Transgenic expression of nonclassically secreted FGF suppresses kidney repair

Matrix metalloproteinase-21 promotes metastasis via increasing the recruitment and M2 polarization of macrophages in HCC

MMP-21 is a newly identified member of the matrix metalloproteinase family and has been reported to regulate both embryonic development and tumor progression. However, the roles of MMP-21 in hemofiltrate C-C chemokine (HCC) remain largely unclear. In this study, we used western blot, qPCR and immunohistochemistry (IHC) to determine the upregulation of MMP-21 in HCC tissues, and showed that the increase in MMP-21 was associated with vascular invasion and poor prognosis. Although changing levels of MMP-21 in HCC cell lines had no significant effect on cell migration or invasion abilities in in vitro transwell tests, both IHC analysis and in vivo mouse models proved that upregulated MMP-21 promoted metastasis. Functional enrichments of MMP-21 using The Cancer Genome Atlas (TCGA) data suggested that MMP-21 might regulate metastasis via macrophages. Further experiments proved that MMP-21 enhanced macrophage recruitment by increasing CCL-14 levels and promoted M2-type polarization of macrophage by elevating the expression of CSF-1 and FGF-1. Taken together, this study revealed that MMP-21 controlled the tumor microenvironment remodeling and functional regulation of macrophages to regulate HCC metastasis.

The Role of Fibroblast Growth Factor (FGF) Signaling in Tissue Repair and Regeneration

Fibroblast growth factors (FGFs) are a large family of secretory molecules that act through tyrosine kinase receptors known as FGF receptors. They play crucial roles in a wide variety of cellular functions, including cell proliferation, survival, metabolism, morphogenesis, and differentiation, as well as in tissue repair and regeneration. The signaling pathways regulated by FGFs include RAS/mitogen-activated protein kinase (MAPK), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)–protein kinase B (AKT), phospholipase C gamma (PLCγ), and signal transducer and activator of transcription (STAT). To date, 22 FGFs have been discovered, involved in different functions in the body. Several FGFs directly or indirectly interfere with repair during tissue regeneration, in addition to their critical functions in the maintenance of pluripotency and dedifferentiation of stem cells. In this review, we summarize the roles of FGFs in diverse cellular processes and shed light on the importance of FGF signaling in mechanisms of tissue repair and regeneration.

Cellular Mechanisms of FGF-Stimulated Tissue Repair

Growth factors belonging to the FGF family play important roles in tissue and organ repair after trauma. In this review, I discuss the regulation by FGFs of the aspects of cellular behavior important for reparative processes. In particular, I focus on the FGF-dependent regulation of cell proliferation, cell stemness, de-differentiation, inflammation, angiogenesis, cell senescence, cell death, and the production of proteases. In addition, I review the available literature on the enhancement of FGF expression and secretion in damaged tissues resulting in the increased FGF supply required for tissue repair.

FGF/FGFR2 Protects against Tubular Cell Death and Acute Kidney Injury Involving Erk1/2 Signaling Activation

Background

Fibroblast growth factors (FGFs) are heparin-binding proteins involved in a variety of biological processes, and part of them may act through binding with cell membrane receptor FGFR2.

Objectives

To clarify the role and mechanisms of FGFR2 signaling in tubular cell survival and acute kidney injury (AKI).

Method

In this study, kidney ischemia/reperfusion (IR) or cisplatin injection was used to induce AKI in mice.

Results

In the kidneys after IR or cisplatin injection, the expression of FGFs and Erk1/2 phosphorylation were elevated. To investigate the role of FGFs in tubular cell survival and AKI, a mouse model with tubular cell specific FGFR2 gene disruption was generated. The knockouts were born normal. At 2 months of age, about one-third of the knockouts developed mild hydronephrosis. Ablation of FGFR2 in tubular cells aggravated acute kidney dysfunction as well as tubular cell apoptosis induced by IR or cisplatin. In addition, Erk1/2 phosphorylation was less in the knockout kidneys than in control littermates at day 1 after cisplatin injection. In cultured NRK-52E cells, recombinant FGF2 protein induced Erk1/2 phosphorylation and inhibited cisplatin-induced cell death. PD98059 abolished Erk1/2 phosphorylation and partly reversed the protective effect of FGF2 on cisplatin-induced cell death.

Conclusions

This study indicates that FGF/FGFR2 signaling plays an important role in protecting against tubular cell death and AKI, which is partly through stimulating Erk1/2 activation.

Resistance to visceral obesity is associated with increased locomotion in mice expressing an endothelial cell-specific fibroblast growth factor 1 transgene

Overdevelopment of visceral adipose is positively correlated with the etiology of obesity-associated pathologies including cardiovascular disease and insulin resistance. However, identification of genetic, molecular, and physiological factors regulating adipose development and function in response to nutritional stress is incomplete. Fibroblast Growth Factor 1 (FGF1) is a cytokine expressed and released by both adipocytes and endothelial cells under hypoxia, thermal, and oxidative stress. Expression of Fibroblast Growth Factor 1 (FGF1) in adipose is required for normal depot development and remodeling. Loss of FGF1 leads to deleterious changes in adipose morphology, metabolism, and insulin resistance. Conversely, diabetic and obese mice injected with recombinant FGF1 display improvements in insulin sensitivity and a reduction in adiposity. We report in this novel, in vivo study that transgenic mice expressing an endothelial-specific FGF1 transgene (FGF1-Tek) are resistant to high-fat diet-induced abdominal adipose accretion and are more glucose-tolerant than wild-type control animals. Metabolic chamber analyses indicate that suppression of the development of visceral adiposity and insulin resistance was not associated with alterations in appetite or resting metabolic rate in the FGF1-Tek strain. Instead, FGF1-Tek mice display increased locomotor activity that likely promotes the utilization of dietary fatty acids before they can accumulate in adipose and liver. This study provides insight into the impact that genetic differences dictating the production of FGF1 has on the risk for developing obesity-related metabolic disease in response to nutritional stress.

FGF1 - a new weapon to control type 2 diabetes mellitus

A hypercaloric diet combined with a sedentary lifestyle is a major risk factor for the development of insulin resistance, type 2 diabetes mellitus (T2DM) and associated comorbidities. Standard treatment for T2DM begins with lifestyle modification, and includes oral medications and insulin therapy to compensate for progressive β-cell failure. However, current pharmaceutical options for T2DM are limited in that they do not maintain stable, durable glucose control without the need for treatment intensification. Furthermore, each medication is associated with adverse effects, which range from hypoglycaemia to weight gain or bone loss. Unexpectedly, fibroblast growth factor 1 (FGF1) and its low mitogenic variants have emerged as potentially safe candidates for restoring euglycaemia, without causing overt adverse effects. In particular, a single peripheral injection of FGF1 can lower glucose to normal levels within hours, without the risk of hypoglycaemia. Similarly, a single intracerebroventricular injection of FGF1 can induce long-lasting remission of the diabetic phenotype. This Review discusses potential mechanisms by which centrally administered FGF1 improves central glucose-sensing and peripheral glucose uptake in a sustained manner. Specifically, we explore the potential crosstalk between FGF1 and glucose-sensing neuronal circuits, hypothalamic neural stem cells and synaptic plasticity. Finally, we highlight therapeutic considerations of FGF1 and compare its metabolic actions with FGF15 (rodents), FGF19 (humans) and FGF21.

Sustained Inhibition of Proliferative Response After Transient FGF Stimulation Is Mediated by Interleukin 1 Signaling

Transient FGF stimulation of various cell types results in FGF memory--a sustained blockage of efficient proliferative response to FGF and other growth factors. FGF memory establishment requires HDAC activity, indicating its epigenetic character. FGF treatment stimulates proinflammatory NFκB signaling, which is also critical for FGF memory formation. The search for FGF-induced mediators of FGF memory revealed that FGF stimulates HDAC-dependent expression of the inflammatory cytokine IL1α. Similarly to FGF, transient cell treatment with recombinant IL1α inhibits the proliferative response to further FGF and EGF stimulation, but does not prevent FGF receptor-mediated signaling. Interestingly, like cells pretreated with FGF1, cells pretreated with IL1α exhibit enhanced restructuring of actin cytoskeleton and increased migration in response to FGF stimulation. IRAP, a specific inhibitor of IL 1 receptor, and a neutralizing anti-IL1α antibody prevent the formation of FGF memory and rescue an efficient proliferative response to FGF restimulation. A similar effect results following treatment with the anti-inflammatory agents aspirin and dexamethasone. Thus, FGF memory is mediated by proinflammatory IL1 signaling. It may play a role in the limitation of proliferative response to tissue damage and prevention of wound-induced hyperplasia.

Angiogenic response following renal ischemia reperfusion injury: new players

Ischemia-reperfusion (IR) injury can negatively influence the short- and long-term outcomes of kidney transplantation because it promotes acute tubular necrosis and tissue scarring and activates innate alloimmunity. The adaptive responses to IR are centrally involved in reducing tissue damage but can also be deleterious when they activate programmed cell death and inflammation. The HIF-1α-mediated angiogenic responses following IR at early and late stages are complex and poorly understood. The early stages of IR seem to be associated with an antiangiogenic response, whereas the hypoxia that follows IR at later stages may activate angiogenic factors such as vascular endothelial growth factor (VEGF) and may be beneficial by stabilizing the microvasculature and favoring local blood supply. In addition to HIF-1α, new players in angiogenesis, including mTOR and the unfolded protein response, may lead to innovative therapeutic strategies for treating patients with ischemia- and reperfusion-associated tissue inflammation and organ dysfunction.

Angiogenic cytokines in renovascular disease: do they have potential for therapeutic use?

Experimental and clinical studies suggest that the damage of the renal microvascular function and architecture may participate in the early steps of renal injury in chronic renal disease, irrespective of the cause. This supporting evidence has provided the impetus to targeting the renal microvasculature as an attempt to interfere with the progressive nature of the disease process. Chronic renovascular disease is often associated with renal microvascular dysfunction, damage, loss, and defective renal angiogenesis associated with progressive renal dysfunction and damage. It is possible that damage of the renal microvasculature in renovascular disease constitutes an initiating event for renal injury and contributes towards progressive and later on irreversible renal injury. Recent studies have suggested that protection of the renal microcirculation can slow or halt the progression of renal injury in this disease. This brief review will focus on the therapeutic potential and feasibility of using angiogenic cytokines to protect the kidney microvasculature in chronic renovascular disease. There is limited but provocative evidence showing that stimulation of vascular proliferation and repair using vascular endothelial growth factor or hepatocyte growth factor can slow the progression of renal damage, stabilize renal function, and protect the renal parenchyma. Such interventions may potentially constitute a sole strategy to preserve renal function and/or a co-adjuvant tool to improve the success of current therapeutic approaches in renovascular disease.

Protein-phospholipid interactions in nonclassical protein secretion: problem and methods of study

Extracellular proteins devoid of signal peptides use nonclassical secretion mechanisms for their export. These mechanisms are independent of the endoplasmic reticulum and Golgi. Some nonclassically released proteins, particularly fibroblast growth factors (FGF) 1 and 2, are exported as a result of their direct translocation through the cell membrane. This process requires specific interactions of released proteins with membrane phospholipids. In this review written by a cell biologist, a structural biologist and two membrane engineers, we discuss the following subjects: (i) Phenomenon of nonclassical protein release and its biological significance; (ii) Composition of the FGF1 multiprotein release complex (MRC); (iii) The relationship between FGF1 export and acidic phospholipid externalization; (iv) Interactions of FGF1 MRC components with acidic phospholipids; (v) Methods to study the transmembrane translocation of proteins; (vi) Membrane models to study nonclassical protein release.

Mouse model of ischemic acute kidney injury: technical notes and tricks

Renal ischemia-reperfusion leads to acute kidney injury (AKI), a major kidney disease associated with an increasing prevalence and high mortality rates. A variety of experimental models, both in vitro and in vivo, have been used to study the pathogenic mechanisms of ischemic AKI and to test renoprotective strategies. Among them, the mouse model of renal clamping is popular, mainly due to the availability of transgenic models and the relatively small animal size for drug testing. However, the mouse model is generally less stable, resulting in notable variations in results. Here, we describe a detailed protocol of the mouse model of bilateral renal ischemia-reperfusion. We share the lessons and experiences gained from our laboratory in the past decade. We further discuss the technical issues that account for the variability of this model and offer relevant solutions, which may help other investigators to establish a well-controlled, reliable animal model of ischemic AKI.