Pneumocystis stimulates MCP-1 production by alveolar epithelial cells through a JNK-dependent mechanism
ABSTRACT Pneumocystis carinii is an opportunistic fungal pathogen that causes pneumonia (PCP) in immunocompromised individuals. Recent studies have demonstrated that the host's immune response is clearly responsible for the majority of the pathophysiological changes associated with PCP. P. carinii interacts closely with alveolar epithelial cells (AECs); however, the nature and pathological consequences of the epithelial response remain poorly defined. Monocyte chemotactic protein-1 (MCP-1) is involved in lung inflammation, immunity, and epithelial repair and is upregulated during PCP. To determine whether AECs are an important source of MCP-1 in the P. carinii-infected lung, in vivo and in vitro studies were performed. In situ hybridization showed that MCP-1 mRNA was localized to cells with morphological characteristics of AECs in the lungs of infected mice. In vitro studies demonstrated that P. carinii stimulated a time- and dose-dependent MCP-1 response in primary murine type II cells that was preceded by JNK activation. Pharmacological inhibition of JNK nearly abolished P. carinii-stimulated MCP-1 production, while ERK, p38 MAPK, and TNF receptor signaling were not required. Furthermore, delivery of a JNK inhibitory peptide specifically to pulmonary epithelial cells using a recombinant adenovirus vector blocked the early lung MCP-1 response following intratracheal instillation of infectious P. carinii. JNK inhibition did not affect P. carinii-stimulated production of macrophage inflammatory protein-2 in vitro or in vivo, indicating that multiple signaling pathways are activated in P. carinii-stimulated AECs. These data demonstrate that AECs respond to P. carinii in a proinflammatory manner that may contribute to the generation of immune-mediated lung injury.
- SourceAvailable from: Gautam Sethi[Show abstract] [Hide abstract]
ABSTRACT: Identification of active constituents and their molecular targets from traditional medicine is an enormous opportunity for modern pharmacology. Celastrol is one such compound that was originally identified from traditional Chinese medicine (Thunder of God Vine) almost three decades ago and generally used for the treatment of inflammatory and auto-immune diseases. Celastrol has attracted great interest recently, especially for its potential anti-inflammatory and anti-cancer activities. The anti-inflammatory effects of this triterpene have been demonstrated in animal models of different inflammatory diseases, including arthritis, Alzheimer's disease, asthma, and systemic lupus erythematosus. This triterpene has also been found to inhibit the proliferation of a variety of tumor cells and suppress tumor initiation, promotion and metastasis in various cancer models in vivo. Celastrol's ability to modulate the expression of pro-inflammatory cytokines, MHC II, HO-1, iNOS, NF-κB, Notch-1, AKT/mTOR, CXCR4, TRAIL receptors DR4 and DR5, CHOP, JNK, VEGF, adhesion molecules, proteasome activity, topoisomerase II, potassium channels, and heat shock response has been reported. This review describes the various molecular targets of celastrol, cellular responses to celastrol, and animal studies with celastrol in cancer and other inflammatory disorders.Cancer letters 12/2010; 303(1):9-20. DOI:10.1016/j.canlet.2010.10.025
- [Show abstract] [Hide abstract]
ABSTRACT: Influenza virus leads to acute respiratory disease resulting in seasonal epidemics and periodic pandemics. Little is known about the signaling events that regulate host defense to influenza. One particular pathway, the c-Jun amino-terminal kinase (JNK) cascade is activated following influenza infection and blocking JNK leads to enhanced viral replication. We hypothesize that Mixed Lineage Kinase 3 (MLK3), an upstream regulator of JNK, is involved in the host response to influenza. To test this, wild-type and MLK3-/- mice were infected with pathogenic strain of influenza A virus, A/PR/8/34 (PR8). Although, cellular and humoral immune responses were similar between wild-type and MLK3-/- hosts, the viral load in the lungs was comparatively higher in MLK3-/- mice at day 8 post-infection. Consistent with this, MLK3-/- murine lung fibroblast and epithelial cells had prolonged survival and increased virion production following infection compared to wild-type. These findings support a role for MLK3 in viral production during influenza infection.Virology 02/2010; 400(2):224-32. DOI:10.1016/j.virol.2010.02.001
- [Show abstract] [Hide abstract]
ABSTRACT: Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that plays an important role in the recruitment of macrophages. Although previous studies have demonstrated the importance of MCP-1 in the pathogenesis of diabetic nephropathy (DN) in terms of inflammation, the role of MCP-1 and its receptor (C-C chemokine receptor 2; CCR2) in extracellular matrix (ECM) accumulation under diabetic conditions has been largely unexplored. This study was undertaken to investigate the functional role of the MCP-1/CCR2 system in high glucose-induced ECM (fibronectin and type IV collagen) protein expression in cultured mesangial cells (MCs). Mouse MCs were exposed to medium containing 5.6 mM glucose (NG), NG+24.4 mM mannitol (NG+M), or 30 mM glucose (HG) with or without mutant MCP-1 (mMCP-1), CCR2 small interfering (si)RNA, or CCR2 inhibitor (RS102895). To examine the relationship between MCP-1 and transforming growth factor (TGF)-beta1, MCs were also treated with TGF-beta1 (2 ng/ml) with or without mMCP-1 or CCR2 siRNA. Transient transfection was performed with Lipofectamine 2000 for 24 h. Cell viability was determined by an MTT assay, mouse and human MCP-1 and TGF-beta1 levels by ELISA, and CCR2 and ECM protein expression by Western blotting. Transfections of mMCP-1 and CCR2 siRNA increased human MCP-1 levels and inhibited CCR2 expression, respectively. HG-induced ECM protein expression and TGF-beta1 levels were significantly attenuated by mMCP-1, CCR2 siRNA, and RS102895 (P < 0.05). MCP-1 directly increased ECM protein expression, and this increase was inhibited by an anti-TGF-beta1 antibody. In addition, TGF-beta1-induced ECM protein expression was significantly abrogated by the inhibition of the MCP-1/CCR2 system (P < 0.05). These results suggest that an interaction between the MCP-1/CCR2 system and TGF-beta1 may contribute to ECM accumulation in DN.American journal of physiology. Renal physiology 06/2008; 295(3):F749-57. DOI:10.1152/ajprenal.00547.2007