Expression and role of adiponectin receptor 1 in lipopolysaccharide-induced proliferation of cultured rat adventitial fibroblasts

Role of Adiponectin Peptide I (APNp1) in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disease that can cause central vision loss, particularly in the elderly population. There are 2 classes of AMD, wet-type and dry-type. Wet-type involves excess angiogenesis around the macula, referred to as choroidal neovascularization (CNV). This can result in leaky vessels, often causing more severe vision loss than dry-type AMD. Adiponectin peptide 1 (APNp1) has been shown to slow the progression of CNV. Here, we used a mouse model and FITC-labeled APNp1 to determine if APNp1 could be delivered effectively as an eye drop. Our experiment revealed that topically applied FITC-APNp1 could reach the macula of the eye, which is crucial for treating wet-type AMD. We also tested delivery of APNp1 via injection of an adeno-associated virus (AAV) vector in a mouse model of CNV. AAV is a harmless virus easy to manipulate and is very often used for protein or peptide deliveries. Results revealed an increase in the expression of APNp1 in the retina and choroid over a 28-day period. Finally, we investigated the mechanism by which APNp1 affects CNV by examining the expression of adiponectin receptor 1 (AdipoR1) and proliferating cell nuclear antigen (PCNA) in the retinal and choroidal tissue of the mouse eyes. AdipoR1 and PCNA were overexpressed in these tissues in mice with laser-induced CNV compared to naïve mice. Based on our data shown here, we think it will enhance our understanding of APNp1 as a therapeutic agent for wet-type AMD and possible treatment alternatives that could be more beneficial for patients.

Adiponectin inhibits the activation of lung fibroblasts and pulmonary fibrosis by regulating the nuclear factor kappa B (NF-κB) pathway

Idiopathic pulmonary fibrosis (IPF) is a common pulmonary interstitial disease with a high mortality rate. Adiponectin (APN) is reportedly an effective therapy for fibrosis-related diseases. This study aimed to investigate the potential effects of APN on IPF. Male BALB/c mice were injected with bleomycin (BLM) and treated with different doses of APN (0.1, 0.25, and 0.5 mg/kg). The body weights of the mice were recorded. Immunohistochemical, hematoxylin and eosin, and Masson staining were performed to evaluate pulmonary histopathological changes. Enzyme-linked immunosorbent assay (ELISA) and western blotting were performed to assess tissue inflammation. The human lung fibroblasts HELF were stimulated with TGF-β1 and treated with different doses of APN (2.5, 5, and 10 μg/ml). Cell proliferation, inflammation, and fibrosis were determined by MTT assay, EdU assay, colony formation assay, ELISA, and western blotting. APN significantly attenuated BLM-induced body weight loss, alveolar destruction, and collagen fiber accumulation in mice (p < 0.05). APN decreased the expression of α-SMA and collagen I and reduced the concentration of TNF-α, IL-6, IL-1β, and IL-18 in lung tissues (p < 0.05). In TGF-β1-treated HELF cells, cell proliferation and colony formation were inhibited by APN (p < 0.05). Additionally, the expression of α-SMA, collagen I, and pro-inflammatory cytokines were suppressed by APN (p < 0.05). APN inhibited the phosphorylation of IκB and nuclear translocation of p65. In conclusion, these findings suggest that APN is an effective agent for controlling IPF progression. The antifibrotic effects of APN might be mediated via inhibiting the NF-κB signaling pathway.

Atorvastatin suppresses vascular hypersensitivity and remodeling induced by transient adventitial administration of lipopolysaccharide in rats

Background

The phenotypic transition of vascular smooth muscle cells (VSMCs) from a contractile to a proliferative state markedly affects the pathophysiology of cardiovascular diseases. The adventitial inflammation can promote neointimal formation and vascular remodeling. We used direct administration of lipopolysaccharide (LPS) into the periphery of the carotid artery to investigate the influence of transient adventitial inflammation on vascular remodeling and its potential mechanism.

Methods

Male 15-week-old Wistar rats were randomly assigned to four groups with six rats in each group. The rats of groups I and II were administered distilled water, and group III and IV were treated with fasudil and atorvastatin respectively. All treatments were given daily for 11 days. On day 8, the adventitia in group I was injected with 5 µL sterile saline, and the group II-IV were injected with 5 µL sterilized LPS. The carotid blood flow and femoral blood pressure were measured in vivo, and the thickness of vascular intima and middle layer was measured in vitro. Serum interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) were determined using enzyme-linked immunosorbent assay (ELISA) assay. And the Rho-associated coiled-coil-containing protein kinase 2 (ROCK2), myosin phosphatase target subunit 1 (MYPT1), myosin light chain (MLC), myocardin, SM-α actin or glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were detected by western blot. The comparisons were made by one-way analysis of variance with Bonferroni's post hoc test. A value of P<0.05 was considered to represent a statistically significant difference.

Results

Transient adventitial inflammation induced by LPS caused no obvious change in basal blood flow, but did lead to vascular hypersensitivity to serotonin. Morphological examinations revealed that the medial layer was the only domain affected, and showed VSMC proliferation and rearrangement. LPS increased serum IL-6 and TNFα contents, ROCK2 expression and activity, and caused changes in the expression levels of some stereotypical VSMC genes. Similar to the Rho-kinase inhibitor fasudil, atorvastatin completely restored the morphological alterations, even increased blood flow.

Conclusions

Our study confirms the beneficial effect of atorvastatin on the vascular system in terms of morphology and function.

Macrophage migration inhibitory factor enhances lipopolysaccharide-induced fibroblast proliferation by inducing toll-like receptor 4

BACKGROUND

Fibroblast proliferation is a common manifestation of chronic inflammatory diseases, including rheumatoid arthritis (RA), Crohn's disease and ulcerative colitis, etc. To alleviate patient suffering, the mechanism underlying fibroblast proliferation should be elucidated.

METHODS

CCK-8 assay was used to assess the stimulatory effect of LPS and macrophage migration inhibitory factor (MIF) on fibroblast proliferation. Then, TLR4 expression on fibroblast cell membrane was carried out by confocal scanning microscopy. Finally, real-time fluorescent quantitative PCR and flow cytometry were applied to determine the expression of TLR4 after MIF challenge.

RESULTS

LPS alone directly stimulated the fibroblast proliferation. In addition, MIF showed co-stimulatory effect on LPS-induced fibroblast proliferation. Interestingly, fibroblast overtly expressed TLR4 without stimulation. After MIF stimulation, real-time PCR showed TLR4 mRNA levels were increased by about 33% in the fibroblasts; in agreement, TLR4 expression on the fibroblast membrane was increased by about 20%, as shown by flow cytometry.

CONCLUSIONS

These findings indicated MIF elevates TLR4 expression in fibroblast, enhancing LPS-induced cell proliferation.

Adventitial fibroblasts from apoE(-/-) mice exhibit the characteristics of transdifferentiation into myofibroblasts

Adventitial fibroblasts (AFs) are the main cell type in the adventitia, however, their role in atherosclerosis remains unclear. We have investigate the role of AFs in atherosclerotic lesion formation by comparing the characteristics of AFs from apoE(-/-) to C57BL/6 mice. A minority of AFs from apoE(-/-) mice expressed α-SM-actin, but no α-SM-actin-positive cells were found in AFs from C57BL/6 mice. The content of total collagens, and the mRNA levels of collagen I and collagen III in AFs of apoE(-/-) mice, were higher than in C57BL/6 mice. AFs from apoE(-/-) mice proliferate and migrate faster, and synthesized more TGF-β(1) , MCP-1, and PDGF-b AFs from apoE(-/-) mice have the characteristics of transdifferentiation into myofibroblasts, including enhanced proliferation and migration, along with synthesis of collagens and cytokines compared to AFs from C57BL/6 mice. The histological and functional characteristics of AFs may contribute to early atherosclerotic lesion formation.

Epigenetic regulation of Thy-1 gene expression by histone modification is involved in lipopolysaccharide-induced lung fibroblast proliferation

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.

Lipopolysaccharide induces lung fibroblast proliferation through Toll-like receptor 4 signaling and the phosphoinositide3-kinase-Akt pathway

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.