Role of the phosphatase PTEN in early vascular remodeling

Prediction of the Mechanism of Sodium Butyrate against Radiation-Induced Lung Injury in Non-Small Cell Lung Cancer Based on Network Pharmacology and Molecular Dynamic Simulations and Molecular Dynamic Simulations

Background

Radiation-induced lung injury (RILI) is a severe side effect of radiotherapy for non-small cell lung cancer (NSCLC) ,and one of the major hindrances to improve the efficacy of radiotherapy. Previous studies have confirmed that sodium butyrate (NaB) has potential of anti-radiation toxicity. However, the mechanism of the protective effect of NaB against RILI has not yet been clarified. This study aimed to explore the underlying protective mechanisms of NaB against RILI in NSCLC through network pharmacology, molecular docking, molecular dynamic simulations and in vivo experiments.

Methods

The predictive target genes of NaB were obtained from the PharmMapper database and the literature review. The involved genes of RILI and NSCLC were predicted using OMIM and GeneCards database. The intersectional genes of drug and disease were identified using the Venny tool and uploaded to the Cytoscape software to identify 5 core target genes of NaB associated with RILI. The correlations between the 5 core target genes and EGFR, PD-L1, immune infiltrates, chemokines and chemokine receptors were analyzed using TIMER 2.0, TIMER and TISIDB databases. We constructed the mechanism maps of the 3 key signaling pathways using the KEGG database based on the results of GO and KEGG analyses from Metascape database. The 5 core target genes and drug were docked using the AutoDock Vina tool and visualized using PyMOL software. GROMACS software was used to perform 100 ns molecular dynamics simulation. Irradiation-induced lung injury model in mice were established to assess the therapeutic effects of NaB.

Results

A total of 51 intersectional genes involved in NaB against RILI in NSCLC were identified. The 5 core target genes were AKT1, TP53, NOTCH1, SIRT1, and PTEN. The expressions of the 5 core target genes were significantly associated with EGFR, PD-L1, immune infiltrates, chemokines and chemokine receptors, respectively. The results from GO analysis of the 51 intersectional genes revealed that the biological processes were focused on the regulation of smooth muscle cell proliferation, oxidative stress and cell death, while the three key KEGG pathways were enriched in PI3K-Akt signal pathway, p53 signal pathway, and FOXO signal pathway. The docking of NaB with the 5 core target genes showed affinity and stability, especially AKT1. In vivo experiments showed that NaB treatment significantly protected mice from RILI, with reduced lung histological damage. In addition, NaB treatment significantly inhibited the PI3K/Akt signaling pathway.

Conclusions

NaB may protect patients from RILI in NSCLC through multiple target genes including AKT1, TP53, NOTCH1, SIRT1 and PTEN, with multiple signaling pathways involving, including PI3K-Akt pathway, p53 pathway, and FOXO pathways. Our findings effectively provide a feasible theoretical basis to further elucidate the mechanism of NaB in the treatment of RILI.

Mitochondria-actin cytoskeleton crosstalk in cell migration

Mitochondria perform diverse functions in the cell and their roles during processes such as cell survival, differentiation, and migration are increasingly being appreciated. Mitochondrial and actin cytoskeletal networks not only interact with each other, but this multifaceted interaction shapes their functional dynamics. The interrelation between mitochondria and the actin cytoskeleton extends far beyond the requirement of mitochondrial ATP generation to power actin dynamics, and impinges upon several major aspects of cellular physiology. Being situated at the hub of cell signaling pathways, mitochondrial function can alter the activity of actin regulatory proteins and therefore modulate the processes downstream of actin dynamics such as cellular migration. As we will discuss, this regulation is highly nuanced and operates at multiple levels allowing mitochondria to occupy a strategic position in the regulation of migration, as well as pathological events that rely on aberrant cell motility such as cancer metastasis. In this review, we summarize the crosstalk that exists between mitochondria and actin regulatory proteins, and further emphasize on how this interaction holds importance in cell migration in normal as well as dysregulated scenarios as in cancer.

DNA Methylation in Atherosclerosis: A New Perspective

Atherosclerotic cardiovascular diseases, in which atherosclerosis (AS) is the main pathologic basis, are currently the primary diseases leading to human deaths. Emerging evidence showed that DNA methylation, which could affect the transcription and expression of critical regulatory genes, has key roles in AS. Aberrant DNA methylation including aberrant hypomethylation and hypermethylation plays key roles in endothelial-cell dysfunction, macrophage inflammation, abnormal proliferation of vascular smooth muscle cells, plaque rupture, and thrombosis in AS. Chinese herbal medicines, including single compounds and formulations, showed light on the treatment of AS through regulating the aberrant DNA methylation in AS. Targeting the aberrant DNA methylation may be one of the most important treatment strategies in the cure and prevention of AS. In this review, we focus on the relationship between DNA methylation and AS, as well as the beneficial effects of Chinese herbal medicines on DNA methylation in AS.

Potential Target miR-455 Delaying Arterial Stenosis Progression Through PTEN

Background: Vascular smooth muscle cells (VSMC) underwent phenotypic switching upon stimulation signals, and this is the prerequisite for their proliferation and migration. Previous work revealed that miR-455 may be involved in vascular stenosis. Thus, this study aimed to explore potential targets and mechanisms underlying the dynamics of miR-455 in vascular stenosis.

Methods: miR-455 and PTEN expression levels were studied in normal and stenosis tissue, as well as in VSMC in proliferation model. Manipulating miR-455 expression levels was achieved by transfection of either miR-455 mimic or inhibitor, and its effect on cell proliferation was studied by CCK-8 assay. Its effect on gene expression was studied by RT-qPCR and western blot. The expression regulation mechanism was studied by luciferase reporter system. Finally, the effect of miR-455 on regulating vascular stenosis was studied using a rat balloon-injured carotid artery stenosis model.

Results: High expression levels of miR-455 were detected in both stenosis arterial tissues and VSMC proliferation models. In contrast, the expression levels of PTEN were downregulated in these systems. miR-455 transfected VSMC showed higher levels of proliferation and decreased levels of PTEN. Potential binding sites between miR-455 and PTEN 3′UTR were predicted and confirmed. NF-kB p65 was found to bind directly on miR-455 promoter region and regulate its transcription. The progression of arterial stenosis could be delayed by introducing miR-455 antagomir.

Conclusions: The p65/miR-455/PTEN signaling pathway plays a crucial role in regulating VSMC proliferation and vascular stenosis. This indicated that miR-455 is a novel target that would help improve treatment outcomes in patients suffering from vascular stenosis.

Identification of DNA hydroxymethylation associated genes in osteoarthritis by combined analysis of hydroxymethylation and gene expression

BACKGROUND

Our study aimed to explore more mechanistic insights into the epigenetic regulation of osteoarthritis (OA).

METHODS

The expression profiles (accession number: GSE64393 and GSE64394) were downloaded from the Gene Expression Omnibus database. The differentially hydroxymethylated regions (DhMRs) and differentially expressed genes (DEGs) between OA and control groups were identified. The distribution of DhMRs in the whole genome and the correlation between DhMRs and DEGs were analyzed. Functional module mining for the DEGs and DhMRs was conducted, followed by protein-protein interaction (PPI) analysis. The transcriptional factor (TF) was predicted.

RESULTS

Total 52,282 DhMRs were obtained, among which 31,452 ones were annotated to 9726 genes. Additionally, 1806 DEGs were selected. Hydroxymethylation mainly occurred in gene body region. Correlation analysis revealed that more than 70% of DhMRs were uncorrelated with DEGs expression. Functional module mining for the DEGs and DhMRs identified 2 functional modules, which were involved in pathways of regulation of actin cytoskeleton, and TGF-β signaling pathway. A PPI network was constructed, and ITGB3 had the highest degree. Furthermore, 7 TFs were predicted, which regulated 12 candidate genes, such as HES1-PTEN.

CONCLUSIONS

The onset and progression of OA may be associated with the upregulated hydroxymethylation in gene body region of PTEN. HES1 may be important TF in the pathogenesis of OA. Additionally, pathways of regulation of actin cytoskeleton, and TGF-beta signaling pathway may also play important roles in OA progression.

MicroRNA-214 protects L6 skeletal myoblasts against hydrogen peroxide-induced apoptosis

MicroRNAs (miRNAs) have been reported as key gene regulators, and they control many fundamental biological processes. Previously, we demonstrated that miR-214 had a protective effect against myocardial apoptosis and myocardial fibrosis. In this study, we sought to investigate the expression of miR-214 in L6 skeletal myoblast (SKM), the regulatory effect of miR-214 on hydrogen peroxide (H₂O₂) induced cell apoptosis and the underlying mechanisms of the antiapoptotic effect. MiR-214 expression was up-regulated by H₂O₂ in a dose and time-dependent manner in L6 SKMs. To investigate the regulatory effects of miR-214 on L6 SKM, both gain-of-function and loss-of-function approaches were applied. The results showed that miR-214 improved cell survival and inhibited cell apoptosis, and blockage of miR-214 abrogated the protective effect on cell survival and resistance to apoptosis. Phosphatase and tensin homolog (PTEN) was negatively regulated by miR-214, and PTEN inhibitor obviously reversed the effect of miR-214 blockage on enhancing cell apoptosis. In addition, miR-214 up-regulated antiapoptotic protein Bcl-2, down-regulated proapoptotic protein Bax, prevented release of cytochrome c and inhibited caspase-3 activation. In summary, H₂O₂-induced injury increases miR-214 expression in L6 SKM, and miR-214 contributes to the protection of L6 SKM against apoptosis via lowering PTEN and subsequently inhibiting the mitochondrial-mediated caspase-dependent apoptotic signaling pathway.

Antioxidant-Conjugated Peptide Attenuated Metabolic Reprogramming in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is a chronic cardiopulmonary disorder instigated by pulmonary vascular cell proliferation. Activation of Akt was previously reported to promote vascular remodeling. Also, the irreversible nitration of Y350 residue in Akt results in its activation. NitroAkt was increased in PAH patients and the SU5416/Hypoxia (SU/Hx) PAH model. This study investigated whether the prevention of Akt nitration in PAH by Akt targeted nitroxide-conjugated peptide (NP) could reverse vascular remodeling and metabolic reprogramming. Treatment of the SU/Hx model with NP significantly decreased nitration of Akt in lungs, attenuated right ventricle (RV) hypertrophy, and reduced RV systolic pressure. In the PAH model, Akt-nitration induces glycolysis by activation of the glucose transporter Glut4 and lactate dehydrogenase-A (LDHA). Decreased G6PD and increased GSK3β in SU/Hx additionally shunted intracellular glucose via glycolysis. The increased glycolytic rate upregulated anaplerosis due to activation of pyruvate carboxylase in a nitroAkt-dependent manner. NP treatment resolved glycolytic switch and activated collateral pentose phosphate and glycogenesis pathways. Prevention of Akt-nitration significantly controlled pyruvate in oxidative phosphorylation by decreasing lactate and increasing pyruvate dehydrogenases activities. Histopathological studies showed significantly reduced pulmonary vascular proliferation. Based on our current observation, preventing Akt-nitration by using an Akt-targeted nitroxide-conjugated peptide could be a useful treatment option for controlling vascular proliferation in PAH.

MiR-210 inhibits hypoxia-induced apoptosis of smooth muscle cells via targeting MEF2C

BACKGROUND

Vascular smooth muscle cell (VSMC) apoptosis plays an important role in vascular remodeling and atherosclerotic plaque instability. Growing evidence suggests that microRNAs (miRNAs) play a critical role in VSMC function, however, the underlying mechanism remains unclear.

METHODS

This study used a hypoxic-induced VSMC apoptosis model. Expression of miR-210, its target MEF2C, and other key factors of apoptosis were detected and measured by real-time PCR and western blot. Luciferase reporter assay was performed to detect the miR-210 target. The function of miR-210 in apoptosis was determined using flow cytometric cell apoptosis assays. The relationship between miR-210 and MEF2C was confirmed and key apoptosis factors were detected.

RESULTS

The restoration of miR-210 function in cells transfected with a miR-210 mimic inhibited VSMC apoptosis compared to control. MiR-210 overexpression inhibited the expression of Bax, Bad, cleaved Caspase-3, and promoted the expression of Bcl-2, Caspase-3, Caspase-9 and mitochondrial cytochrome c at both the mRNA and protein levels. Results also found that MEF2C was a direct target of miR-210 in hypoxic VSMCs. Further, miR-210 suppressed MEF2C expression by directly binding to its 3'-untranslated region and the expression of miR-210 was negatively correlated with MEF2C mRNA levels.

CONCLUSIONS

Results from this study provide the first evidence that miR-210 can inhibit apoptosis by targeting MEF2C in hypoxic VSMCs and may support the development of new biomarkers and therapeutic targets for atherosclerosis.

MicroRNA-21 promotes TGF-β1-induced epithelial-mesenchymal transition in gastric cancer through up-regulating PTEN expression

This study aimed to explore the effects of miR-21 and PTEN/Akt signaling pathway on TGF-β1-induced epithelial-mesenchymal transition (EMT) in gastric cancer (GC). GC tissues and adjacent tissues were collected from 83 patients. The qRT-PCR assay was performed to detect miR-21 expression. The expressions of PTEN, Akt and p-Akt were detected by immunohistochemistry. After 48 h of treatment with TGF-β1 (10 ng/mL), the SGC-7901 and KATO-III cells were divided into the blank, negative control (NC), miR-21 inhibitors, PTEN-siRNA and miR-21 inhibitors + PTEN-siRNA groups. EMT related factors and PTEN expressions were detected by qRT-PCR assay and Western blotting. The scratch test was conducted to observe cell migration. Xenograft tumor model in nude mice was used to evaluate the effects of miR-21 on EMT of GC cells in vivo. In GC tissues, the expressions of miR-21, Akt and p-Akt were up-regulated, while PTEN expression was down-regulated. Gene and protein expressions of E-cadherin and PTEN in the miR-21 inhibitors group were higher than the blank, NC, PTEN-siRNA and miR-21 inhibitors + PTEN-siRNA groups, while the expressions of N-cadherin, β-catenin, Vimentin and Slug in the miR-21 inhibitors group were lower than other groups. MiR-21 inhibitors significantly inhibit cell migration and invasion in GC cell lines. In vivo xenograft experiment revealed that miR-21 inhibitor inhibits the growth of transplanted tumor through up-regulating E-cadherin and PTEN expressions and down-regulating the expressions of N-cadherin, β-catenin, Vimentin and Slug. These results suggest that miR-21 could promote TGF-β1-induced EMT in GC cells through up-regulating PTEN expression.

Homocysteine-induced proliferation of vascular smooth muscle cells occurs via PTEN hypermethylation and is mitigated by Resveratrol

Vascular smooth muscle cell (VSMC) proliferation is a primary pathological event in the development of atherosclerosis (AS), and the presence of homocysteine (Hcy) acts as an independent risk factor for AS. However, the underlying mechanisms remain to be elucidated. Phosphatase and tensin homologue on chromosome 10 (PTEN), is endogenously expressed in VSMCs and induces multiple signaling networks involved in cell proliferation, survival and inflammation, however, the specific role of PTEN is still unknown. The present study detected the proliferation ratio of VSMCs following treatment with Hcy and Resveratrol (RSV). In the 100 µM Hcy group, the proliferation ratio increased, and treatment with RSV decreased the proliferation ratio induced by Hcy. Reverse transcription‑quantitative polymerase chain reaction and western blotting were used to analyze PTEN expression, RSV treatment was associated with decreased PTEN expression levels in VSMCs. PTEN levels were decreased in Hcy treated cells, and the proliferation ratio of VSMCs were increased following treated with Hcy. To study the mechanism of regulation of PTEN by Hcy, the present study detected PTEN methylation levels in VSMCs, and PTEN DNA methylation levels were demonstrated to be increased in the 100 µM Hcy group, whereas treatment with RSV decreased the methylation status. DNA methyltransferase 1 is important role in the regulation of PTEN methylation. Overall, Hcy impacts the methylation status of PTEN, which is involved in cell proliferation, and induces the proliferation of VSMCs. This effect is alleviated by treatment with RSV, which exhibits an antagonistic mechanism against Hcy.

SHP-1 activation inhibits vascular smooth muscle cell proliferation and intimal hyperplasia in a rodent model of insulin resistance and diabetes

AIMS/HYPOTHESIS

Accelerated migration and proliferation of vascular smooth muscle cells (VSMCs) enhances arterial restenosis after angioplasty in insulin resistance and diabetes. Elevation of Src homology 2-containing protein tyrosine phosphatase 1 (SHP-1) induces apoptosis in the microvasculature. However, the role of SHP-1 in intimal hyperplasia and restenosis has not been clarified in insulin resistance and diabetes.

METHODS

We used a femoral artery wire injury mouse model, rodent models with insulin resistance and diabetes, and patients with type 2 diabetes. Further, we modulated SHP-1 expression using a transgenic mouse that overexpresses SHP-1 in VSMCs (Shp-1-Tg). SHP-1 agonists were also employed to study the molecular mechanisms underlying the regulation of SHP-1 by oxidised lipids.

RESULTS

Mice fed a high-fat diet (HFD) exhibited increased femoral artery intimal hyperplasia and decreased arterial SHP-1 expression compared with mice fed a regular diet. Arterial SHP-1 expression was also decreased in Zucker fatty rats, Zucker diabetic fatty rats and in patients with type 2 diabetes. In primary cultured VSMCs, oxidised LDL suppressed SHP-1 expression by activating Mek-1 (also known as Map2k1) and increased DNA methylation of the Shp-1 promoter. VSMCs from Shp-1-Tg mice exhibited impaired platelet-derived growth factor (PDGF)-stimulated tyrosine phosphorylation with a concomitant decrease in PDGF-stimulated VSMC proliferation and migration. Similarly, HFD-fed Shp-1-Tg mice and mice treated with the SHP-1 inducer, Icariside II, were protected from the development of intimal hyperplasia following wire injury.

CONCLUSIONS/INTERPRETATION

Suppression of SHP-1 by oxidised lipids may contribute to the excessive VSMC proliferation, inflammatory cytokine production and intimal hyperplasia observed in arteries from diabetes and insulin resistance. Augmenting SHP-1 levels is a potential therapeutic strategy to maintain stent patency in patients with insulin resistance and diabetes.

Effect of Phosphatase and Tensin Homologue on Chromosome 10 on Angiotensin II-Mediated Proliferation, Collagen Synthesis, and Akt/P27 Signaling in Neonatal Rat Cardiac Fibroblasts

Cardiac fibroblasts (CFs) play a key role in cardiac fibrosis by regulating the balance between extracellular matrix synthesis and breakdown. Although phosphatase and tensin homologue on chromosome 10 (PTEN) has been found to play an important role in cardiovascular disease, it is not clear whether PTEN is involved in functional regulation of CFs. In the present study, PTEN was overexpressed in neonatal rat CFs via recombinant adenovirus-mediated gene transfer. The effects of PTEN overexpression on cell-cycle progression and angiotensin II- (Ang II-) mediated regulation of collagen metabolism, synthesis of matrix metalloproteinases, and Akt/P27 signaling were investigated. Compared with uninfected cells and cells infected with green fluorescent protein-expressing adenovirus (Ad-GFP), cells infected with PTEN-expressing adenovirus (Ad-PTEN) significantly increased PTEN protein and mRNA levels in CFs (P < 0.05). The proportion of CFs in the G1/S cell-cycle phase was significantly higher for PTEN-overexpressing cells. In addition, Ad-PTEN decreased mRNA expression and the protein synthesis rate of collagen types I and III and antagonized Ang II-induced collagen synthesis. Overexpression of PTEN also decreased Ang II-induced matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1) production as well as gelatinase activity. Moreover, Ad-PTEN decreased Akt expression and increased P27 expression independent of Ang II stimulation. These results suggest that PTEN could regulate its functional effects in neonatal rat CFs partially via the Akt/P27 signaling pathway.

Inhibitory effects of hydroxysafflor yellow A on PDGF‑BB‑induced proliferation and migration of vascular smooth muscle cells via mediating Akt signaling

The abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) are key pathological factors in the initiation and progression of vascular disorders, including arteriosclerosis and restenosis following percutaneous coronary intervention (PCI). Hydroxysafflor yellow A (HSYA), the main component of the safflower yellow pigments, has widely been used for the treatment of cardiovascular diseases in traditional Chinese medicine. However, to the best of our knowledge, there are no studies investigating the pharmaceutical effect of HSYA on VSMCs or the underlying molecular mechanism. The present study aimed to investigate the effect of HSYA on platelet‑derived growth factor (PDGF)‑BB‑stimulated VSMC proliferation and migration. HSYA significantly inhibited PDGF‑BB‑stimulated VSMC proliferation and, in response to PDGF‑BB‑stimulation, VSMCs dedifferentiated into a proliferative phenotype. However, HSYA effectively reversed this phenotype switching. In addition, the production of nitrous oxide and cyclic guanosine monophosphate induced by PDGF‑BB was also suppressed by HSYA, and HSYA markedly inhibited PDGF‑BB‑stimulated VSMC migration. Investigation of the molecular mechanism revealed that HSYA inhibited PDGF‑BB‑induced activation of Akt signaling. In addition, HSYA also suppressed PDGF‑BB‑stimulated upregulation of cell cycle related proteins and heme oxygenase‑1. In conclusion, HSYA was able to inhibit PDGF‑BB‑stimulated VSMC proliferation and migration, partially via suppressing PDGF‑BB‑induced Akt signaling activation. Therefore, HSYA may be useful for the prevention and treatment of cardiovascular diseases, including atherosclerosis and restenosis following PCI.

PTEN regulates matrix synthesis in adult human chondrocytes under oxidative stress

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) was identified as an important tumor suppressor gene. PTEN functions as a negative regulator of phosphoinositol-3-kinase (PI3K)-Akt and MEK/ERK signaling. The PI3K-Akt pathway is critical for cell survival, differentiation, and matrix synthesis. Oxidative stress is considered a critical factor in the onset and progression of osteoarthritis (OA). Therefore, we investigated the function of PTEN in OA chondrocytes under oxidative stress. Chondrocytes were treated with insulin-like growth factor-1 (IGF-1) and/or tert-butyl hydroperoxide (tBHP), which causes oxidative stress. The expression levels of type2 collagen (Col2a1) and aggrecan were analyzed by real-time PCR, and phosphorylation of Akt and ERK1/2 was analyzed by Western blotting. Chondrocytes were treated with PTEN-specific small interfering RNA (siRNA), as well as IGF-1 and/or tBHP. PTEN and IGF-1 expressions in OA chondrocytes were increased. The downregulation of PTEN expression increased the expression levels of Col2a1 and aggrecan, and increased proteoglycan synthesis under oxidative stress. Oxidative stress decreased the phosphorylation of Akt and increased that of ERK1/2. The downregulation of PTEN expression increased Akt phosphorylation, but did not increase that of ERK 1/2. Our results suggest that PTEN regulates matrix synthesis via the PI3K-Akt pathway under oxidative stress.

Inhibition of phosphatase and tensin homolog deleted on chromosome 10 decreases rat cortical neuron injury and blood-brain barrier permeability, and improves neurological functional recovery in traumatic brain injury model

BACKGROUND AND PURPOSE

Recent evidence has supported the neuroprotective effect of bpV (pic), an inhibitor of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), in models of ischemic stroke. However, whether PTEN inhibitors improve long-term functional recovery after traumatic brain injury (TBI) and whether PTEN affects blood brain barrier (BBB) permeability need further elucidation. The present study was performed to address these issues.

METHODS

Adult Sprague-Dawley rats were subjected to fluid percussion injury (FPI) after treatment with a well-established PTEN inhibitor bpV (pic) or saline starting 24 h before FPI. Western blotting, real-time quantitative PCR, or immunostaining was used to measure PTEN, p-Akt, or MMP-9 expression. We determined the presence of neuron apoptosis by TUNEL assay. Evans Blue dye extravasation was measured to evaluate the extent of BBB disruption. Functional recovery was assessed by the neurological severity score (NSS), and Kaplan-Meier analysis was used for survival analysis.

RESULTS

PTEN expression was up-regulated after TBI. After bpV (pic) treatment, p-Akt was also up-regulated. We found that bpV (pic) significantly decreased BBB permeability and reduced the number of TUNEL-positive cells. We further demonstrated that PTEN inhibition improved neurological function recovery in the early stage after TBI.

CONCLUSION

These data suggest that treatment with the PTEN inhibitor bpV (pic) has a neuroprotective effect in TBI rats.

Blockade of reactive oxygen species and Akt activation is critical for anti-inflammation and growth inhibition of metformin in phosphatase and tensin homolog-deficient RAW264.7 cells

CONTEXT

Metformin is widely used for treatment of type 2 diabetes and has a potential application on the treatment of inflammation and cancer. Phosphatase and tensin homolog (PTEN) plays a critical role in cancer cell growth and inflammation; however, precise mechanisms remain unclear.

OBJECTIVE

We aimed to investigate the possible mechanisms of how PTEN regulates metformin against cell growth and inflammation.

MATERIALS AND METHODS

We established PTEN knockdown in RAW264.7 murine macrophages (shPTEN cells) to detect inflammatory mediators using commercial kits, production of reactive oxygen species (ROS) by flow cytometry, cell growth by MTT assay and phosphorylated levels of signal molecules by western blot.

RESULTS

The shPTEN cells had a significant large amount of inflammatory mediators, such as inducible nitric oxide synthase (iNOS)/nitric oxide (NO) and cyclooxygenase-2 (COX-2)/prostaglandin E(2) (PGE(2)); and also elevated the production of ROS and increased cell proliferation. These effects were accompanied with the activation of Akt and p38 mitogen-activated protein kinase (MAPK), and the inactivation of an AMP-activated protein kinase (AMPK) activator and extracellular signal-regulated kinase 1/2. Pretreatment with metformin not only blocked these inflammatory mediators, but also caused growth inhibition induced by significant apoptosis. Furthermore, inactivation of Akt, blockade of ROS generation and independence of activations of AMPK and MAPK by metformin were also observed.

CONCLUSION

Macrophages with PTEN deficiency developed a continuous inflammatory microenvironment, which further aggravated tumor cell growth. Moreover, metformin affected PTEN-deficient cells dependent of inhibition of ROS production and Akt activation against enlarged inflammatory mediators and/or cell growth in shPTEN cells.