manner, which represent an important mode of intercellular communication. EVs serve as vehicles for transfer between cells of membrane and cytosolic proteins, lipids and RNA. Furthermore, certain bacterial protein toxins, or possibly their derived messages, can be transferred cell to cell via EVs. We have herein demonstrated that eukaryotic EVs represent an additional route of cell-to-cell propagation for the Escherichia coli protein toxin cytotoxic necrotizing factor 1 (CNF1). Our results prove that EVs from CNF1 pre-infected epithelial cells can induce cytoskeleton changes, Rac1 and NF-κB activation comparable to that triggered by CNF1. The observation that the toxin is detectable inside EVs derived from CNF1-intoxicated cells strongly supports the hypothesis that extracellular vesicles can offer to the toxin a novel route to travel from cell to cell. Since anthrax and tetanus toxins have also been reported to engage in the same process, we can hypothesize that EVs represent a common mechanism exploited by bacterial toxins to enhance their pathogenicity.

Effect of omega-3 polyunsaturated fatty acids on the cytoskeleton: an open-label intervention study.

BACKGROUND: Omega-3 polyunsaturated fatty acids (n-3 PUFAs) show beneficial effects on cardiovascular health and cognitive functions, but the underlying molecular mechanisms are not completely understood. Because of the fact that cytoskeleton dynamics affect almost every cellular process, the regulation of cytoskeletal dynamics could be a new pathway by which n-3 PUFAs exert their effects on cellular level. METHODS: A 12-week open-label intervention study with 12 healthy men was conducted to determine the effects of 2.7 g/d n-3 PUFA on changes in mRNA expression of cytoskeleton-associated genes by quantitative real-time PCR in whole blood. Furthermore, the actin content in red blood cells was analyzed by immunofluorescence imaging. RESULTS: N-3 PUFA supplementation resulted in a significant down-regulation of cytoskeleton-associated genes, in particular three GTPases (RAC1, RHOA, CDC42), three kinases (ROCK1, PAK2, LIMK), two Wiskott-Aldrich syndrome proteins (WASL, WASF2) as well as actin related protein 2/3 complex (ARPC2, ARPC3) and cofilin (CFL1). Variability in F-actin content between subjects was high; reduced actin content was only reduced within group evaluation. CONCLUSIONS: Reduced cytoskeleton-associated gene expression after n-3 PUFA supplementation suggests that regulation of cytoskeleton dynamics might be an additional way by which n-3 PUFAs exert their cellular effects. Concerning F-actin, this analysis did not reveal unmistakable results impeding a generalized conclusion.

The small GTPase Rac1 is required for smooth muscle contraction.

The role of the small GTP-binding protein Rac1 in smooth muscle contraction was examined using small molecule inhibitors (EHT1864, NSC23766) and a novel smooth muscle-specific, conditional, Rac1 knockout mouse strain. EHT1864, which affects nucleotide binding and inhibits Rac1 activity, concentration-dependently inhibited the contractile responses induced by several different modes of activation (high-K+, phenylephrine, carbachol and protein kinase C activation by phorbol-12,13-dibutyrate) in several different visceral (urinary bladder, ileum) and vascular (mesenteric artery, saphenous artery, aorta) smooth muscle tissues. This contractile inhibition was associated with inhibition of the Ca2+ transient. Knockout of Rac1 (with a 50% loss of Rac1 protein) lowered active stress in the urinary bladder and the saphenous artery consistent with a role of Rac1 in facilitating smooth muscle contraction. NSC23766, which blocks interaction between Rac1 and some guanine nucleotide exchange factors, specifically inhibited the α1 receptor responses (phenylephrine) in vascular tissues and potentiated prostaglandin F2α and thromboxane (U46619) receptor responses. The latter potentiating effect occurred at lowered intracellular [Ca2+]. These results show that Rac1 activity is required for active contraction in smooth muscle, probably via enabling an adequate Ca2+ transient. At the same time, specific agonists recruit Rac1 signalling via upstream modulators, resulting in either a potentiation of contraction via Ca2+ mobilization (α1 receptor stimulation) or an attenuated contraction via inhibition of Ca2+ sensitization (prostaglandin and thromboxane receptors).

Oxidative stress causes mineralocorticoid receptor activation in rat cardiomyocytes: role of small GTPase Rac1.

Overactivation of the mineralocorticoid receptor signaling is implicated in cardiovascular disease, including hypertensive heart disease. Oxidative stress is suggested to augment mineralocorticoid receptor signal transduction, but the precise mechanisms remain unclear. Mineralocorticoid receptor activity is regulated by multiple factors, in addition to plasma ligand levels. We previously identified Rac1 GTPase as a modulator of mineralocorticoid receptor activity. Here we show that oxidative stress induces mineralocorticoid receptor activation in a ligand-independent, Rac1-depenent manner in cardiomyocytes. Oxidant stress was induced in rat cultured cardiomyocytes (H9c2) by l-buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis. BSO depleted intracellular glutathione and concomitantly increased reactive oxygen species (199%; P<0.01). BSO significantly enhanced the corticosterone-induced, mineralocorticoid receptor-dependent luciferase reporter activity (186%; P<0.01) and basal luciferase activity without ligand stimulation. These effects were inhibited by the antioxidant N-acetylcysteine. The ligand independency of BSO action was indicated using a mutant mineralocorticoid receptor that does not bind ligands. With this mutant mineralocorticoid receptor, BSO-evoked mineralocorticoid receptor activation remained intact, whereas ligand-induced mineralocorticoid receptor activation was abolished. We next examined the involvement of Rac1. BSO increased active Rac1 in a redox-dependent fashion, and Rac inhibition suppressed the enhancing effect of BSO. Constitutively active Rac1, indeed, potentiated mineralocorticoid receptor transactivation. Furthermore, mineralocorticoid receptor transactivation by BSO was accompanied by enhanced nuclear accumulation of mineralocorticoid receptor. We conclude that alteration of redox state modulates mineralocorticoid receptor-dependent transcriptional activity via Rac1 in the heart. This redox-sensitive, ligand-independent mineralocorticoid receptor activation may contribute to the processes by which oxidant stress promotes cardiac injury.

Phenylboronic acid is a more potent inhibitor than boric acid of key signaling networks involved in cancer cell migration.

Previous studies from our lab have shown that both boric (BA) and phenylboronic- acid (PBA) inhibit the migration of prostate cancer cell lines, as well as non-tumorigenic prostate cells. Our results indicate that PBA is more potent than BA in targeting metastatic and proliferative properties of cancer cells. Here we focus on the impact of BA and PBA on Rho family of GTP-binding proteins and their downstream targets. Treatment with 1mM PBA and BA decreases activities of RhoA, Rac1, and Cdc42 in DU-145 metastatic prostate cancer cells, but not in normal RWPE-1 prostate cells. Furthermore, ROCKII activity and phosphorylation of myosin light chain kinase decrease as a result of either PBA or BA treatment in DU-145 cells, suggesting these compounds target actomyosin-based contractility.

Azithromycin may inhibit interleukin-8 through suppression of Rac1 and a nuclear factor-kappa B pathway in KB cells stimulated with lipopolysaccharide.

BACKGROUND: Recent studies have shown that the 15-member macrolide antibiotic azithromycin (AZM) not only has antibacterial activity, but also results in the role of immunomodulator. Interleukin (IL)-8 is an important inflammatory mediator in periodontal disease. However, there have been no reports on the effects of AZM on IL-8 production from human oral epithelium. Therefore, we investigated the effects of AZM on IL-8 production in an oral epithelial cell line. METHODS: KB cells were stimulated by Escherichia coli or Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) lipopolysaccharide (LPS) with or without AZM. IL-8 mRNA and protein expression and production in response to LPS were analyzed by quantitative polymerase chain reaction, flow cytometry, and enzyme-linked immunosorbent assay. The activation of nuclear factor-kappa B (NF-κB) and Rac1, which is important for IL-8 expression, was analyzed by enzyme-linked immunosorbent assay and Western blotting, respectively. RESULTS: IL-8 mRNA expression, IL-8 production, and NF-κB activation in LPS-stimulated KB cells were inhibited by the addition of AZM. LPS-induced Rac1 activation was also suppressed by AZM. CONCLUSIONS: This study suggests that AZM inhibits LPS-induced IL-8 production in an oral epithelial cell line, in part caused by the suppression of Rac1 and NF-κB activation. The use of AZM might provide possible benefits in periodontal therapy, with respect to both its antibacterial action and apparent anti-inflammatory effect.

Simvastatin stimulates apoptosis in cholangiocarcinoma by inhibition of Rac1 activity.

BACKGROUND: Simvastatin is a cholesterol-lowering drug that is widely used to prevent and treat atherosclerotic cardiovascular disease. Simvastatin exhibits numerous pleiotropic effects including anti-cancer activity. However, the effect of simvastatin on cholangiocarcinoma has not been evaluated. AIM: The aim of our study was to determine the effect of simvastatin on cholangiocarcinoma proliferation. METHODS: The effect of simvastatin was evaluated in five human cholangiocarcinoma cell lines (Mz-ChA-1, HuH-28, TFK-1, SG231, and HuCCT1) and normal cholangiocyte cell line (HiBEpiC). RESULTS: We found that simvastatin stimulates a reduction in cell viability and apoptosis of cholangiocarcinoma cell lines, whilst in normal human cholangiocytes, HiBEpiC, simvastatin inhibits proliferation with no effect on apoptosis. Simvastatin-induced reduction of cell viability was partially blocked by pre-treatment with metabolites of the mevalonate pathway. In Mz-ChA-1 cells, pre-treatment with cholesterol alone stimulated an increase in the number of viable cells and fully restored cell viability following simvastatin treatment. Treatment with simvastatin triggered the loss of lipid raft localised Rac1 and reduction of Rac1 activity in Mz-ChA-1 cells. This effect was prevented by pre-treatment with cholesterol. CONCLUSION: Collectively, our results demonstrate that simvastatin induces cholangiocarcinoma cancer cell death by disrupting Rac1/lipid raft colocalisation and depression of Rac1 activity.

Phospholipase C, Ca2+, and calmodulin signaling are required for 5-HT2A receptor-mediated transamidation of Rac1 by transglutaminase.

RATIONALE: Serotonin and especially serotonin 2A (5-HT(2A)) receptor signaling are important in the etiology and treatment of schizophrenia and affective disorders. We previously reported a novel 5-HT(2A) receptor effector, increased transglutaminase (TGase)-catalyzed transamidation, and activation of the small G protein Rac1 in A1A1v cells, a rat embryonic cortical cell line. OBJECTIVES: In this study, we explore the signaling pathway involved in 5-HT(2A) receptor-mediated Rac1 transamidation. METHODS: A1A1v cells were pretreated with pharmacological inhibitors of phospholipase C (PLC) or calmodulin (CaM), and then stimulated by the 5-HT(2A) receptor agonist, 2,5-dimethoxy-4-iodoamphetamine (DOI). Intracellular Ca(2+) concentration and TGase-modified Rac1 transamidation were monitored. The effect of manipulation of intracellular Ca(2+) by a Ca(2+) ionophore or a chelating agent on Rac1 transamidation was also evaluated. RESULTS: In cells pretreated with a PLC inhibitor U73122, DOI-stimulated increases in the intracellular Ca(2+) concentration and TGase-modified Rac1 were significantly attenuated as compared to those pretreated with U73343, an inactive analog. The membrane-permeant Ca(2+) chelator, BAPTA-AM strongly reduced TGase-catalyzed Rac1 transamidation upon DOI stimulation. Conversely, the Ca(2+) ionophore ionomycin, at a concentration that induced an elevation of cytosolic Ca(2+) to a level comparable to cells treated with DOI, produced an increase in TGase-modified Rac1 without 5-HT(2A) receptor activation. Moreover, the CaM inhibitor W-7, significantly decreased Rac1 transamidation in a dose-dependent manner in DOI-treated cells. CONCLUSIONS: These results indicate that 5-HT(2A) receptor-coupled PLC activation and subsequent Ca(2+) and CaM signaling are necessary for TGase-catalyzed Rac1 transamidation, and an increase in intracellular Ca(2+) is sufficient to induce Rac1 transamidation.

Pleiotropic role of Rac in mast cell activation revealed by a cell permeable Bordetella dermonecrotic fusion toxin.

To activate the GTPase Rac in rat basophilic leukemia (RBL) cells and mouse bone marrow-derived mast cells (BMMC) a TAT fusion toxin of Bordetella dermonecrotic toxin (DNT-TAT) was constructed. The fusion toxin activated Rac1 and RhoA in vitro but only Rac in RBL cells and BMMC. DNT-TAT caused an increase in inositol phosphate formation, calcium mobilization, ERK activation and degranulation of mast cells. All these effects were inhibited by the Rho GTPase-inactivating Clostridium difficile toxin B and Clostridium sordellii lethal toxin. Also the calcium ionophore A23187 caused mast cell activation, including ERK phosphorylation, by processes involving an activation of Rac. The data indicate pleiotropic functions of Rac in mast cell activation.