Hepatocyte growth factor inhibits apoptosis by the profibrotic factor angiotensin II via extracellular signal-regulated kinase 1/2 in endothelial cells and tissue explants

Identification and Modulation of Microenvironment Is Crucial for Effective Mesenchymal Stromal Cell Therapy in Acute Lung Injury

Rationale: There are controversial reports on applications of mesenchymal stromal cells (MSCs) in patients with acute respiratory distress syndrome (ARDS). Objectives: We hypothesized that lung microenvironment was the main determinant of beneficial versus detrimental effects of MSCs during ARDS. Methods: Lung proteome was profiled in three models of injury induced by acid instillation and/or mechanical ventilation in mice. Human gene of glutathione peroxidase-1 was delivered before MSC administration; or MSCs carrying human gene of IL-10 or hepatocyte growth factor were administered after lung injury. An inhibitory cocktail against IL-6, fibronectin, and oxidative stress was used in in vitro studies using human small airway epithelial cells and human MSCs after exposure to plasma of patients with ARDS. Measurements and Main Results: Distinct proteomic profiles were observed in three lung injury models. Administration of MSCs protected lung from ventilator-induced injury, whereas it worsened acid-primed lung injuries associated with fibrotic development in lung environment that had high levels of IL-6 and fibronectin along with low antioxidant capacity. Correction of microenvironment with glutathione peroxidase-1, or treatment with MSCs carrying human gene of IL-10 or hepatocyte growth factor after acid-primed injury, reversed the detrimental effects of native MSCs. Proteomic profiles obtained in the mouse models were also similarly observed in human ARDS. Treatment with the inhibitory cocktail in samples of patients with ARDS retained protective effects of MSCs in small airway epithelial cells. Conclusions: MSCs can be beneficial or detrimental depending on microenvironment at the time of administration. Identification of potential beneficiaries seems to be crucial to guide MSC therapy in ARDS.

H2 relaxin ameliorates angiotensin II-induced endothelial dysfunction through inhibition of excessive mitochondrial fission

The physiological function of endothelial cells plays an important role in maintaining normal cardiovascular function. Endothelial dysfunction induced by AngII (angiotensin II) is the pathological mechanism of occurrence and development of cardiovascular diseases. Human recombinant relaxin-2 (H2 relaxin), which has protective effect on cardiovascular functions, ameliorates damage to endothelial cells induced by angiotensin II (AngII) treatment. However, the exact mechanisms remain unclear. In this study, we researched the mechanisms of H2 relaxin inhibiting AngII-induced endothelial dysfunction from the protective effect of H2 relaxin on endothelial function though inhibiting excessive mitochondrial fission. Here, we found that H2 relaxin increased eNOS, SOD1 expression, inhibited excessive mitochondrial fission and decreased ROS level in HUVECs treated with AngII. However, overexpression of fission protein 1 (Fis1) prevented H2 relaxin from protecting against AngII-induced low eNOS, SOD1 expression, excessive mitochondrial fission and increased ROS level in HUVECs. Our study indicated that excessive mitochondrial fission could be a target for H2 relaxin to treat endothelial dysfunction in angiocardiopathy.

Hepatocyte growth factor promotes proliferation, invasion, and metastasis of myeloid leukemia cells through PI3K-AKT and MAPK/ERK signaling pathway

This study aims to investigate effects of HGF expression on biological behaviors of Kasumi-1 and HL60. Expression of HGF and c-Met gene were detected using qRT-PCR. Short hairpin RNA (shRNA) was used to reduce HGF expression. Silencing effect of shRNA was verified by qRT-PCR and western blot. Cell reproductive capacity, cell clonality and cell cycle (apoptosis) were detected by CCK-8, clone formation, flow cytometry (FCM), respectively. Cell adhesion, cell invasion ability and cell proliferation were also examined. Changes of PI3K-AKT, MAPK/ERK signaling factors were detected by western blot. HGF and c-Met expression in first-vist AML group was significantly higher than in AML-relief and normal control group. HGF shRNA can inhibit cell proliferation, inhibit cloning ability. Compared with control group, apoptosis ratios of Kasumi-1 and HL60 cell in interference groups were significantly higher. After shRNA interference, the number of adherent cells and transmembrane cells were significantly decreased compared with control group. Meanwhile, shRNA also down-regulated Bad, Bcl-XL, Bcl-2, CDK1, Cyclin B, MMP2, MMP9, and up-regulated cleaved caspase9, cleaved caspase3, cleaved PARP, Bax, and P21. Moreover, phosphorylated c-Met, AKT, Erk, and mTOR were also reduced. In conclusion, HGF and c-Met gene highly expressed among first-visit AML patients, but decreased after relief treatment. HGF may promote proliferation, invasion, and metastasis of AML cells through PI3K-AKT and MAPK/ERK signaling pathway. Therefore, proliferation and invasion ability of AML cell can be inhibited by down-regulating HGF gene to retardate cell in G2/M stage.

The hepatocyte growth factor isoform NK2 activates motogenesis and survival but not proliferation due to lack of Akt activation

Hepatocyte growth factor (HGF) is a pleiotrophic factor involved in cellular proliferation, migration and morphogenesis. HGF is required for normal tissue and organ development during embryogenesis, but in the adult HGF has been demonstrated to drive normal tissue repair and inhibit fibrotic remodeling. HGF has two naturally occurring human isoforms as a result of alternative splicing, NK1 and NK2. While NK1 has been defined as an agonist for HGF receptor, Met, NK2 is defined as a partial Met antagonist. Furthermore, under conditions of fibrotic remodeling, NK2 is still expressed while full length HGF is suppressed. Furthermore, the mechanism by which NK2 partially signals through Met is not completely understood. Here, we investigated the mitogenic, motogenic, and anti-apoptotic activities of NK2 compared with full length HGF in primary human bronchial epithelial cells (BEpC) and bovine pulmonary artery endothelial cells (PAEC). In human BEpC, NK2 partial activated Met, inducing Met phosphorylation at Y1234/1235 in the tyrosine-kinase domain but not at Y1349 site in the multifunctional docking domain. Partial phosphorylation of Met by NK2 resulted in activation of MAPK and STAT3, but not AKT. This correlated with motogenesis and survival in a MAPK-dependent manner, but not cell proliferation. Overexpression of a constitutively active AKT complemented NK2 signaling, allowing NK2 to induce cell proliferation. These data indicate that NK2 and HGF drive motogenic and anti-apoptotic signaling but only HGF drives cell proliferation by activating AKT-pathway signaling. These results have implications for the biological consequences of differential regulation of the two isoforms under pro-fibrotic conditions.

Cilostazol suppresses angiotensin II-induced apoptosis in endothelial cells

Patients with essential hypertension undergo endothelial dysfunction, particularly in the conduit arteries. Cilostazol, a type III phosphodiesterase inhibitor, serves a role in the inhibition of platelet aggregation and it is widely used in the treatment of peripheral vascular diseases. Previous studies have suggested that cilostazol suppresses endothelial dysfunction; however, it remains unknown whether cilostazol protects the endothelial function in essential hypertension. The aim of the present study was to investigate whether, and how, cilostazol suppresses angiotensin II (angII)-induced endothelial dysfunction. Human umbilical vein endothelial cells (HUVECs) and Sprague Dawley rats were exposed to angII and treated with cilostazol. Endothelial cell apoptosis and function, nitric oxide and superoxide production, phosphorylation (p) of Akt, and caspase-3 protein expression levels were investigated. AngII exposure resulted in the apoptosis of endothelial cells in vitro and in vivo. In vitro, cilostazol significantly suppressed the angII-induced apoptosis of HUVECs; however, this effect was reduced in the presence of LY294002, a phosphoinositide 3 kinase (PI3K) inhibitor. Furthermore, cilostazol suppressed the angII-induced p-Akt downregulation and cleaved caspase-3 upregulation. These effects were also alleviated by LY294002. In vivo, cilostazol suppressed the angII-induced endothelial cell apoptosis and dysfunction. Cilostazol was also demonstrated to partially reduced the angII-induced increase in superoxide production. The results of the present study suggested that cilostazol suppresses endothelial apoptosis and dysfunction by modulating the PI3K/Akt pathway.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

Phosphorylation and changes in the distribution of nucleolin promote tumor metastasis via the PI3K/Akt pathway in colorectal carcinoma

Here, we investigated the molecular mechanism underlying the changes in the distribution of nucleolin. Our study identified PI3K/Akt signaling as an essential pathway regulating the distribution of nucleolin. Furthermore, nucleolin can interact with phospho-PI3K-p55, and changes in the distribution of nucleolin were related to its phosphorylation. Subsequently, we analyzed the correlation of VEGF and nucleolin, and found that distribution of nucleolin related to metastatic potential. Finally, blocking cell surface nucleolin influences the process of epithelial-mesenchymal transitions. This indicates that nucleolin may be a novel cancer therapy target and a predictive marker for tumor migration in colorectal carcinoma.

Activation of NAD(P)H oxidase by tryptophan-derived 3-hydroxykynurenine accelerates endothelial apoptosis and dysfunction in vivo

RATIONALE

The kynurenine (Kyn) pathway is the major route for tryptophan (Trp) metabolism in mammals. The Trp-Kyn pathway is reported to regulate several fundamental biological processes, including cell death.

OBJECTIVE

The aim of this study was to elucidate the contributions and molecular mechanism of Trp-Kyn pathway to endothelial cell death.

METHODS AND RESULTS

Endogenous reactive oxygen species, endothelial cell apoptosis, and endothelium-dependent and endothelium-independent vasorelaxation were measured in aortas of wild-type mice or mice deficient for nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase subunits (p47(phox) or gp91(phox)) or indoleamine-pyrrole 2,3-dioxygenase 1 with or without angiotensin (Ang) II infusion. As expected, AngII increased plasma levels of Kyn- and 3-hydroxykynurenine-modified proteins in endothelial cells in vivo. Consistent with this, AngII markedly increased the expression of indoleamine-pyrrole 2,3-dioxygenase in parallel with increased expression of interferon-γ. Furthermore, in wild-type mice, AngII significantly increased oxidative stress, endothelial cell apoptosis, and endothelial dysfunction. These effects of AngII infusion were significantly suppressed in mice deficient for p47(phox), gp91(phox), or indoleamine-pyrrole 2,3-dioxygenase 1, suggesting that AngII-induced enhancement of Kynurenines via NAD(P)H oxidase-derived oxidants causes endothelial cell apoptosis and dysfunction in vivo. Furthermore, interferon-γ neutralization eliminates AngII-increased superoxide products and endothelial apoptosis by inhibiting AngII-induced Kynurenines generation, suggesting that AngII-activated Kyn pathway is interferon-γ-dependent. Mechanistically, we found that AngII-enhanced 3-hydroxykynurenine promoted the generation of NAD(P)H oxidase-mediated superoxide anions by increasing the translocation and membrane assembly of NAD(P)H oxidase subunits in endothelial cells, resulting in accelerated apoptosis and consequent endothelial dysfunction.

CONCLUSIONS

Kyn pathway activation accelerates apoptosis and dysfunction of the endothelium by upregulating NAD(P)H-derived superoxide.

Hepatocyte growth factor and lung fibrosis

Idiopathic pulmonary fibrosis is currently believed to be driven by alveolar epithelial cells, with abnormally activated alveolar epithelial cells accumulating in an attempt to repair injured alveolar epithelium (1). Thus, targeting the alveolar epithelium to prevent or inhibit the development of pulmonary fibrosis might be an interesting therapeutic option in this disease. Hepatocyte growth factor (HGF) is a growth factor for epithelial and endothelial cells, which is secreted by different cell types, especially fibroblasts and neutrophils. HGF has mitogenic, motogenic, and morphogenic properties and exerts an antiapoptotic action on epithelial and endothelial cells. HGF has also proangiogenic effect. In vitro, HGF inhibits epithelial-to-mesenchymal cell transition and promotes myofibroblast apoptosis. In vivo, HGF has antifibrotic properties demonstrated in experimental models of lung, kidney, heart, skin, and liver fibrosis. Hence, the modulation of HGF may be an attractive target for the treatment of lung fibrosis.

Mechanisms for vascular cell adhesion molecule-1 activation of ERK1/2 during leukocyte transendothelial migration

BACKGROUND

During inflammation, adhesion molecules regulate recruitment of leukocytes to inflamed tissues. It is reported that vascular cell adhesion molecule-1 (VCAM-1) activates extracellular regulated kinases 1 and 2 (ERK1/2), but the mechanism for this activation is not known. Pharmacological inhibitors of ERK1/2 partially inhibit leukocyte transendothelial migration in a multi-receptor system but it is not known whether VCAM-1 activation of ERK1/2 is required for leukocyte transendothelial migration (TEM) on VCAM-1.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we identified a mechanism for VCAM-1 activation of ERK1/2 in human and mouse endothelial cells. VCAM-1 signaling, which occurs through endothelial cell NADPH oxidase, protein kinase Cα (PKCα), and protein tyrosine phosphatase 1B (PTP1B), activates endothelial cell ERK1/2. Inhibition of these signals blocked VCAM-1 activation of ERK1/2, indicating that ERK1/2 is activated downstream of PTP1B during VCAM-1 signaling. Furthermore, VCAM-1-specific leukocyte migration under physiological laminar flow of 2 dynes/cm(2) was blocked by pretreatment of endothelial cells with dominant-negative ERK2 K52R or the MEK/ERK inhibitors, PD98059 and U0126, indicating for the first time that ERK regulates VCAM-1-dependent leukocyte transendothelial migration.

CONCLUSIONS/SIGNIFICANCE

VCAM-1 activation of endothelial cell NADPH oxidase/PKCα/PTP1B induces transient ERK1/2 activation that is necessary for VCAM-1-dependent leukocyte TEM.

Angiotensin II activates AMPK for execution of apoptosis through energy-dependent and -independent mechanisms

At the cellular level, 5'-AMP-activated protein kinase (AMPK) serves as a critical link between energy homeostasis and the regulation of fundamental biological activities, including apoptosis. Angiotensin (Ang) II plays a key role in fibrotic lung remodeling. We recently demonstrated that Ang II induces apoptosis in pulmonary artery endothelial cells (PAEC) through the Ang type 2 receptor (AT(2)). AT(2) activates Src-homology two-domain-containing phosphatase-2 (SHP-2) in a signaling cascade leading to Bcl-x(L) mRNA destabilization and initiation of intrinsic apoptosis. We investigated the requirement of AMPK and ATP generation for Ang II-induced apoptosis in PAEC. Ang II activated AMPK, which was required for ATP generation. Inhibition of ATP production by compound C, an AMPK inhibitor, or by oligomycin suppressed Ang II-induced apoptosis. Experiments in Chinese hamster ovary-K1 cells expressing ectopic AT(2) (wild-type, mutant D90A, or carboxy terminal truncated mutant tC319) demonstrated that AT(2) activation of AMPK required the active conformation of the receptor and the carboxy terminal 44 amino acids. AMPK associated with and activated SHP-2 and was required for Bcl-x(L) mRNA destabilization. These are the first findings demonstrating that AMPK is activated by Ang II to produce ATP required for apoptosis. Our data also indicate that AMPK plays an energy-independent role by mediating SHP-2 activation.