Inhibition of protein geranylgeranylation and RhoA/RhoA kinase pathway induces apoptosis in human endothelial cells

mTORC1-CTLH E3 ligase regulates the degradation of HMG-CoA synthase 1 through the Pro/N-degron pathway

Mammalian target of rapamycin (mTOR) senses changes in nutrient status and stimulates the autophagic process to recycle amino acids. However, the impact of nutrient stress on protein degradation beyond autophagic turnover is incompletely understood. We report that several metabolic enzymes are proteasomal targets regulated by mTOR activity based on comparative proteome degradation analysis. In particular, 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) synthase 1 (HMGCS1), the initial enzyme in the mevalonate pathway, exhibits the most significant half-life adaptation. Degradation of HMGCS1 is regulated by the C-terminal to LisH (CTLH) E3 ligase through the Pro/N-degron motif. HMGCS1 is ubiquitylated on two C-terminal lysines during mTORC1 inhibition, and efficient degradation of HMGCS1 in cells requires a muskelin adaptor. Importantly, modulating HMGCS1 abundance has a dose-dependent impact on cell proliferation, which is restored by adding a mevalonate intermediate. Overall, our unbiased degradomics study provides new insights into mTORC1 function in cellular metabolism: mTORC1 regulates the stability of limiting metabolic enzymes through the ubiquitin system.

Differential expression of miR-140-3p and its potential role during the development of the acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS) is a category of cardiovascular disease with a high fatality rate.

AIMS

We searched the differential expressed miRNAs (DEmiRNAs) in ACS based on bioinformatic analysis and investigated the diagnostic value of plasma miR-140-3p in patients with ACS and its potential functional role in ACS.

METHODS

The miRNAs (GSE94605, GSE49823, and GSE185729) microarray datasets of ACS were downloaded from the GEO datasets. After integrating the miRNA and mRNA interaction, a protein-protein interaction (PPI) network was constructed with 36 overlapped target mRNAs using STRING database. The plasma levels of miR-140-3p were detected by RT-qPCR, and its clinical diagnostic value was evaluated using the ROC curve. The potential effects of the miR-140-3p/RHOA axis in ACS were explored using human coronary endothelial cells (HCAECs).

RESULTS

After overlapping the GEO datasets, miR-140-3p was identified in the microarray datasets of ACS. The plasma miR-140-3p expression levels were highly expressed in ACS patients than in healthy control and had diagnostic significance. The target mRNAs of miR-140-3p were predicted using TargetScan, miRWalk, TarBase, and miRDB databases. The PPI network identified ten hub genes. miR-140-3p could decrease the HCAECs' cell viability, while RHOA reversed the inhibition effect of miR-140-3p.

CONCLUSIONS

The plasma expression of miR-140-3p was upregulated in ACS patients. miR-140-3p could decrease the HCAECs' cell viability, while RHOA reversed the inhibition effect of miR-140-3p. The miR-140-3p may be a potential diagnostic biomarker for the early detection of ACS.

Lipophilic Statins Eliminate Senescent Endothelial Cells by inducing Anoikis-Related Cell Death

Pre-clinical studies from the recent past have indicated that senescent cells can negatively affect health and contribute to premature aging. Targeted eradication of these cells has been shown to improve the health of aged experimental animals, leading to a clinical interest in finding compounds that selectively eliminate senescent cells while sparing non-senescent ones. In our study, we identified a senolytic capacity of statins, which are lipid-lowering drugs prescribed to patients at high risk of cardiovascular events. Using two different models of senescence in human vascular endothelial cells (HUVECs), we found that statins preferentially eliminated senescent cells, while leaving non-senescent cells unharmed. We observed that the senolytic effect of statins could be negated with the co-administration of mevalonic acid and that statins induced cell detachment leading to anoikis-like apoptosis, as evidenced by real-time visualization of caspase-3/7 activation. Our findings suggest that statins possess a senolytic property, possibly also contributing to their described beneficial cardiovascular effects. Further studies are needed to explore the potential of short-term, high-dose statin treatment as a candidate senolytic therapy.

Structure of human TRPV4 in complex with GTPase RhoA

Transient receptor potential (TRP) channel TRPV4 is a polymodal cellular sensor that responds to moderate heat, cell swelling, shear stress, and small-molecule ligands. It is involved in thermogenesis, regulation of vascular tone, bone homeostasis, renal and pulmonary functions. TRPV4 is implicated in neuromuscular and skeletal disorders, pulmonary edema, and cancers, and represents an important drug target. The cytoskeletal remodeling GTPase RhoA has been shown to suppress TRPV4 activity. Here, we present a structure of the human TRPV4-RhoA complex that shows RhoA interaction with the membrane-facing surface of the TRPV4 ankyrin repeat domains. The contact interface reveals residues that are mutated in neuropathies, providing an insight into the disease pathogenesis. We also identify the binding sites of the TRPV4 agonist 4α-PDD and the inhibitor HC-067047 at the base of the S1-S4 bundle, and show that agonist binding leads to pore opening, while channel inhibition involves a π-to-α transition in the pore-forming helix S6. Our structures elucidate the interaction interface between hTRPV4 and RhoA, as well as residues at this interface that are involved in TRPV4 disease-causing mutations. They shed light on TRPV4 activation and inhibition and provide a template for the design of future therapeutics for treatment of TRPV4-related diseases.

Pitavastatin Induces Apoptosis of Cutaneous Squamous Cell Carcinoma Cells through Geranylgeranyl Pyrophosphate-Dependent c-Jun N-Terminal Kinase Activation

BACKGROUND

Pitavastatin is a cholesterol-lowering drug and is widely used clinically. In addition to this effect, pitavastatin has shown the potential to induce apoptosis in cutaneous squamous cell carcinoma (SCC) cells.

OBJECTIVE

The purpose of this study is to investigate the effects and possible action mechanisms of pitavastatin.

METHODS

SCC cells (SCC12 and SCC13 cells) were treated with pitavastatin, and induction of apoptosis was confirmed by Western blot. To examine whether pitavastatin-induced apoptosis is related to a decrease in the amount of intermediate mediators in the cholesterol synthesis pathway, the changes in pitavastatin-induced apoptosis after supplementation with mevalonate, squalene, geranylgeranyl pyrophosphate (GGPP) and dolichol were investigated.

RESULTS

Pitavastatin dose-dependently induced apoptosis of cutaneous SCC cells, but the viability of normal keratinocytes was not affected by pitavastatin at the same concentrations. In supplementation experiments, pitavastatin-induced apoptosis was inhibited by the addition of mevalonate or downstream metabolite GGPP. As a result of examining the effect on intracellular signaling, pitavastatin decreased Yes1 associated transcriptional regulator and Ras homolog family member A and increased Rac family small GTPase 1 and c-Jun N-terminal kinase (JNK) activity. All these effects of pitavastatin on signaling molecules were restored when supplemented with either mevalonate or GGPP. Furthermore, pitavastatin-induced apoptosis of cutaneous SCC cells was inhibited by a JNK inhibitor.

CONCLUSION

These results suggest that pitavastatin induces apoptosis of cutaneous SCC cells through GGPP-dependent JNK activation.

Role of statins in regulating molecular pathways following traumatic brain injury: A system pharmacology study

Traumatic brain injury (TBI) is a serious disorder with debilitating physical and psychological complications. Previous studies have indicated that genetic factors have a critical role in modulating the secondary phase of injury in TBI. Statins have interesting pleiotropic properties such as antiapoptotic, antioxidative, and anti-inflammatory effects, which make them a suitable class of drugs for repurposing in TBI. In this study, we aimed to explore how statins modulate proteins and pathways involved in TBI using system pharmacology. We first explored the target associations with statins in two databases to discover critical clustering groups, candidate hub and critical hub genes in the network of TBI, and the possible connections of statins with TBI-related genes. Our results showed 1763 genes associated with TBI. Subsequently, the analysis of centralities in the PPI network displayed 55 candidate hub genes and 15 hub genes. Besides, MCODE analysis based on threshold score:10 determined four modular clusters. Intersection analysis of genes related to TBI and statins demonstrated 204 shared proteins, which suggested that statins influence 31 candidate hub and 9 hub genes. Moreover, statins had the highest interaction with MCODE1. The biological processes of the 31 shared proteins are related to gene expression, inflammation, antioxidant activity, and cell proliferation. Biological enriched pathways showed Programmed Cell Death proteins, AGE-RAGE signaling pathway, C-type lectin receptor signalling pathway, and MAPK signaling pathway as top clusters. In conclusion, statins could target several critical post-TBI genes mainly involved in inflammation and apoptosis, supporting the previous research results as a potential therapeutic agent.

Insights into the post-translational modification and its emerging role in shaping the tumor microenvironment

More and more in-depth studies have revealed that the occurrence and development of tumors depend on gene mutation and tumor heterogeneity. The most important manifestation of tumor heterogeneity is the dynamic change of tumor microenvironment (TME) heterogeneity. This depends not only on the tumor cells themselves in the microenvironment where the infiltrating immune cells and matrix together forming an antitumor and/or pro-tumor network. TME has resulted in novel therapeutic interventions as a place beyond tumor beds. The malignant cancer cells, tumor infiltrate immune cells, angiogenic vascular cells, lymphatic endothelial cells, cancer-associated fibroblastic cells, and the released factors including intracellular metabolites, hormonal signals and inflammatory mediators all contribute actively to cancer progression. Protein post-translational modification (PTM) is often regarded as a degradative mechanism in protein destruction or turnover to maintain physiological homeostasis. Advances in quantitative transcriptomics, proteomics, and nuclease-based gene editing are now paving the global ways for exploring PTMs. In this review, we focus on recent developments in the PTM area and speculate on their importance as a critical functional readout for the regulation of TME. A wealth of information has been emerging to prove useful in the search for conventional therapies and the development of global therapeutic strategies.

Geranylgeranyl pyrophosphate-mediated protein geranylgeranylation regulates endothelial cell proliferation and apoptosis during vasculogenesis in mouse embryo

Vascular development is essential for the establishment of the circulatory system during embryonic development and requires the proliferation of endothelial cells. However, the underpinning regulatory mechanisms are not well understood. Here, we report that geranylgeranyl pyrophosphate (GGPP), a metabolite involved in protein geranylgeranylation, plays an indispensable role in embryonic vascular development. GGPP is synthesized by geranylgeranyl pyrophosphate synthase (GGPPS) in the mevalonate pathway. The selective knockout of Ggpps in endothelial cells led to aberrant vascular development and embryonic lethality, resulting from the decreased proliferation and enhanced apoptosis of endothelial cells during vasculogenesis. The defect in protein geranylgeranylation induced by GGPP depletion inhibited the membrane localization of RhoA and enhanced yes-associated protein (YAP) phosphorylation, thereby prohibiting the entry of YAP into the nucleus and the expression of YAP target genes related to cell proliferation and the antiapoptosis process. Moreover, inhibition of the mevalonate pathway by simvastatin induced endothelial cell proliferation defects and apoptosis, which were ameliorated by GGPP. Geranylgeraniol (GGOH), a precursor of GGPP, ameliorated the harmful effects of simvastatin on vascular development of developing fetuses in pregnant mice. These results indicate that GGPP-mediated protein geranylgeranylation is essential for endothelial cell proliferation and the antiapoptosis process during embryonic vascular development.

The effects of statins with a high hepatoselectivity rank on the extra-hepatic tissues; New functions for statins

Statins, as the most common treatment for hyperlipidemia, exert effects beyond their lipid-lowering role which are known as pleiotropic effects. These effects are mainly due to the inhibition of isoprenoids synthesis and consequently blocking prenylation of proteins involved in the cellular signaling pathways regulating cell development, growth, and apoptosis. Statins target cholesterol synthesis in the liver as the major source of cholesterol in the body and so reduce whole-body cholesterol. The reduced level of cholesterol forces other organs to an adaptive homeostatic reaction to increase their cholesterol synthesis capacity, however, this only occurs when statins have unremarkable access to the extra-hepatic tissues. In order to reduce the adverse effects of statin on the skeletal muscle, most recent efforts have been towards formulating new statins with the highest level of hepatoselectivity rank and the least level of access to the extra-hepatic tissues; however, the inaccessibility of statins for the extra-hepatic tissues may induce several biological reactions. In this review, we aim to evaluate the effects of statins on the extra-hepatic tissues when statins have unremarkable access to these tissues.

IL-1β and Statin Treatment in Patients with Myocardial Infarction and Diabetic Cardiomyopathy

Statins are effective lipid-lowering drugs with a good safety profile that have become, over the years, the first-line therapy for patients with dyslipidemia and a real cornerstone of cardiovascular (CV) preventive therapy. Thanks to both cholesterol-related and "pleiotropic" effects, statins have a beneficial impact against CV diseases. In particular, by reducing lipids and inflammation statins, they can influence the pathogenesis of both myocardial infarction and diabetic cardiomyopathy. Among inflammatory mediators involved in these diseases, interleukin (IL)-1β is a pro-inflammatory cytokine that recently been shown to be an effective target in secondary prevention of CV events. Statins are largely prescribed to patients with myocardial infarction and diabetes, but their effects on IL-1β synthesis and release remain to be fully characterized. Of interest, preliminary studies even report IL-1β secretion to rise after treatment with statins, with a potential impact on the inflammatory microenvironment and glycemic control. Here, we will summarize evidence of the role of statins in the prevention and treatment of myocardial infarction and diabetic cardiomyopathy. In accordance with the dual lipid-lowering and anti-inflammatory effect of these drugs and in light of the important results achieved by IL-1β inhibition through canakinumab in CV secondary prevention, we will dissect the current evidence linking statins with IL-1β and outline the possible benefits of a potential double treatment with statins and canakinumab.

ROCK Inhibition Drives Resolution of Acute Inflammation by Enhancing Neutrophil Apoptosis

Uncontrolled inflammation leads to tissue damage and it is central for the development of chronic inflammatory diseases and autoimmunity. An acute inflammatory response is finely regulated by the action of anti-inflammatory and pro-resolutive mediators, culminating in the resolution of inflammation and restoration of homeostasis. There are few studies investigating intracellular signaling pathways associated with the resolution of inflammation. Here, we investigate the role of Rho-associated kinase (ROCK), a serine/threonine kinase, in a model of self-resolving neutrophilic inflammatory. We show that ROCK activity, evaluated by P-MYPT-1 kinetics, was higher during the peak of lipopolysaccharide-induced neutrophil influx in the pleural cavity of mice. ROCK inhibition by treatment with Y-27632 decreased the accumulation of neutrophils in the pleural cavity and was associated with an increase in apoptotic events and efferocytosis, as evaluated by an in vivo assay. In a model of gout, treatment with Y-27632 reduced neutrophil accumulation, IL-1β levels and hypernociception in the joint. These were associated with reduced MYPT and IκBα phosphorylation levels and increased apoptosis. Finally, inhibition of ROCK activity also induced apoptosis in human neutrophils and destabilized cytoskeleton, extending the observed effects to human cells. Taken together, these data show that inhibition of the ROCK pathway might represent a potential therapeutic target for neutrophilic inflammatory diseases.

Pseudomonas aeruginosa ExoS Induces Intrinsic Apoptosis in Target Host Cells in a Manner That is Dependent on its GAP Domain Activity

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes serious infections in immunocompromised individuals and cystic fibrosis patients. ExoS and ExoT are two homologous bifunctional Type III Secretion System (T3SS) virulence factors that induce apoptosis in target host cells. They possess a GTPase Activating Protein (GAP) domain at their N-termini, which share ~76% homology, and an ADP-ribosyltransferase (ADPRT) domain at their C-termini, which target non-overlapping substrates. Both the GAP and the ADPRT domains contribute to ExoT's cytotoxicity in target epithelial cells, whereas, ExoS-induced apoptosis is reported to be primarily due to its ADPRT domain. In this report, we demonstrate that ExoS/GAP domain is both necessary and sufficient to induce mitochondrial apoptosis. Our data demonstrate that intoxication with ExoS/GAP domain leads to enrichment of Bax and Bim into the mitochondrial outer-membrane, disruption of mitochondrial membrane and release of and cytochrome c into the cytosol, which activates initiator caspase-9 and effector caspase-3, that executes cellular death. We posit that the contribution of the GAP domain in ExoS-induced apoptosis was overlooked in prior studies due to its slower kinetics of cytotoxicity as compared to ADPRT. Our data clarify the field and reveal a novel virulence function for ExoS/GAP as an inducer of apoptosis.

A current view of G protein-coupled receptor - mediated signaling in pulmonary hypertension: finding opportunities for therapeutic intervention

Pathological vascular remodeling is observed in various cardiovascular diseases including pulmonary hypertension (PH), a disease of unknown etiology that has been characterized by pulmonary artery vasoconstriction, right ventricular hypertrophy, vascular inflammation, and abnormal angiogenesis in pulmonary circulation. G protein-coupled receptors (GPCRs) are the largest family in the genome and widely expressed in cardiovascular system. They regulate all aspects of PH pathophysiology and represent therapeutic targets. We overview GPCRs function in vasoconstriction, vasodilation, vascular inflammation-driven remodeling and describe signaling cross talk between GPCR, inflammatory cytokines, and growth factors. Overall, the goal of this review is to emphasize the importance of GPCRs as critical signal transducers and targets for drug development in PH.

High-throughput tool to discriminate effects of NMs (Cu-NPs, Cu-nanowires, CuNO3, and Cu salt aged): transcriptomics in Enchytraeus crypticus

The current testing of nanomaterials (NMs) via standard toxicity tests does not cover many of the NMs specificities. One of the recommendations lays on understanding the mechanisms of action, as these can help predicting long-term effects and safe-by-design production. In the present study, we used the high-throughput gene expression tool, developed for Enchytraeus crypticus (4 × 44k Agilent microarray), to study the effects of exposure to several copper (Cu) forms. The Cu treatments included two NMs (spherical and wires) and two copper-salt treatments (CuNO₃ spiked and Cu salt field historical contamination). To relate gene expression with higher effect level, testing was done with reproduction effect concentrations (EC₂₀, EC₅₀), using 3 and 7 days as exposure periods. Results showed that time plays a major role in the transcriptomic response, most of it occurring after 3 days. Analysis of gene expression profiles showed that Cu-salt-aged and Cu-nanowires (Nwires) differed from CuNO₃ and Cu-nanoparticles (NPs). Functional analysis revealed specific mechanisms: Cu-NPs uniquely affected senescence and cuticle pattern formation, which can result from the contact of the NPs with the worms' tegument. Cu-Nwires affected reproduction via male gamete generation and hermaphrodite genitalia development. CuNO₃ affected neurotransmission and locomotory behavior, both of which can be related with avoidance response. Cu salt-aged uniquely affected phagocytosis and reproductive system development (via different mechanisms than Cu-Nwires). For the first time for Cu (nano)materials, the adverse outcome pathways (AOPs) drafted here provide an overview for common and unique effects per material and linkage with apical effects.

[Direct mechanism of action in toxic myopathies]

Toxic myopathies are a large group of disorders generated by surrounding agents and characterized by structural and/or functional disturbances of muscles. The most recurrent are those induced by commonly used medications. Illicit drugs, environmental toxins from animals, vegetables, or produced by micro-organisms as well as chemical products commonly used are significant causes of such disorders. The muscle toxicity results from multiple mechanisms at different biological levels. Many agents can induce myotoxicity through a direct mechanism in which statins, glucocorticoids and ethyl alcohol are the most representative. Diverse mechanisms were highlighted as interaction with macromolecules and induction of metabolic and cellular dysfunctions. Muscle damage can be related to amphiphilic properties of some drugs (chloroquine, hydroxychloroquine, etc.) leading to specific lysosomal disruptions and autophagic dysfunctions. Some agents affect the whole muscle fiber by inducing oxidative stress (ethyl alcohol and some statins) or triggering cell death pathways (apoptosis or necrosis) resulting in extensive alterations. More studies on these mechanisms are needed. They would allow a better knowledge of the intracellular mediators involved in these pathologies in order to develop targeted therapies of high efficiency.

RhoA inhibits the hypoxia-induced apoptosis and mitochondrial dysfunction in chondrocytes via positively regulating the CREB phosphorylation

Chondrocytes that are embedded within the growth plate or the intervertebral disc are sensitive to environmental stresses, such as inflammation and hypoxia. However, little is known about the molecular signalling pathways underlining the hypoxia-induced mitochondrial dysfunction and apoptosis in chondrocytes. In the present study, we firstly examined the hypoxia-induced apoptosis, mitochondrial dysfunction and the activation of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) signalling in human chondrocyte cell line, C28/I2 and then investigated the regulatory role of RhoA, a well-recognized apoptosis suppressor, in such process, with gain-of-function strategy. Our results indicated that hypoxia induced apoptosis and inhibited CREB phosphprylation in chondrocytes, meanwhile, the dysfunctional mitochondria with up-regulated mitochondrial superoxide and reactive oxygen species (ROS) levels, whereas with a reduced mitochondrial membrane potential (MMP) and Complex IV activity were observed in the hypoxia-treated C28/I2 cells. However, the overexpressed RhoA blocked the hypoxia-mediated reduction in CREB phosphprylation and inhibited the apoptosis induction, along with an ameliorated mitochondrial function in the hypoxia-treated C28/I2 cells. In conclusion, the present study confirmed the reduced CREB phosphorylation, along with the apoptosis induction and mitochondrial dysfunction in the hypoxia-treated chondrocyte cells. And the overexpression of RhoA ameliorated the hypoxia-induced mitochondrial dysfunction and apoptosis via blocking the hypoxia-mediated reduction in CREB phosphorylation.

Anti-proliferative Effect of C3 Exoenzyme in Fibroblasts is Mediated by c-Jun Phosphorylation

The ADP-ribosyltransferase C3 exoenzyme from C. botulinum selectively inactivates Rho and is therefore often used as an inhibitor for investigations on Rho signaling. Previous studies of our group revealed that C3 inhibited cell proliferation in HT22 cells accompanied by increased transcriptional activities of Sp1 and c-Jun and reduced levels of cyclin D1, p21 and phosphorylated p38. By use of a p38α-deficient and a p38α-expressing control cell line, the impact of p38 on C3-mediated inhibition of cell proliferation and alterations on MAPK signaling was studied by growth kinetic experiments and Western blot analyses. The cell growth of p38α-expressing cells was impaired by C3, while the p38α-deficient cells did not exhibit any C3-induced effect. The activity of the MKK3/6-p38 MAPK signaling cascade as well as the phosphorylation of c-Jun and JNK was reduced by C3 exclusively in the presence of p38α. Moreover, the activity of upstream MAPKKK TAK1 was lowered in the p38α-expressing cells. These results indicated a resistance of p38α-deficient cells to C3-mediated inhibition of cell growth. This anti-proliferative effect was highly associated with the decreased activity of c-Jun and upstream p38 and JNK MAPK signaling as a consequence of the absence of p38α in these cells.

Molecular mechanisms linking geranylgeranyl diphosphate synthase to cell survival and proliferation

Geranylgeranyl diphosphate is a 20-carbon isoprenoid phospholipid whose lipid moiety can be post-translationally incorporated into proteins to promote membrane association. The process of geranylgeranylation has been implicated in anti-proliferative effects of clinical agents that inhibit enzymes of the mevalonate pathway (i.e. statins and nitrogenous bisphosphonates) as well as experimental agents that deplete geranylgeranyl diphosphate. Inhibitors of geranylgeranyl diphosphate synthase are an attractive way to block geranylgeranylation because they possess a calcium-chelating substructure to allow localization to bone and take advantage of a unique position of the enzyme within the biosynthetic pathway. Here, we describe recent advances in geranylgeranyl diphosphate synthase expression and inhibitor development with a particular focus on the molecular mechanisms that link geranylgeranyl diphosphate to cell proliferation via geranylgeranylated small GTPases.

C3 exoenzyme impairs cell proliferation and apoptosis by altering the activity of transcription factors

C3 exoenzyme from C. botulinum is an ADP-ribosyltransferase that inactivates selectively RhoA, B, and C by coupling an ADP-ribose moiety. Rho-GTPases are involved in various cellular processes, such as regulation of actin cytoskeleton, cell proliferation, and apoptosis. Previous studies of our group with the murine hippocampal cell line HT22 revealed a C3-mediated inhibition of cell proliferation after 48 h and a prevention of serum-starved cells from apoptosis. For both effects, alterations of various signaling pathways are already known, including also changes on the transcriptional level. Investigations on the transcriptional activity in HT22 cells treated with C3 for 48 h identified five out of 48 transcription factors namely Sp1, ATF2, E2F-1, CBF, and Stat6 with a significantly regulated activity. For validation of identified transcription factors, studies on the protein level of certain target genes were performed. Western blot analyses exhibited an enhanced abundance of Sp1 target genes p21 and COX-2 as well as an increase in phosphorylation of c-Jun. In contrast, the level of p53 and apoptosis-inducing GADD153, a target gene of ATF2, was decreased. Our results reveal that C3 regulates the transcriptional activity of Sp1 and ATF2 resulting downstream in an altered protein abundance of various target genes. As the affected proteins are involved in the regulation of cell proliferation and apoptosis, thus the C3-mediated anti-proliferative and anti-apoptotic effects are consequences of the Rho-dependent alterations of the activity of certain transcriptional factors.

Upregulation of HIF-1α protects neuroblastoma cells from hypoxia-induced apoptosis in a RhoA-dependent manner

Hypoxic conditions regulate several metabolic enzymes and transcription factors that are involved in cancer, ischemia and pulmonary diseases. The Ras homolog (Rho) family, including Rho member A (RhoA), is involved in reorganization of the actin cytoskeleton, cell migration and in the regulation of apoptosis and gene transcription. The aim of the present study was to investigate the expression of hypoxia‑inducible factor (HIF)‑α and the activity of RhoA in PC12 neuroblastoma cells under hypoxic conditions. The upregulation of HIF‑α and RhoA by hypoxia was determined using reverse transcription‑quantitative polymerase chain reaction and western blot assays, cell apoptosis was analyzed using flow cytometry, and the activity of caspase 3 was examined using a western blot assay and caspase 3 activity assay kit. The PC12 cells were induced to apoptosis following exposure to hypoxia, and exhibited increased expression of HIF‑α and increased mRNA and protein expression levels of RhoA. The overexpression of HIF‑α attenuated the hypoxia‑induced apoptosis of the PC12 cells. In addition, RhoA knockdown using small interfering RNA abrogated the antagonism of HIF‑1α towards hypoxia‑induced apoptosis. The results of the present study confirmed the protective role of HIF‑1α and RhoA in hypoxia‑induced PC12 cell apoptosis, and that the upregulation of HIF‑1α by hypoxia is RhoA‑dependent.

Effects of Artificial Ligaments with Different Porous Structures on the Migration of BMSCs

Polyethylene terephthalate- (PET-) based artificial ligaments (PET-ALs) are commonly used in anterior cruciate ligament (ACL) reconstruction surgery. The effects of different porous structures on the migration of bone marrow mesenchymal stem cells (BMSCs) on artificial ligaments and the underlying mechanisms are unclear. In this study, a cell migration model was utilized to observe the migration of BMSCs on PET-ALs with different porous structures. A rabbit extra-articular graft-to-bone healing model was applied to investigate the in vivo effects of four types of PET-ALs, and a mechanical test and histological observation were performed at 4 weeks and 12 weeks. The BMSC migration area of the 5A group was significantly larger than that of the other three groups. The migration of BMSCs in the 5A group was abolished by blocking the RhoA/ROCK signaling pathway with Y27632. The in vivo study demonstrated that implantation of 5A significantly improved osseointegration. Our study explicitly demonstrates that the migration ability of BMSCs can be regulated by varying the porous structures of the artificial ligaments and suggests that this regulation is related to the RhoA/ROCK signaling pathway. Artificial ligaments prepared using a proper knitting method and line density may exhibit improved biocompatibility and clinical performance.

RhoA/mDia-1/profilin-1 signaling targets microvascular endothelial dysfunction in diabetic retinopathy

BACKGROUND

Diabetic retinopathy (DR) is a major cause of blindness in the working-age populations of developed countries, and effective treatments and prevention measures have long been the foci of study. Patients with DR invariably demonstrate impairments of the retinal microvascular endothelium. Many observational and preclinical studies have shown that angiogenesis and apoptosis play crucial roles in the pathogenesis of DR. Increasing evidence suggests that in DR, the small guanosine-5'-triphosphate-binding protein RhoA activates its downstream targets mammalian Diaphanous homolog 1 (mDia-1) and profilin-1, thus affecting important cellular functions, including cell morphology, motility, secretion, proliferation, and gene expression. However, the specific underlying mechanism of disease remains unclear.

CONCLUSION

This review focuses on the RhoA/mDia-1/profilin-1 signaling pathway that specifically triggers endothelial dysfunction in diabetic patients. Recently, RhoA and profilin-1 signaling has attracted a great deal of attention in the context of diabetes-related research. However, the precise molecular mechanism by which the RhoA/mDia-1/profilin-1 pathway is involved in progression of microvascular endothelial dysfunction (MVED) during DR has not been determined. This review briefly describes each feature of the cascade before exploring the most recent findings on how the pathway may trigger endothelial dysfunction in DR. When the underlying mechanisms are understood, novel therapies seeking to restore the endothelial homeostasis comprised in DR will become possible.

Effects of zoledronic acid and docetaxel on small GTP-binding proteins in prostate cancer

Increasingly, in castration-resistant prostate cancer, patients are often treated with docetaxel and the bisphosphonate zoledronic acid concurrently, yet there is still a paucity in the literature regarding the molecular basis of how this drug combination works. The study was performed on the hormone-resistant cell line PC-3. Cells were treated with clinically relevant concentrations of docetaxel and zoledronic acid either as single agents or in sequence and combination. Cell viability and apoptosis were assessed along with the prenylation status of the GTPases Ras and RhoA. Following 1-mM zoledronic acid treatment, inhibition of the prenylation of H-Ras and Rho A was observed along with an increase in the unprenylated form in the cytoplasm. Docetaxel 1 nM and zoledronic acid 1 mM also showed an increase in the unprenylated form of both small GTP-binding proteins in the cytoplasm and a reduction of protein in the membrane fraction. Overall, zoledronic acid followed by docetaxel was the best regimen producing the greatest reduction in cell viability and increase in apoptosis. At the highest concentrations of zoledronic acid and docetaxel, zoledronic acid followed by docetaxel was also the most effective at reducing the prenylation of both H-Ras and RhoA at the membrane. We have demonstrated that clinically achievable concentrations of zoledronic acid and docetaxel cause a reduction in the prenylation of both H-Ras and Rho A and a reduction of protein movement into the membrane. The most effective regimen overall was high-dose zoledronic acid followed by docetaxel, suggesting that this regimen may be of benefit in clinical practice.

Fluvastatin attenuated the effect of expression of β1 integrin in PAN-treated podocytes by inhibiting reactive oxygen species

It is well accepted that β1 integrin plays a key role in maintaining normal podocytes form and functions; however, its mechanism of the potential protective effect remains unclear. Furthermore, the investigation and understanding of the non-lipid-dependent renal protection of Statins in addition to well-known lipid-lowering effect may provide the therapeutic utility and ultimately improve clinical outcome for patients with renal diseases. In the present study, we investigated the effect and mechanism of fluvastatin (FLV) on the expression of β1 integrin in puromycin aminonucleoside (PAN)-treated podocytes in vitro. Cultured human podocytes were treated with PAN, and/or different concentrations of FLV (1 × 10(-8)-1 × 10(-5 )mol/l), superoxide dismutase (SOD), or H2O2, respectively. The expression of β1 integrin and reactive oxygen species (ROS) in human podocytes under each experimental condition was evaluated by western blot, RT-PCR, and 2'7'-dichlorofluorescein 3'6'-diacetate, respectively. The viability of podocytes was also assessed by MTT colorimetry in the present study. The expression of β1 integrin was significantly decreased, and the synthesis of ROS was significantly increased in podocytes following either PAN or H2O2 treatment (p < 0.05). The up-regulation of β1 integrin and down-regulation of ROS were also observed in PAN-treated podocytes following lower concentrations of FLV or SOD treatment (p < 0.05, respectively). The cytotoxicity data derived from MTT assay revealed that lower podocyte viability was found in the presence of higher concentrations of FLV, PAN, or H2O2. Lower concentration of FLV or SOD can protect podocytes from being impaired by PAN treatment. FLV attenuated the podocyte injury induced by PAN and increased the production of β1 integrin in human podocytes in vitro. This underlying mechanism of FLV may be through inhibiting the activity of ROS in human podocytes.

The impact of statins on FGF-2-stimulated human umbilical vein endothelial cells

AIM

To determine the effects of different types of statins on proliferative and migrative behaviors of basic fibroblastic growth factor (FGF)-2-stimulated endothelial cells.

MATERIALS AND METHODS

Human umbilical vein endothelial cells (HUVECs) were isolated and cultured. Groups were arranged in order to observe the impact of each individual substance alone, or under stimulation with statin on FGF-2-stimulated endothelial cells. Endothelial cells were stimulated with human growth factor (HGF), statins, methyl-β-cyclodextrin (β-MCD), and either farnesyl pyrophosphate (FPP) ammonium salt, or geranylgeranyl-pyrophosphate (GGPP), respectively. Cell proliferation analyses were performed 48 hours after stimulation and gaps between migration borders were used in migration analyses.

RESULTS

The statins showed significant antiproliferative and anti-migrative effects and inhibited the proliferative behavior of FGF-2. However, endothelial cell proliferation and migration were significantly increased after mevalonate co-incubation. Experiments with β-MCD indicated that the destruction of lipid rafts had a negative impact on the action of FGF-2. Stimulation of statin-incubated cells with FPP had no additional effect on proliferation or migration. Notably, although FGF-2 exerted a pro-migrative effect, the effect was not shown in the FPP + FGF-2 group. The anti-migrative actions of statins along with disruption of membrane integrity were reversed by the addition of GGPP.

CONCLUSION

The angiogenic effect of FGF-2 is suppressed through inhibition of the intracellular cholesterol biosynthesis via statins. Inhibitory effects of statins on FGF-2-stimulated HUVECs were observed to result from both the inhibition of isoprenylation and the destruction of lipid rafts on the cell membrane.

The Rho GTPase RhoE is a p53-regulated candidate tumor suppressor in cancer cells

Previous studies have shown that RhoE, an atypical member of the Rho GTPase family, may play an opposite role to RhoA in regulating cell proliferation and invasion. To explore the relationship between RhoE and the malignant phenotypes of human cancer, we have determined the expression patterns of RhoE in varying grade of human cancer tissues and tested the effects of RhoE expression in several RhoE underexpressing cancer cell lines. Systemic immunocytochemistry analyses of gastric, colorectal, lung and breast carcinomas, respectively, showed that RhoE protein expression was significantly decreased in most cancer cases compared with that of adjacent normal tissues. Enhanced RhoE expression could markedly inhibit proliferation, migration and invasion and induce apoptosis of the cancer cells which have relatively low levels of endogenous RhoE expression. Wild-type p53 (wt-p53) could strongly increase RhoE expression in p53-transfected cells. Furthermore, the luciferase assays indicated that wt-p53 significantly enhanced the activities of RhoE promoter compared with mutant p53 (mt-p53) in PC3 cells (p53 null). Collectively, data are presented showing that RhoE may participate in human cancer progression and act as a candidate target of p53, and these findings also strongly suggest that RhoE may be a new candidate tumor suppressor and could serve as a potential target in the gene therapy of cancer.

Increased cytoplasmic localization of p27(kip1) and its modulation of RhoA activity during progression of chronic myeloid leukemia

The role of p27^kip1 in Chronic Myeloid Leukemia (CML) has been well studied in relation to its function as a cell cycle inhibitor. However, its cytoplasmic function especially in CML remains to be seen. We studied the localization of p27^kip1 and its function during the progression of CML from chronic to blast phase. Our investigations revealed an increased localization of p27^kip1 in the cytoplasm of CD34⁺ cells in the blast phase compared to chronic phase. Cytoplasmic p27^kip1 was found to modulate RhoA activity in CD34⁺ stem and progenitor cells. Further, RhoA activity was shown to be dependent on cytoplasmic p27^kip1 which in turn was dependent on p210^Bcr-Abl kinase activity. Interestingly, RhoA activity was observed to affect cell survival in the presence of imatinib through the SAPK/JNK pathway. Accordingly, inhibition of SAPK/JNK pathway using SP600125 increased apoptosis of K562 cells in presence of imatinib. Our results, for the first time, thus reveal a crucial link between cytoplasmic p27^kip1, RhoA activity and SAPK/JNK signalling. To this effect we observed a correlation between increased cytoplasmic p27^kip1, increased RhoA protein levels, decreased RhoA-GTP levels and increased SAPK/JNK phosphorylation in blast phase CD34⁺ cells compared to chronic phase CD34⁺ cells.

RhoA modulates functional and physical interaction between ROCK1 and Erk1/2 in selenite-induced apoptosis of leukaemia cells

RhoA GTPase dysregulation is frequently reported in various tumours and haematologic malignancies. RhoA, regulating Rho-associated coiled-coil-forming kinase 1 (ROCK1), modulates multiple cell functions, including malignant transformation, metastasis and cell death. Therefore, RhoA/ROCK1 could be an ideal candidate target in cancer treatment. However, the roles of RhoA/ROCK1 axis in apoptosis of leukaemia cells remain elusive. In this study, we explored the effects of RhoA/ROCK1 cascade on selenite-induced apoptosis of leukaemia cells and the underlying mechanism. We found selenite deactivated RhoA/ROCK1 and decreased the association between RhoA and ROCK1 in leukaemia NB4 and Jurkat cells. The inhibited RhoA/ROCK1 signalling enhanced the phosphorylation of Erk1/2 in a Mek1/2-independent manner. Erk1/2 promoted apoptosis of leukaemia cells after it was activated. Intriguingly, it was shown that both RhoA and ROCK1 were present in the multimolecular complex containing Erk1/2. GST pull-down analysis showed ROCK1 had a direct interaction with GST-Erk2. In addition, selenite-induced apoptosis in an NB4 xenograft model was also found to be associated with the RhoA/ROCK1/Erk1/2 pathway. Our data demonstrate that the RhoA/ROCK1 signalling pathway has important roles in the determination of cell fates and the modulation of Erk1/2 activity at the Mek–Erk interplay level.

Increased Expression of RhoA in Epithelium and Smooth Muscle of Obese Mouse Models: Implications for Isoprenoid Control of Airway Smooth Muscle and Fibroblasts

The simultaneous rise in the prevalence of asthma and obesity has prompted epidemiologic studies that establish obesity as a risk factor for asthma. The alterations in cell signaling that explain this link are not well understood and warrant investigation so that therapies that target this asthma phenotype can be developed. We identified a significant increase in expression of the small GTPase RhoA in nasal epithelial cells and tracheal smooth muscle cells from leptin-deficient (ob/ob) mice compared to their wild-type counterparts. Since RhoA function is dependent on isoprenoid modification, we sought to determine the role of isoprenoid-mediated signaling in regulating the viability and proliferation of human airway smooth muscle cells (ASM) and normal human lung fibroblasts (NHLF). Inhibiting isoprenoid signaling with mevastatin significantly decreased the viability of ASM and NHLF. This inhibition was reversed by geranylgeranyl pyrophosphate (GGPP), but not farnesyl pyrophosphate (FPP), suggesting specificity to the Rho GTPases. Conversely, increasing isoprenoid synthesis significantly increased ASM proliferation and RhoA protein expression. RhoA expression is inherently increased in airway tissue from ob/ob mice, and obesity-entrained alterations in this pathway may make it a novel therapeutic target for treating airway disease in the obese population.

The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) pathway regulates developmental cerebral-vascular stability via prenylation-dependent signalling pathway

Spontaneous intracranial hemorrhage is a debilitating form of stroke, often leading to death or permanent cognitive impairment. Many of the causative genes and the underlying mechanisms implicated in developmental cerebral-vascular malformations are unknown. Recent in vitro and in vivo studies in mice have shown inhibition of the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) pathway to be effective in stabilizing cranial vessels. Using a combination of pharmacological and genetic approaches to specifically inhibit the HMGCR pathway in zebrafish (Danio rerio), we demonstrate a requirement for this metabolic pathway in developmental vascular stability. Here we report that inhibition of HMGCR function perturbs cerebral-vascular stability, resulting in progressive dilation of blood vessels, followed by vessel rupture, mimicking cerebral cavernous malformation (CCM)-like lesions in humans and murine models. The hemorrhages in the brain are rescued by prior exogenous supplementation with geranylgeranyl pyrophosphate (GGPP), a 20-carbon metabolite of the HMGCR pathway, required for the membrane localization and activation of Rho GTPases. Consistent with this observation, morpholino-induced depletion of the β-subunit of geranylgeranyltransferase I (GGTase I), an enzyme that facilitates the post-translational transfer of the GGPP moiety to the C-terminus of Rho family of GTPases, mimics the cerebral hemorrhaging induced by the pharmacological and genetic ablation of HMGCR. In embryos with cerebral hemorrhage, the endothelial-specific expression of cdc42, a Rho GTPase involved in the regulation of vascular permeability, was significantly reduced. Taken together, our data reveal a metabolic contribution to the stabilization of nascent cranial vessels, requiring protein geranylgeranylation acting downstream of the HMGCR pathway.

Transgelin 2 participates in lovastatin-induced anti-angiogenic effects in endothelial cells through a phosphorylated myosin light chain-related mechanism

Background

Anti-angiogenic activity is considered to play a key role in the statin-induced anti-tumor effects. We aimed to identify new targets underlying this pleiotropic effect of lovastatin.

Methodology/Principal Findings

We investigated the inhibitory effects of lovastatin on endothelial cell biology and angiogenesis in vitro. Lovastatin at high doses inhibited endothelial cell migration and tube formation. Using two-dimensional gel electrophoresis followed by mass spectrometry, we identified the up-regulation of the actin-binding protein transgelin 2 in endothelial cells following treatment with lovastatin. Changes in transgelin 2 levels were confirmed by Western blot and confocal microscopy. We further demonstrated that the Rho signaling inactivation and actin depolymerization contributed to the up-regulation of transgelin 2. The knockdown of transgelin 2 by siRNA dramatically enhanced endothelial migration and tube formation, and meanwhile attenuated the inhibitory effects of lovastatin on cell motility. Moreover, the lovastatin-induced inhibition of myosin light chain phosphorylation was also reversed by transgelin 2 knockdown. The activation of Rho GTPase in the absence of transgelin 2 may represent a mechanism underlying the regulation of phosphorylated myosin light chain by transgelin 2.

Conclusions/Significance

These results strongly imply a novel role for transgelin 2 in the angiostatic activities of lovastatin.

Regulation of GPCR-mediated smooth muscle contraction: implications for asthma and pulmonary hypertension

Contractile G-protein-coupled receptors (GPCRs) have emerged as key regulators of smooth muscle contraction, both under healthy and diseased conditions. This brief review will discuss some key topics and novel insights regarding GPCR-mediated airway and vascular smooth muscle contraction as discussed at the 7th International Young Investigators' Symposium on Smooth Muscle (2011, Winnipeg, Manitoba, Canada) and will in particular focus on processes driving Ca(2+)-mobilization and -sensitization.

Geranylgeranyl transferase 1 modulates autophagy and apoptosis in human airway smooth muscle

Geranylgeranyl transferase 1 (GGT1) is involved in the posttranslational prenylation of signaling proteins, such as small GTPases. We have shown that blocking the formation of isoprenoids with statins regulates survival of human lung mesenchymal cells; thus, we tested the hypothesis that GGT1 may specifically modulate programmed cell death pathways in these cells. To this end, human airway smooth muscle (HASM) cells were treated with the selective GGT1 inhibitor GGTi-298. Apoptosis was seen using assays for cellular DNA content and caspase activation. Induction of autophagy was observed using transmission electron microscopy, immunoblotting for LC3 lipidation and Atg5-12 complex content, and confocal microscopy to detect formation of lysosome-localized LC3 punctae. Notably, GGT1 inhibition induced expression of p53-dependent proteins, p53 upregulated modulator of apoptosis (Noxa), and damage-regulated autophagy modulator (DRAM), this was inhibited by the p53 transcriptional activation inhibitor cyclic-pifithrin-α. Inhibition of autophagy with bafilomycin-A1 or short-hairpin RNA silencing of Atg7 substantially augmented GGTi-298-induced apoptosis. Overall, we demonstrate for the first time that pharmacological inhibition of GGT1 induces simultaneous p53-dependent apoptosis and autophagy in HASM. Moreover, autophagy regulates apoptosis induction. Thus, our findings identify GGT1 as a key regulator of HASM cell viability.

Inhibition of geranylgeranyl transferase-I decreases cell viability of HTLV-1-transformed cells

Human T-cell leukemia virus type-1 (HTLV-1) is the etiological agent of adult T-cell leukemia (ATL), an aggressive and highly chemoresistant malignancy. Rho family GTPases regulate multiple signaling pathways in tumorigenesis: cytoskeletal organization, transcription, cell cycle progression, and cell proliferation. Geranylgeranylation of Rho family GTPases is essential for cell membrane localization and activation of these proteins. It is currently unknown whether HTLV-1-transformed cells are preferentially sensitive to geranylgeranylation inhibitors, such as GGTI-298. In this report, we demonstrate that GGTI-298 decreased cell viability and induced G₂/M phase accumulation of HTLV-1-transformed cells, independent of p53 reactivation. HTLV-1-LTR transcriptional activity was inhibited and Tax protein levels decreased following treatment with GGTI-298. Furthermore, GGTI-298 decreased activation of NF-κB, a downstream target of Rho family GTPases. These studies suggest that protein geranylgeranylation contributes to dysregulation of cell survival pathways in HTLV-1-transformed cells.

Simvastatin inhibits IFN regulatory factor 4 expression and Th17 cell differentiation in CD4+ T cells derived from patients with multiple sclerosis

Subsequent to the clinical trial of simvastatin in patients with relapsing remitting multiple sclerosis (RR MS), which demonstrated the ability of simvastatin to inhibit new inflammatory CNS lesion formation, the current in vitro study has characterized the mechanisms through which simvastatin inhibits Th17 cell differentiation. The anti-inflammatory effects of statins are mediated by the inhibition of isoprenylation, which ensures proper membrane insertion and function of proteins. Small GTPases, involved in multiple signal transduction pathways, are the key targets for isoprenylation. We report that simvastatin, one of the most hydrophobic statins with good CNS penetration, inhibited Th17 cell differentiation and IL-17A, IL-17F, IL-21, and IL-22 secretion in in vitro-differentiated naive CD4(+) T cells from RR MS patients. Simvastatin exerted a less prominent effect on the cells from healthy controls, as it inhibited only IL-17F secretion. The inhibition of Th17 cell differentiation was mediated via inhibition of IFN regulatory factor 4 (IRF4) expression, which was identified as a key transcription factor for human Th17 cell differentiation using both IRF4 gene knockdown and overexpression experiments. In studies addressing which isoprenylation pathway--geranylgeranylation or farnesylation--is inhibited by simvastatin, we demonstrated that the geranylgeranyl transferase inhibitor replicated the effect of simvastatin. Selective inhibition of geranylgeranylated RhoA-associated kinase replicated the effect of simvastatin on the inhibition of IRF4 expression and IL-17A, IL-17F, IL-21, and IL-22 secretion, presenting a promising new therapeutic approach for this disabling disease.

Synergistic Effect of Geranylgeranyltransferase Inhibitor, GGTI, and Docetaxel on the Growth of Prostate Cancer Cells

Most advanced prostate cancers progress to castration resistant prostate cancer (CRPC) after a few years of androgen deprivation therapy and the prognosis of patients with CRPC is poor. Although docetaxel and cabazitaxel can prolong the survival of patients with CRPC, inevitable progression appears following those treatments. It is urgently required to identify better or alternative therapeutic strategies. The purpose of this study was to confirm the anti-cancer activity of zoledronic acid (Zol) and determine whether inhibition of geranylgeranylation in the mevalonate pathway could be a molecular target of prostate cancer treatment. We examined the growth inhibitory effect of Zol in prostate cancer cells (LNCaP, PC3, DU145) and investigated a role of geranylgeranylation in the anticancer activity of Zol. We, then, evaluated the growth inhibitory effect of geranylgeranyltransferase inhibitor (GGTI), and analyzed the synergy of GGTI and docetaxel by combination index and isobolographic analysis. Zol inhibited the growth of all prostate cancer cell lines tested in a dose-dependent manner through inhibition of geranylgeranylation. GGTI also inhibited the prostate cancer cell growth and the growth inhibitory effect was augmented by a combination with docetaxel. Synergism between GGTI and docetaxel was observed across a broad range of concentrations. In conclusion, our results demonstrated that GGTI can inhibit the growth of prostate cancer cells and has synergistic effect with docetaxel, suggesting its potential role in prostate cancer treatment.

Simvastatin induces apoptosis by a Rho-dependent mechanism in cultured cardiac fibroblasts and myofibroblasts

Several clinical trials have shown the beneficial effects of statins in the prevention of coronary heart disease. Additionally, statins promote apoptosis in vascular smooth muscle cells, in renal tubular epithelial cells and also in a variety of cell lines; yet, the effects of statins on cardiac fibroblast and myofibroblast, primarily responsible for cardiac tissue healing are almost unknown. Here, we investigated the effects of simvastatin on cardiac fibroblast and myofibroblast viability and studied the molecular cell death mechanism triggered by simvastatin in both cell types.

METHODS

Rat neonatal cardiac fibroblasts and myofibroblasts were treated with simvastatin (0.1-10μM) up to 72h. Cell viability and apoptosis were evaluated by trypan blue exclusion method and by flow cytometry, respectively. Caspase-3 activation and Rho protein levels and activity were also determined by Western blot and pull-down assay, respectively.

RESULTS

Simvastatin induces caspase-dependent apoptosis of cardiac fibroblasts and myofibroblasts in a concentration- and time-dependent manner, with greater effects on fibroblasts than myofibroblasts. These effects were prevented by mevalonate, farnesylpyrophosphate and geranylgeranylpyrophosphate, but not squalene. These last results suggest that apoptosis was dependent on small GTPases of the Rho family rather than Ras.

CONCLUSION

Simvastatin triggered apoptosis of cardiac fibroblasts and myofibroblasts by a mechanism independent of cholesterol synthesis, but dependent of isoprenilation of Rho protein. Additionally, cardiac fibroblasts were more susceptible to simvastatin-induced apoptosis than cardiac myofibroblasts. Thus simvastatin could avoid adverse cardiac remodeling leading to a less fibrotic repair of the damaged tissues.

Focal adhesion kinase and endothelial cell apoptosis

Focal adhesion kinase (FAK) is a key component of cell-substratum adhesions, known as focal adhesion complexes. Growing evidence indicates that FAK is important in maintenance of normal cell survival and that disruption of FAK signaling results in loss of substrate adhesion and anoikis (apoptosis) of anchorage-dependent cells, such as endothelial cells. Basal FAK activity in non-stimulated endothelial cells is important in maintaining cell adhesion to integrins via PI3 kinase/Akt signaling. FAK activity is dependent upon small GTPase signaling. FAK also appears to be important in cardiomyocyte hypertrophy and hypoxia/reoxygenation-induced cell death. This review summarizes the signaling pathways of FAK in prevention of apoptosis and the role of FAK in mediating adenosine and homocysteine-induced endothelial cell apoptosis and in cardiovascular diseases.

Chemopreventive effects of β-ionone and geraniol during rat hepatocarcinogenesis promotion: distinct actions on cell proliferation, apoptosis, HMGCoA reductase, and RhoA

Chemopreventive activities of the dietary isoprenoids β-ionone (βI) and geraniol (GOH) were evaluated during the promotion phase of hepatocarcinogenesis. Over 5 consecutive weeks, rats received daily 16 mg/100 g body weight (b.w.) of βI (βI group), 25 mg/100 g b.w. of GOH (GOH group), or only corn oil (CO group, controls). Compared to the CO group, the following was observed: only the βI group showed a decrease in the mean number of visible hepatocyte nodules (P<.05); βI and GOH groups had reduced mean number of persistent preneoplastic lesions (pPNLs) (P<.05), but no differences regarding number of remodeling PNL (rPNLs) were observed; only the βI group exhibited smaller rPNL size and percentage of liver sections occupied by pPNLs (P<.05), whereas the GOH group displayed a smaller percentage of liver sections occupied by rPNLs (P<.05); a trend was observed in the βI group, which showed reduced cell proliferation of pPNLs (P<.10), and the GOH group had increased apoptosis in pPNLs and rPNLs (P<.05); only the βI group displayed reduced total plasma cholesterol concentrations (P<.05) and increased hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase mRNA levels (P<.05); only the GOH group had lower hepatic membrane RhoA protein levels (P<.05); both the βI- and GOH-treated groups had higher hepatic concentrations of βI and GOH, respectively (P<.05). Given these data, βI and GOH show promising chemopreventive effects during promotion of hepatocarcinogenesis by acting through distinct mechanism of actions: βI may inhibit cell proliferation and modulate HMGCoA reductase, and GOH can induce apoptosis and inhibit RhoA activation.

Mevalonate cascade regulation of airway mesenchymal cell autophagy and apoptosis: a dual role for p53

Statins inhibit the proximal steps of cholesterol biosynthesis, and are linked to health benefits in various conditions, including cancer and lung disease. We have previously investigated apoptotic pathways triggered by statins in airway mesenchymal cells, and identified reduced prenylation of small GTPases as a primary effector mechanism leading to p53-mediated cell death. Here, we extend our studies of statin-induced cell death by assessing endpoints of both apoptosis and autophagy, and investigating their interplay and coincident regulation. Using primary cultured human airway smooth muscle (HASM) and human airway fibroblasts (HAF), autophagy, and autophagosome formation and flux were assessed by transmission electron microscopy, cytochemistry (lysosome number and co-localization with LC3) and immunoblotting (LC3 lipidation and Atg12-5 complex formation). Chemical inhibition of autophagy increased simvastatin-induced caspase activation and cell death. Similarly, Atg5 silencing with shRNA, thus preventing Atg5-12 complex formation, increased pro-apoptotic effects of simvastatin. Simvastatin concomitantly increased p53-dependent expression of p53 up-regulated modulator of apoptosis (PUMA), NOXA, and damage-regulated autophagy modulator (DRAM). Notably both mevalonate cascade inhibition-induced autophagy and apoptosis were p53 dependent: simvastatin increased nuclear p53 accumulation, and both cyclic pifithrin-α and p53 shRNAi partially inhibited NOXA, PUMA expression and caspase-3/7 cleavage (apoptosis) and DRAM expression, Atg5-12 complex formation, LC3 lipidation, and autophagosome formation (autophagy). Furthermore, the autophagy response is induced rapidly, significantly delaying apoptosis, suggesting the existence of a temporally coordinated p53 regulation network. These findings are relevant for the development of statin-based therapeutic approaches in obstructive airway disease.

Inhibition of Rho-ROCK signaling induces apoptotic and non-apoptotic PS exposure in cardiomyocytes via inhibition of flippase

Subsequent to myocardial infarction, cardiomyocytes within the infarcted areas and border zones expose phosphatidylserine (PS) in the outer plasma membrane leaflet (flip-flop). We showed earlier that in addition to apoptosis, this flip-flop can be reversible in cardiomyocytes. We now investigated a possible role for Rho and downstream effector Rho-associated kinase (ROCK) in the process of (reversible) PS exposure and apoptosis in cardiomyocytes. In rat cardiomyoblasts (H9c2 cells) and isolated adult ventricular rat cardiomyocytes Clostridium difficile Toxin B (TcdB), a Rho GTPase family inhibitor, C3 transferase (C3), a Rho(A,B,C) inhibitor and the ROCK inhibitors Y27632 and H1152 were used to inhibit Rho-ROCK signaling. PS exposure was assessed via flow cytometry and fluorescent digital imaging microscopy using annexin V. Akt expression and phosphorylation were analyzed via Western blot, and Akt activity was inhibited by wortmannin. The cellular concentration activated caspase 3 was determined as a measure of apoptosis, and flippase activity was assessed via flow cytometry using NBD-labeled PS. TcdB, C3, Y27632 and H1152 all significantly increased PS exposure. TcdB, Y27632 and H1152 all significantly inhibited phosphorylation of the anti-apoptotic protein Akt and Akt inhibition by wortmannin lead to increased PS exposure. However, only TcdB and C3, but not ROCK- or Akt inhibition led to caspase 3 activation and thus apoptosis. Notably, pancaspase inhibitor zVAD only partially inhibited TcdB-induced PS exposure indicating the existence of apoptotic and non-apoptotic PS exposure. The induced PS exposure coincided with decreased flippase activity as measured with NBD-labeled PS flip-flop. In this study, we show a regulatory role for a novel signaling route, Rho-ROCK-flippase signaling, in maintaining asymmetrical membrane phospholipid distribution in cardiomyocytes.

Effects of statins on nitric oxide/cGMP signaling in human umbilical vein endothelial cells

Human umbilical vein endothelial cells (HUVECs) were established as in vitro models for the modulation of endothelial function and cell viability by statins. Emphasis was placed on the biphasic effects of the drugs on nitric oxide (NO) bioavailability and cytotoxicity, as well as drug interference with the interaction of endothelial NO synthase (eNOS) with caveolin-1 (Cav-1). Incubation of HUVECs with fluvastatin, lovastatin or cerivastatin for 24 h caused an approximately 3-fold upregulation of eNOS expression that was associated with increased eNOS activity and accumulation of cGMP. Cerivastatin exhibited the highest potency with an EC50 of 13.8 +/- 2 nM after 24 h, while having no effect after only 30 min. The effects of statins on eNOS expression were similar in control and Cav-1 knockdown cells, but the increase in eNOS activity was less pronounced in Cav-1-deficient cells. Statin-triggered cytotoxicity occurred at approximately 10-fold higher drug concentrations (maximal toxicity at 1-10 microM), was sensitive to mevalonate, and was significantly enhanced in the presence of NG-nitro-L-arginine. The overexpression of eNOS induced by clinically relevant concentrations of statins may contribute to the beneficial vascular effects of the drugs in patients. Stimulation of NO synthesis and cytotoxicity appear to share a common initial mechanism but involve distinct downstream signaling cascades that exhibit differential sensitivity to HMG-CoA reductase inhibition.

Efficient procurement of epithelial stem cells from human tissue specimens using a Rho-associated protein kinase inhibitor Y-27632

The efficient culture of stem cells from epithelial tissues such as skin and corneas is important for both experimental studies and clinical applications of tissue engineering. We now demonstrate that treatment of human-skin-derived keratinocytes with a Rho-associated protein kinase inhibitor Y-27632 for the initial 6 days of primary culture can increase the number of keratinocytes that possess stem cell properties to form colonies during in vitro culture of freshly isolated cells and subsequent passage (50-fold). Further, we show that Y-27632 treatment can increase the total number of prostate epithelial cells derived from human prostate specimens. Therefore, the use of Y-27632 during primary cultures offers a simple and effective way to prepare a large number of epithelial stem cells from various human epithelial tissues.