Ji-Qiang Chen

Inhibition of Rac activity alleviates lipopolysaccharide-induced acute pulmonary injury in mice

BACKGROUND Rac small GTPases play important roles in cytoskeleton and many cell functions including cell cycle, cell growth, cell adhesion and gene transcription. Here, we investigated the roles of Rac including Rac1 and Rac2 in lipopolysaccharide (LPS)-induced pulmonary injury. METHODS After LPS was intratracheally instilled to lungs in mice, Rac, CDC42 and RhoA activation assay by pull-down and West blot, inflammatory cell infiltration assay by counting cell numbers and lung histological examination, pro-inflammatory mediator mRNA expression assay by quantitative RT-PCR, measurement of myeloperoxidase (MPO) activity, Evans Blue and albumin accumulation by spectrophotometry were performed to evaluate the roles of Rac in pulmonary injury by using its specific inhibitor, NSC23766. RESULTS LPS challenge led to increases of both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and intraperitoneal administration with NSC23766 inhibited both Rac1 and Rac2, but not CDC42 or RhoA activities. Treatment with NSC23766 at 1 or 3mg/kg not only reduced the inflammatory cells infiltration and MPO activities, but also inhibited pro-inflammatory mediators, tumor necrosis factor-α and interleukin-1β, mRNA expression. Moreover, in vitro neutrophil migration assay and in vivo microvascular permeability assay indicated that NSC23766 not only inhibited neutrophil transwell migration toward a chemoattractant, fMLP, but also reduced Evans Blue and albumin accumulation in LPS-challenged lungs. LPS activated both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and specific inhibition of Rac activities by NSC23766 effectively alleviated LPS-induced injury. GENERAL SIGNIFICANCE Rac could be a potential target for therapeutic intervention of pulmonary inflammation.

Zl-n-91, a selective phosphodiesterase 4 inhibitor, suppresses inflammatory response in a COPD-like rat model.

Chronic obstructive pulmonary disease (COPD) is defined as a disease state characterized by poorly reversible airflow limitation induced by cigarette smoking and/or other noxious particle and gases. Phosphodiesterase (PDE) 4 inhibitors are known to elevated cAMP concentrations in inflammatory cells, leading to inhibition of inflammatory response, relaxation of smooth muscle in the airway, and modulation of sensory nerves in the lung as well. To investigate whether Zl-n-91, a new selective PDE4 inhibitor, could decrease inflammation and improve lung function in a COPD-like rat model, male Sprague-Dawley rats are used to challenge with lipopolysaccharide (LPS) and cigarette smoking (CS) exposure to induce COPD-like animal model. Administration of Zl-n-91 at different dosages results in decreases of inflammatory cell in bronchoalveolar lavage fluid (BALF) as compared with vehicle treatment. Zl-n-91 at 0.03, 0.3 or 3mg/kg not only dose-dependently inhibited PDE4 activity, but also decreased MMP-9 level in lungs and improved dynamic compliance (C(dyn)) as compared with vehicle treatment. Therefore, Zl-n-91 could inhibit inflammatory responses in rats after cigarette smoking exposure and LPS challenge, and it could be of some therapeutic potential as an alternative medicine in treatment of pulmonary diseases such as COPD.

Action of a Novel PDE4 inhibitor ZL-n-91 on lipopolysaccharide-induced acute lung injury

In the present study, we investigated the effect of classic PDE4 inhibitor rolipram and novel PDE4 inhibitor ZL-n-91 on LPS-induced acute lung injury (ALI) in mice and its mechanism. ALI was induced in ICR mice by instilling intratracheally with LPS, and mice were divided into seven groups: control (Saline), LPS group, ZL-n-91 (3 microg, 10 microg, and 30 microg kg(-1), ip), Rolipram (1.0 mg kg(-1), ip) and dexamethasone (0.5 mg kg(-1), ip). After the 6h of instilling intratracheally with LPS in mice, total leukocyte number, neutrophil number and protein content in BALF increased rapidly, a large number of neutrophil infiltration around the pulmonary vessel and airway, the lung wet weight/dry weight (w/d)ratio raised significantly. MPO activity, TNF-alpha level and cAMP-PDE, PDE4 activity in lung homogenate raised significantly. P(a)O(2), P(a)CO(2) and PH value in peripheral arterial blood also changed obviously, P(a)O(2) and PH value dropped slightly and P(a)CO(2) increased significantly in LPS group. ZL-n-91 (3 microg, 10 microg, 30 microg kg(-1)) dose-dependently reduced the total leukocyte number, neutrophil number and total protein content in BALF, MPO activity, TNF-alpha level and cAMP-PDE, PDE4 activity in lung homogenate, but the effect of ZL-n-91 in pathological changes and lung wet w/d ratio is slight; Rol and Dex significantly reduced lung wet w/d ratio and improved pathological changes, neutrophil around the pulmonary vessel and airway significantly reduced, symptoms of lung edema relieved; The PH value, P(a)O(2) and P(a)CO(2) in ZL-n-91 high dosage group and Rol group had changes, but there was no significant difference compared with LPS group or saline group; After the administration, the righting reflex recovery time significantly shorten in every group of ZL-n-91. the righting reflex recovery time of Rol group was similar with ZL-n-91 30 microg kg(-1) group, while Dex group was similar with saline group. The present study confirms that the inhibitory effect of ZL-n-91(30 microg kg(-1)) on the inflammatory reactivity, including inhibition of inflammatory cell and protein exudation, MPO and PDE4 activity, improvement of the blood gas, those effects were equivalent with rolipram 1 mg kg(-1), and suggested that ZL-n-91 was stronger than rolipram in PDE4 inhibition. So we speculated that ZL-n-91 may have stronger therapeutic potential for treatment of inflammatory disease than rolipram, meantime have stronger nervous system effect than rolipram.

Changes of 5-lipoxygenase pathway and proinflammatory mediators in cerebral cortex and lung tissue of sensitized rats.

AbstractAim:To explore the change of 5-lipoxygenase (5-LO) pathway expression and proinflammatory mediators level of lung tissue and cerebral cortex, and the possible regulatory mechanism through central nervous 5-LO pathways to pulmonary inflammatory status in antigen repeated challenged rats.Methods:Four groups of rats were treated as control, asthma model, asthma model treatment with dexamethasone (DXM, 0.5 mg/kg, ip) and ketotifen (5 mg/kg, ig). Tumor necrosis factor (TNF)-α, interleukin (IL)-4, interferon (IFN)-γ, and nitric oxide (NO) were detected by ELISA kits. The mRNA expression of 5-LO and LTA4-hydrolase (LTA4-H) was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), and the protein content of 5-LO was measured by Western blot.Results:Increase of TNF-α, IL-4, NO level, and decrease of IFN-γ level in bronchoalveolar lavage fluid (BALF) and cerebral cortex in sensitized rats were shown after repeated antigen challenge. The expression of 5-LO and LTA4-H mRNA, and 5-LO protein levels were increased in lung tissue and cerebral cortex in asthma rats. In comparison with the asthma model, DXM significantly inhibited the increase of cytokine levels and the expression of 5-LO pathway enzyme (P0.05). Ketotifen also inhibited the increase of TNF-α level and 5-LO pathway enzyme expression in lung and cerebral cortex, but had no effect on the level of NO, IL-4, and IFN-γ.Conclusion:The correlative increase of 5-LO pathway enzyme expression and proinflammatory mediators of brain may have a regulatory effect on pulmonary inflammation in asthma.

Effects of local anesthetics on contractions of pregnant and non-pregnant rat myometrium in vitro.

In order to determine whether local anesthetics directly affect the propagation and strength of myometrial contractions, we compared the effects of bupivacaine, ropivacaine, lidocaine and tetracaine on the contractions of myometrium isolated from pregnant and non-pregnant rats. Full-thickness myometrial strips were obtained from 18- to 21-day pregnant and non-pregnant Sprague-Dawley rats and incubated in an organ bath. When spontaneous contractions became regular, strips were exposed to cumulative concentrations of the four local anesthetics ranging from 0.01 to 300 μmol/L and the amplitude and frequency of contraction were recorded. All four compounds caused a concentration-dependent inhibition of the contractility of pregnant and non-pregnant uterine muscle. In pregnant myometrium, the concentration that caused 50% inhibition (IC(50)) was 100 μmol/L for bupivacaine, 157 μmol/L for ropivacaine, > 1000 μmol/L for lidocaine, and 26.3 μmol/L for tetracaine. In non-pregnant myometrium, the IC(50) was 26.9 μmol/L for bupivacaine, 40 μmol/L for ropivacaine, 384 μmol/L for lidocaine, and 7.4 μmol/L for tetracaine. These results suggested that local anesthetics do inhibit myometrial contractions in pregnant and non-pregnant rats in a concentration-dependent manner.

Effects of Inactivated Bordetella pertussis on Phosphodiesterase in the Lung of Ovalbumin Sensitized and Challenged Rats

This paper indicated that inactivated Bordetella pertussis (iBp) can enhance the lung airway hyperreactivity of the rats sensitized and challenged with OVA. The mechanisms were involved in the upregulation of cAMP-PDE activity and PDE4A, PDE4D, and PDE3 gene expression in the lungs. But only PDE4 activity was different between the OVA and OVA+iBp groups, and PDE4D expression was significantly increased in iBp rats alone. So, our data suggested that cosensitization with OVA and iBp affects lung airway reactivity by modulating the lung cAMP-PDE activity and PDE4D gene expression.

Potential role of phosphodiesterases in the development of multiple organ dysfunction

Background. Multiple organ dysfunction syndrome (MODS) is the commonest cause of death in intensive care units. Growing recognition of this disease in the last 30 years may be due to advances in early resuscitation unmasking delayed sequelae in those who would have died previously. MODS occurs after shock of various etiologies, especially sepsis, and may be the result of overactivated systemic inflammation. As yet, therapies directed at preventing or improving MODS have not dramatically altered the outcomes. Phosphodiesterases (PDEs) are enzymes primarily responsible for the breakdown of the intracellular second messengers adenosine 3′,5′-cyclic monophosphate and guanosine 3′,5′-cyclic monophosphate. Although these enzymes were initially described many years ago, new families and subtypes of PDEs continue to be discovered. There is also a wide variation in the distribution of PDEs among tissues or species. This tissue-specific distribution has led to differential pharmacologic actions of PDE inhibitors. E...