Inhibition of Rho GTPases with protein prenyltransferase inhibitors prevents leukocyte recruitment to the central nervous system and attenuates clinical signs of disease in an animal model of multiple sclerosis

Unsupervised Machine Learning Revealed that Repeat Transcranial Magnetic Stimulation is More Suitable for Stroke Patients with Statin

INTRODUCTION

Repeat transcranial magnetic stimulation (rTMS) demonstrates beneficial effects for stroke patients, though its efficacy varies due to the complexity of patient conditions and disease progression. Unsupervised machine learning could be the optimal solution for identifying target patients for transcranial magnetic stimulation treatment.

METHODS

We collected data from ischaemic stroke patients treated with rTMS. Unsupervised machine learning methods, including K-means and Hierarchical Clustering, were used to explore the clinical characteristics of patients suitable for rTMS. We then utilized a prospective observational cohort to validate the effect of selected characteristics. For the validated cohort, outcomes included the presence of motor evoked potentials (MEP), favorable functional outcomes (FFO), and changes in the Fugl-Meyer Assessment (FMA) at 3 and 6 months.

RESULTS

Hierarchical clustering methods revealed that patients in the better prognosis group were more likely to take statins. The validated cohort was grouped based on statin intake. Patients taking statins exhibited a higher rate of MEP (p = 0.006), a higher rate of FFO at 3 months (p = 0.003) and 6 months (p = 0.021), and a more significant change in FMA (p < 0.001) at both 3 and 6 months. Statin intake was associated with FFO and changes in FMA at 3 and 6 months. This relationship persisted across all subgroups for FMA changes and some FFO subgroups.

CONCLUSION

Stroke patients undergoing rTMS treatment taking statins exhibited greater MEP, FFO, and changes in FMA. Statin intake was associated with a better prognosis in these patients.

Protein lipidation in health and disease: molecular basis, physiological function and pathological implication

Posttranslational modifications increase the complexity and functional diversity of proteins in response to complex external stimuli and internal changes. Among these, protein lipidations which refer to lipid attachment to proteins are prominent, which primarily encompassing five types including S-palmitoylation, N-myristoylation, S-prenylation, glycosylphosphatidylinositol (GPI) anchor and cholesterylation. Lipid attachment to proteins plays an essential role in the regulation of protein trafficking, localisation, stability, conformation, interactions and signal transduction by enhancing hydrophobicity. Accumulating evidence from genetic, structural, and biomedical studies has consistently shown that protein lipidation is pivotal in the regulation of broad physiological functions and is inextricably linked to a variety of diseases. Decades of dedicated research have driven the development of a wide range of drugs targeting protein lipidation, and several agents have been developed and tested in preclinical and clinical studies, some of which, such as asciminib and lonafarnib are FDA-approved for therapeutic use, indicating that targeting protein lipidations represents a promising therapeutic strategy. Here, we comprehensively review the known regulatory enzymes and catalytic mechanisms of various protein lipidation types, outline the impact of protein lipidations on physiology and disease, and highlight potential therapeutic targets and clinical research progress, aiming to provide a comprehensive reference for future protein lipidation research.

Navigating the landscape of Rho GTPase signalling system in autoimmunity: A bibliometric analysis spanning over three decades (1990 to 2023)

Ras-homologous (Rho) guanosine triphosphatases (GTPases) are considered a central player in regulating various biological processes, extending to immune regulation. Perturbations in Rho GTPase signalling have been implicated in immune-related dysregulation, contributing to the development of autoimmunity. This study presents a scientometric analysis exploring the interlink between the Rho GTPase signalling system and autoimmunity, while also delving into the trends of past studies. A total of 967 relevant publications from 1990 to 2023 were retrieved from the Web of Science Core Collection database after throrough manual filtering of irrelevant articles. The findings show an upward trajectory in publications related to this field since 2006. Over the past three decades, the United States of America (41.68%) emerged as the primary contributor in advancing our understanding of the association between the Rho GTPase signalling system and autoimmunity. Research in autoimmunity has mainly centered around therapeutic interventions, with an emphasis on studying leukocyte (macrophage) and endothelial remodelling. Interestingly, within the domains of multiple sclerosis and rheumatoid arthritis, the current focus has been directed towards comprehending the role of RhoA, Rac1, and Cdc42. Notably, certain subfamilies of Rho (such as RhoB and RhoC), Rac (including Rac2 and RhoG), Cdc42 (specifically RhoJ), and other atypical Rho GTPases (like RhoE and RhoH) consistently demonstrating compelling link with autoimmunity, but still warrants emphasis in the future study. Hence, strategic manipulation of the Rho signalling system holds immense promise as a pivotal approach to addressing the global challenge of autoimmunity.

Comparative Proteomic Profiling Identifies Reciprocal Expression of Mitochondrial Proteins Between White and Gray Matter Lesions From Multiple Sclerosis Brains

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system, where ongoing demyelination and remyelination failure are the major factors for progressive neurological disability. In this report, we employed a comprehensive proteomic approach and immunohistochemical validation to gain insight into the pathobiological mechanisms that may be associated with the progressive phase of MS. Isolated proteins from myelinated regions, demyelinated white-matter lesions (WMLs), and gray-matter lesions (GMLs) from well-characterized progressive MS brain tissues were subjected to label-free quantitative mass spectrometry. Using a system-biology approach, we detected increased expression of proteins belonging to mitochondrial electron transport complexes and oxidative phosphorylation pathway in WMLs. Intriguingly, many of these proteins and pathways had opposite expression patterns and were downregulated in GMLs of progressive MS brains. A comparison to the human MitoCarta database mapped the mitochondrial proteins to mitochondrial subunits in both WMLs and GMLs. Taken together, we provide evidence of opposite expression of mitochondrial proteins in response to demyelination of white- and gray-matter regions in progressive MS brain.

Protein prenylation restrains innate immunity by inhibiting Rac1 effector interactions

Rho family proteins are prenylated by geranylgeranyltransferase type I (GGTase-I), which normally target proteins to membranes for GTP-loading. However, conditional deletion of GGTase-I in mouse macrophages increases GTP-loading of Rho proteins, leading to enhanced inflammatory responses and severe rheumatoid arthritis. Here we show that heterozygous deletion of the Rho family gene Rac1, but not Rhoa and Cdc42, reverses inflammation and arthritis in GGTase-I-deficient mice. Non-prenylated Rac1 has a high affinity for the adaptor protein Ras GTPase-activating-like protein 1 (Iqgap1), which facilitates both GTP exchange and ubiquitination-mediated degradation of Rac1. Consistently, inactivating Iqgap1 normalizes Rac1 GTP-loading, and reduces inflammation and arthritis in GGTase-I-deficient mice, as well as prevents statins from increasing Rac1 GTP-loading and cytokine production in macrophages. We conclude that blocking prenylation stimulates Rac1 effector interactions and unleashes proinflammatory signaling. Our results thus suggest that prenylation normally restrains innate immune responses by preventing Rac1 effector interactions.

Macrophage specific deletion of GGTase-I, a prenylation enzyme, in mice induces inflammatory response and rheumatoid arthritis. Here the authors show that GGTase-I deficiency and the resulting reduction of RAC1 prenylation increase RAC1 interaction with the adaptor protein IQGAP1, leading to GTP-loading of RAC1 and enhanced proinflammatory cytokine production.

Fingolimod targets cerebral endothelial activation to block leukocyte recruitment in the central nervous system

Fingolimod (FTY720), an immunomodulator, is approved as an oral treatment for patients with relapsing forms of multiple sclerosis. Its effects are largely attributed to its mechanism of selectively retaining lymphocytes in the lymph nodes to reduce autoreactive T-cell recruitment in the CNS. In this study, we investigated the therapeutic effect of FTY720 on an animal model of CNS inflammation induced by intracerebral ventricle LPS injection. We found that FTY720 treatment significantly prevented LPS-induced neutrophil recruitment in the CNS by inhibiting leukocyte recruitment in cerebral microvessels. Furthermore, FTY720 also inhibited the expressions of adhesion molecules on the cerebral endothelium, but did not affect the expression levels of pro-inflammatory cytokines (TNF-α and IL-6) and chemokines (CXCL1 and CXCL2) in the CNS parenchyma. The inhibition of endothelial activation was accompanied by reduced phosphorylation of signaling molecules, including serine/threonine-specific protein kinase (Akt), STAT6, and nuclear factor-κB. This FTY720-attenuated inhibition of leukocyte recruitment and endothelial activation was reversed by blocking the functions of sphingosine kinase 2 or sphingosine-1-phosphate receptor 1. Our study demonstrated, for the first time, that FTY720 directly inhibits the phosphorylation of multiple signaling molecules in endothelial cells, thereby effectively blocking leukocyte recruitment in the CNS.

New tricks for human farnesyltransferase inhibitor: cancer and beyond

Human protein farnesyltransferase (FTase) catalyzes the addition of a C15-farnesyl lipid group to the cysteine residue located in the COOH-terminal tetrapeptide motif of a variety of important substrate proteins, including well-known Ras protein superfamily. The farnesylation of Ras protein is required both for its normal physiological function, and for the transforming capacity of its oncogenic mutants. Over the last several decades, FTase inhibitors (FTIs) were developed to disrupt the farnesylation of oncogenic Ras as anti-cancer agents, and some of them have entered cancer clinical investigation. On the other hand, some substrates of FTase were demonstrated to be related with other human diseases, including Hutchinson-Gilford progeria syndrome, chronic hepatitis D, and cardiovascular diseases. In this review, we summarize the roles of FTase in malignant transformation, proliferation, apoptosis, angiogenesis, and metastasis of tumor cells, and the recently anticancer clinical research advances of FTIs. The therapeutic prospect of FTIs on several other human diseases is also discussed.

Serum-borne bioactivity caused by pulmonary multiwalled carbon nanotubes induces neuroinflammation via blood-brain barrier impairment

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) causes indirect systemic inflammation through unknown pathways. MWCNTs translocate only minimally from the lungs into the systemic circulation, suggesting that extrapulmonary toxicity may be caused indirectly by lung-derived factors entering the circulation. To assess a role for MWCNT-induced circulating factors in driving neuroinflammatory outcomes, mice were acutely exposed to MWCNTs (10 or 40 µg/mouse) via oropharyngeal aspiration. At 4 h after MWCNT exposure, broad disruption of the blood-brain barrier (BBB) was observed across the capillary bed with the small molecule fluorescein, concomitant with reactive astrocytosis. However, pronounced BBB permeation was noted, with frank albumin leakage around larger vessels (>10 µm), overlain by a dose-dependent astroglial scar-like formation and recruitment of phagocytic microglia. As affirmed by elevated inflammatory marker transcription, MWCNT-induced BBB disruption and neuroinflammation were abrogated by pretreatment with the rho kinase inhibitor fasudil. Serum from MWCNT-exposed mice induced expression of adhesion molecules in primary murine cerebrovascular endothelial cells and, in a wound-healing in vitro assay, impaired cell motility and cytokinesis. Serum thrombospondin-1 level was significantly increased after MWCNT exposure, and mice lacking the endogenous receptor CD36 were protected from the neuroinflammatory and BBB permeability effects of MWCNTs. In conclusion, acute pulmonary exposure to MWCNTs causes neuroinflammatory responses that are dependent on the disruption of BBB integrity.

Selective Gas-Phase Oxidation and Localization of Alkylated Cysteine Residues in Polypeptide Ions via Ion/Ion Chemistry

The thiol group in cysteine residues is susceptible to several post-translational modifications (PTMs), including prenylation, nitrosylation, palmitoylation, and the formation of disulfide bonds. Additionally, cysteine residues involved in disulfide bonds are commonly reduced and alkylated prior to mass spectrometric analysis. Several of these cysteine modifications, specifically S-alkyl modifications, are susceptible to gas-phase oxidation via selective ion/ion reactions with periodate anions. Multiply protonated peptides containing modified cysteine residues undergo complex formation upon ion/ion reaction with periodate anions. Activation of the ion/ion complexes results in oxygen transfer from the reagent to the modified sulfur residue to create a sulfoxide functionality. Further activation of the sulfoxide derivative yields abundant losses of the modification with the oxidized sulfur as a sulfenic acid (namely, XSOH) to generate a dehydroalanine residue. This loss immediately indicates the presence of an S-alkyl cysteine residue, and the mass of the loss can be used to easily deduce the type of modification. An additional step of activation can be used to localize the modification to a specific residue within the peptide. Selective cleavage to create c- and z-ions N-terminal to the dehydroalanine residue is often noted. As these types of ions are not typically observed upon collision-induced dissociation (CID), they can be used to immediately indicate where in the peptide the PTM was originally located.

Recent insights into endothelial control of leukocyte extravasation

In the process of leukocyte migration from the circulation across the vascular wall, the crosstalk with endothelial cells that line the blood vessels is essential. It is now firmly established that in endothelial cells important signaling events are initiated upon leukocyte adhesion that impinge on the regulation of cell-cell contact and control the efficiency of transendothelial migration. In addition, several external factors such as shear force and vascular stiffness were recently identified as important regulators of endothelial signaling and, consequently, leukocyte transmigration. Here, I review recent insights into endothelial signaling events that are linked to leukocyte migration across the vessel wall. In this field, protein phosphorylation and Rho-mediated cytoskeletal dynamics are still widely studied using increasingly sophisticated mouse models. In addition, activation of tyrosine phosphatases, changes in endothelial cell stiffness as well as different vascular beds have all been established as important factors in endothelial signaling and leukocyte transmigration. Finally, I address less-well-studied but interesting components in the endothelium that also control transendothelial migration, such as the ephrins and their Eph receptors, that provide novel insights in the complexity associated with this process.

Protein prenylation: enzymes, therapeutics, and biotechnology applications

Protein prenylation is a ubiquitous covalent post-translational modification found in all eukaryotic cells, comprising attachment of either a farnesyl or a geranylgeranyl isoprenoid. It is essential for the proper cellular activity of numerous proteins, including Ras family GTPases and heterotrimeric G-proteins. Inhibition of prenylation has been extensively investigated to suppress the activity of oncogenic Ras proteins to achieve antitumor activity. Here, we review the biochemistry of the prenyltransferase enzymes and numerous isoprenoid analogs synthesized to investigate various aspects of prenylation and prenyltransferases. We also give an account of the current status of prenyltransferase inhibitors as potential therapeutics against several diseases including cancers, progeria, aging, parasitic diseases, and bacterial and viral infections. Finally, we discuss recent progress in utilizing protein prenylation for site-specific protein labeling for various biotechnology applications.

Rho kinase as a target for cerebral vascular disorders

The development of novel pharmaceutical treatments for disorders of the cerebral vasculature is a serious unmet medical need. These vascular disorders are typified by a disruption in the delicate Rho signaling equilibrium within the blood vessel wall. In particular, Rho kinase overactivation in the smooth muscle and endothelial layers of the vessel wall results in cytoskeletal modifications that lead to reduced vascular integrity and abnormal vascular growth. Rho kinase is thus a promising target for the treatment of cerebral vascular disorders. Indeed, preclinical studies indicate that Rho kinase inhibition may reduce the formation/growth/rupture of both intracranial aneurysms and cerebral cavernous malformations.

Amelioration of cisplatin-induced experimental peripheral neuropathy by a small molecule targeting p75 NTR

Cisplatin is an effective and widely used first-line chemotherapeutic drug for treating cancers. However, many patients sustain cisplatin-induced peripheral neuropathy (CIPN), often leading to a reduction in drug dosages or complete cessation of treatment altogether. Therefore, it is important to understand cisplatin mechanisms in peripheral nerve tissue mediating its toxicity and identify signaling pathways for potential intervention. Rho GTPase activation is increased following trauma in several models of neuronal injury. Thus, we investigated whether components of the Rho signaling pathway represent important neuroprotective targets with the potential to ameliorate CIPN and thereby optimize current chemotherapy treatment regimens. We have developed a novel CIPN model in the mouse. Using this model and primary neuronal culture, we determined whether LM11A-31, a small-molecule, orally bioavailable ligand of the p75 neurotrophin receptor (p75(NTR)), can modulate Rho GTPase signaling and reduce CIPN. Von Frey filament analysis of sural nerve function showed that LM11A-31 treatment prevented decreases in peripheral nerve sensation seen with cisplatin treatment. Morphometric analysis of harvested sural nerves revealed that cisplatin-induced abnormal nerve fiber morphology and the decreases in fiber area were alleviated with concurrent LM11A-31 treatment. Cisplatin treatment increased RhoA activity accompanied by the reduced tyrosine phosphorylation of SHP2, which was reversed by LM11A-31. LM11A-31 also countered the effects of calpeptin, which activated RhoA by inhibiting SHP2 tyrosine phosphatase. Therefore, suppression of RhoA signaling by LM11A-31 that modulates p75(NTR) or activates SHP2 tyrosine phosphatase downstream of the NGF receptor enhances neuroprotection in experimental CIPN in mouse model.

Axon growth inhibition by RhoA/ROCK in the central nervous system

Rho kinase (ROCK) is a serine/threonine kinase and a downstream target of the small GTPase Rho. The RhoA/ROCK pathway is associated with various neuronal functions such as migration, dendrite development, and axonal extension. Evidence from animal studies reveals that RhoA/ROCK signaling is involved in various central nervous system (CNS) diseases, including optic nerve and spinal cord injuries, stroke, and neurodegenerative diseases. Given that RhoA/ROCK plays a critical role in the pathophysiology of CNS diseases, the development of therapeutic agents targeting this pathway is expected to contribute to the treatment of CNS diseases. The RhoA/ROCK pathway mediates the effects of myelin-associated axon growth inhibitors—Nogo, myelin-associated glycoprotein (MAG), oligodendrocyte-myelin glycoprotein (OMgp), and repulsive guidance molecule (RGM). Blocking RhoA/ROCK signaling can reverse the inhibitory effects of these molecules on axon outgrowth, and promotes axonal sprouting and functional recovery in animal models of CNS injury. To date, several RhoA/ROCK inhibitors have been under development or in clinical trials as therapeutic agents for neurological disorders. In this review, we focus on the RhoA/ROCK signaling pathway in neurological disorders. We also discuss the potential therapeutic approaches of RhoA/ROCK inhibitors for various neurological disorders.

Rho Kinase and Dopaminergic Degeneration

The small GTP-binding protein Rho plays an important role in several cellular functions. RhoA, which is a member of the Rho family, initiates cellular processes that act on its direct downstream effector Rho-associated kinase (ROCK). ROCK inhibition protects against dopaminergic cell death induced by dopaminergic neurotoxins. It has been suggested that ROCK inhibition activates neuroprotective survival cascades in dopaminergic neurons. Axon-stabilizing effects in damaged neurons may represent another mechanism of neuroprotection of dopaminergic neurons by ROCK inhibition. However, it has been shown that microglial cells play a crucial role in neuroprotection by ROCK inhibition and that activation of microglial ROCK mediates major components of the microglial inflammatory response. Additional mechanisms such as interaction with autophagy may also contribute to the neuroprotective effects of ROCK inhibition. Interestingly, ROCK interacts with several brain factors that play a major role in dopaminergic neuron vulnerability such as NADPH-oxidase, angiotensin, and estrogen. ROCK inhibition may provide a new neuroprotective strategy for Parkinson’s disease. This is of particular interest because ROCK inhibitors are currently used against vascular diseases in clinical practice. However, it is necessary to develop more potent and selective ROCK inhibitors to reduce side effects and enhance the efficacy.

Farnesyltransferase and geranylgeranyltransferase I: structures, mechanism, inhibitors and molecular modeling

Farnesyltransferase (FTase) and geranylgeranyltransferase type I (GGTase-I) have crucial roles in the post-translational modifications of Ras proteins and, therefore, they are promising therapeutic targets for the treatment of various Ras-induced cancers and several other kinds of diseases. In this review, we provide an overview of the structures and biological functions of FTase and GGTase-I. Then, we summarize the typical inhibitors of FTase and GGTase-I, and highlight the drug candidates in clinical trials. In addition, we survey some recent advances in computer-aided drug design (CADD) and molecular modeling studies of FTase and GGTase-I.

Novel role of Cdc42 and RalA GTPases in TNF-α mediated secretion of CCL2

Transendothelial migration of autoreactive leukocytes into peripheral nerves is an early pathological hallmark of acute inflammatory demyelinating polyneuropathy (AIDP), a North American and European variant of Guillain-Barré Syndrome. Whereas the clinical management of AIDP is currently limited to non-selective immune modulating therapies, recent experimental studies support selective targeting of leukocyte trafficking as a promising alternative therapeutic strategy. Here, using a combination of targeted siRNA knockdown and pharmacological inhibitors, we report a novel role of both Cdc42 and RalA GTPases in facilitating TNF-α mediated CCL2 trafficking and release from immortalized rat peripheral nerve microvascular endoneurial endothelial cells. These findings raise interest in Cdc42 and RalA GTPases as potential therapeutic targets for the management of autoimmune inflammatory peripheral nerve disease.

Farnesyltransferase regulates neutrophil recruitment and tissue damage in acute pancreatitis

OBJECTIVES

The signaling mechanisms controlling organ damage in the pancreas in severe acute pancreatitis (AP) remain elusive. Herein, we examined the role of farnesyltransferase signaling in AP.

METHODS

Pancreatitis was provoked by the infusion of taurocholate into the pancreatic duct in C57BL/6 mice. Animals were treated with a farnesyltransferase inhibitor FTI-277 (25 mg/kg) before pancreatitis induction.

RESULTS

FTI-277 decreased the blood amylase levels, pancreatic neutrophil infiltration, hemorrhage, and edema formation in the pancreas in mice challenged with taurocholate. Farnesyltransferase inhibition reduced the myeloperoxidase levels in the pancreas and lungs in response to taurocholate infusion. However, FTI-277 had no effect on the taurocholate-provoked formation of macrophage inflammatory protein-2 in the pancreas. Interestingly, farnesyltransferase inhibition abolished the neutrophil expression of macrophage-1 antigen in mice with pancreatitis. In addition, FTI-277 decreased the taurocholate-induced activation of the rat sarcoma protein in the pancreas. An important role of farnesyltransferase was confirmed in L-arginine-induced pancreatitis.

CONCLUSIONS

These results demonstrate that farnesyltransferase signaling plays a significant role in AP by regulating neutrophil infiltration and tissue injury via the neutrophil expression of macrophage-1 antigen. Thus, our findings not only elucidate novel signaling mechanisms in pancreatitis but also suggest that farnesyltransferase might constitute a target in the management of severe AP.

Inhibition of geranylgeranyltransferase attenuates neutrophil accumulation and tissue injury in severe acute pancreatitis

Leukocyte infiltration and acinar cell necrosis are hallmarks of severe AP, but the signaling pathways regulating inflammation and organ injury in the pancreas remain elusive. In the present study, we investigated the role of geranylgeranyltransferase in AP. Male C57BL/6 mice were treated with a geranylgeranyltransferase inhibitor GGTI-2133 (20 mg/kg) prior to induction of pancreatitis by infusion of taurocholate into the pancreatic duct. Pretreatment with GGTI-2133 reduced plasma amylase levels, pancreatic neutrophil recruitment, hemorrhage, and edema formation in taurocholate-evoked pancreatitis. Moreover, administration of GGTI-2133 decreased the taurocholate-induced increase of MPO activity in the pancreas and lung. Treatment with GGTI-2133 markedly reduced levels of CXCL2 in the pancreas and IL-6 in the plasma in response to taurocholate challenge. Notably, geranylgeranyltransferase inhibition abolished neutrophil expression of Mac-1 in mice with pancreatitis. Finally, inhibition of geranylgeranyltransferase had no direct effect on secretagogue-induced activation of trypsinogen in pancreatic acinar cells in vitro. A significant role of geranylgeranyltransferase was confirmed in an alternate model of AP induced by L-arginine challenge. Our findings show that geranylgeranyltransferase regulates neutrophil accumulation and tissue damage via expression of Mac-1 on neutrophils and CXCL2 formation in AP. Thus, these results reveal new signaling mechanisms in pancreatitis and indicate that targeting geranylgeranyltransferase might be an effective way to ameliorate severe AP.

Geranylgeranyl transferase regulates CXC chemokine formation in alveolar macrophages and neutrophil recruitment in septic lung injury

Overwhelming accumulation of neutrophils is a significant component in septic lung damage, although the signaling mechanisms behind neutrophil infiltration in the lung remain elusive. In the present study, we hypothesized that geranylgeranylation might regulate the inflammatory response in abdominal sepsis. Male C57BL/6 mice received the geranylgeranyl transferase inhibitor, GGTI-2133, before cecal ligation and puncture (CLP). Bronchoalveolar lavage fluid and lung tissue were harvested for analysis of neutrophil infiltration, as well as edema and CXC chemokine formation. Blood was collected for analysis of Mac-1 on neutrophils and CD40L on platelets. Gene expression of CXC chemokines, tumor necrosis factor-α (TNF-α), and CCL2 chemokine was determined by quantitative RT-PCR in isolated alveolar macrophages. Administration of GGTI-2133 markedly decreased CLP-induced infiltration of neutrophils, edema, and tissue injury in the lung. CLP triggered clear-cut upregulation of Mac-1 on neutrophils. Inhibition of geranylgeranyl transferase reduced CLP-evoked upregulation of Mac-1 on neutrophils in vivo but had no effect on chemokine-induced expression of Mac-1 on isolated neutrophils in vitro. Notably, GGTI-2133 abolished CLP-induced formation of CXC chemokines, TNF-α, and CCL2 in alveolar macrophages in the lung. Geranylgeranyl transferase inhibition had no effect on sepsis-induced platelet shedding of CD40L. In addition, inhibition of geranylgeranyl transferase markedly decreased CXC chemokine-triggered neutrophil chemotaxis in vitro. Taken together, our findings suggest that geranylgeranyl transferase is an important regulator of CXC chemokine production and neutrophil recruitment in the lung. We conclude that inhibition of geranylgeranyl transferase might be a potent way to attenuate acute lung injury in abdominal sepsis.

Statin use and ocular inflammatory disease risk

Background

This study aims to evaluate the effect of oral statin medication use on the subsequent development of ocular inflammatory disease (OID). A retrospective nested case–control study was carried out on patient records from the Birmingham Veterans Affairs Medical Center. All male patients with a new diagnosis of OID over a 5-year period were included. Ten control subjects (without OID) were age-matched to each OID case. Prescription files of all subjects were queried for statin use. Information on selected comorbid medical conditions was also obtained. Conditional logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for risk of OID development in the context of statin use, controlling for comorbid conditions.

Results

Ninety-two incident cases of OID were identified. A trend toward a reduction in the risk of new OID development was found in patients that used statins compared to those that did not (OR 0.50, 95% CI 0.20 to 1.23, p = 0.13). The longer the duration of statin use, the greater is the effect.

Conclusions

Use of oral statins may be associated with a reduced risk for the development of OID. This reduced risk increases with increasing duration of use. Larger clinical studies would be required to definitively establish the effectiveness of statins in lowering the incidence of OID.

Prenyltransferase Inhibitors: Treating Human Ailments from Cancer to Parasitic Infections

The posttranslational modification of protein prenylation is a covalent lipid modification on the C-terminus of substrate proteins that serves to enhance membrane affinity. Oncogenic proteins such as Ras have this modification and significant effort has been placed into developing inhibitors of the prenyltransferase enzymes for clinical therapy. In addition to cancer therapy, prenyltransferase inhibitors have begun to find important therapeutic uses in other diseases, including progeria, hepatitis C and D, parasitic infections, and other maladies. This review will trace the evolution of prenyltransferase inhibitors from their initial use as cancer therapeutics to their expanded applications for other diseases.

Signal transduction pathways in chronic inflammatory autoimmune disease: small GTPases

Ras superfamily small GTPases represent a wide and diverse class of intracellular signaling proteins that are highly conserved during evolution. These enzymes serve as key checkpoints in coupling antigen receptor, growth factor, cytokine and chemokine stimulation to cellular responses. Once activated, via their ability to regulate multiple downstream signaling pathways, small GTPases amplify and diversify signaling cascades which regulate cellular proliferation, survival, cytokine expression, trafficking and retention. Small GTPases, particularly members of the Ras, Rap, and Rho family, critically coordinate the function and interplay of immune and stromal cells during inflammatory respones, and increasing evidence indicates that alterations in small GTPase signaling contribute to the pathological behavior of these cell populations in human chronic inflammatory diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Here, we review how Ras, Rap, and Rho family GTPases contribute to the biology of cell populations relevant to human chronic inflammatory disease, highlight recent advances in understanding how alterations in these pathways contribute to pathology in RA and SLE, and discuss new therapeutic strategies that may allow specific targeting of small GTPases in the clinic.

Streptococcal m1 protein triggers farnesyltransferase-dependent formation of CXC chemokines in alveolar macrophages and neutrophil infiltration of the lungs

The M1 serotype of Streptococcus pyogenes plays an important role in streptococcal toxic shock syndrome. Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has been shown to inhibit streptococcal M1 protein-induced acute lung damage, although downstream mechanisms remain elusive. Protein isoprenylation, such as farnesylation and geranylgeranylation, has been suggested to regulate anti-inflammatory effects exerted by statins. Here, we examined the effect of a farnesyltransferase inhibitor (FTI-277) on M1 protein-triggered lung inflammation. Male C57BL/6 mice were treated with FTI-277 prior to M1 protein challenge. Bronchoalveolar fluid and lung tissue were harvested for quantification of neutrophil recruitment, edema, and CXC chemokine formation. Flow cytometry was used to determine Mac-1 expression on neutrophils. The gene expression of CXC chemokines was determined in alveolar macrophages by using quantitative reverse transcription (RT)-PCR. We found that the administration of FTI-277 markedly decreased M1 protein-induced accumulation of neutrophils, edema formation, and tissue damage in the lung. Notably, inhibition of farnesyltransferase abolished M1 protein-evoked production of CXC chemokines in the lung and gene expression of CXC chemokines in alveolar macrophages. Moreover, FTI-277 completely inhibited chemokine-induced neutrophil migration in vitro. However, farnesyltransferase inhibition had no effect on M1 protein-induced expression of Mac-1 on neutrophils. Our findings suggest that farnesyltransferase is a potent regulator of CXC chemokine formation in alveolar macrophages and that inhibition of farnesyltransferase not only reduces neutrophil recruitment but also attenuates acute lung injury provoked by streptococcal M1 protein. We conclude that farnesyltransferase activity is a potential target in order to attenuate acute lung damage in streptococcal infections.

Targeting protein prenylation for cancer therapy

Protein farnesylation and geranylgeranylation, together referred to as prenylation, are lipid post-translational modifications that are required for the transforming activity of many oncogenic proteins, including some RAS family members. This observation prompted the development of inhibitors of farnesyltransferase (FT) and geranylgeranyl-transferase 1 (GGT1) as potential anticancer drugs. In this Review, we discuss the mechanisms by which FT and GGT1 inhibitors (FTIs and GGTIs, respectively) affect signal transduction pathways, cell cycle progression, proliferation and cell survival. In contrast to their preclinical efficacy, only a small subset of patients responds to FTIs. Identifying tumours that depend on farnesylation for survival remains a challenge, and strategies to overcome this are discussed. One GGTI has recently entered the clinic, and the safety and efficacy of GGTIs await results from clinical trials.

A3 adenosine receptor agonist reduces brain ischemic injury and inhibits inflammatory cell migration in rats

A3 adenosine receptor (A3AR) is recognized as a novel therapeutic target for ischemic injury; however, the mechanism underlying anti-ischemic protection by the A3AR agonist remains unclear. Here, we report that 2-chloro-N(6)-(3-iodobenzyl)-5'-N-methylcarbamoyl-4'-thioadenosine (LJ529), a selective A3AR agonist, reduces inflammatory responses that may contribute to ischemic cerebral injury. Postischemic treatment with LJ529 markedly reduced cerebral ischemic injury caused by 1.5-hour middle cerebral artery occlusion, followed by 24-hour reperfusion in rats. This effect was abolished by the simultaneous administration of the A3AR antagonist MRS1523, but not the A2AAR antagonist SCH58261. LJ529 prevented the infiltration/migration of microglia and monocytes occurring after middle cerebral artery occlusion and reperfusion, and also after injection of lipopolysaccharides into the corpus callosum. The reduced migration of microglia by LJ529 could be related with direct inhibition of chemotaxis and down-regulation of spatiotemporal expression of Rho GTPases (including Rac, Cdc42, and Rho), rather than by biologically relevant inhibition of inflammatory cytokine/chemokine release (eg, IL-1β, TNF-α, and MCP-1) or by direct inhibition of excitotoxicity/oxidative stress (not affected by LJ529). The present findings indicate that postischemic activation of A3AR and the resultant reduction of inflammatory response should provide a promising therapeutic strategy for the treatment of ischemic stroke.

Brain endothelial barrier passage by monocytes is controlled by the endothelin system

Homeostasis of the brain is dependent on the blood-brain barrier (BBB). This barrier tightly regulates the exchange of essential nutrients and limits the free flow of immune cells into the CNS. Perturbations of BBB function and the loss of its immune quiescence are hallmarks of a variety of brain diseases, including multiple sclerosis (MS), vascular dementia, and stroke. In particular, diapedesis of monocytes and subsequent trafficking of monocyte-derived macrophages into the brain are key mediators of demyelination and axonal damage in MS. Endothelin-1 (ET-1) is considered as a potent pro-inflammatory peptide and has been implicated in the development of cardiovascular diseases. Here, we studied the role of different components of the endothelin system, i.e., ET-1, its type B receptor (ET(B)) and endothelin-converting enzyme-1 (ECE-1) in monocyte diapedesis of a human brain endothelial cell barrier. Our pharmacological inhibitory and specific gene knockdown studies point to a regulatory function of these proteins in transendothelial passage of monocytes. Results from this study suggest that the endothelin system is a putative target within the brain for anti-inflammatory treatment in neurological diseases.

Therapeutic potential of experimental autoimmune encephalomyelitis by Fasudil, a Rho kinase inhibitor

The migration of aberrant inflammatory cells into the central nervous system plays an important role in the pathogenesis of demyelinating diseases potentially through the Rho/Rho-kinase (Rock) pathway, but direct evidence from human and animal models remains inadequate. Here we further confirm that Fasudil, a selective Rock inhibitor, has therapeutic potential in a mouse model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). The results show that Fasudil decreased the development of EAE in C57BL/6 mice. Immunohistochemistry disclosed that expression of Rock-II in the perivascular spaces and vascular endothelial cells of spleens, spinal cords, and brains was elevated in EAE and was inhibited in the Fasudil-treated group. T-cell proliferation specific to MOG(35-55) was markedly reduced, together with a significant down-regulation of interleukin (IL)-17, IL-6, and MCP-1. In contrast, secretion of IL-4 was increased, and IL-10 was slightly elevated. There were no differences in the percentages of CD4(+)CD25(+), CD8(+)CD28(-), and CD8(+)CD122(+) in mononuclear cells. Histological staining disclosed a marked decrease of inflammatory cells in spinal cord and brain of Fasudil-treated mice. These results, together with previous studies showing the inhibitory effect of Fasudil on T-cell migration, might expand its clinical application as a new therapy for multiple sclerosis by decreasing cell migration and regulating immune balance.

A molecular mechanism for ibuprofen-mediated RhoA inhibition in neurons

Ibuprofen is a nonsteroidal anti-inflammatory drug widely used to relieve pain and inflammation in many disorders via inhibition of cyclooxygenases. Recently, we have demonstrated that ibuprofen inhibits intracellular signaling of RhoA and promotes significant axonal growth and functional recovery following spinal cord lesions in rodents. In addition, another study suggests that ibuprofen reduces generation of amyloid-beta42 peptide via inactivation of RhoA signaling, although it may also regulate amyloid-beta42 formation by direct inhibition of the gamma-secretase complex. The molecular mechanisms by which ibuprofen inhibits the RhoA signal in neurons, however, remain unclear. Here, we report that the transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) is essential for coupling ibuprofen to RhoA inhibition and subsequent neurite growth promotion in neurons. Ibuprofen activates PPARgamma in neuron-like PC12 and B104 cells. Activation of PPARgamma with traditional agonists mimics the RhoA-inhibiting properties of ibuprofen in PC12 cells and, like ibuprofen, promotes neurite elongation in primary cultured neurons exposed to axonal growth inhibitors. Protein knockdown with small interfering RNA specific for PPARgamma blocks RhoA suppression of PPARgamma agonists in PC12 cells. Moreover, the effect of ibuprofen on RhoA activity and neurite growth in neuronal cultures is prevented by selective PPARgamma inhibition. These findings support that PPARgamma plays an essential role in mediating the RhoA-inhibiting effect of ibuprofen. Elucidation of the novel molecular mechanisms linking ibuprofen to RhoA inhibition may provide additional therapeutic targets to the disorders characterized by RhoA activation, including spinal cord injuries and Alzheimer's disease.

RGMA and IL21R show association with experimental inflammation and multiple sclerosis

Rat chromosome 1 harbors overlapping quantitative trait loci (QTL) for cytokine production and experimental models of inflammatory diseases. We fine-dissected this region that regulated cytokine production, myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), anti-MOG antibodies and pristane-induced arthritis (PIA) in advanced intercross lines (AILs). Analysis in the tenth and twelfth generation of AILs resolved the region in two narrow QTL, Eae30 and Eae31. Eae30 showed linkage to MOG-EAE, anti-MOG antibodies and levels of interleukin-6 (IL-6). Eae31 showed linkage to EAE, PIA, anti-MOG antibodies and levels of tumor necrosis factor (TNF) and IL-6. Confidence intervals defined a limited set of potential candidate genes, with the most interesting being RGMA, IL21R and IL4R. We tested the association with multiple sclerosis (MS) in a Nordic case-control material. A single nucleotide polymorphism in RGMA associated with MS in males (odds ratio (OR)=1.33). Polymorphisms of RGMA also correlated with changes in the expression of interferon-gamma (IFN-gamma) and TNF in cerebrospinal fluid of MS patients. In IL21R, there was one positively associated (OR=1.14) and two protective (OR=0.87 and 0.68) haplotypes. One of the protective haplotypes correlated to lower IFN-gamma expression in peripheral blood mononuclear cells of MS patients. We conclude that RGMA and IL21R and their pathways are crucial in MS pathogenesis and warrant further studies as potential biomarkers and therapeutic targets.

Tissue-type plasminogen activator is a regulator of monocyte diapedesis through the brain endothelial barrier

Inflammatory cell trafficking into the brain complicates several neurological disorders including multiple sclerosis. Normally, reliable brain functioning is maintained and controlled by the blood-brain barrier (BBB), which is essential to restrict the entry of potentially harmful molecules and cells from the blood into the brain. The BBB is a selective barrier formed by dedicated brain endothelial cells and dependent on the presence of intracellular tight junctions. In multiple sclerosis, a severe dysfunction of the BBB is observed, which is key to monocyte infiltration and inflammation in the brain. Proteolytic activity has been associated with these inflammatory processes in the brain. Our studies in plasma of rats indicated that the extracellular protease tissue-type plasminogen activator (tPA) correlates with the clinical signs of experimental allergic encephalomyelitis, a rat model of multiple sclerosis. In this study, we studied the function of the tPA during diapedesis of monocytes through a rat and human brain endothelial barrier. Monocyte-brain endothelial cell coculture experiments showed that monocytes induce the release of tPA by brain endothelial cells, which subsequently activates the signal transduction protein extracellular signal related kinase (ERK1/2), both involved in monocyte diapedesis. Importantly, live imaging and immunoblot analyses of rat brain endothelial cells revealed that tPA and ERK1/2 control the breakdown of the tight junction protein occludin. These studies identify tPA as a novel and relevant pathological mediator of neuroinflammation and provide a potential mechanism for this.

Combined medication of lovastatin with rolipram suppresses severity of experimental autoimmune encephalomyelitis

Combinations of new medications or existing therapies are gaining momentum over monotherapy to treat central nervous system (CNS) demyelinating diseases including multiple sclerosis (MS). Recent studies established that statins (HMG-CoA reductase inhibitors) are effective in experimental autoimmune encephalomyelitis (EAE), an MS model and are promising candidates for future MS medication. Another drug, rolipram (phosphodiesterase-4 inhibitor) ameliorates the clinical severity of EAE via induction of various anti-inflammatory and neuroprotective activities. In this study, we tested whether combining the suboptimal doses of these drugs can suppress the severity of EAE. Prophylactic studies revealed that combined treatment with suboptimal doses of statins perform better than their individually administered optimal doses in EAE as evidenced by delayed clinical scores, reduced disease severity, and rapid recovery. Importantly, combination therapy suppressed the progression of disease in an established EAE case via attenuation of inflammation, axonal loss and demyelination. Combination treatment attenuated inflammatory T(H)1 and T(H)17 immune responses and induced T(H)2-biased immunity in the peripheral and CNS as revealed by serological, quantitative, and immunosorbant assay-based analyses. Moreover, the expansion of T regulatory (CD25(+)/Foxp3(+)) cells and self-immune tolerance was apparent in the CNS. These effects of combined drugs were reduced or minimal with either drug alone in this setting. In conclusion, our findings demonstrate that the combination of these drugs suppresses EAE severity and provides neuroprotection thereby suggesting that this pharmacological approach could be a better future therapeutic strategy to treat MS patients.

Dexamethasone suppresses infiltration of RhoA+ cells into early lesions of rat traumatic brain injury

Inflammatory cell infiltration is a major part of secondary tissue damage in traumatic brain injury (TBI). RhoA is an important member of Rho GTPases and is involved in leukocyte migration. Inhibition of RhoA and its downstream target, Rho-associated coiled kinase (ROCK), has been proven to promote axon regeneration and function recovery following injury in the central nervous system (CNS). Previously, we showed that dexamethasone, an immunosuppressive corticosteroid, attenuated early expression of three molecules associated with microglia/macrophages activation following TBI in rats. Here, the effects of dexamethasone on the early expression of RhoA have been investigated in brains of TBI rats by immunohistochemistry. In brains of rats treated with TBI alone, significant RhoA+ cell accumulation was observed at 18 h post-injury and continuously increased during our observed time period. The accumulated RhoA+ cells were distributed to the areas of pannecrosis and selective neuronal loss. Most accumulated RhoA+ cells were identified as active microglia/macrophages by double-labelling. Dexamethasone (1 mg/kg body weight) was intraperitoneally injected on day 0 and 2 immediately following brain injury. Numbers of RhoA+ cells were significantly reduced on day 1 and 2 following administration of dexamethasone but returned to vehicle control level on day 4. However, dexamethasone treatment did not change the proportion of RhoA+ cells. These observations suggest that dexamethasone has only a transient effect on early leukocyte recruitment.

Therapeutic potential of statins in multiple sclerosis: immune modulation, neuroprotection and neurorepair

Statins as inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A reductase are widely used as cholesterol-lowering drugs. Recent studies provide evidence that the anti-inflammatory activity of statins, which is independent of their cholesterol-lowering effects, may have potential therapeutic implications for neuroinflammatory diseases such as multiple sclerosis (MS), Alzheimer's disease and brain tumors, as well as traumatic spinal cord and brain injuries. Studies with animal models of MS suggest that, in addition to immunomodulatory activities similar to the ones observed with approved MS medications, statin treatment also protects the BBB, protects against neurodegeneration and may also promote neurorepair. Although the initial human studies on statin treatment for MS are encouraging, prospective randomized clinical studies will be required to evaluate their efficacy in the larger patient population.

A "block and rescue" pharmacogenetic approach to dissecting a biochemical pathway controlling germ cell migration

Specific small molecule inhibitors of the de novo cholesterol synthesis pathway (statins) and the protein prenylation pathway were used to study their effect on germ cell migration. Hydroxymethylglutaryl-Coenzyme A reductase (HMGCoAR) catalyzes the rate-limiting step in the mevalonate pathway that produces isoprenoids and cholesterol. Pharmacological HMGCoAR inhibition by statins alters zebrafish development and germ cell migration. These effects were completely blocked by prior injection of mevalonate, the product of HMGCoAR activity, or the prenylation precursors farnesol and geranylgeraniol. Finally, pharmacological inhibition of geranylgeranyl transferase I activity, an enzyme downstream from mevalonate synthesis and responsible for the transfer of a lipid to target proteins, resulted in abnormal germ cell migration. These data together with new data from Drosophila demonstrate that protein prenylation is an evolutionarily conserved pathway mediating germ cell migration. Further, pharmacological block-and-rescue approach provided detailed information about the elements of isoprenoid biosynthesis that contribute to germ cell migration. A key question raised by this work is the identity of the prenylated protein which facilitates proper germ cell migration. Work from other laboratories suggests that germ cell migration might be a general model for the long-range migration of other cell types including cancer metastasis.

Inhibition of rho family functions by lovastatin promotes myelin repair in ameliorating experimental autoimmune encephalomyelitis

Impaired remyelination is critical to neuroinflammation in multiple sclerosis (MS), which causes chronic and relapsing neurological impairments. Recent studies revealed that immunomodulatory activity of statins in an experimental autoimmune encephalomyelitis (EAE) model of MS are via depletion of isoprenoids (farnesyl-pyrophosphate and geranylgeranyl-pyrophosphate) rather than cholesterol in immune cells. In addition, we previously documented that lovastatin impedes demyelination and promotes myelin repair in treated EAE animals. To this end, we revealed the underlying mechanism of lovastatin-induced myelin repair in EAE using in vitro and in vivo approaches. Survival, proliferation (chondroitin sulfate proteoglycan-NG2(+) and late oligodendrocyte progenitor marker(+)), and terminal-differentiation (myelin basic protein(+)) of OPs was significantly increased in association with induction of a promyelinating milieu by lovastatin in mixed glial cultures stimulated with proinflammatory cytokines. Lovastatin-induced effects were reversed by cotreatment with mevalonolactone or geranylgeranyl-pyrophosphate, but not by farnesyl-pyrophosphate or cholesterol, suggesting that depletion of geranygeranyl-pyrophosphate is more critical than farnesyl-pyrophosphate in glial cells. These effects of lovastatin were mimicked by inhibitors of geranylgeranyl-transferase (geranylgeranyl transferase inhibitor-298) and downstream effectors {i.e., Rho-family functions (C3-exoenzyme) and Rho kinase [Y27632 (N-(4-pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide dihydrochloride)]} but not by an inhibitor of farnesyl-transferase (farnesyl transferase inhibitor-277). Moreover, activities of Rho/Ras family GTPases were reduced by lovastatin in glial cells. Corresponding with these findings, EAE animals exhibiting demyelination (on peak clinical day; clinical scores >/=3.0) when treated with lovastatin and aforementioned agents validated these in vitro findings. Together, these data provide unprecedented evidence that-like immune cells-geranylgeranyl-pyrophosphate depletion and thus inhibition of Rho family functions in glial cells by lovastatin promotes myelin repair in ameliorating EAE.

Geranylgeranylation but not GTP loading determines rho migratory function in T cells

Rho GTPases orchestrate signaling pathways leading to cell migration. Their function depends on GTP loading and isoprenylation by geranylgeranyl pyrophosphate (GGpp). In this study, we show that in human T cells, geranylgeranylation-and not GTP loading-is necessary for RhoA-mediated downstream events. As a result of GGpp depletion with the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor atorvastatin, RhoA was sequestered from the membrane to the cytosol and, notwithstanding increased GTP loading, the constitutive activation of its substrate Rho-associated coiled-coil protein kinase-1 was blocked. In line with this, T cells expressing increased GTP-RhoA failed to form an intact cytoskeleton and to migrate toward a chemokine gradient. In vivo treatment with atorvastatin in the rodent model of multiple sclerosis markedly decreased the capacity of activated T cells to traffic within the brain, as demonstrated by multiphoton analysis. Thus, tethering of RhoA to the membrane by GGpp is determinant for T cell migration and provides a mechanism for preventing T cell infiltration into inflamed compartments by 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors.