[Show abstract][Hide abstract] ABSTRACT: Abnormal and uncontrolled proliferation of lung fibroblasts may contribute to pulmonary fibrosis. Lipopolysaccharide (LPS) can induce fibroblast proliferation and differentiation through activation of phosphoinositide3-Kinase (PI3-K) pathway. However, the detail mechanism by which LPS contributes to the development of lung fibrosis is not clearly understood. To investigate the role of phosphatase and tensin homolog (PTEN), a PI3-K pathway suppressor, on LPS-induced lung fibroblast proliferation, differentiation, collagen secretion and activation of PI3-K, we transfected PTEN overexpression lentivirus into cultured mouse lung fibroblasts with or without LPS treatment to evaluate proliferation by MTT and Flow cytometry assays. Expression of PTEN, alpha-smooth muscle actin (alpha-SMA), glycogen synthase kinase 3 beta (GSK3beta) and phosphorylation of Akt were determined by Western-blot or real-time RT-PCR assays. The PTEN phosphorylation activity was measured by a malachite green-based assay. The content of C-terminal propeptide of type I procollagen (PICP) in cell culture supernatants was examined by ELISA.
We found that overexpression of PTEN effectively increased expression and phosphatase activity of PTEN, and concomitantly inhibited LPS-induced fibroblast proliferation, differentiation and collagen secretion. Phosphorylation of Akt and GSK3beta protein expression levels in the LPS-induced PTEN overexpression transfected cells were significantly lower than those in the LPS-induced non-transfected cells, which can be reversed by the PTEN inhibitor, bpV(phen).
Collectively, our results show that overexpression and induced phosphatase activity of PTEN inhibits LPS-induced lung fibroblast proliferation, differentiation and collagen secretion through inactivation of PI3-K-Akt-GSK3beta signaling pathways, which can be abrogated by a selective PTEN inhibitor. Thus, expression and phosphatase activity of PTEN could be a potential therapeutic target for LPS-induced pulmonary fibrosis. Compared with PTEN expression level, phosphatase activity of PTEN is more crucial in affecting lung fibroblast proliferation, differentiation and collagen secretion.
[Show abstract][Hide abstract] ABSTRACT: Lipopolysaccharide (LPS)-induced pulmonary fibrosis is characterized by aberrant proliferation and activation of lung fibroblasts. Epigenetic regulation of thymocyte differentiation antigen 1 (Thy-1) is associated with lung fibroblast phenotype transformation that results in aberrant cell proliferation. However, it is not clear whether the epigenetic regulation of Thy-1 expression is required for LPS-induced lung fibroblast proliferation. To address this issue and better understand the relative underlying mechanisms, we used mouse lung fibroblasts as model to observe the changes of Thy-1 expression and histone deacetylation after LPS challenge. The results showed that cellular DNA synthesis, measured by BrdU incorporation, was impacted less in the early stage (24 hrs) after the challenge of LPS, but significantly increased at 48 or 72 hrs after the challenge of LPS. Meanwhile, Thy-1 expression, which was detected by real-time PCR and Western blot, in lung fibroblasts decreased with increased time after LPS challenge and diminished at 72 hrs. We also found that the acetylation of either histone H3 or H4 decreased in the LPS-challenged lung fibroblasts. ChIP assay revealed that the acetylation of histone H4 (Ace-H4) decreased in the Thy-1 promoter region in response to LPS. In addition, all the above changes could be attenuated by depletion of TLR4 gene. Our studies indicate that epigenetic regulation of Thy-1 gene expression by histone modification is involved in LPS-induced lung fibroblast proliferation.
Journal of Cellular and Molecular Medicine 01/2013; · 4.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVE: Postoperative cognitive dysfunction occurs frequently after cardiac surgeries with cardiopulmonary bypass (CPB). Available data from rat CPB models are conflicting. However, none of them was designed to investigate the role of isoflurane (the main anesthetic in all of these studies) in the neurocognitive dysfunction after CPB. Isoflurane has documented neuroprotective effects so the present authors hypothesized that isoflurane prevents the neurocognitive dysfunction in rats after CPB. DESIGN: A prospective, interventional study. SETTING: A university research laboratory. PARTICIPANTS: Male Sprague-Dawley rats. INTERVENTIONS: Male Sprague-Dawley rats were divided into 5 groups: the isoflurane CPB group, the animals were anesthetized with isoflurane and underwent 60 minutes of normothermic CPB; the chloral hydrate CPB group, the animals were anesthetized with chloral hydrate and underwent 60 minutes of normothermic CPB; the isoflurane sham group, the animals were subjected only to cannulation and the same duration of anesthesia but no CPB; the chloral hydrate sham group, the animals received only cannulation and the same duration of anesthesia but no CPB; and the naive group, the animals received no treatment. The neurocognitive function of all rats was measured on days 4 to 6 (short-term) and 31 to 33 after CPB (long-term). After the behavior tests, the animals were sacrificed, and the brain was harvested for the measurement of acetylcholinesterase (AChE) and choline acetyltransferase protein levels. MEASUREMENTS AND MAIN RESULTS: Short-term (days 4-6 after CPB) learning and memory were impaired after CPB when the animals were anesthetized with chloral hydrate. When isoflurane was used, the learning and memory did not change after CPB. No long-term (days 31-33 after CPB) neurocognitive changes were found after CPB. AChE decreased significantly after isoflurane anesthesia regardless of whether CPB was performed. CONCLUSIONS: Isoflurane prevented the neurocognitive dysfunction induced by CPB, which might involve the cerebral cholinergic system.
Journal of cardiothoracic and vascular anesthesia 11/2012; · 1.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pulmonary fibrosis is characterized by lung fibroblast proliferation and collagen secretion. In lipopolysaccharide (LPS)-induced acute lung injury (ALI), aberrant proliferation of lung fibroblasts is initiated in early disease stages, but the underlying mechanism remains unknown. In this study, we knocked down Toll-like receptor 4 (TLR4) expression in cultured mouse lung fibroblasts using TLR4-siRNA-lentivirus in order to investigate the effects of LPS challenge on lung fibroblast proliferation, phosphoinositide3-kinase (PI3K)-Akt pathway activation, and phosphatase and tensin homolog (PTEN) expression. Lung fibroblast proliferation, detected by BrdU assay, was unaffected by 1 mug/mL LPS challenge up to 24 hours, but at 72 hours, cell proliferation increased significantly. This proliferation was inhibited by siRNA-mediated TLR4 knockdown or treatment with the PI3K inhibitor, Ly294002. In addition, siRNA-mediated knockdown of TLR4 inhibited the LPS-induced up-regulation of TLR4, down-regulation of PTEN, and activation of the PI3K-Akt pathway (overexpression of phospho-Akt) at 72 hours, as detected by real-time PCR and Western blot analysis. Treatment with the PTEN inhibitor, bpV(phen), led to activation of the PI3K-Akt pathway. Neither the baseline expression nor LPS-induced down-regulation of PTEN in lung fibroblasts was influenced by PI3K activation state. PTEN inhibition was sufficient to exert the LPS effect on lung fibroblast proliferation, and PI3K-Akt pathway inhibition could reverse this process. Collectively, these results indicate that LPS can promote lung fibroblast proliferation via a TLR4 signaling mechanism that involves PTEN expression down-regulation and PI3K-Akt pathway activation. Moreover, PI3K-Akt pathway activation is a downstream effect of PTEN inhibition and plays a critical role in lung fibroblast proliferation. This mechanism could contribute to, and possibly accelerate, pulmonary fibrosis in the early stages of ALI/ARDS.
PLoS ONE 01/2012; 7(4):e35926. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although many studies have shown that isoflurane exposure impairs spatial memory in aged animals, there are no clinical treatments available to prevent this memory deficit. The anticholinergic properties of volatile anesthetics are a biologically plausible cause of cognitive dysfunction in elderly subjects. We hypothesized that pretreatment with the acetylcholinesterase inhibitor donepezil, which has been approved by the Food and Drug Administration (FDA) for the treatment of Alzheimer's disease, prevents isoflurane-induced spatial memory impairment in aged mice. In present study, eighteen-month-old mice were administered donepezil (5 mg/kg) or an equal volume of saline by oral gavage with a feeding needle for four weeks. Then the mice were exposed to isoflurane (1.2%) for six hours. Two weeks later, mice were subjected to the Morris water maze to examine the impairment of spatial memory after exposure to isoflurane. After the behavioral test, the mice were sacrificed, and the protein expression level of acetylcholinesterase (AChE), choline acetylase (ChAT) and α7 nicotinic receptor (α7-nAChR) were measured in the brain. Each group consisted of 12 mice. We found that isoflurane exposure for six hours impaired the spatial memory of the mice. Compared with the control group, isoflurane exposure dramatically decreased the protein level of ChAT, but not AChE or α7-nAChR. Donepezil prevented isoflurane-induced spatial memory impairments and increased ChAT levels, which were downregulated by isoflurane. In conclusions, pretreatment with the AChE inhibitor donepezil prevented isoflurane-induced spatial memory impairment in aged mice. The mechanism was associated with the upregulation of ChAT, which was decreased by isoflurane.
PLoS ONE 01/2011; 6(11):e27632. · 3.53 Impact Factor