Pravastatin Induces Rat Aortic Endothelial Cell Proliferation and Migration via Activation of PI3K/Akt/mTOR/p70 S6 Kinase Signaling

Neuroprotective effects of pravastatin in cerebral venous infarction in a rat model

Objectives

Pravastatin sodium is reported to have multiple beneficial effects in cerebral atherosclerosis and neuronal injury; however, the preventive effects on cerebral venous ischemia are still unknown. Herein, we aimed to examine the neuroprotective effects of transoral prior administration of pravastatin sodium against cerebral cortical venous ischemia with suppression of apoptosis.

Methods

Thirty 8-week-old male Wistar rats were divided equally into two study groups (n = 15 vs. n = 15); the pravastatin group was fed 1% pravastatin sodium with their usual diet for 2 weeks, while the control group only received the usual diet. Two-vein occlusion (2VO) model was applied for this study, and two adjacent cortical veins in each animal were permanently occluded photochemically with rose bengal dye. During photo-thrombosis, regional changes of the cerebral blood flow (CBF) in area of the venous ischemia were recorded. At 48-h after 2VO, animals were euthanized using perfusion fixation, and we histologically measured ratios of infarcted area to contralateral hemisphere, and counted Bax- and Bcl-2-positive cells in the penumbra to investigate the implications for apoptosis.

Results

The ratio of infarcted area was significantly decreased in the pravastatin group compared to the control group (P < 0.01). The number of Bax-positive cells also decreased significantly in the pravastatin group (P < 0.01). In contrast, immunolabeling for Bcl-2 was essentially negative in all areas in both groups. There were also no significant differences in regional CBF changes after 2VO between the two groups (P = 0.13).

Conclusions

Pre-emptive administration of pravastatin sodium mixed in the food has neuroprotective effects against cerebral cortical venous ischemia with suppression of apoptosis associated with inhibition of Bax expression but has little influence on regional CBF.

Statins block mammalian target of rapamycin pathway: a possible novel therapeutic strategy for inflammatory, malignant and neurodegenerative diseases

Inflammation plays a critical role in several diseases such as cancer, gastric, heart and nervous system diseases. Data suggest that the activation of mammalian target of rapamycin (mTOR) pathway in epithelial cells leads to inflammation. Statins, the inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA), seem to be able to inhibit the mTOR. Statins are considered to have favorable effects on inflammatory diseases by reducing the complications caused by inflammation and by regulating the inflammatory process and cytokines secretion. This critical review collected data on this topic from clinical, in vivo and in vitro studies published between 1998 and June 2022 in English from databases including PubMed, Google Scholar, Scopus, and Cochrane libraries.

Exosomes Derived From CTF1-Modified Bone Marrow Stem Cells Promote Endometrial Regeneration and Restore Fertility

Background: Thin endometrial tissue is a leading cause of embryo transfer failure, potentially contributing to sustained infertility and associated adverse outcomes. The application of exosomes derived from autologous or allogeneic bone marrow-derived stem cells (BMSCs) has been used to promote uterine repair following injury, and there is also prior evidence that stem cell transplantation can bolster fertility. Genetic modifications represent a primary approach to enhancing exosomal therapy strategies. The present study thus explored the effects of Cardiotrophin-1 (CTF1)-modified BMSCs-exo on fertility-related outcomes.

Methods: An adenoviral vector was used to generate CTF1-overexpressing BMSCs (C-BMSCs), after which exosomes were isolated from control BMSCs (BMSC-exos) and C-BMSCs (C-BMSC-exos). The angiogenic effects of C-BMSC-exo treatment were assessed through analyses of endothelial cell proliferation and tube formation. Model rats exhibiting endometrial thinning were administered C-BMSCs-exo, after which the effects of such treatment were assessed through H&E staining, Masson’s trichrome staining, and immunofluorescence analyses. The mechanistic basis for the proangiogenic effects of CTF1 as a driver of endometrial regeneration was additionally explored.

Results: C-BMSC-exo treatment of HUVECs was associated with enhanced neovascularization, as evidenced by improved in vitro proliferation, migration, and tube formation. Importantly, such treatment was also linked to tissue regeneration, neovascularization, and the suppression of localized tissue fibrosis in vivo. Regenerated endometrial tissue exhibited higher embryo receptivity and was associated with higher birth rates in treated rats. The upregulation of the JAK/PI3K/mTOR/STAT3 signaling pathways in C-BMSC-exo-treated rats may underscore the mechanistic basis whereby CTF1 can positively impact endometrial angiogenesis and regeneration.

Conclusion: Our data suggest that exosomes produced by CTF1-modified BMSCs can more effectively promote the regeneration of endometrial and myometrial tissues, driving neovascularization in a manner that improves endometrial receptivity in a rat model system, highlighting the therapeutic promise of this approach for patients diagnosed with endometrial thinning.

The impact of statins on wound healing: an ally in treating the highly comorbid patient

OBJECTIVE

To identify the impact that HMG-CoA reductase inhibitors (statins) use has on wound healing outcomes in patients with comorbidities.

METHOD

A retrospective chart review evaluating all new patients presenting to our tertiary wound care centre in 2013 with lower extremity wounds. Patients were divided into two groups depending on whether they took statins or not. Data on wound healing outcomes and wound/patient characteristics were collected. Primary outcomes included healing rate and progression to complete wound healing. Patients were excluded if they had incomplete data or were lost to follow-up before healing status could be confirmed.

RESULTS

A total of 194 patients met the inclusion criteria and were allocated to either the statin group (n=89) or to the non-statin group (n=105). Median initial wound size was 0.6cm³ (Interquartile range (IQR): 0.15-2.4) (p=0.684). In the statin group, 54 (60.6%) patients progressed to complete wound healing compared with 47 (44.7%) in the non-statin group (p=0.027). Median rate of wound healing was 6.7×10^-3cm³/day (IQR: 1.5×10^-3-2.6×10^-2) compared with 3.8×10^-3cm³/day (IQR: 1.7×10^-3-1.3×10^-2) in the non-statin group (p=0.773). Increased age and a higher number of comorbidities were reported in the statin group (p<0.001), respectively). A total of seven patients required amputation: five patients in the statin group and two patients in the non-statin group (p=0.250).

CONCLUSION

This study revealed increased progression to wound healing in patients who were taking statins. The influence of statins on wound healing is promising, but future trials are needed to justify use of this medication class independent of cardiovascular benefit and exclusively for wound healing.

mTORC2 Activation Mediated by Mesenchymal Stem Cell-Secreted Hepatocyte Growth Factors for the Recovery of Lipopolysaccharide-Induced Vascular Endothelial Barrier

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is characterized by pulmonary microvascular endothelial barrier dysfunction. Mesenchymal stem cell-secreted hepatocyte growth factor (HGF) has positive effects of lipopolysaccharide- (LPS-) induced pulmonary endothelial barrier. Studies have exhibited the mammalian TORC1 (mTORC1) signaling is of potent angiogenesis effects. The mTOR protein kinase has two distinct multiprotein complexes mTORC1 and mTORC2 that regulate different branches of the mTOR network. However, detailed mTORC2 mechanisms of HGF protective effects remain poorly defined. Therefore, the aim of this study was to determine whether mTORC2 mediated protective effects of MSC-secreted HGF against LPS-induced pulmonary microvascular endothelial barrier dysfunction activated like mTORC1 activation. We introduced MSC-PMVEC coculture transwell system and recombinant murine HGF on LPS-induced endothelial cell barrier dysfunction in vitro and then explored potential mechanisms by lentivirus vector-mediated HGF, mTORC1 (raptor), and mTORC2 (rictor) gene knockdown modification. Endothelial paracellular and transcellular permeability, adherent junction protein (VE-Cadherin), cell proliferation, apoptosis, and mTOR-associated proteins were tested. These revealed that HGF could promote quick reestablishment of adherent junction VE-cadherin and decrease endothelial paracellular and transcellular permeability during LSP-induced endothelial dysfunction with the involvement of mTORC2 (rictor) and mTORC1 (raptor) pathways. Raptor and rictor knockdown in LPS-induced PMEVECs with stimulation of HGF increased apoptosis ratio, activated Cleaved-Caspase-3 expression, and downregulated cell proliferation. Moreover, mTORC2/Akt but not mTORC2/PKC had significance on HGF endothelial protective effects. Taken together, these highlight activation mTORC2 pathway could also contribute to vascular endothelial barrier recovery by MSC-secreted HGF in LPS stimulation.

Effect of oral statin use on mitomycin-C augmented trabeculectomy outcomes

Purpose

The effect of statins on wound healing is controversial, and their effect on trabeculectomy outcomes remains unclear. This study aimed to examine the relationship between oral statin use and trabeculectomy outcomes.

Methods

Medical records of patients who underwent primary mitomycin-C augmented trabeculectomy with 2 years of follow-up were reviewed. Pre- and postoperative intraocular pressures (IOP) and numbers of medications, subconjunctival 5-fluorouracil (5-FU) injections, and bleb-needling procedures were compared between statin users and nonusers. Failure was defined as an eye that failed to achieve a 20% lowering of IOP from baseline or had an IOP > 21 mm Hg, as well as an eye that required further surgical intervention, developed hypotony, or had no light perception visual acuity.

Results

In total, 158 subjects were enrolled, with 47 eyes from statin users and 111 eyes from statin nonusers. The 24-month cumulative probability of failure was 78.7% for statin users and 60.4% for nonusers (P = .013). Cox proportional-hazards modeling showed a significantly higher hazard risk in statin users (adjusted hazard ratio 1.61, P = .026). There were no significant between-group differences in mean IOPs or number of medications (both P > .05) at 24 months. Multivariable Poisson regression analysis that statin use was associated with increased numbers of 5-FU injections (P = .014) and bleb-needling procedures (P = .031).

Conclusions

This study demonstrated that oral statin use was associated with higher rates of trabeculectomy failure and increased numbers of 5-FU injections and bleb-needling procedures.

Pravastatin Promotes Endothelial Colony-Forming Cell Function, Angiogenic Signaling and Protein Expression In Vitro

Endothelial dysfunction is a primary feature of several cardiovascular diseases. Endothelial colony-forming cells (ECFCs) represent a highly proliferative subtype of endothelial progenitor cells (EPCs), which are involved in neovascularization and vascular repair. Statins are known to improve the outcome of cardiovascular diseases via pleiotropic effects. We hypothesized that treatment with the 3-hydroxy-3-methyl-glutaryl–coenzyme A (HMG-CoA) reductase inhibitor pravastatin increases ECFCs’ functional capacities and regulates the expression of proteins which modulate endothelial health in a favourable manner. Umbilical cord blood derived ECFCs were incubated with different concentrations of pravastatin with or without mevalonate, a key intermediate in cholesterol synthesis. Functional capacities such as migration, proliferation and tube formation were addressed in corresponding in vitro assays. mRNA and protein levels or phosphorylation of protein kinase B (AKT), endothelial nitric oxide synthase (eNOS), heme oxygenase-1 (HO-1), vascular endothelial growth factor A (VEGF-A), placental growth factor (PlGF), soluble fms-like tyrosine kinase-1 (sFlt-1) and endoglin (Eng) were analyzed by real time PCR or immunoblot, respectively. Proliferation, migration and tube formation of ECFCs were enhanced after pravastatin treatment, and AKT- and eNOS-phosphorylation were augmented. Further, expression levels of HO-1, VEGF-A and PlGF were increased, whereas expression levels of sFlt-1 and Eng were decreased. Pravastatin induced effects were reversible by the addition of mevalonate. Pravastatin induces beneficial effects on ECFC function, angiogenic signaling and protein expression. These effects may contribute to understand the pleiotropic function of statins as well as to provide a promising option to improve ECFCs’ condition in cell therapy in order to ameliorate endothelial dysfunction.

mTOR/STAT-3 pathway mediates mesenchymal stem cell-secreted hepatocyte growth factor protective effects against lipopolysaccharide-induced vascular endothelial barrier dysfunction and apoptosis

Mesenchymal stem cells (MSCs) protect the endothelial barrier complex and survival, implicated in the pathogenesis of acute lung injury (ALI) via paracrine hepatocyte growth factor (HGF). However, the mechanism of HGF in endothelial regulation remains unclear. Here, we introduced a coculture protocol of pulmonary microvascular endothelial cells (PMVECs) and overexpression of the HGF gene of MSCs (MSC-HGF). Immunofluorescence and endothelial permeability analysis revealed that MSC-HGF protected endothelial tight junction protein occludin expression and attenuated cellular permeability as well as endothelial apoptosis. To investigate the novel mechanism mammalian TOR (mTOR)/ signal transducer and activator of transcription 3 (STAT-3) signaling in HGF protective effects against endothelial barrier and apoptosis, we used recombinant mouse HGF in endothelial cells. In addition, we used mTOR inhibitor rapamycin to inhibit the mTOR pathway. Our study demonstrated that rapamycin decreased the protective effects of HGF on the endothelium by decreasing tight junction protein occludin expression and cell proliferation, and raising lipopolysaccharide (LPS)-induced endothelial permeability, endothelial cell injury factors ET-1 and vWF. Similarly, the protective effects of HGF on reducing endothelial barrier and apoptosis were weakened when PMVECs were treated with the STAT-3 inhibitor S3I-201. Moreover, mTOR/STAT-3 were activated by HGF demonstrated as raising mTOR (Ser2448) and STAT3 (Ser727) phosphorylation proteins, leading to endothelial barrier improvement and survival. Reversely, rapamycin or S3I-201 inhibited mTOR/STAT-3 activation. Taken together, our findings highlight that the activation of the mTOR/STAT-3 pathway provides novel mechanistic insights into MSC-secreted HGF protection against LPS-induced vascular endothelial permeability dysfunction and apoptosis, which contributes to decreasing microvascular loss and lung injury.

Atorvastatin, but not pravastatin, inhibits cardiac Akt/mTOR signaling and disturbs mitochondrial ultrastructure in cardiac myocytes

Statins, which reduce LDL-cholesterol by inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, are among the most widely prescribed drugs. Skeletal myopathy is a known statin-induced adverse effect associated with mitochondrial changes. We hypothesized that similar effects would occur in cardiac myocytes in a lipophilicity-dependent manner between 2 common statins: atorvastatin (lipophilic) and pravastatin (hydrophilic). Neonatal cardiac ventricular myocytes were treated with atorvastatin and pravastatin for 48 h. Both statins induced endoplasmic reticular (ER) stress, but only atorvastatin inhibited ERK1/2^T202/Y204, Akt^Ser473, and mammalian target of rapamycin signaling; reduced protein abundance of caveolin-1, dystrophin, epidermal growth factor receptor, and insulin receptor-β; decreased Ras homolog gene family member A activation; and induced apoptosis. In cardiomyocyte-equivalent HL-1 cells, atorvastatin, but not pravastatin, reduced mitochondrial oxygen consumption. When male mice underwent atorvastatin and pravastatin administration per os for up to 7 mo, only long-term atorvastatin, but not pravastatin, induced elevated serum creatine kinase; swollen, misaligned, size-variable, and disconnected cardiac mitochondria; alteration of ER structure; repression of mitochondria- and endoplasmic reticulum-related genes; and a 21% increase in mortality in cardiac-specific vinculin-knockout mice during the first 2 months of administration. To our knowledge, we are the first to demonstrate in vivo that long-term atorvastatin administration alters cardiac ultrastructure, a finding with important clinical implications.-Godoy, J. C., Niesman, I. R., Busija, A. R., Kassan, A., Schilling, J. M., Schwarz, A., Alvarez, E. A., Dalton, N. D., Drummond, J. C., Roth, D. M., Kararigas, G., Patel, H. H., Zemljic-Harpf, A. E. Atorvastatin, but not pravastatin, inhibits cardiac Akt/mTOR signaling and disturbs mitochondrial ultrastructure in cardiac myocytes.

The balance between induction and inhibition of mevalonate pathway regulates cancer suppression by statins: A review of molecular mechanisms

Statins are widely used drugs for their role in decreasing cholesterol in hypercholesterolemic patients. Statins through inhibition of Hydroxy Methyl Glutaryl-CoA Reductase (HMGCR), the main enzyme of the cholesterol biosynthesis pathway, inhibit mevalonate pathway that provides isoprenoids for prenylation of different proteins such as Ras superfamily which has an essential role in cancer developing. Inhibition of the mevalonate/isoprenoid pathway is the cause of the cholesterol independent effects of statins or pleotropic effects. Depending on their penetrance into the extra-hepatic cells, statins have different effects on mevalonate/isoprenoid pathway. Lipophilic statins diffuse into all cells and hydrophilic ones use a variety of membrane transporters to gain access to cells other than hepatocytes. It has been suggested that the lower accessibility of statins for extra-hepatic tissues may result in the compensatory induction of mevalonate/isoprenoid pathway and so cancer developing. However, most of the population-based studies have demonstrated that statins have no effect on cancer developing, even decrease the risk of different types of cancer. In this review we focus on the cancer developing "potentials" and the anti-cancer "activities" of statins regarding the effects of statins on mevalonate/isoprenoid pathway in the liver and extra-hepatic tissues.

Effectiveness of Cardiac Rehabilitation for Prevention and Treatment of Sarcopenia in Patients with Cardiovascular Disease - A Retrospective Cross-Sectional Analysis

OBJECTIVE

Sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength, with the risk of frailty and poor quality of life. This study aimed to clarify the clinical characteristics of sarcopenia and to investigate the effects of comprehensive cardiac rehabilitation (CCR), including nutrition, physical exercise and medication, in patients with cardiovascular disease (CVD).

METHODS

We retrospectively studied 322 inpatients with CVD (age 72±12 years). Muscle mass, muscle strength and physical performance were assessed before and after exercise training in patients with and without sarcopenia, which was defined as either a gait speed of <0.8 m/s or reduced handgrip strength (<26 kg in males and <18 kg in females), together with lower skeletal muscle index (SMI) (<7.0 kg/m2 in males and <5.7 kg/m2 in females). The actual daily total calorie and nutrient intake was also calculated.

RESULTS

Sarcopenia was identified in 28% of patients with CVD, these patients having a higher prevalence of symptomatic chronic heart failure and chronic kidney disease. SMI was significantly associated with protein intake and statin treatment. The ratio of peak VO2 and SMI was significantly higher in the statin treatment group. Handgrip strength, gait speed, leg weight bearing index, and nutritional intake improved after exercise training in patients both with and without sarcopenia.

CONCLUSIONS

The present findings suggest that CCR is a promising strategy for prevention and treatment of sarcopenia in patients with CVD.

Low Oxygen Tension Primes Aortic Endothelial Cells to the Reparative Effect of Tissue-Protective Cytokines

Erythropoietin (EPO) has both erythropoietic and tissue-protective properties. The EPO analogues carbamylated EPO (CEPO) and pyroglutamate helix B surface peptide (pHBSP) lack the erythropoietic activity of EPO but retain the tissue-protective properties that are mediated by a heterocomplex of EPO receptor (EPOR) and the β common receptor (βCR). We studied the action of EPO and its analogues in a model of wound healing where a bovine aortic endothelial cells (BAECs) monolayer was scratched and the scratch closure was assessed over 24 h under different oxygen concentrations. We related the effects of EPO and its analogues on repair to their effect on BAECs proliferation and migration (evaluated using a micro-Boyden chamber). EPO, CEPO and pHBSP enhanced scratch closure only at lower oxygen (5%), while their effect at atmospheric oxygen (21%) was not significant. The mRNA expression of EPOR was doubled in 5% compared with 21% oxygen, and this was associated with increased EPOR assessed by immunofluorescence and Western blot. By contrast, βCR mRNA levels were similar in 5% and 21% oxygen. EPO and its analogues increased both BAECs proliferation and migration, suggesting that both may be involved in the reparative process. The priming effect of low oxygen tension on the action of tissue-protective cytokines may be of relevance to vascular disease, including atherogenesis and restenosis.

Inhibition of phosphatidylinositol 3-kinase/Akt signaling attenuates hypoxia-induced pulmonary artery remodeling and suppresses CREB depletion in arterial smooth muscle cells

Hypoxia-induced pulmonary hypertension is characterized by progressive remodeling of the pulmonary artery (PA) system and loss of the transcription factor, cAMP response element binding protein (CREB) in PA smooth muscle cells (SMCs). Previous in vitro studies suggested that platelet-derived growth factor, a mitogen produced in the hypoxic arterial wall, elicits loss of CREB in medial SMCs via the PI3K/Akt pathway. These events trigger switching of SMCs from a quiescent, contractile phenotype to a proliferative, migratory, dedifferentiated, and synthetic phenotype, which contributes to PA thickening. Here, we investigated whether inhibition of PI3K or Akt could attenuate arterial remodeling in the lung and prevent CREB loss in PA medial SMCs in rats subjected to chronic hypoxia. Inhibition of either enzyme-blunted hypoxia-induced PA remodeling and SMC CREB depletion and diminished SMC proliferation and collagen deposition. Inhibition of Akt, but not PI3K, suppressed muscularization of distal arterioles and blunted right ventricular hypertrophy. Interestingly, mean PA pressure was elevated equally by hypoxia in untreated and inhibitor-treated groups but was normalized acutely by the Rho kinase inhibitor, Fasudil. We conclude that PI3K and Akt inhibitors can attenuate hypoxia-induced PA remodeling and SMC CREB depletion but fail to block the development of pulmonary hypertension because of their inability to repress Rho kinase-mediated vasoconstriction.

Pravastatin-induced proangiogenic effects depend upon extracellular FGF-2

The HMG-CoA reductase inhibitors (statins) have been shown to exert several protective effects on the vasculature that are unrelated to changes in the cholesterol profile, and to induce angiogenesis. The proangiogenic effect exerted by statins has been attributed to the activation of the PI3K/Akt pathway in endothelial cells; however, it is unclear how statins activate this pathway. Pravastatin-mediated activation of Akt and MAPK occurs rapidly (within 10 min.) and at low doses (10 nM). Here, we hypothesized that FGF-2 contributes to the proangiogenic effect of statins. We found that pravastatin, a hydrophilic statin, induced phosphorylation of the FGF receptor (FGFR) in human umbilical vein endothelial cells. SU5402, an inhibitor of FGFR, abolished pravastatin-induced PI3K/Akt and MAPK activity. Likewise, anti-FGF-2 function-blocking antibodies inhibited Akt and MAPK activity. Moreover, depletion of extracellular FGF-2 by heparin prevented pravastatin-induced phosphorylation of Akt and MAPK. Treatment with FGF-2 antibody inhibited pravastatin-enhanced endothelial cell proliferation, migration and tube formation. These observations indicate that pravastatin exerts proangiogenic effects in endothelial cells depending upon the extracellular FGF-2.

Topical simvastatin accelerates wound healing in diabetes by enhancing angiogenesis and lymphangiogenesis

Impaired wound healing is a major complication of diabetes. Recent studies have reported reduced lymphangiogenesis and angiogenesis during diabetic wound healing, which are thought to be new therapeutic targets. Statins have effects beyond cholesterol reduction and can stimulate angiogenesis when used systemically. However, the effects of topically applied statins on wound healing have not been well investigated. The present study tested the hypothesis that topical application of simvastatin would promote lymphangiogenesis and angiogenesis during wound healing in genetically diabetic mice. A full-thickness skin wound was generated on the back of the diabetic mice and treated with simvastatin or vehicle topically. Simvastatin administration resulted in significant acceleration of wound recovery, which was notable for increases in both angiogenesis and lymphangiogenesis. Furthermore, simvastatin promoted infiltration of macrophages, which produced vascular endothelial growth factor C in granulation tissues. In vitro, simvastatin directly promoted capillary morphogenesis and exerted an antiapoptotic effect on lymphatic endothelial cells. These results suggest that the favorable effects of simvastatin on lymphangiogenesis are due to both a direct influence on lymphatics and indirect effects via macrophages homing to the wound. In conclusion, a simple strategy of topically applied simvastatin may have significant therapeutic potential for enhanced wound healing in patients with impaired microcirculation such as that in diabetes.

The Role of PTEN in Tumor Angiogenesis

During the past 20 years, the phosphatase and tensin homolog PTEN has been shown to be involved in major physiological processes, and its mutation or loss is often associated with tumor formation. In addition PTEN regulates angiogenesis not only through its antagonizing effect on the PI3 kinase pathway mainly, but also through some phosphatase-independent functions. In this paper we delineate the role of this powerful tumor suppressor in tumor angiogenesis and dissect the underlying molecular mechanisms. Furthermore, it appears that, in a number of cancers, the PTEN status determines the response to chemotherapy, highlighting the need to monitor PTEN expression and to develop PTEN-targeted therapies.

Downregulation of PTEN at corneal wound sites accelerates wound healing through increased cell migration

PURPOSE

The PI3K/Akt pathway is required for cell polarization and migration, whereas the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) has inhibitory effects on the PI3K/Akt pathway. The authors therefore hypothesized that wounding would downregulate PTEN and that this downregulation would enhance wound healing.

METHODS

In human corneal epithelial (HCE) cell monolayer and rat cornea scratch wound models, the authors investigated PTEN and Akt expression using Western blot and immunofluorescence analyses. The effects of PTEN and PI3K inhibitors dipotassium bisperoxo (picolinato) oxovanadate (bpv(pic)) and LY294002 on cell migration and wound closure were investigated using time-lapse imaging. Finally, the authors investigated the effect of PTEN inhibition on wound healing in whole rat eyes.

RESULTS

In HCE cell monolayer and rat cornea, PTEN was downregulated at the wound edges within 30 minutes of wounding. The downregulation of PTEN was causal in a simultaneous increase in Akt activation, which was responsible for a significant increase in individual cell migration rate from 8.8 μm/h to 17.3 μm/h. An increased migration rate was maintained for 20 hours. PTEN inhibition significantly enhanced the wound healing rate in the HCE cell monolayer from 10 minutes onward after treatment and reduced the healing time in eye organ culture from 30 to 20 hours.

CONCLUSIONS

Injury to the corneal epithelium downregulates the expression of PTEN at wound edges, allowing increased PI3K/Akt signaling, thereby contributing to a significant enhancement of cell migration and wound healing. These results suggest that PTEN inhibition may be an effective treatment for corneal injury.

Simvastatin enhances hippocampal long-term potentiation in C57BL/6 mice

Statins inhibit 3-hydroxy-3-methylglutaryl CoA reductase, the rate-limiting enzyme in the cholesterol biosynthetic pathway, and they are widely used to control plasma cholesterol levels and prevent cardiovascular disease. However, emerging evidence indicates that the beneficial effects of statins extend to the CNS. Statins have been shown to improve the outcome of stroke and traumatic brain injury, and statin use has been associated with a reduced prevalence of Alzheimer's disease (AD) and dementia. However, prospective studies with statins in AD have produced mixed results. Recently, we reported that simvastatin, a widely used statin in humans, enhances learning and memory in non-transgenic mice as well as in transgenic mice with AD-like pathology on a mixed genetic background. However, the cellular and molecular mechanisms underlying the beneficial effects of simvastatin on learning and memory remain elusive. The present study was undertaken to investigate the effect of acute simvastatin treatment on hippocampal long-term potentiation (LTP), a cellular model of learning and memory, in brain slices from C57BL/6 mice. Our results demonstrate that a prolonged in vitro simvastatin treatment for 2-4 h, but not a short-term 20-min exposure, significantly increases the magnitude of LTP at CA3-CA1 synapses without altering basal synaptic transmission or the paired-pulse facilitation ratio in hippocampal slices. Furthermore, we show that phosphorylation of Akt (protein kinase B) is increased significantly in the CA1 region following 2-hour treatment with simvastatin, and that inhibition of Akt phosphorylation suppresses the simvastatin-induced enhancement of LTP. These findings suggest activation of Akt as a molecular pathway for augmented hippocampal LTP by simvastatin treatment, and implicate enhancement of hippocampal LTP as a potential cellular mechanism underlying the beneficial effects of simvastatin on cognitive function.

PI3K/PTEN signaling in angiogenesis and tumorigenesis

Phosphatidylinositol 3-kinase (PI3K) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) signaling pathway play an important role in multiple cellular functions such as cell metabolism, proliferation, cell-cycle progression, and survival. PI3K is activated by growth factors and angiogenesis inducers such as vascular endothelial growth factor (VEGF) and angiopoietins. The amplification and mutations of PI3K and the loss of the tumor suppressor PTEN are common in various kinds of human solid tumors. The genetic alterations of upstream and downstream of PI3K signaling molecules such as receptor tyrosine kinases and AKT, respectively, are also frequently altered in human cancer. PI3K signaling regulates tumor growth and angiogenesis by activating AKT and other targets, and by inducing HIF-1 and VEGF expression. Angiogenesis is required for tumor growth and metastasis. In this review, we highlight the recent studies on the roles and mechanisms of PI3K and PTEN in regulating tumorigenesis and angiogenesis, and the roles of the downstream targets of PI3K for transmitting the signals. We also discuss the crosstalk of these signaling molecules and cellular events during tumor growth, metastasis, and tumor angiogenesis. Finally, we summarize the potential applications of PI3K, AKT, and mTOR inhibitors and their outcome in clinical trials for cancer treatment.

Ablation of cholesterol biosynthesis in neural stem cells increases their VEGF expression and angiogenesis but causes neuron apoptosis

Although sufficient cholesterol supply is known to be crucial for neurons in the developing mammalian brain, the cholesterol requirement of neural stem and progenitor cells in the embryonic central nervous system has not been addressed. Here we have conditionally ablated the activity of squalene synthase (SQS), a key enzyme for endogenous cholesterol production, in the neural stem and progenitor cells of the ventricular zone (VZ) of the embryonic mouse brain. Mutant embryos exhibited a reduced brain size due to the atrophy of the neuronal layers, and died at birth. Analyses of the E11.5-E15.5 dorsal telencephalon and diencephalon revealed that this atrophy was due to massive apoptosis of newborn neurons, implying that this progeny of the SQS-ablated neural stem and progenitor cells was dependent on endogenous cholesterol biosynthesis for survival. Interestingly, the neural stem and progenitor cells of the VZ, the primary target of SQS inactivation, did not undergo significant apoptosis. Instead, vascular endothelial growth factor (VEGF) expression in these cells was strongly upregulated via a hypoxia-inducible factor-1-independent pathway, and angiogenesis in the VZ was increased. Consistent with an increased supply of lipoproteins to these cells, the level of lipid droplets containing triacylglycerides with unsaturated fatty acyl chains was found to be elevated. Our study establishes a direct link between intracellular cholesterol levels, VEGF expression, and angiogenesis. Moreover, our data reveal a hitherto unknown compensatory process by which the neural stem and progenitor cells of the developing mammalian brain evade the detrimental consequences of impaired endogenous cholesterol biosynthesis.

Atorvastatin prevents hippocampal cell death due to quinolinic acid-induced seizures in mice by increasing Akt phosphorylation and glutamate uptake

Statins are cholesterol-lowering agents due to the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Recent studies have shown statins possess pleiotropic effects, which appear to be independent from its cholesterol-lowering action. In this study, we investigated whether atorvastatin would have protective effects against hippocampal cell death promoted by quinolinic acid (QA)-induced seizures in mice. Mice were pretreated with Atorvastatin (1 or 10 mg/kg) or vehicle (saline, 0.9%), orally, once a day for 7 days before the intracerebroventricular (i.c.v.) QA infusion (36.8 nmol/site). Atorvastatin treatment with 1 mg/kg/day did not significantly prevent QA-induced seizures (13.34%). However, administration of atorvastatin 10 mg/kg/day prevented the clonic and/or tonic seizures induced by QA in 29.41% of the mice. Additionally, administration of atorvastatin 10 mg/kg/day significantly prevented QA-induced cell death in the hippocampus. Atorvastatin treatment promoted an increased Akt phosphorylation, which was sustained after QA infusion in both convulsed and non-convulsed mice. Moreover, atorvastatin pretreatment prevented the reduction in glutamate uptake into hippocampal slices induced by QA i.c.v. infusion. These results show that atorvastatin attenuated QA-induced hippocampal cellular death involving the Akt pathway and glutamate transport modulation. Therefore, atorvastatin treatment might be a useful strategy in the prevention of brain injury caused by the exacerbation of glutamatergic toxicity in neurological diseases such as epilepsy.

Rokitamycin induces a mitochondrial defect and caspase-dependent apoptosis in human T-cell leukemia Jurkat cells

Macrolides are a well-known family of oral antibiotics whose antibacterial spectrum of activity covers most relevant bacterial species responsible for respiratory infectious disease. In recent years, it has been reported that macrolides have not only bactericidal activity but also direct immunomodulating activity in mammals. In this study, we observed new physiological activity of macrolides and examined whether various macrolides induce apoptosis in human leukemia cell lines. We investigated the effects of 13 different macrolides on the viability of Jurkat and HL-60 cells. Among all the macrolides used in this study, rokitamycin, a semisynthetic macrolide with a 16-member ring, effectively induced cell death. Rokitamycin induced DNA fragmentation and caspase activation, resembling the progression of apoptosis. Moreover, rokitamycin reduced the mitochondrial transmembrane potential and released cytochrome c from mitochondria to the cytosol, suggesting that mitochondrial perturbation is involved in rokitamycin-induced apoptosis. These results suggest that rokitamycin possesses not only bactericidal activity but also pro-apoptotic activity in human leukemia cells.

Potential therapeutic role of statins in neurological disorders

Statins, the inhibitors of HMG-CoA reductase, are currently among the most commonly prescribed agents for the prevention of cardiovascular disease. It is well established that statins reduce cholesterol levels and prevent coronary heart disease. Moreover, evidence suggests that statins have additional properties such as endothelial protection via actions on the nitric oxide synthetase system as well as antioxidant, anti-inflammatory and antiplatelet effects. There is evidence that all these actions might have potential therapeutic implications not only in stroke, but also in various neurological disorders, such as Alzheimer's disease, Parkinson's disease, multiple sclerosis and primary brain tumors. In this review, we summarize the protective effects of statins on various neurological diseases. Currently available data suggest that statins are safe and effective in the treatment of these neurological disorders, although further experiments and new data are required.