Neonatal Streptococcus Pneumoniae pneumonia induces airway SMMHC expression through HMGB1/TLR4/ERK.

BACKGROUND: Our previous study showed that neonatal S. pneumoniae pneumonia promoted airway smooth muscle myosin heavy chain (SMMHC) expression and AHR development. Researches demonstrated HMGB1, TLR4 and ERK are involved in smooth muscle contractile protein expression, so we hypothesis that HMGB1/TLR4/ERK pathway participated in airway SMMHC overexpression in neonatal S. pneumoniae pneumonia model. METHOD: Neonatal (1-week-old) BALB/c mice were intranasal inoculated with D39 to establish non-lethal S. pneumoniae pneumonia model. TLR4 was inhibited 2 weeks after infection with TLR4 specific inhibitor (TAK-242). Five weeks after infection, the bronchoalveolar lavage fluid (BALF) and lungs of neonatal S. pneumoniae pneumonia and mock infection mice with or without TLR4 inhibition were collected to assess the expressions of HMGB1, TLR4 and p-ERK1/2. Airway Hyperresponsiveness (AHR) of the three groups was determined by whole-body plethysmograph. RESULTS: Our results demonstrated that neonatal S. pneumoniae pneumonia promoted HMGB1/TLR4 production, SMMHC expression and AHR development significantly, with ERK1/2 phosphorylation decreased remarkably. TLR4 inhibition after pneumonia significantly increased ERK1/2 phosphorylation, reversed airway SMMHC overexpression and alleviated AHR. CONCLUSION: Neonatal S. pneumoniae pneumonia promotes airway SMMHC expression and AHR through HMGB1/TLR4/ERK.

The modulation of large airway smooth muscle phenotype and effects of epidermal growth factor receptor inhibition in the repeatedly allergen-challenged rat.

Allergen challenges induce airway hyperresponsiveness (AHR) and increased airway smooth muscle (ASM) mass in the sensitized rat. Whether the remodeled ASM changes its phenotype is uncertain. We examined, in sensitized Brown Norway rats, the effects of multiple ovalbumin (Ova) challenges on ASM remodeling and phenotype and the role of the epidermal growth factor receptor (EGFR) in these processes. Rats were sensitized with Ova and challenged three times at 5-day intervals with phosphate-buffered saline or Ova and pretreated with the EGFR inhibitor AG-1478 (5 mg/kg) or its vehicle dimethyl sulfoxide. Ova challenges increased ASM mass in all-sized airways and in large airway mRNA expression of smooth muscle myosin heavy chain (sm-MHC), assessed by laser capture. Myosin light chain kinase and the fast myosin isoform SM-B mRNA expressions were not affected. Ova induced AHR to methacholine, and, based on the constant-phase model, this was largely attributable to the small airways and lung derecruitment at 48 h that recovered by 1 wk. The EGFR ligands amphiregulin and heparin-binding epidermal growth factor (HB-EGF) were increased in bronchoalveolar lavage fluid at 48 h after Ova exposure. AG-1478 inhibited AHR and prevented ASM growth. Epithelial gene expression of EGFR, HB-EGF, matrix metalloproteinase (MMP)-9, Gro-α, and transforming growth factor-ß was unaffected by Ova challenges. We conclude that EGFR drives remodeling of ASM, which results from repeated Ova challenge. Furthermore, the latter results in excessive small airway and, to a lesser degree, large airway narrowing to methacholine, and large airway gene expression of contractile protein is conserved.

Vascular smooth muscle cell differentiation in human cerebral vascular malformations.

OBJECTIVE: The pathogenesis of central nervous system vascular malformations likely involves the abnormal assembly, differentiation of vascular smooth muscle cells (VSMC), or both in association with dysmorphic vessel wall. We hypothesize that intracranial arteriovenous malformations (AVMs) and cerebral cavernous malformations (CCMs) exhibit distinct patterns of expression of molecular markers of differentiation and maturity of VSMCs. We further speculate that the unique VSMC phenotype in the different lesions is not necessarily maintained in cell culture. METHODS: Paraffin-embedded sections of five AVMs, CCMs, and control brain tissues were stained immunohistochemically with antibodies to alpha-smooth muscle actin (alpha-SMA), myosin heavy chain, and smoothelin, a novel marker for contractile VSMC phenotype. Large (> or =100 microm) and small (<100 microm) vessels were counted and assessed for immunoexpression of each protein, then categorized according to expression of one or more of these markers. Cultured nonendothelial cells isolated from four other excised AVM and CCM lesions were assessed for immunoexpression of the same antibodies. RESULTS: Alpha-SMA was universally expressed in all vessels in AVMs and in control brains. It was expressed in the subendothelial layer of 97% of large caverns and 85% of small caverns and in scattered intercavernous connective tissue fibrocytes in CCMs. Myosin heavy chain was expressed in the majority of brain and AVM vessels, except for normal veins, and in the subendothelial layer of more than half of the caverns in CCMs. Smoothelin expression was less prevalent in large vessels in AVMs than in control brains and was not found in any caverns in CCMs (large vessels in control brains, 40.9%; AVMs, 21.9%; CCMs, 0%; P < 0.0001). Cultured AVM and CCM nonendothelial cells expressed alpha-SMA, but myosin heavy chain was expressed weakly in cells from only one CCM. Smoothelin was negative in all cells. CONCLUSION: We describe vessels with various stages of VSMC differentiation in AVMs and CCMs. The subendothelial layer of CCMs commonly expresses alpha-SMA and less commonly expresses myosin heavy chain. Expression of smoothelin was less prevalent in large AVM vessels than in normal brain, which may reflect the loss of contractile property associated with hemodynamic stress. It is difficult to evaluate VSMC differentiation in culture because of phenotypic change.