Four-and-a-half LIM Domain Protein 2 Research Articles

Promotion of non-small cell lung cancer tumor growth by FHL2 via inducing angiogenesis and vascular permeability.

Antiangiogenetic therapy is one of the effective strategies for non-small cell lung cancer (NSCLC) treatment. Four-and-a-half LIM-domain protein 2 (FHL2) serves as a key function in cell growth and metastasis of multiple cancers, but the role of FHL2 in NSCLC angiogenesis has not been intensely examined. FHL2 expression in NSCLC tissues and cell lines and its correlation with patients prognosis were investigated by using The Cancer Genome Atlas (TCGA) database and quantitative polymerase chain reaction (qPCR). Cell Counting Kit-8 (CCK-8) assay, EdU (5-ethynyl-2'-deoxyuridine) assay, and a xenograft model were used to investigate the effects of FHL2 on NSCLC progression in vitro and in vivo. CCK-8, wound-healing, Transwell invasion, tube formation, and permeability assays were performed to determine the roles of FHL2 in angiogenesis and vascular permeability. Vascular endothelial growth factor A (VEGFA) enzyme-linked immunosorbent assay (ELISA) assay, Western blot analysis, and MK-2206 were used to investigate the specific mechanism mediated by FHL2. We demonstrated that FHL2 was significantly upregulated in NSCLC tissues and cell lines and was associated with poor prognosis. FHL2 overexpression enhanced the cell viability of NSCLC cells, as well as the proliferation, migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs). In addition, we determined that FHL2 activated the AKT-mTOR signaling pathway in HUVECs by promoting VEGFA secretion from NSCLC cells, thereby inducing angiogenesis and vascular leakiness. We further confirmed that FHL2 also promoted NSCLC tumor growth in vivo. Our study revealed the role of FHL2 in NSCLC and the mechanism by which FHL2 promotes NSCLC tumorigenesis, providing novel insights into targeted therapy for NSCLC.

Four-and-a-Half LIM-Domain Protein 2 (FHL2) Induces Neuropeptide Y (NPY) in Macrophages in Visceral Adipose Tissue and Promotes Diet-Induced Obesity.

Obesity is characterized by the expansion of the adipose tissue, usually accompanied by inflammation, with a prominent role of macrophages infiltrating the visceral adipose tissue (VAT). This chronic inflammation is a major driver of obesity-associated comorbidities. Four-and-a-half LIM-domain protein 2 (FHL2) is a multifunctional adaptor protein that is involved in the regulation of various biological functions and the maintenance of the homeostasis of different tissues. In this study, we aimed to gain new insights into the expression and functional role of FHL2 in VAT in diet-induced obesity. We found enhanced FHL2 expression in the VAT of mice with Western-type diet (WTD)-induced obesity and obese humans and identified macrophages as the cellular source of enhanced FHL2 expression in VAT. In mice with FHL2 deficiency (FHL2KO), WTD feeding resulted in reduced body weight gain paralleled by enhanced energy expenditure and uncoupling protein 1 (UCP1) expression, indicative of activated thermogenesis. In human VAT, FHL2 was inversely correlated with UCP1 expression. Furthermore, macrophage infiltration and the expression of the chemokine MCP-1, a known promotor of macrophage accumulation, was significantly reduced in WTD-fed FHL2KO mice compared with wild-type (wt) littermates. While FHL2 depletion did not affect the differentiation or lipid metabolism of adipocytes in vitro, FHL2 depletion in macrophages resulted in reduced expressions of MCP-1 and the neuropeptide Y (NPY). Furthermore, WTD-fed FHL2KO mice showed reduced NPY expression in VAT compared with wt littermates, and NPY expression was enhanced in VAT resident macrophages of obese individuals. Stimulation with recombinant NPY induced not only UCP1 expression and lipid accumulation but also MCP-1 expression in adipocytes. Collectively, these findings indicate that FHL2 is a positive regulator of NPY and MCP-1 expression in macrophages and herewith closely linked to the mechanism of obesity-associated lipid accumulation and inflammation in VAT. Thus, FHL2 appears as a potential novel target to interfere with the macrophage-adipocyte crosstalk in VAT for treating obesity and related metabolic disorders.

SPmel17 Secreted by Ultraviolet B-Exposed Melanocytes Alters the Intercellular Adhesion of Keratinocytes

Repigmentation of the skin in patients with vitiligo represents an intricate process in which the depigmented epidermis is replenished by functional melanocytes (MCs) that migrate from undamaged hair follicles and/or surrounding areas. We characterized whether MCs release a secreted form of Pmel17 (sPmel17) protein after exposure to UVB, thereby weakening the cell-cell adhesions of keratinocytes (KCs), which provides MCs the opportunity to migrate to areas devoid of MCs. At first, we examined the interactions of sPmel17 and FHL2 (four-and-a-half LIM domain protein 2) in KCs treated with the conditioned media (CM) from MCs exposed to UVB. The results showed that both the protein and mRNA levels of FHL2 were significantly upregulated in KCs treated with sPmel17-enriched CM from UVB-exposed MCs. We also found that there are physical interactions between sPmel17 and FHL2 as analyzed by reciprocal coimmunoprecipitation assays and double immunofluorescence staining. The CM from UVB-exposed MCs signaled KCs to remodel the actin cytoskeleton and reduce E-cadherin expression. However, the CM from UVB-exposed and Pmel17-silenced or from UVB-unexposed MCs failed to do this. To further determine the in situ distributions of sPmel17, FHL2, and E-cadherin, we examined the expression profiles of those proteins in the skin from healthy subjects and from depigmented or repigmented vitiligo using immunofluorescence and immunohistochemical staining. The results showed that the expression of sPmel17 was positively correlated with FHL2 but not to E-cadherin. The colocalization of FHL2 and sPmel17 was also observed in UVB-exposed mouse tail skin. Together, the upregulation of FHL2 in KCs requires stimulation by sPmel17 secreted from MCs and activation of the sPmel17-FHL2-E-cadherin axis offers a potential therapeutic target to expedite the repigmentation process in patients with vitiligo.

Four-and-a-half LIM domain protein 2 (FHL2) deficiency protects mice from diet-induced obesity and high FHL2 expression marks human obesity

ObjectiveFour-and-a-Half-LIM-domain-protein 2 (FHL2) modulates multiple signal transduction pathways but has not been implicated in obesity or energy metabolism. In humans, methylation and expression of the FHL2 gene increases with age, and high FHL2 expression is associated with increased body weight in humans and mice. This led us to hypothesize that FHL2 is a determinant of diet-induced obesity. MethodsFHL2-deficient (FHL2−/−) and wild type male mice were fed a high-fat diet. Metabolic phenotyping of these mice, as well as transcriptional analysis of key metabolic tissues was performed. Correlation of the expression of FHL2 and relevant genes was assessed in datasets from white adipose tissue of individuals with and without obesity. ResultsFHL2 Deficiency protects mice from high-fat diet-induced weight gain, whereas glucose handling is normal. We observed enhanced energy expenditure, which may be explained by a combination of changes in multiple tissues; mild activation of brown adipose tissue with increased fatty acid uptake, increased cardiac glucose uptake and browning of white adipose tissue. Corroborating our findings in mice, expression of FHL2 in human white adipose tissue positively correlates with obesity and negatively with expression of browning-associated genes. ConclusionOur results position FHL2 as a novel regulator of obesity and energy expenditure in mice and human. Given that FHL2 expression increases during aging, we now show that low FHL2 expression associates with a healthy metabolic state.

Four-And-A-Half LIM-Domain Protein 2 (FHL2) Deficiency Aggravates Cholestatic Liver Injury.

Cholestasis occurs in different clinical circumstances and leads to severe hepatic disorders. The four-and-a-half LIM-domain protein 2 (FHL2) is a scaffolding protein that modulates multiple signal transduction pathways in a tissue- and cell context-specific manner. In this study, we aimed to gain insight into the function of FHL2 in cholestatic liver injury. FHL2 expression was significantly increased in the bile duct ligation (BDL) model in mice. In Fhl2-deficient (Fhl2-ko) mice, BDL caused a more severe portal and parenchymal inflammation, extended portal fibrosis, higher serum transaminase levels, and higher pro-inflammatory and pro-fibrogenic gene expression compared to wild type (wt) mice. FHL2 depletion in HepG2 cells with siRNA resulted in a higher expression of the bile acid transporter Na+-taurocholate cotransporting polypeptide (NTCP) gene. Furthermore, FHL2-depleted HepG2 cells showed higher expression of markers for oxidative stress, lower B-cell lymphoma 2 (Bcl2) expression, and higher Bcl2-associated X protein (BAX) expression after stimulation with deoxycholic acid (DCA). In hepatic stellate cells (HSCs), FHL2 depletion caused an increased expression of TGF-β and several pro-fibrogenic matrix metalloproteinases. In summary, our study shows that deficiency in FHL2 aggravates cholestatic liver injury and suggests FHL2-mediated effects on bile acid metabolisms and HSCs as potential mechanisms for pronounced hepatocellular injury and fibrosis.

LIM-only protein FHL2 attenuates inflammation in vascular smooth muscle cells through inhibition of the NFκB pathway

Despite the advent of new-generation drug-eluting stents, in-stent restenosis remains a significant problem in patients with coronary artery disease. In- stent restenosis is defined as the gradual re-narrowing of a stented coronary artery lesion due to arterial damage with subsequent local inflammation of the vessel wall and excessive growth of the vascular smooth muscle cells (vSMCs). Four-and-a-half LIM-domain protein 2 (FHL2) is a scaffold protein involved in regulating vSMC function and inflammation. Previously we have demonstrated that FHL2 prevents vSMC proliferation in a murine carotid artery ligation model. However, the effect of FHL2 on the inflammatory response of the vSMCs is not investigated. Therefore, we studied the inflammatory response in the vessel wall of FHL2-deficient (-KO) mice after carotid artery ligation. We found that circulating cytokines and local macrophage infiltration in the ligated carotid vessels were increased in FHL2-KO mice after carotid artery ligation. Moreover, FHL2-KO vSMCs showed increased secretion of cytokines such as SDF-1α and RANTES, and enhanced activation of the NFκB pathway. Finally, we found that blocking the NFκB signalling pathway abrogated this pro-inflammatory state in FHL2-KO vSMCs. Taken together, our results demonstrate that FHL2 decreases the inflammatory response of vSMCs through inhibition of the NFkB-signalling pathway.

Pirfenidone attenuates lung fibrotic fibroblast responses to transforming growth factor-\u03b21

BackgroundPirfenidone, an antifibrotic agent used for the treatment of idiopathic pulmonary fibrosis (IPF), functions by inhibiting myofibroblast differentiation, which is involved in transforming growth factor (TGF)-β1-induced IPF pathogenesis. However, unlike normal lung fibroblasts, the relationship between pirfenidone responses of TGF-β1-induced human fibrotic lung fibroblasts and lung fibrosis has not been elucidated.MethodsThe effects of pirfenidone were evaluated in lung fibroblasts isolated from fibrotic human lung tissues after TGF-β1 exposure. The ability of two new pharmacological targets of pirfenidone, collagen triple helix repeat containing protein 1(CTHRC1) and four-and-a-half LIM domain protein 2 (FHL2), to mediate contraction of collagen gels and migration toward fibronectin were assessed in vitro.ResultsCompared to control lung fibroblasts, pirfenidone significantly restored TGF-β1-stimulated fibroblast-mediated collagen gel contraction, migration, and CTHRC1 release in lung fibrotic fibroblasts. Furthermore, pirfenidone attenuated TGF-β1- and CTHRC1-induced fibroblast activity, upregulation of bone morphogenic protein-4(BMP-4)/Gremlin1, and downregulation of α-smooth muscle actin, fibronectin, and FHL2, similar to that observed post-CTHRC1 inhibition. In contrast, FHL2 inhibition suppressed migration and fibronectin expression, but did not downregulate CTHRC1.ConclusionsOverall, pirfenidone suppressed fibrotic fibroblast-mediated fibrotic processes via inverse regulation of CTHRC1-induced lung fibroblast activity. Thus, CTHRC1 can be used for predicting pirfenidone response and developing new therapeutic targets for lung fibrosis.

The Four-and-a-Half LIM Domain Protein 2 Supports Influenza A Virus–Induced Lung Inflammation by Restricting the Host Adaptive Immune Response

Four-and-a-half LIM domain protein 2 (FHL2) is a multifunctional adaptor protein with fine-tuning adjustment properties. It acts as a regulator of signaling cascades but also as a cofactor of transcription and controls several anti-inflammatory immune responses. Recently, we described FHL2 as a novel regulator of influenza A virus propagation. We have shown that invitro FHL2 restricts viral replication by accelerating the interferon regulatory factor 3-dependent transcription of the Ifnb1 gene. In this work, we unraveled an ambiguous role of FHL2 during influenza A virus infection invivo. Although FHL2 restrained viral replication during the first 24 hours of infection, it significantly delayed viral clearance afterward. Comparison of lung immune status of wild-type and FHL2 knockout mice during influenza virus infection did not acknowledge significant differences in the innate host immune response but revealed an improved migration of dendritic cells from infected lungs into draining lymph nodes as well as increased levels of activated CD8+ T lymphocytes accumulated in the lungs of FHL2 knockout mice.

Abstract 250: Four-And-A-Half LIM Domain Protein 2 Plays a Critical Role in Spleen T-Cell Dependent Antibody Response

Background: Four-and-a-half LIM domain protein 2 (FHL2) is an adaptor molecule that regulates signalling cascades and gene transcription. We have uncovered vasculoprotective and atheroprotective effects of FHL2 knockout in mice. Since B cells could regulate these processes, we investigated the potential role of FHL2 in B cell function and activity. Methods and Results: Under basal conditions, FHL2-/- mice presented a mild splenomegaly (84.0±9.0 vs 68.0±5.0mg), associated with bigger spleen follicles (1.6 fold) and higher proportions of spleen B cells (56.0±2.0 vs 40.0±9.0%) vs WT mice. Flow cytometry confirmed significantly higher (p<0.05) proportions of B cells in the follicles (Fo)(CD23+CD21lo/int) (77.0±1.0 vs 67.0±3.0%) and the marginal zone (Mz)(CD23-,CD21+)(7.0±1.0 vs 2.5±1.0%) of FHL2-/- vs WT mice. Mice were injected with sheep red blood cells (SRBC) to elicit a T cell-dependent B cell activation. SRBC did not influence Fo and Mz B cell numbers, but it did affect germinal center (GC) formation. GCs are zones within Fo where T cells activate B cells to produce high affinity antibodies. SRBC induced a 5- and 2.5-fold increase in B cells (GL7+) within FHL2-/- and WT GCs, respectively. However, there was no increase in plasma IgG1 levels in FHL2-/- mice in response to SRBC, whereas a 3-fold increase was observed in WT mice (1158±227 vs 2943±226ng/ml; p<0.05). Instead, plasma IgM levels were higher in FHL2-/- than WT SRBC mice. Moreover, SRBC only induced a modest, 1.3-fold fold increase in Fo T helper cells (CXCR5+PD1+) in FHL2-/- compared with a 6-fold increase in WT. Nevertheless, FHL2-/- B cells successfully proliferated and underwent class switch recombination in response to LPS, anti-CD40 and IL-4 in vitro, indicating that these cells were not defective. Conclusion: These results suggest that FHL2 plays a critical role in spleen antibody production in response to a T-dependent antigen, possibly by affecting activation or antigen presentation by Fo T helper cells.

Abstract 2867: Functional role of FHL2 in the splicing machinery of liver cells

Abstract Hepatocellular carcinoma (HCC) is a highly lethal cancer with increasing worldwide incidence. The four-and-a-half LIM domain protein 2 (FHL2) has been identified as an oncogene / tumor suppressor gene in a tissue/cell specific manner by acting as an adaptor protein to form different complexes and involving in various signaling pathways. To clarify the intriguing functions of FHL2, we have identified a batch of interacting partners of FHL2 by immunoprecipitation and liquid chromatography coupling with mass spectrometry. Many of these proteins, including SNRNP70, DAZAP1, SFPQ, TIAL1 and so on, are involved in spliceosome components and mRNA surveillance. The interaction among several proteins and FHL2 has been confirmed by co-immunoprecipitation. To further elucidate the functional role of FHL2 in the splicing process in liver cancer cells, we have studied the transcriptomes of FHL2 overexpression and FHL2 knockdown liver cells, whereas empty vector and scrambled siRNA were used as controls respectively. Followed by bioinformatics analysis, we found significant concordance between the immunoprecipitation and transcriptome datasets. Selected genes were further validated by real-time PCR such as FGFR4. In summary, FHL2 is probably regulating the mRNA splicing by interacting with components of the splicing machinery and modulating splicing related genes at the transcriptional level. Citation Format: Ye Cao, Minghua Liu, Yi Yang, Yinfeng Zhang, Kwok Wing Tsui. Functional role of FHL2 in the splicing machinery of liver cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2867.

Abstract 5049: SIAH2 E3 ligase targets LIM-domain proteins for degradation to modulate focal adhesion and cell motility

Abstract Introduction: The RAS signaling pathway is an important growth-promoting pathway that controls cell proliferation and survival in multicellular organisms. During oncogenesis, activation of EGFR/HER2/K-RAS signaling pathway reduces focal adhesion, increases cell motility, promote tumorigenesis and accelerate tumor invasion and metastasis. SIAH2, which is the human homologue of a highly conserved family of RING-domain E3 ubiquitin ligase, is a key downstream signaling component which is essential for RAS signal transduction. We noticed that SIAH2 can regulate cell migration, tumorigenesis and metastasis by unknown mechanisms. Methods: Using HIV-based lentiviral system, we introduced an anti-SIAH molecule, the proteolysis-deficient mutant form of SIAH2 (SIAH2PD), into multiple types of human cancer cell lines. The changes of cell morphology, focal adhesion and adherens junction were examined by immunofluorescence (IF) staining. Images were captured on day 3 post infection experiments to show the changes in cell focal adhesion/junction. Using lentiviral system, we introduced exogenous LIM-domain proteins into human cancer cell lines which already expressed SIAH2PD, and then check the cell focal adhesion rescue by immunofluorescence staining. Results: We identified and validated three proteins that interact with SIAH2, contain LIM domains, and regulate focal adhesion and cell attachment. Through in vitro and in vivo experiments, we show that SIAH2 binds, ubiquitinates and degrades thyroid receptor-interacting protein 6 (TRIP6), Four-and-a-half LIM domain protein 2 (FHL2) and Leupaxin (LPXN), indicating that these evolutionarily conserved LIM-domain proteins are bona fide SIAH2 substrates and their double zinc finger motif might serve as a degron signal for SIAH2 E3 ligase. Our staining results showed that SIAH-deficiency would disrupt Trip6/FHL2/LPXN localization at the focal adhesion site, and inhibit cell motility. By introducing exogenous Trip6/FHL2/LPXN proteins into cancer cells, the focal adhesion deficiency and cell death caused by SIAHPD can be rescued, and the ability of cell migration and tumor initiation can be restored. Conclusions: We show that in cancer cells, SIAH2 antagonizes TRIP6, FHL2 and LPXN in modulating focal adhesions and cell motility. This interaction could be important in cell dissemination, invasion and metastasis. The suppression of cell motility and tumorigenesis in response to SIAH-deficiency could provide a new molecular mechanism to reveal the importance of RAS/SIAH signaling pathway in cancer cells. By circumventing this essential cell growth signaling pathway in cancer, we hope to develop novel anti-SIAH-based therapeutic drugs, which may help to inhibit cancer cell dissemination, invasion and metastasis. Citation Format: Minglei Bian, Yang Liao, Monicah Njogu, Rebecca Schmidt, Rie Takahashi, Zandra Walton, Amy H. Tang. SIAH2 E3 ligase targets LIM-domain proteins for degradation to modulate focal adhesion and cell motility. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5049.

FHL2 switches MITF from activator to repressor of Erbin expression during cardiac hypertrophy

BackgroundCongestive heart failure (CHF) is a significant health care burden in developed countries. However, the molecular events leading from cardiac hypertrophy to CHF are unclear and preventive therapeutic approaches are limited. We have previously described that microphthalmia-associated transcription factor (MITF) is a key regulator of cardiac hypertrophy, but its cardiac targets are still uncharacterized. Methods and resultsGene array analysis of hearts from MITF-mutated mice indicated that ErbB2 interacting protein (Erbin) is a candidate target gene for MITF. We have recently demonstrated that Erbin is decreased in human heart failure and plays a role as a negative modulator of pathological cardiac hypertrophy. Here we show that Erbin expression is regulated by MITF. Under basal conditions MITF activates Erbin expression by direct binding to its promoter. However, under β-adrenergic stimulation Erbin expression is decreased only in wild type mice, but not in MITF-mutated mice. Yeast two-hybrid screening, using MITF as bait, identified an interaction with the cardiac-predominant four-and-a-half LIM domain protein 2 (FHL2), which was confirmed by co-immunoprecipitation in both mouse and human hearts. Upon β-adrenergic stimulation, FHL2 and MITF bind Erbin promoter as a complex and repress MITF-directed Erbin expression. Overexpression of FHL2 alone had no effect on Erbin expression, but in the presence of MITF, Erbin expression was decreased. FHL2–MITF association was also increased in biopsies of heart failure patients. ConclusionMITF unexpectedly regulates both the activation and the repression of Erbin expression. This ligand mediated fine tuning of its gene expression could be an important mechanism in the process of cardiac hypertrophy and heart failure.

TGF-β1-dependent induction and nuclear translocation of FHL2 promotes keratin expression in pilomatricoma.

Pilomatricoma is a tumour derived from hair matrix cells, which shows progressive keratin expression. Tumorigenesis is frequently associated with activating mutations in β-catenin gene inducing nuclear expression of β-catenin protein. The present study analysed the role of transforming growth factor-β1 (TGF-β1) and four-and-a-half LIM domain protein 2 (FHL2) in pilomatricoma in synopsis with their expression patterns in human anagen hair. Human anagen hair showed TGF-β1 and nuclear FHL2 expression in the outer root sheath layer separated from nuclear β-catenin staining, which was observed in cells of matrix and inner root sheath layers. Correspondingly, 41 out of 50 pilomatricomas showed co-labelling of TGF-β1 and nuclear FHL2 in tumour cells, which mostly lacked nuclear β-catenin expression. Tumoural proliferation (ki67) was associated with nuclear β-catenin staining but not with expression of nuclear FHL2. In early pilomatricomas, TGF-β1 expression was observed in few peripheral tumour cells showing absent or faint nuclear FHL2 co-staining. TGF-β1 expression extended in growing tumours going along with strong nuclear FHL2 co-labelling as well as progressive keratin 14 and keratin 1 expression. In vitro, cultured human keratinocytes showed weak to marked autocrine TGF-β1 expression; in case of enhanced TGF-β1 expression associated with keratin 10 staining. TGF-β1-treatment of cultured human keratinocytes induced nuclear and cytoplasmatic FHL2 staining as well as keratin 14 staining. Accordingly, siRNA-mediated FHL2 knockdown of TGF-β1-stimulated keratinocytes reduced keratin 14 staining. In conclusion, tumoural TGF-β1 secretion seems to induce nuclear translocation of co-factor FHL2 mediating progressive keratin expression in pilomatricoma.

Abstract 12315: Four-and-a-Half LIM Domain Protein-2 Absence Reduces Atherogenesis in Apolipoprotein E-deficient Mice: Role of Monocytic Immune Cells

Background: Four-and-a-half LIM domain protein-2 (FHL2) is expressed in endothelial and vascular smooth muscle cells. It negatively regulates endothelial cell survival and migration, but its role in atherogenesis is unknown. Methods and Results: FHL2-deficient (FHL2-/-) mice were crossed with apolipoprotein E-deficient (ApoE-/-) mice to generate ApoE/FHL2-/- mice. After high-fat, high-cholesterol diet, ApoE/FHL2-/- mice displayed significantly smaller atherosclerotic plaques than ApoE-/- mice in the aortic sinus, the brachiocephalic artery and the aorta. This was associated with significantly enhanced collagen and smooth muscle cell contents and a significant 2-fold reduction of macrophage content within the plaques of ApoE/FHL-2-/- vs ApoE-/- mice. There was a significant reduction in aortic ICAM-1 mRNA and VCAM-1 protein expression in the plaques of ApoE/FHL2-/- mice. Aortic gene expression of CX3CL1 and CCL5 was significantly increased in ApoE/FHL2-/- vs ApoE-/- mice. Peritoneal thioglycollate injection elicited equivalent numbers of monocytes and macrophages in both groups, but a significantly lower number of pro-inflammatory Ly6C-high monocytes were recruited in ApoE/FHL2-/- vs ApoE-/- mice. Furthermore, mRNA levels of CX3CR1 were 2-fold higher in monocytes from ApoE/FHL2-/- vs ApoE-/- mice. Finally, we investigated the potential importance of myeloid cell FHL2 deficiency in atherosclerosis. After being irradiated, ApoE-/- or ApoE/FHL2-/- mice were transplanted with ApoE-/- or ApoE/FHL2-/- bone marrow. After high-fat, high-cholesterol diet, both chimeric groups developed significantly smaller plaques than ApoE-/- mice transplanted with ApoE-/- bone marrow. Conclusion: These results suggest that FHL2 in both myeloid and vascular cells may play an important role in atherogenesis by promoting pro-inflammatory chemokine production, adhesion molecule expression, and pro-inflammatory monocyte recruitment.

ABSENCE OF FOUR-AND-A-HALF LIM DOMAIN PROTEIN 2 DECREASES ATHEROSCLEROSIS IN APOE-/- MICE: ROLE OF MONOCYTIC IMMUNE CELLS

Four-and-a-half LIM domain protein-2 (FHL2) is expressed in endothelial and vascular smooth muscle cells. It negatively regulates endothelial cell survival and migration, but its role in atherogenesis is unknown. To investigate the role of FHL2 in atherosclerosis, FHL2-deficient (FHL2-/-) mice were crossed with ApoE-deficient (ApoE -/-) mice, to generate ApoE/FHL2-/- mice. After 7 weeks of high fat diet, ApoE/FHL2-/- mice had significantly smaller (P<0.05) atherosclerotic plaques than ApoE-/- mice in the aortic sinus (0.14±0.02 vs. 0.29±0.04 mm2), the brachiocephalic artery (0.03±0.008 vs. 0.07±0.01 mm2) and the aorta (6.9±0.9 vs 10.3±1%), assessed by oil red O staining. This was associated with enhanced collagen (16±2 vs 8.6±3 %) and smooth muscle cell (4.5±0.8 vs 1.8±0.5%) contents within the plaques of ApoE/FHL-2-/- mice. Moreover, macrophage content within plaques was reduced 2-fold in ApoE/FHL2-/- vs ApoE-/- mice (P<0.05). This could be explained, in part, by the 40% reduction in aortic ICAM-1 mRNA and 55% reduction in VCAM-1 protein expression in the plaque. Furthermore, aortic gene expression of Cx3cl1 and Ccl5 was increased in ApoE/FHL2-/- vs ApoE-/- mice, suggesting that different monocyte populations might be recruited to the plaques. Peritoneal thioglycollate injection elicited equivalent numbers of monocytes and macrophages in both groups, but a significantly lower number of pro-inflammatory Ly6C high monocytes were recruited in ApoE/FHL2-/- vs ApoE-/- mice (8±3 vs 18±4%). Furthermore, mRNA levels of Cx3cr1 were 2-fold higher in monocytes from ApoE/FHL2-/- mice compared with ApoE-/- mice. Finally, we also investigated the potential importance of myeloid cell FHL2 deficiency in atherosclerosis. ApoE-/- or ApoE/FHL2-/- mice were lethally irradiated and transplanted with ApoE-/- or ApoE/FHL2-/- bone marrow. After recovery and 7 weeks of high fat diet, both chimeric groups developed smaller plaques than ApoE-/- mice transplanted with ApoE-/- bone marrow. These results suggest that FHL2 in both myeloid and vascular cells may play an important role in atherosclerosis by promoting pro-inflammatory chemokine production, adhesion molecule expression, and pro-inflammatory monocyte recruitment.

Abstract 643: Absence of Four-and-a-Half LIM Domain Protein 2 Decreases Atherosclerosis in ApoE-/- Mice: Role of Monocytic Immune Cells

Four-and-a-half LIM domain protein-2 (FHL2) is expressed in endothelial and vascular smooth muscle cells. It negatively regulates endothelial cell survival and migration, but its role in atherogenesis is unknown. To investigate the role of FHL2 in atherosclerosis, FHL2-deficient (FHL2-/-) mice were crossed with ApoE-deficient (ApoE -/-) mice, to generate ApoE/FHL2-/- mice. After 7 weeks of high fat diet, ApoE/FHL2-/- mice had significantly smaller (P&lt;0.05) atherosclerotic plaques than ApoE-/- mice in the aortic sinus (0.14±0.02 vs. 0.29±0.04 mm2), the brachiocephalic artery (0.03±0.008 vs. 0.07±0.01 mm2) and the aorta (6.9±0.9 vs 10.3±1%), assessed by oil red O staining. This was associated with enhanced collagen (16±2 vs 8.6±3 %) and smooth muscle cell (4.5±0.8 vs 1.8±0.5%) contents within the plaques of ApoE/FHL-2-/- mice. Moreover, macrophage content within plaques was reduced 2-fold in ApoE/FHL2-/- vs ApoE-/- mice (P&lt;0.05). This could be explained, in part, by the 40% reduction in aortic ICAM-1 mRNA and 55% reduction in VCAM-1 protein expression in the plaque. Furthermore, aortic gene expression of Cx3cl1 and Ccl5 was increased in ApoE/FHL2-/- vs ApoE-/- mice, suggesting that different monocyte populations might be recruited to the plaques. Peritoneal thioglycollate injection elicited equivalent numbers of monocytes and macrophages in both groups, but a significantly lower number of pro-inflammatory Ly6C high monocytes were recruited in ApoE/FHL2-/- vs ApoE-/- mice (8±3 vs 18±4%). Furthermore, mRNA levels of Cx3cr1 were 2-fold higher in monocytes from ApoE/FHL2-/- mice compared with ApoE-/- mice. Finally, we also investigated the potential importance of myeloid cell FHL2 deficiency in atherosclerosis. ApoE-/- or ApoE/FHL2-/- mice were lethally irradiated and transplanted with ApoE-/- or ApoE/FHL2-/- bone marrow. After recovery and 7 weeks of high fat diet, both chimeric groups developed smaller plaques than ApoE-/- mice transplanted with ApoE-/- bone marrow. These results suggest that FHL2 in both myeloid and vascular cells may play an important role in atherosclerosis by promoting pro-inflammatory chemokine production, adhesion molecule expression, and pro-inflammatory monocyte recruitment.

Inhibition of Four-and-a-Half LIM Domain Protein-2 Increases Survival, Migratory Capacity, and Paracrine Function of Human Early Outgrowth Cells Through Activation of the Sphingosine Kinase-1 Pathway

Rationale: Inhibition of four-and-a-half LIM domain protein-2 (FHL2) attenuates atherosclerotic lesion formation and increases endothelial cell migration. Early outgrowth cells (EOCs) contribute substantially to endothelial repair. Objective: We investigated the role of FHL2 in the regulation of EOCs. Methods and Results: Human EOCs were cultured from peripheral blood. FHL2 knockdown in EOCs by siRNA resulted in increased EOC numbers and reduced apoptosis, as indicated by decreased cleaved caspase-III and reduced Bax/Bcl-2 expression ratio. This was mediated through increased phosphorylation and membrane translocation of sphingosine kinase-1, increased sphingosine-1-phosphate levels, and Akt phosphorylation. FHL2 knockdown increased stromal cell–derived factor-1–induced EOC migration through upregulation of αv/β3, αv/β5, and β2 integrins, associated with increased cortactin expression. Reduced apoptosis, increased EOC migration, and cortactin upregulation by FHL2 siRNA were prevented by CAY10621, the sphingosine kinase-1 inhibitor, and the sphingosine-1-phosphate receptor-1/-3 antagonist VPC23019. These findings were confirmed using spleen-derived EOCs from FHL2 −/− mice. Apoptosis was decreased and migration increased in endothelial cells exposed to the conditioned medium of FHL2 −/− versus wild-type (WT) EOCs. These paracrine effects were abolished by VPC23019. Importantly, reendothelialization after focal carotid endothelial injury in WT mice was significantly increased after intravenous injection of FHL2 −/− versus WT EOCs. Conclusions: Our findings suggest that FHL2 negatively regulates EOC survival, migration, and paracrine function. FHL2 inhibition in EOCs reduces apoptosis and enhances survival and migratory capacity of both EOCs and surrounding endothelial cells by activation of the sphingosine kinase-1/sphingosine-1-phosphate pathway, resulting in improvement of endothelial regeneration.

The LIM-Only Protein FHL2 Attenuates Lung Inflammation during Bleomycin-Induced Fibrosis

Fibrogenesis is usually initiated when regenerative processes have failed and/or chronic inflammation occurs. It is characterised by the activation of tissue fibroblasts and dysregulated synthesis of extracellular matrix proteins. FHL2 (four-and-a-half LIM domain protein 2) is a scaffolding protein that interacts with numerous cellular proteins, regulating signalling cascades and gene transcription. It is involved in tissue remodelling and tumour progression. Recent data suggest that FHL2 might support fibrogenesis by maintaining the transcriptional expression of alpha smooth muscle actin and the excessive synthesis and assembly of matrix proteins in activated fibroblasts. Here, we present evidence that FHL2 does not promote bleomycin-induced lung fibrosis, but rather suppresses this process by attenuating lung inflammation. Loss of FHL2 results in increased expression of the pro-inflammatory matrix protein tenascin C and downregulation of the macrophage activating C-type lectin receptor DC-SIGN. Consequently, FHL2 knockout mice developed a severe and long-lasting lung pathology following bleomycin administration due to enhanced expression of tenascin C and impaired activation of inflammation-resolving macrophages.

Inhibition of Four- and-a-Half-Lim Domain Protein-2 Decreases Atherosclerosis in APOE -/- Mice Model: Role of Immune T-Cells

Four-and-a-half LIM domain protein-2 (FHL2), a member of the FHL family of proteins, is expressed in endothelial and vascular smooth muscle cells. FHL2 negatively regulates endothelial cell survival and migration, but its role in atherogenesis is unknown.

Four-and-a-half LIM domain protein-2 (FHL-2) inhibition reduces atherosclerosis in apolipoprotein E-deficient mice

Background: Four-and-a-half LIM domain protein-2 (FHL-2), a member of the FHL family of proteins, is expressed in vascular endothelial and smooth muscle cells and negatively regulates endothelial cell survival and migration. However, its role in atherogenesis is unknown. Methods and results: To investigate the role of FHL-2 in atherosclerosis, we crossed FHL-2 knockout (FHL-2-/-) with apolipoprotein E-deficient (ApoE-/-) mice, and fed them a high-cholesterol, high-fat diet for 7 weeks. FHL-2-/-ApoE-/- mice displayed significantly less atherosclerotic plaque formation, as assessed by oil red O staining, in the aortic sinus (0.14±0.02 vs. 0.29±0.04 mm2) and aorta (6.9±0.9 vs 10.3±1%), compared with ApoE-/- mice. This was associated with enhanced collagen (16±2 vs 8.6±3%) and smooth muscle cell (4.5±0.8 vs 1.8±0.5%) contents within the plaques in the aortic sinus of FHL-2-/-ApoE-/- mice, as determined by Sirius red and alpha-actin staining, respectively, compared with ApoE-/- mice. These results suggest that absence of FHL-2 promotes smaller and more stable plaques. However, relative monocyte/macrophage content within the atherosclerotic plaques, as determined by MOMA-2 immunostaining, and in spleens, as determined by FACS analysis, was equivalent in both animals groups. Decreased plaque formation in FHL-2-/-ApoE-/- mice was associated with significantly reduced aortic ICAM-1 mRNA levels by 40%. Moreover, FACS analysis of T cells in spleens showed a significant increase in CD4+CD25+Foxp3+ regulatory T cell numbers, in FHL-2-/-ApoE-/- compared with ApoE-/- mice (19.5±1.6 vs. 16.2±2% of CD3+CD4+ cells, respectively). Conclusions: These results suggest that FHL-2 may play an important role in atherogenesis by promoting plaque formation, involving upregulation of adhesion molecule expression and suppression of regulatory T cells.