Rosiglitazone attenuates the metalloprotease/anti-metalloprotease imbalance in emphysema induced by cigarette smoke: involvement of extracellular signal-regulated kinase and NFκB signaling

The TIMP protein family: diverse roles in pathophysiology

The tissue inhibitors of matrix metalloproteinases (TIMPs) are a family of four matrisome proteins classically defined by their roles as the primary endogenous inhibitors of metalloproteinases (MPs). Their functions however are not limited to MP inhibition, with each family member harboring numerous MP-independent biological functions that play key roles in processes such as inflammation and apoptosis. Because of these multifaceted functions, TIMPs have been cited in diverse pathophysiological contexts. Herein, we provide a comprehensive overview of the MP-dependent and -independent roles of TIMPs across a range of pathological conditions. The potential therapeutic and biomarker applications of TIMPs in these disease contexts are also considered, highlighting the biomedical promise of this complex and often misunderstood protein family.

Chinese Herbs and Repurposing Old Drugs as Therapeutic Agents in the Regulation of Oxidative Stress and Inflammation in Pulmonary Diseases

Several pro-inflammatory factors and proteins have been characterized that are involved in the pathogenesis of inflammatory diseases, including acute respiratory distress syndrome, chronic obstructive pulmonary disease, and asthma, induced by oxidative stress, cytokines, bacterial toxins, and viruses. Reactive oxygen species (ROS) act as secondary messengers and are products of normal cellular metabolism. Under physiological conditions, ROS protect cells against oxidative stress through the maintenance of cellular redox homeostasis, which is important for proliferation, viability, cell activation, and organ function. However, overproduction of ROS is most frequently due to excessive stimulation of either the mitochondrial electron transport chain and xanthine oxidase or reduced nicotinamide adenine dinucleotide phosphate (NADPH) by pro-inflammatory cytokines, such as interleukin-1β and tumor necrosis factor α. NADPH oxidase activation and ROS overproduction could further induce numerous inflammatory target proteins that are potentially mediated via Nox/ROS-related transcription factors triggered by various intracellular signaling pathways. Thus, oxidative stress is considered important in pulmonary inflammatory processes. Previous studies have demonstrated that redox signals can induce pulmonary inflammatory diseases. Thus, therapeutic strategies directly targeting oxidative stress may be effective for pulmonary inflammatory diseases. Therefore, drugs with anti-inflammatory and anti-oxidative properties may be beneficial to these diseases. Recent studies have suggested that traditional Chinese medicines, statins, and peroxisome proliferation-activated receptor agonists could modulate inflammation-related signaling processes and may be beneficial for pulmonary inflammatory diseases. In particular, several herbal medicines have attracted attention for the management of pulmonary inflammatory diseases. Therefore, we reviewed the pharmacological effects of these drugs to dissect how they induce host defense mechanisms against oxidative injury to combat pulmonary inflammation. Moreover, the cytotoxicity of oxidative stress and apoptotic cell death can be protected via the induction of HO-1 by these drugs. The main objective of this review is to focus on Chinese herbs and old drugs to develop anti-inflammatory drugs able to induce HO-1 expression for the management of pulmonary inflammatory diseases.

Cigarette Smoke Extract Stimulates MMP-2 Production in Nasal Fibroblasts via ROS/PI3K, Akt, and NF-κB Signaling Pathways

Cigarette smoke exposure has been shown to be associated with chronic rhinosinusitis and tissue remodeling. The present study aimed to investigate the effects of cigarette smoke extract (CSE) on matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) production in nasal fibroblasts and to determine the underlying molecular mechanisms. Primary nasal fibroblasts from six patients were isolated and cultured. After the exposure of fibroblasts to CSE, the expression levels of MMP-2, MMP-9, TIMP-1, and TIMP-2 were measured by real-time PCR, ELISA, and immunofluorescence staining. The enzymatic activities of MMP-2 and MMP-9 were measured by gelatin zymography. Reactive oxygen species (ROS) production was analyzed using dichloro-dihydro-fluorescein diacetate and Amplex Red assays. PI3K/Akt phosphorylation and NF-κB activation were determined by Western blotting and luciferase assay. CSE significantly increased MMP-2 expression and inhibited TIMP-2 expression but did not affect MMP-9 and TIMP-1 expression. Furthermore, CSE significantly induced ROS production. However, treatment with ROS scavengers, specific PI3K/Akt inhibitors, NF-κB inhibitor, and glucocorticosteroids significantly decreased MMP-2 expression and increased TIMP-2 expression. Our results suggest that steroids inhibit CSE-regulated MMP-2 and TIMP-2 production and activation through the ROS/ PI3K, Akt, and NF-κB signaling pathways in nasal fibroblasts. CSE may contribute to the pathogenesis of chronic rhinosinusitis by regulating MMP-2 and TIMP-2 expression.

Suhuang Antitussive Capsules-Ameliorative Effects on LPS-Induced Sputum Obstruction in Mice Through Promoting HGF Secretion

Sputum obstruction is one of common cough complications, which is tightly associated with airway inflammation. Suhuang antitussive capsule (SH Capsule), a classic traditional Chinese medicine prescription, has been used for the treatment of post-cold cough and cough variant asthma in the long clinical application. This study aims to investigate the effects and underlying mechanisms of SH Capsule on LPS-induced sputum obstruction in mice. The results showed that SH Capsule effectively promoted the tracheal phenol red output and mucociliary clearance. SH Capsule also alleviated airway inflammation-mediated mucin 5AC (MUC5AC) level through EGFR-ERK signaling. A further in vivo analysis showed that HGF inhibitor SU11274 abrogated the effects of SH Capsule on MUC5AC, well demonstrating that HGF was required for the beneficial effects of SH Capsule on expectoration in vivo. Moreover, SH Capsule promoted HGF secretion in a colon-dependent manner, which reached lung tissues via blood circulation. Collectively, this study provided new pharmacological data for clinical use of SH Capsule, and proposed a novel mechanism by which SH Capsule was pharmacologically promising for treating sputum obstruction.

Salidroside mitigates skeletal muscle atrophy in rats with cigarette smoke-induced COPD by up-regulating myogenin and down-regulating myostatin expression

OBJECTIVES

The present study aimed at investigating the therapeutic effect of Salidroside on skeletal muscle atrophy in a rat model of cigarette smoking-induced chronic obstructive pulmonary disease (COPD) and its potential mechanisms.

METHODS

Male Wistar rats were randomized, and treated intraperitoneally (IP) with vehicle (injectable water) or a low, medium or high dose of Salidroside, followed by exposure to cigarette smoking daily for 16 weeks. A healthy control received vehicle injection and air exposure. Their lung function, body weights and gastrocnemius (GN) weights, grip strength and cross-section area (CSA) of individual muscular fibers in the GN were measured. The levels of TNF-α, IL-6, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) in serum and GN tissues as well as myostatin and myogenin expression in GN tissues were measured.

RESULTS

In comparison with that in the healthy control, long-term cigarette smoking induced emphysema, significantly impaired lung function, reduced body and GN weights and CSA values in rats, accompanied by significantly increased levels of TNF-α, IL-6 and MDA, but decreased levels of SOD and GSH in serum and GN tissues. Furthermore, cigarette smoking significantly up-regulated myostatin expression, but down-regulated myogenin expression in GN tissues. Salidroside treatment decreased emphysema, significantly ameliorated lung function, increased antioxidant, but reduced MDA, IL-6 and TNF-α levels in serum and GN tissues of rats, accompanied by decreased myostain, but increased myogenin expression in GN tissues.

CONCLUSION

Salidroside mitigates the long-term cigarette smoking-induced emphysema and skeletal muscle atrophy in rats by inhibiting oxidative stress and inflammatory responses and regulating muscle-specific transcription factor expression.

Lipoxin A4 ameliorates alveolar fluid clearance disturbance in lipopolysaccharide-induced lung injury via aquaporin 5 and MAPK signaling pathway

Background

A characteristic of acute lung injury (ALI) is the inflammatory damage of alveolar fluid transport. Lipoxins are endogenous lipids involving in the resolution of inflammation. It is found that lipoxin A4 (LXA4) has the distinct properties to improve the anti-edema and pro-resolution function in inflammation. Since aquaporins (AQPs) have essential roles in the integrity of barrier function during fluid transport, especially AQP5 in the maintaining of the epithelium permeability, the current study is aimed to evaluate the potential role of LXA4 in regulating alveolar fluid clearance (AFC) during fluid transport and the corresponding change of AQP5 in the lung.

Methods

ALI was induced by the lipopolysaccharide (LPS) intraperitoneal injection, and LXA4 treatment was given 8 hours after LPS administration. We investigated changes in the capacity of AFC, pro-inflammatory cytokine concentrations in bronchoalveolar lavage fluid (BALF) and the severity of ALI. Then AQP5 expression in lung tissue and potential regulatory pathways in LPS-induced ALI was explored.

Results

LXA4 treatment was found to inhibit AFC capacity, inflammatory cytokine release, partially, alleviate ALI severity, and restored AQP5 expression partially. Additionally, we found that LXA4 played a protective role by the inhibition of the phosphorylation of p38 and JNK.

Conclusions

In summary, our results suggest that LXA4 plays a protective role in lipopolysaccharide-induced ALI by restoring AFC capacity and upregulating AQP5 expression and inhibiting the phosphorylation of p38 and JNK. These findings suggest potential new mechanism of LXA4 as anti-inflammation therapy for the impairment of alveolar fluid transport in ALI.

A retinoid X receptor partial agonist attenuates pulmonary emphysema and airway inflammation

Background

Retinoid X receptors (RXRs) are members of the nuclear receptor (NR) superfamily that mediate signalling by 9-cis retinoic acid, a vitamin A derivative. RXRs play key roles not only as homodimers but also as heterodimeric partners, e.g., for retinoic acid receptors, vitamin D receptors, and peroxisome proliferator-activated receptors. The NR family may also play important roles in the development of emphysema. However, the role of RXRs in the pathogenesis of emphysema is not well defined.

Methods

We developed a novel RXR partial agonist (NEt-4IB) and investigated its effect and mechanism compared to a full agonist (bexarotene) in a murine model of emphysema. For emphysema induction, BALB/c mice received intraperitoneal cigarette smoke extract (CSE) or intratracheal porcine pancreas elastase (PPE). Treatment with RXR agonists was initiated before or after emphysema induction.

Results

Treatment with NEt-4IB significantly suppressed the increase in static lung compliance and emphysematous changes in CSE-induced emphysema and PPE-induced established and progressive emphysema. NEt-4IB significantly suppressed PPE-induced neutrophilic airway inflammation and the levels of keratinocyte chemoattractant (KC), C-X-C motif ligand5 (CXCL5), interferon (IFN)-γ and IL-17. NEt-4IB also improved the matrix metalloproteinase-9 (MMP-9)/tissue inhibitor of metalloproteinase-1 (TIMP-1) imbalance and the reduced anti-oxidant activity in bronchoalveolar lavage (BAL) fluid. NEt-4IB suppressed PPE-induced vascular endothelial growth factor (VEGF) expression in the airway. Treatment with NEt-4IB and bexarotene significantly suppressed the increase in static lung compliance and emphysematous changes. However, adverse effects of RXR agonists, including hypertriglyceridemia and hepatomegaly, were observed in bexarotene-treated mice but not in NEt-4IB-treated mice.

Conclusion

These data suggest that RXRs play crucial roles in emphysema and airway inflammation, and novel partial RXR agonists could be potential therapeutic strategies for the treatment of PPE- and CSE-induced emphysema.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0963-0) contains supplementary material, which is available to authorized users.

So-Cheong-Ryoung-Tang Attenuates Pulmonary Inflammation Induced by Cigarette Smoke in Bronchial Epithelial Cells and Experimental Mice

So-Cheong-Ryoung-Tang is a traditionally used herbal formula for the treatment of pulmonary diseases in China, Korea, and Japan. We investigated the protective effects of So-Cheong-Ryong-Tang water extract (SCWE) in cigarette smoke concentrate (CSC) stimulated human airway epithelial cell line NCI-H292 and mice exposed cigarette smoke (CS) and lipopolysaccharide (LPS). In the CSC-stimulated NCI-H292 cells, SCWE inhibited proinflammatory cytokines in a concentration-dependent manner, as evidenced by a reduction in their mRNA levels. Also, SCWE significant reduced inducible nitric oxide synthase (iNOS) expression and nuclear factor kappa B (NF-κB) phosphorylation in CSC-stimulated cells. The mice were exposed to CS for 1 h per day (a total of eight cigarettes per day) for 7 days and received LPS intranasally on day 5. The mice were administered a dose of SCWE (100 and 200 mg/kg) 1 h before CS exposure. In in vivo, SCWE decreased the inflammatory cell count and reduced the expression of the proinflammatory cytokines in the broncho-alveolar lavage fluid (BALF) compared with CS and LPS exposed mice. SCWE attenuated inflammatory cell infiltration in airway induced by CS and LPS exposure, and this decrease was accompanied by a reduction in the expression levels of iNOS and MMP-9 in lung tissue. The extract also inhibited the phosphorylation of inhibitor of kappa B alpha (IκBα) and NF-κB induced by CS and LPS exposure in lung tissue. These results suggest that SCWE may effectively inhibit airway inflammatory responses induced by CS and LPS exposure via the NF-κB pathway. Therefore, SCWE may be a potential treatment for airway inflammatory diseases, such as chronic obstructive pulmonary disease (COPD).

Peroxisome Proliferator-Activated Receptor (PPARγ) Plays a Protective Role in Cigarette Smoking-Induced Inflammation via AMP-Activated Protein Kinase (AMPK) Signaling

BACKGROUND Cigarette smoking is a well-known risk factor in multiple chronic pulmonary diseases. This study aims to investigate the role of peroxisome proliferator-activated receptor (PPAR) g in cigarette smoking-induced inflammation. MATERIAL AND METHODS Cigarette smoking extract (CSE) was employed to induce inflammation in bronchial epithelial cells (BECs). After CSE administration, several autophagy-related proteins (Beclin1, autophagy-related gene (ATG)5, ATG7, p62, and LC3) and PPARg levels were examined by western blot. Subsequently, PPARg agonists and antagonist were used to treat CSE-induced BECs, several inflammatory factors (interleukin (IL)-6, IL-8, inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2) and autophagy-related proteins were detected to measure the inflammatory and autophagy levels. Then LC3 knockdown was performed to verify the role of autophagy in CSE-induced inflammation. Finally, the AMP-activated protein kinase (AMPK) and its downstream S6 kinase (S6K) were detected in CSE-stimulated BECs. RESULTS CSE administration caused insufficient autophagy and the decrease of PPARγ in BECs. The PPARγ agonists ameliorate the CSE-induced inflammation and promote the autophagy development, evidenced by the changes of inflammatory factors and autophagy-related proteins. Loss-of-function experiments demonstrated that the PPARγ played an anti-inflammatory role in an autophagy-dependent manner. In addition, CSE administration inactivated the AMPK signaling, which was restored by PPARγ agonists. The effects of PPARγ agonists on inflammation and autophagy could be abolished by AMPK inhibitor. CONCLUSIONS We demonstrated that PPARγ played a protective role in CSE-induced inflammation and autophagy by activating AMPK signaling in BECs, which may provide investigation basis for clinical therapy of chronic pulmonary diseases.

Increased matrix metalloproteinase-9 to tissue inhibitor of metalloproteinase-1 ratio in smokers with airway hyperresponsiveness and accelerated lung function decline

Background

Airway hyperresponsiveness (AHR) is associated with airway inflammation and a rapid decline in lung function and is a predictor of future risk of COPD among smokers. Alveolar macrophages (AMs) from patients with COPD release a greater amount of matrix metalloproteinase (MMP)-9. We hypothesized that the imbalance between MMP-9 and tissue inhibitor of metalloproteinase-1 (TIMP-1) is related to AHR in smokers.

Patients and methods

Healthy smokers with AHR (AHR + S) or smokers without AHR (AHR − S; divided according to a methacholine challenge test) and nonsmokers without AHR (AHR − NS) were enrolled. Spirometry was performed during enrollment and repeated after 5 years. Initially, AMs recovered from bronchoalveolar lavage (BAL) fluid were cultured in the presence of p38 mitogen-activated protein kinase (MAPK) inhibitor (SB203580), MAPK kinase (MEK) 1/2 (the MEK of extracellular signal-regulated kinase [ERK] inhibitor, PD98059), or medium alone for 24 h. The release of MMP-9 and TIMP-1 in culture supernatants was measured by enzyme-linked immunosorbent assay.

Results

A greater reduction in forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC), FEV₁ (as a percentage of the predicted value [%pred]), and maximal mid-expiratory flow (MMEF) was observed among AHR + S in the 5-year period. There was a higher proportion of neutrophils and a lower proportion of AMs in BAL fluid recovered from AHR + S. Compared to AMs from AHR − NS and AHR − S, AMs from nonsmokers with AHR (AHR + NS) released more MMP-9 and less TIMP-1, with an increase in MMP-9/TIMP-1 ratios. The MMP-9/TIMP-1 ratio in smokers was positively correlated with the annual decline in FEV₁%pred, FVC%pred, and MMEF%pred. Both SB203580 and PD98059 significantly reduced MMP-9, but not TIMP-1, from AMs of smokers.

Conclusion

AMs of AHR + NS produce excessive MMP-9 over TIMP-1, which may be a predictor of the development of airway obstruction. Inhibition of p38 MAPK and ERK suppresses the generation of MMP-9 by AMs from smokers.

GHK Peptide Inhibits Bleomycin-Induced Pulmonary Fibrosis in Mice by Suppressing TGFβ1/Smad-Mediated Epithelial-to-Mesenchymal Transition

Objective: Idiopathic pulmonary fibrosis is an irreversible and progressive fibrotic lung disease that leads to declines in pulmonary function and, eventually, respiratory failure and has no effective treatment. Gly-His-Lys (GHK) is a tripeptide involved in the processes of tissue regeneration and wound healing and has significant inhibitory effects on transforming growth factor (TGF)-β1 secretion. The effect of GHK on fibrogenesis in pulmonary fibrosis and the exact underlying mechanism have not been studied previously. Thus, this study investigated the effects of GHK on bleomycin (BLM)-induced fibrosis and identified the pathway that is potentially responsible for these effects.

Methods: Intratracheal injections of 3 mg/kg BLM were administered to induce pulmonary fibrosis in C57BL/6 mice. GHK was administered intraperitoneally at doses of 2.6, 26, and 260 μg/ml/day every other day from the 4th to the 21st day after BLM instillation. Three weeks after BLM instillation, pulmonary injury and pulmonary fibrosis was evaluated by the hematoxylin-eosin (HE) and Masson’s trichrome (MT) staining. Chronic inflammation index was used for the histological assessments by two pathologists blindly to each other. Tumor necrosis factor (TNF)-α and IL-6 levels in BALF and myeloperoxidase (MPO) activity in lung extracts were measured. For the pulmonary fibrosis evaluation, the fibrosis index calculated based on MT staining, collagen deposition and active TGF-β1 expression detected by ELISA, and the expression of TGF-β1, α-smooth muscle actin (SMA), fibronectin, MMP-9, and TIMP-1 by western blotting. The epithelial mesenchymal transition index, E-cadherin, and vimentin was also detected by western blot. The statistical analysis was performed by one-way ANOVA and the comparison between different groups were performed.

Results: Treatment with GHK at all three doses reduced inflammatory cell infiltration and interstitial thickness and attenuated BLM-induced pulmonary fibrosis in mice. GHK treatment significantly improved collagen deposition, and MMP-9/TIMP-1 imbalances in lung tissue and also reduced TNF-α, IL-6 expression in bronchoalveolar lavage fluid (BALF) and MPO in lung extracts. Furthermore, GHK reversed BLM-induced increases in TGF-β1, p-Smad2, p-Smad-3 and insulin-like growth factor-1 (IGF-1) expression.

Conclusion: GHK inhibits BLM-induced fibrosis progression, the inflammatory response and EMT via the TGF-β1/Smad 2/3 and IGF-1 pathway. Thus, GHK may be a potential treatment for pulmonary fibrosis.

Peroxisome proliferator-activated receptor-γ in induced sputum is correlated with MMP-9/TIMP-1 imbalance and formation of emphysema in COPD patients

Background

The development of chronic obstructive pulmonary disease (COPD) is modulated by the symmetry of matrix metalloproteinases (MMPs) and the counter-acting tissue inhibitors of metalloproteinases (TIMPs). We investigated the interaction between peroxisome proliferator-activated receptor gamma (PPARγ) expression and the imbalance of MMP-9/TIMP-1 in the induced sputum of stable COPD patients.

Methods

Sixty-six stable COPD patients were enrolled and the induced sputum samples were gathered. The correlation between PPARγ and other index, including MMP-9, TIMP-1, pulmonary function and the index of emphysema-the percentage of low attenuation area (LAA%), was analyzed.

Results

PPARγ and TIMP-1 concentrations were decreased and the concentration of MMP-9 and the ratio of MMP9/TIMP1 were enhanced in the induced sputum of COPD patients, compared to the healthy controls. Among COPD patients, those with worse lung function or patients with emphysema exhibited increased MMP-9 expression with decreased TIMP-1 and PPARγ expression. Besides, the concentration of PPARγ of the induced sputum was correlated with the forced expiratory volume in one second percentage (FEV1%) positively and the expression of TIMP-1; while it was negatively correlated with the residual volume (RV), RV/total lung capacity (TLC), LAA%, and MMP-9 expression.

Conclusions

Our findings reveal the protective role of PPARγ in the maintenance of the dynamic balance of MMP-9/TIMP-1 in COPD, thus providing evidence on which to base the potential COPD treatment.

Decreased levels of irisin, a skeletal muscle cell-derived myokine, are related to emphysema associated with chronic obstructive pulmonary disease

Background

Cigarette smoking-induced oxidant–antioxidant imbalance is a factor that contributes to the pathogenesis of COPD through epithelial cell apoptosis. Irisin is a skeletal muscle cell-derived myokine associated with physical activity. Irisin is also known to decrease oxidant-induced apoptosis in patients with diabetes mellitus. However, the correlation between irisin and emphysema in COPD and its role in epithelial cell apoptosis remains unknown.

Subjects and methods

Forty patients with COPD were enrolled in this study. Pulmonary function tests and measurements of the percentage of low-attenuation area on high-resolution computed tomography images were performed, and the results were evaluated for correlation with serum irisin levels. The effect of irisin on cigarette-smoke extract-induced A549 cell apoptosis and the expression of Nrf2, a transcription factor for antioxidants, was also examined in vitro.

Results

Serum irisin levels were significantly correlated with lung diffusing capacity for carbon monoxide divided by alveolar volume (r=0.56, P<0.01) and percentage of low-attenuation area (r=−0.79, P<0.01). Moreover, irisin significantly enhanced Nrf2 expression (P<0.05) and reduced cigarette-smoke extract-induced A549 cell apoptosis (P<0.05).

Conclusion

Decreased serum irisin levels are related to emphysema in patients with COPD and involved in epithelial apoptosis, resulting in emphysema. Irisin could be a novel treatment for emphysema in patients with COPD.

Human lung fibroblasts produce proresolving peroxisome proliferator-activated receptor-γ ligands in a cyclooxygenase-2-dependent manner

Human lung fibroblasts (HLFs) act as innate immune sentinel cells that amplify the inflammatory response to injurious stimuli. Here, we use targeted lipidomics to explore the hypothesis that HLFs also play an active role in the resolution of inflammation. We detected cyclooxygenase-2 (COX-2)-dependent production of both proinflammatory and proresolving prostaglandins (PGs) in conditioned culture medium from HLFs treated with a proinflammatory stimulus, IL-1β. Among the proresolving PGs in the HLF lipidome were several known ligands for peroxisome proliferator-activated receptor-γ (PPARγ), a transcription factor whose activation in the lung yields potent anti-inflammatory, antifibrotic, and proresolving effects. Next, we used a cell-based luciferase reporter to confirm the ability of HLF supernatants to activate PPARγ, demonstrating, for the first time, that primary HLFs activated with proinflammatory IL-1β or cigarette smoke extract produce functional PPARγ ligands; this phenomenon is temporally regulated, COX-2- and lipocalin-type PGD synthase-dependent, and enhanced by arachidonic acid supplementation. Finally, we used luciferase reporter assays to show that several of the PGs in the lipidome of activated HLFs independently activate PPARγ and/or inhibit NFκB. These results indicate that HLFs, as immune sentinels, regulate both proinflammatory and proresolving responses to injurious stimuli. This novel endogenous resolution pathway represents a new therapeutic target for globally important inflammatory diseases such as chronic obstructive pulmonary disease.

Ursolic acid reduces the metalloprotease/anti-metalloprotease imbalance in cerebral ischemia and reperfusion injury

BACKGROUND

Activators of PPARs, particularly PPARγ, may be effective neuroprotective drugs against inflammatory responses in cerebral ischemia and reperfusion injury. Ursolic acid (UA) may act as a PPARγ agonist and serve as an anti-inflammatory agent. In this study, we used a rat middle cerebral artery occlusion and reperfusion model to examine how UA acts as a neuroprotective agent to modulate the metalloprotease/anti-metalloprotease balance.

METHODS

The middle cerebral artery occlusion and reperfusion model (occlusion for 2 hours followed by reperfusion for 48 hours) was induced in male Sprague Dawley rats. UA was administered intragastrically 0.5, 24, and 47 hours after reperfusion. Bisphenol A diglycidyl ether (a PPARγ antagonist) was intraperitoneally administered 1, 24.5, and 47.5 hours after reperfusion. Forty-eight hours after reperfusion, neurological deficits and infarct volume were estimated. The PPARγ level and the metalloprotease/anti-metalloprotease balance were examined by Western blotting and immunohistochemistry. The activation of MAPK signaling pathways was also assessed.

RESULTS

UA-treated (5, 10, or 20 mg/kg) rats showed significant improvement in neurological deficit score, infarct volume, and the number of intact neurons compared with control rats (P<0.01). Both the PPARγ protein level and the percentage of PPARγ-positive cells were increased in the UA-treated groups (P<0.01). Compared with the control group, the UA-treated groups exhibited reduced protein levels of MMP2, MMP9, and activated MAPKs (P<0.01) but an increased level of TIMP1 (P<0.01). UA exerted its protective effects in a dose-dependent manner. Co-treatment with UA and bisphenol A diglycidyl ether completely abolished the UA-induced changes in PPARγ expression; however UA continued to exert a significant but partial neuroprotective effect.

CONCLUSION

UA can act as a PPARγ agonist to improve the metalloprotease/anti-metalloprotease balance, possibly by inhibiting the activation of the MAPK signaling pathway, thereby attenuating cerebral ischemia and reperfusion injury. Therefore, UA may serve as a novel neuroprotective therapeutic agent.