Regulation of basic fibroblast growth factor (bFGF) gene and protein expression following its release from sublethally injured endothelial cells

The Microenvironment of the Pathogenesis of Cardiac Hypertrophy

Pathological cardiac hypertrophy is a key risk factor for the development of heart failure and predisposes individuals to cardiac arrhythmia and sudden death. While physiological cardiac hypertrophy is adaptive, hypertrophy resulting from conditions comprising hypertension, aortic stenosis, or genetic mutations, such as hypertrophic cardiomyopathy, is maladaptive. Here, we highlight the essential role and reciprocal interactions involving both cardiomyocytes and non-myocardial cells in response to pathological conditions. Prolonged cardiovascular stress causes cardiomyocytes and non-myocardial cells to enter an activated state releasing numerous pro-hypertrophic, pro-fibrotic, and pro-inflammatory mediators such as vasoactive hormones, growth factors, and cytokines, i.e., commencing signaling events that collectively cause cardiac hypertrophy. Fibrotic remodeling is mediated by cardiac fibroblasts as the central players, but also endothelial cells and resident and infiltrating immune cells enhance these processes. Many of these hypertrophic mediators are now being integrated into computational models that provide system-level insights and will help to translate our knowledge into new pharmacological targets. This perspective article summarizes the last decades' advances in cardiac hypertrophy research and discusses the herein-involved complex myocardial microenvironment and signaling components.

Angiopoietin-1 prevents severe bleeding complications induced by heparin-like drugs and fibroblast growth factor-2 in mice

Critically ill children can develop bleeding complications when treated with heparin-like drugs. These events are usually attributed to the anticoagulant activity of these drugs. However, previous studies showed that fibroblast growth factor-2 (FGF-2), a heparin-binding growth factor released in the circulation of these patients, could precipitate intestinal hemorrhages in mice treated with the heparin-like drug pentosan polysulfate (PPS). Yet very little is known about how FGF-2 induces bleeding complications in combination with heparin-like drugs. Here, we examined the mechanisms by which circulating FGF-2 induces intestinal hemorrhages in mice treated with PPS. We used a well-characterized mouse model of intestinal hemorrhages induced by FGF-2 plus PPS. Adult FVB/N mice were infected with adenovirus carrying Lac-Z or a secreted form of recombinant human FGF-2, and injected with PPS, at doses that do not induce bleeding complications per se. Mice treated with FGF-2 in combination with PPS developed an intestinal inflammatory reaction that increased the permeability and disrupted the integrity of submucosal intestinal vessels. These changes, together with the anticoagulant activity of PPS, induced lethal hemorrhages. Moreover, a genetically modified form of the endothelial ligand angiopoietin-1 (Ang-1*), which has powerful antipermeability and anti-inflammatory activity, prevented the lethal bleeding complications without correcting the anticoagulant status of these mice. These findings define new mechanisms through which FGF-2 and Ang-1* modulate the outcome of intestinal bleeding complications induced by PPS in mice and may have wider clinical implications for critically ill children treated with heparin-like drugs.

Urinary biomarkers of kidney diseases in HIV-infected children

A significant number of children infected with the human immunodeficiency virus 1 (HIV-1) virus all over the world are at risk of developing renal diseases that could have a significant impact on their treatment and quality of life. It is necessary to identify children undergoing the early stages of these renal diseases, as well as the potential renal toxicity that could be caused by antiretroviral drugs, in order to prevent the development of cardiovascular complications and chronic renal failure. This article describes the most common renal diseases seen in HIV-infected children, as well as the value and limitations of the clinical markers that are currently being used to monitor their renal function and histological damage in a noninvasive manner. In addition, we discuss the progress made during the last 10 years in the discovery and validation of new renal biomarkers for HIV-infected children and young adults. Although significant progress has been made during the early phases of the biomarkers discovery, more work remains to be done to validate the new biomarkers in a large number of patients. The future looks promising, however, the new knowledge needs to be integrated and validated in the context of the clinical environment where these children are living.

A pilot study of urinary fibroblast growth factor-2 and epithelial growth factor as potential biomarkers of acute kidney injury in critically ill children

BACKGROUND

Acute kidney injury (AKI) increases the morbidity of critically ill children. Thus, it is necessary to identify better renal biomarkers to follow the outcome of these patients. This prospective case-control study explored the clinical value of a urinary biomarker profile comprised of neutrophil gelatinase lipocalin (uNGAL), fibroblast growth factor-2 (uFGF-2), and epidermal growth factor (uEGF) to follow these patients.

METHODS

Urine samples were collected from 21 healthy children, and 39 critically ill children (mean age 7.5 years ± 6.97 SD) admitted to a pediatric intensive care unit with sepsis or requiring extra corporeal membrane oxygenation (ECMO). uNGAL, uFGF-2, and uEGF levels were measured using ELISA kits during the first 24 h of admission to PICU, at peak of illness, and upon resolution of the critical illness.

RESULTS

On admission, the uNGAL and uFGF-2 levels were increased, and the uEGF levels were decreased, in critically ill children with AKI (n = 19) compared to those without AKI (n = 20), and healthy controls. A biomarker score using the combined cut-off values of uNGAL, uFGF-2, and uEGF (AUC = 0.90) showed the highest specificity to identify children with AKI, relative to each biomarker alone. uNGAL and uFGF-2 on admission showed high sensitivity and specificity to predict mortality (AUC = 0.82).

CONCLUSIONS

The biomarker profile comprised of uNGAL, uFGF-2, and uEGF increased the specificity to detect AKI in critically ill children, when compared to each biomarker used alone. uNGAL and uFGF-2 may also predict the risk of death. Further validation of these findings in a large sample size is warranted.

Transgenic expression of nonclassically secreted FGF suppresses kidney repair

FGF1 is a signal peptide-less nonclassically released growth factor that is involved in angiogenesis, tissue repair, inflammation, and carcinogenesis. The effects of nonclassical FGF export in vivo are not sufficiently studied. We produced transgenic mice expressing FGF1 in endothelial cells (EC), which allowed the detection of FGF1 export to the vasculature, and studied the efficiency of postischemic kidney repair in these animals. Although FGF1 transgenic mice had a normal phenotype with unperturbed kidney structure, they showed a severely inhibited kidney repair after unilateral ischemia/reperfusion. This was manifested by a strong decrease of postischemic kidney size and weight, whereas the undamaged contralateral kidney exhibited an enhanced compensatory size increase. In addition, the postischemic kidneys of transgenic mice were characterized by hyperplasia of interstitial cells, paucity of epithelial tubular structures, increase of the areas occupied by connective tissue, and neutrophil and macrophage infiltration. The continuous treatment of transgenic mice with the cell membrane stabilizer, taurine, inhibited nonclassical FGF1 export and significantly rescued postischemic kidney repair. It was also found that similar to EC, the transgenic expression of FGF1 in monocytes and macrophages suppresses kidney repair. We suggest that nonclassical export may be used as a target for the treatment of pathologies involving signal peptide-less FGFs.

Role of circulating fibroblast growth factor-2 in lipopolysaccharide-induced acute kidney injury in mice

Fibroblast growth factor-2 (FGF-2) is an angiogenic growth factor involved in renal growth and regeneration. Previous studies in rodents revealed that single intrarenal injections of FGF-2 improved the outcome of acute kidney injury (AKI). Septic children usually show elevated plasma levels of FGF-2, and are at risk of developing AKI. However, the role of circulating FGF-2 in the pathogenesis of AKI is not well understood. We have developed a mouse model to determine how FGF-2 released into the circulation modulates the outcome of AKI induced by lipopolysaccharide (LPS). Young FVB/N mice were infected with adenoviruses carrying a secreted form of human FGF-2 or control LacZ vectors. Subsequently, when the circulating levels of FGF-2 were similar to those seen in septic children, mice were injected with a non-lethal dose of LPS or control buffer. All mice injected with LPS developed hypotension and AKI, from which they recovered after 5 days. FGF-2 did not improve the outcome of AKI, and induced more significant renal proliferative and apoptotic changes during the recovery phase. These findings suggest that circulating FGF-2 may not necessarily prevent the development or improve the outcome of AKI. Moreover, the renal accumulation of FGF-2 might cause further renal damage.

Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species

Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm(-2) had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm(-2) plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization.

Postischemic treatment with ethyl pyruvate prevents adenosine triphosphate depletion, ameliorates inflammation, and decreases thrombosis in a murine model of hind-limb ischemia and reperfusion

INTRODUCTION

Experiments were designed to investigate the effects of ethyl pyruvate (EP) in a murine model of hind-limb ischemia-reperfusion (IR) injury.

METHODS

C57BL6 mice underwent 90 minutes of unilateral ischemia followed by 24 hours of reperfusion using two treatment protocols. For the preischemic treatment (pre-I) protocol, mice (n=6) were given 300 mg/kg EP before ischemia, followed by 150 mg/kg of EP just before reperfusion and at 6 hours and 12 hours after reperfusion. In a postischemic treatment (post-I) protocol, mice (n=7) were treated with 300 mg/kg EP at the end of the ischemic period, then 15 minutes later, and 2 hours after reperfusion and 150 mg/kg of EP at 4 hours, 6 hours, 10 hours, 16 hours, and 22 hours after reperfusion. Controls mice for both protocols were treated with lactated Ringers alone at time intervals identical to EP. Skeletal muscle levels of adenosine triphosphate (ATP), interleukin-1β, keratinocyte chemoattractant protein, and thrombin antithrombin-3 complex were measured. Skeletal muscle architectural integrity was assessed microscopically.

RESULTS

ATP levels were higher in mice treated with EP compared with controls under the both treatment protocols (p=0.02). Interleukin-1β, keratinocyte chemoattractant protein, thrombin antithrombin-3 complex (p<0.05), and the percentage of injured fibers (p<0.0001) were significantly decreased in treated versus control mice under the both protocols.

CONCLUSION

Muscle fiber injury and markers of tissue thrombosis and inflammation were reduced, and ATP was preserved with EP in pre-I and post-I protocols. Further investigation of the efficacy of EP to modulate IR injury in a larger animal model of IR injury is warranted.

Endothelial cell proliferation is enhanced by low dose non-thermal plasma through fibroblast growth factor-2 release

Non-thermal dielectric barrier discharge plasma is being developed for a wide range of medical applications, including wound healing, blood coagulation, and malignant cell apoptosis. However, the effect of non-thermal plasma on the vasculature is unclear. Blood vessels are affected during plasma treatment of many tissues and may be an important potential target for clinical plasma therapy. Porcine aortic endothelial cells were treated in vitro with a custom non-thermal plasma device. Low dose plasma (up to 30 s or 4 J cm(-2)) was relatively non-toxic to endothelial cells while treatment at longer exposures (60 s and higher or 8 J cm(-2)) led to cell death. Endothelial cells treated with plasma for 30 s demonstrated twice as much proliferation as untreated cells five days after plasma treatment. Endothelial cell release of fibroblast growth factor-2 (FGF2) peaked 3 h after plasma treatment. The plasma proliferative effect was abrogated by an FGF2 neutralizing antibody, and FGF2 release was blocked by reactive oxygen species scavengers. These data suggest that low dose non-thermal plasma enhances endothelial cell proliferation due to reactive oxygen species mediated FGF2 release. Plasma may be a novel therapy for dose-dependent promotion or inhibition of endothelial cell mediated angiogenesis.

Evidence for a major role of endogenous fibroblast growth factor-2 in apoptotic cortex-induced subventricular zone cell proliferation

In the adult mammalian brain, neural stem cells persist in the subventricular zone (SVZ) of lateral ventricles. It is well established that cortical damage leads to SVZ cell proliferation and neuronal differentiation. We have previously demonstrated in rat that, when treated with the apoptosis-inducing agent staurosporine, cortex explants release heat-labile factors that promote SVZ cell culture proliferation. In the present report, we investigated in vitro mechanisms involved in cortex injury-triggered neurogenesis in the rat. We demonstrated, using immunoblotting analysis and fibroblast growth factor (FGF)-2 enzyme-linked sandwich immunosorbent assay, that treatment of cortex explants with apoptosis-inducing agents increases the release of FGF-2. We next determined the effects of apoptotic cortex-released factors in regulating SVZ cell proliferation and neuronal differentiation by using bromodeoxyuridine incorporation and microtubule-associated protein 2 immunostaining assays, respectively. We found that conditioned media derived from staurosporine-treated cortex explants enhanced SVZ cell culture proliferation and differentiation by over 50 and 80%, respectively. Finally, we showed that immunodepletion of FGF-2 or pharmacological blockade of FGF-2 receptor by SU5402 completely abolished staurosporine-treated cortex mitogenic activity on SVZ cultures but did not alter its activity on neuronal cell differentiation. Altogether, the present report establishes that the release of endogenous FGF-2 by apoptotic cortex explants plays a major role in the induction of SVZ cell proliferation but not neuronal differentiation, which probably depends on the release of other as yet unidentified cortical factors.

A novel role of fibroblast growth factor-2 and pentosan polysulfate in the pathogenesis of intestinal bleeding in mice

Pentosan polysulfate (PPS) is a heparin-like polysaccharide that can affect the binding interactions of fibroblast growth factor (FGF-2) with its high-affinity receptors. Patients with angiogenic tumors frequently show high levels of FGF-2 in the circulation. Since FGF-2 is a heparin-binding angiogenic growth factor, PPS has been used successfully to block its activity in patients with angiogenic tumors. However, because of its heparin-like activity, the major toxic effect of PPS is the development of bleeding disorders. The role that circulating FGF-2 plays in the pathogenesis of bleeding disorders in patients treated with PPS is currently unknown. Here we hypothesized that FGF-2 might play a physiological role in the pathogenesis of intestinal bleeding induced by PPS. This hypothesis is supported by previous studies showing that PPS is accumulated in the intestine and that circulating FGF-2 specifically binds to and modulates the angiogenic activity of intestinal submucosal endothelial cells. We used recombinant adenoviral vectors carrying a secreted form of FGF-2 and LacZ control vectors to determine whether high levels of circulating FGF-2 facilitate the development of intestinal bleeding disorders in FVB/N and C57BL/6J mice treated with PPS. We found that PPS, acting together with FGF-2, induced structural changes in intestinal vessels leading to the development of lethal intestinal hemorrhages. These findings might have wider clinical implications for the systemic use of PPS and other heparinoids in the treatment of patients with angiogenic diseases associated with high levels of circulating FGF-2.

Impact of basic FGF expression in astrocytes on dopamine neuron synaptic function and development

Behavioural sensitization to amphetamine (AMPH) requires action of the drug in the ventral midbrain where dopamine (DA) neurons are located. In vivo studies suggest that AMPH sensitization requires enhanced expression of basic fibroblast growth factor (bFGF) in the nucleus of midbrain astrocytes. One idea is that the AMPH-induced increase in bFGF expression in astrocytes leads to enhanced secretion of this peptide and to long-term plasticity in DA neurons. To study directly the effects of astrocytic expression of bFGF on DA neurons, we established a cell-culture model of mesencephalic astrocytes and DA neurons. Immunolabelling showed that even in the absence of a pharmacological stimulus, the majority of mesencephalic astrocytes in culture express bFGF at a nuclear level. Arguing against the idea that bFGF was secreted, bFGF was undetectable in the extracellular medium (below 10 pg/mL). However, supplementing culture medium with exogenous bFGF at standard concentrations (20 ng/mL) led to a dramatic change in the morphology of astrocytes, increased spontaneous DA release, and inhibited synapse formation by individual DA neurons. RNA interference (siRNA) against bFGF mRNA, caused a reduction in DA release but produced no change in synaptic development. Together these data demonstrate that under basal conditions (in the absence of a pharmacological stimulus such as amphetamine) bFGF is not secreted even though there is abundant nuclear expression in astrocytes. The effects of bFGF seen here on DA neurons are thus likely to be mediated through more indirect glial-neuronal interactions, leading to enhanced DA release without a necessary change in synapse number.

Role of fibroblast growth factor-binding protein in the pathogenesis of HIV-associated hemolytic uremic syndrome

A characteristic finding of childhood HIV-associated hemolytic uremic syndrome (HIV-HUS) is the presence of endothelial injury and microcystic tubular dilation, leading to a rapid progression of the renal disease. We have previously shown that a secreted fibroblast growth factor-binding protein (FGF-BP) is upregulated in kidneys from children affected with HIV-HUS and HIV nephropathy. Here, we sought to determine the potential role of FGF-BP in the pathogenesis of HIV-HUS. By immunohistochemical and in situ hybridization studies, we observed FGF-BP protein and mRNA upregulation in regenerating renal tubular epithelial cells from kidneys of HIV-Tg26mice with late-stage renal disease, that is, associated with the development of microcystic tubular dilatation and accumulation of FGF-2. Moreover, FGF-BP increased the FGF-2-dependent growth and survival of cultured primary human renal glomerular endothelial cells and enhanced FGF-2-induced MAPK/ERK2 activation, as well as the proliferation of immortalized GM7373 endothelial cells. We propose that HIV-Tg26mice are a clinically relevant model system to study the role of FGF-BP in the pathogenesis of HIV-associated renal diseases. Furthermore, the upregulation of FGF-BP by regenerating renal tubular epithelial cells may provide a mechanism by which the regenerative and angiogenic activity of FGF-2 in renal capillaries can be modulated in children with HIV-HUS and other renal disease.

Fibroblast growth factor-2 increases the renal recruitment and attachment of HIV-infected mononuclear cells to renal tubular epithelial cells

The role of circulating growth factors in the pathogenesis of childhood HIV-1-associated nephropathy (HIVAN) is not clearly understood. In previous studies, we found a significant accumulation of fibroblast growth factor-2 (FGF-2) in the circulation and kidneys of children with HIVAN. The purpose of this study was to determine whether circulating FGF-2 may play a role in the pathogenesis of HIVAN by increasing the renal recruitment and attachment of HIV-infected mononuclear cells to renal epithelial cells. Using in vitro cell adhesion assays, we showed that FGF-2 increased the attachment of peripheral blood mononuclear cells (PBMCs) to fibronectin-coated tissue culture dishes by approximately threefold through a mechanism that involved the alpha5 integrin subunit. In addition, we found that FGF-2 induces a similar increase in the attachment of HIV-infected PBMCs and monocytes/macrophages to plastic tissue culture dishes and to monolayers of primary renal tubular epithelial cells harvested from the urine of HIV-infected children with renal disease. Finally, we injected 16 adult C57Bl6/J male mice with recombinant adenoviral vectors carrying either the LacZ gene or a secreted form of human FGF-2 (5 x 10(8)pfu/mouse) and demonstrated that high levels of circulating FGF-2 can increase the renal recruitment of circulating inflammatory cells and induce transient tubulointerstitial injury in vivo. These data suggest that FGF-2 may have an immunomodulatory role in the pathogenesis of HIVAN by recruiting HIV-infected cells in the kidney.

An in vitro model for studying vascular injury after laser microdissection

We have developed an in vitro model for studying vascular injury. After 7-10 days in a three-dimensional collagen gel culture, capillary-like tubes were formed in the collagen gels. We injured these capillary-like tubes with a laser microdissection system or a scrape method with razors and then examined the collagen gel culture by phase contrast and electron microscopy. After laser injury, profuse necrotic cells were observed around the injured capillary-like tubes and within the tubular lumen compared to the razor injury. We then isolated total RNA from these cultures and prepared cDNA for investigations by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Quantitative real time RT-PCR revealed the up-regulation of transcription factor early growth response-1 (Egr-1) after both laser and razor injury, accompanied by the up-regulation of fibroblast growth factor-2 (FGF-2), a proangiogenic factor downstream of Egr-1. The effective laser energy is concentrated on the minute focal spot only. These methods provide a useful in vitro model for studying vascular injury.

Molecular mediators of hypoxic-ischemic injury and implications for epilepsy in the developing brain

Perinatal hypoxia-ischemia (HI) is the most common cause of cerebral palsy, and an important consequence of perinatal HI is epilepsy. Epilepsy is a disorder in which the balance between cerebral excitability and inhibition is tipped toward uncontrolled excitability. Selected neuronal circuits as well as certain populations of glial cells die from the excitotoxicity triggered by HI. Excitotoxicity, a term referring to cell death caused by overstimulation of the excitatory glutamate neurotransmitter receptors, plays a critical role in brain injury caused by perinatal HI. Ample evidence suggests distinct differences between the immature and mature brain with respect to the pathology and consequences of hypoxic-ischemic brain injury. Thus, the intrinsic vulnerability of specific cell types and systems in the developing brain is particularly important in determining the final pattern of damage and functional disability caused by perinatal HI. These patterns of neuronal vulnerability are associated with clinical syndromes of neurologic disorders such as cerebral palsy, epilepsy, and seizures. Recent studies have uncovered important molecular and cellular aspects of hypoxic-ischemic brain injury. The cascade of biochemical and histopathological events initiated by HI can extend for days to weeks after the insult is triggered, which may provide a "therapeutic window" for intervening in the pathogenesis in the developing brain. Activation of apoptotic programs accounts for the majority of HI-induced pathophysiology in neonatal brain disorders. New experimental approaches to protecting brain tissue from the effects of neonatal HI include administration of neuronal growth factors and effective inhibition of the death effector pathways, such as caspase cascade, and their downstream targets, which execute apoptosis and/or induction of their regulatory cellular proteins. Our recent findings that a novel neuronal protein, neuronal pentraxin 1 (NP1), is induced following HI in neonatal brain and that NP1 gene silencing is neuroprotective suggest that NP1 could be a new molecular target in the central neurons for preventing HI injury in developing brain. Most importantly, the specific interactions between NP1 and the excitatory glutamate receptors and their colocalization further implicate a role for this novel neuronal protein in the excitotoxic cascade. Recent experimental work suggests that these approaches may be effective during a longer therapeutic window after the insult, as they are acting on events that are relatively delayed, creating the potential for therapeutic interventions for these lifelong neurological disabilities.

Temporary loss of plasma membrane integrity in orthodontic tooth movement

In these studies, a rat model of orthodontic tooth movement was used to support the premise that periodontal ligament (PDL) cells experience plasma membrane disruption and resealing events upon application of mechanical stress. Immunoelectron microscopy, showed albumin in the cytoplasm of PDL and bone lining cells in the tension side of moved molars. The intracellular localization of this large molecule (60 KDa) suggests that these cells have undergone plasma membrane disruption and resealing. To further assess these and previous findings, fluorescent dyes (FITC-dextran and rhodamine-dextran) were delivered into the vascular system followed by application of 50 g of static load. These large dextran molecules (10 KDa) were preferentially taken up by PDL cells of the buccal (tension side) of moved molars. These cells were determined to be viable since dead cells do not retain these diffusible tracers. These studies provide evidence of a novel cellular mechanism for uptake and release of molecules and suggest a potential role for plasma membrane disruption in the mechanotransduction of orthodontic tooth movement.

A 20-year history of childhood HIV-associated nephropathy

In 1984, physicians in New York and Miami reported HIV-infected adult patients with heavy proteinuria and rapid progression to end-stage renal disease. These patients showed large edematous kidneys with a combination of focal segmental glomerulosclerosis (FSGS) and tubulointerstitial lesions. This renal syndrome, named HIV-associated nephropathy (HIVAN), was found predominantly in African Americans. Subsequent studies confirmed the presence of HIVAN in children, who frequently develop nephrotic syndrome in association with FSGS and/or mesangial hyperplasia with microcystic tubular dilatation. Since then, substantial progress has been made in our understanding of the etiology and pathogenesis of HIVAN. This article reviews 20 years of research into the pathogenesis of HIVAN and discusses how these concepts could be applied to the treatment of children with HIVAN. HIV-1 infection plays a direct role in the pathogenesis of childhood HIVAN, at least partially by affecting the growth and differentiation of glomerular and tubular epithelial cells and enhancing the renal recruitment of infiltrating mononuclear cells and cytokines. An up-regulation of renal heparan sulfate proteoglycans seems to play a relevant role in this process, by increasing the recruitment of heparin-binding growth factors (i.e., FGF-2), chemokines, HIV-infected cells, and viral proteins (i.e., gp120, Tat). These changes enhance the infectivity of HIV-1 in the kidney and induce injury and proliferation of intrinsic renal cells. Highly active anti-retroviral therapy (HAART) appears to be the most promising treatment to prevent the progression of childhood HIVAN. Hopefully, in the near future, better education, prevention, and treatment programs will lead to the eradication of this fatal childhood disease.

Removal of heparan sulfate by heparinase treatment inhibits FGF-2-dependent smooth muscle cell proliferation in injured rat carotid arteries

Smooth muscle cells (SMC) of the rat carotid arterial media proliferate and migrate in response to injury during the formation of a neointima. The interaction of fibroblast growth factor (FGF-2), which is released at the site of injury, with heparan sulfate proteoglycans (HSPGs) is necessary to induce signaling, which elicits an FGF-dependent mitogenic response by arterial smooth muscle cells, and also serves as a mechanism for storage of the growth factor within the extracellular matrix. However, whether these interactions are critical during neointimal formation has not been directly tested. In this study, a model of FGF-2-dependent medial SMC mitogenic response in balloon-injured rat carotid artery was used to test the effect of degradation of vessel wall heparan sulfate on subsequent SMC proliferation. Treatment of balloon-catheterized rat carotid arteries with chondroitin ABC lyase and/or heparin lyases eliminated heparan sulfates in the vessel wall, as determined by immunoperoxidase staining. In contrast, the distribution in the carotid vessel wall of the large core protein of perlecan, a major vessel wall HSPG that binds FGF-2, is not decreased. The effect of glycosaminoglycan digestion in situ on medial SMC proliferation in response to a bolus injection of FGF-2 after injury was determined by measuring the percentage of SMC nuclei that incorporated 5-bromo-2'-deoxyuridine (BrdU) 48 h after injury. Enzymatic removal of heparan sulfate reduced BrdU incorporation into medial SMC by 60-70% (P < 0.001) at 48 h after injury. Moreover, pre-incubation of FGF-2 with heparin prior to injection restored SMC replication to the levels present in injured vessels treated with buffer alone (P < 0.01). These experiments indicate that endogenous HSPGs are essential to promote FGF-2-driven medial SMC proliferation following injury, and that heparinase treatment can abrogate FGF-2-dependent responses in vivo.

FGF-2 regulates neurogenesis and degeneration in the dentate gyrus after traumatic brain injury in mice

We studied the role of FGF-2 on regulation of neurogenesis and cell loss in the granule cell layer (GCL) of the hippocampal dentate gyrus after experimental traumatic brain injury (TBI). In both FGF-2(-/-) and FGF-2(+/+) mice subjected to controlled cortical impact, the number of dividing cells labeled with BrdU, injected on posttrauma days 6 through 8, increased at 9 days after TBI, and the number of BrdU-positive cells colabeled with neuron-specific nuclear antigen significantly increased at 35 days. However, in injured FGF-2-/- mice, BrdU-positive cells and BrdU-positive neurons (days 9, 35) were fewer compared with FGF-2(+/+) mice. There was also a decrease in the volume of the GCL and the number of GCL neurons after TBI in both FGF-2(-/-) and FGF-2(+/+) mice, but the decrease in both was greater in FGF-2-/- mice at 35 days. Overexpression of FGF-2 by intracerebral injection of herpes simplex virus-1 amplicon vectors encoding this factor increased numbers of dividing cells (day 9) and BrdU-positive neurons (day 35) significantly in C57BL/6 mice. Furthermore, the decrease in GCL volume was also attenuated. These results suggest that FGF-2 upregulates neurogenesis and protects neurons against degeneration in the adult hippocampus after TBI, and that FGF-2 supplementation via gene transfer can reduce GCL degeneration after TBI.

Changes in FGF-2 expression in the distal spinal cord stump after complete cord transection: a comparison between infant and adult rats

STUDY DESIGN

Expression patterns of fibroblast growth factor-2 (FGF-2) in distal transected spinal cord in infant and adult rats were determined by reverse-transcription polymerase chain reaction (RT-PCR) and immunostaining.

OBJECTIVE

To reveal the expression pattern of FGF-2 in distal transected cord of infant and adult rats.

SUMMARY OF BACKGROUND DATA

Descending fibers in the spinal cord of infant and adult rats show different regenerative capacity. One explanation is that different levels of FGF-2, an important neurotrophic factor for promoting neurite outgrowth and repair, are expressed in the distal transected cords of the rats, providing different levels of support for severed axons.

MATERIALS AND METHODS

Spinal cords of infant and adult rats were completely transected. At 12, 24, and 72 hours and at 1 week, segments of distal spinal cord tissues were removed and expression of FGF-2 mRNA was evaluated by RT-PCR. The distribution of FGF-2 and the phenotype of FGF-2-positive cells were determined by immunostaining.

RESULTS

Expression of FGF-2 mRNA was shown to be up-regulated in the distal cord of infant rats but not adult rats. Immunohistochemical analysis showed that neurons in distal cord of infant rats were rich in FGF-2 immunoreactivity (IR), whereas in adult rat neurons FGF-2 IR was hardly observed at all, although a few FGF-2-positive astrocytes were observed in the white matter.

CONCLUSION

After complete spinal cord transection, the expression of FGF-2 in the distal cord of infant rats was high compared with that of adults. This may provide neurotrophic support for axonal extension and functional recovery.

Rho and basic fibroblast growth factor involvement in centrosome redistribution and actin microfilament remodeling during early endothelial wound repair

OBJECTIVE

We have shown that centrosome redistribution to the front of the cell and actin microfilament remodeling occurs during the initiation of early porcine aortic endothelial wound repair even before cell migration. Because Ras homologous protein (Rho) induces actin microfilament polymerization, interacts with microtubules, and is believed to be activated by growth factors, we set forth to study the regulatory roles of basic fibroblast growth factor (bFGF) and Rho signaling on centrosome redistribution and actin microfilament remodeling in endothelial cells at an in vitro wound edge.

STUDY DESIGN

With double immunofluorescent confocal microscopy, we studied the distribution of various cytoskeletal proteins in wounded porcine aortic endothelial cells in response to bFGF and exoenzyme C3 treatments.

RESULTS

We showed that the addition of 10 ng/mL bFGF for 3 hours after wounding resulted in a significant increase (P <.05) in cells at the wound edge with central microfilaments oriented perpendicular to the wound. Rho inhibition with 2 microg/mL C3 resulted in the reduction of phosphotyrosine, paxillin, and central microfilament staining. Centrosome redistribution and endothelial cell elongation also were significantly inhibited (P <.05) with C3, resulting in decreased wound closure. However, inhibition was reduced with coincubation of bFGF with C3, which also returned the rate of endothelial wound closure toward control values. This Rho-independent bFGF-induced centrosome redistribution was associated with the cells showing a significant increase (P <.05) in acetylated microtubules that extended from the centrosome to the posterior cell border.

CONCLUSION

We conclude that Rho regulates centrosome redistribution and central microfilament remodeling during early endothelial wound repair, and bFGF promotes actin remodeling through a downstream Rho-dependent pathway and promotes centrosome redistribution, at least in part, with a Rho-independent pathway.

Basic fibroblast growth factor among children with diarrhea-associated hemolytic uremic syndrome

Diarrhea-associated hemolytic uremic syndrome (D+HUS) is characterized by endothelial injury and activation of inflammatory cytokines. Basic fibroblast growth factor (bFGF) is an angiogenic peptide released in response to vascular damage. The plasma concentrations and urinary excretion of bFGF during the course of D+HUS were determined, in comparison with the levels of various inflammatory cytokines, and changes were correlated with clinical and laboratory features of the disease. Serial plasma and urine samples were collected from 31 children with D+HUS, during the acute (days 1 to 7 of hospitalization) and recovery (through day 60 after discharge from the hospital) phases of the disease. The patients were enrolled in the multicenter trial of SYNSORB Pk (SYNSORB Biotech, Calgary, Alberta, Canada) treatment for D+HUS. bFGF, interleukin-1alpha (IL-1alpha), IL-8, and tumor necrosis factor-alpha levels were determined with enzyme-linked immunosorbent assays. bFGF was detected in urine and plasma samples more frequently than were IL-1alpha, IL-8, and tumor necrosis factor-alpha. There was an acute increase in urinary bFGF excretion, which returned to normal during convalescence. Urinary excretion of bFGF during the acute phase was higher among patients who required dialysis, compared with those who did not (48.9 +/- 15.0 and 28.9 +/- 9.0 pg/ml, respectively; P < 0.05). Plasma bFGF concentrations were persistently elevated throughout the period of hospitalization and the follow-up period among patients with D+HUS. Urinary excretion and plasma levels of bFGF were comparable for the SYNSORB Pk-treated (n = 19) and placebo-treated (n = 12) groups. Measurements of urinary and plasma concentrations of bFGF among patients with D+HUS may be useful indices for assessment of the severity of acute renal disease and the timing and adequacy of the systemic angiogenic process during early convalescence.

Regulation of renal proximal tubular epithelial cell fibroblast growth factor-2 generation by heparin

Progression of renal disease is closely correlated to the degree of renal interstitial fibrosis, and evidence is increasing that epithelial cells of the renal proximal tubule (PTCs) may contribute to its pathogenesis. Such cytokines as basic fibroblast growth factor (FGF-2) have been implicated in progressive renal injury, and we previously showed that PTCs are a source of this cytokine. FGF-2 is characterized by its high affinity for heparin, and numerous studies have suggested that heparin may modify the progression of renal disease. The current study examined how heparin influenced FGF-2 generation and bioactivity in the human renal epithelial PTC line, HK-2. Incubation of HK-2 cells with heparin led to a dose- and time-dependent increase in FGF-2 concentration in the culture supernatant that was not accompanied by alterations in FGF-2 messenger RNA expression, assessed by reverse-transcriptase polymerase chain reaction and Northern analysis. The heparin-induced increase in FGF-2 concentration was accompanied by a decrease in the amount of FGF-2 bound to the extracellular matrix, although this accounted for only a small proportion of the total FGF-2 generated. Induction of FGF-2 by 2-O-desulfated heparin, together with a reduction in total cell-associated FGF-2 and anti-FGF-2 antibody binding to fixed permeabilized cells after the addition of heparin, suggested that the FGF-2 released was mainly derived from a preformed intracellular source. That FGF-2 was predominantly derived from an intracellular pool was also confirmed by pulse chase experiments. The addition of heparin resulted in the generation of bioinactive FGF-2, judged by in vitro fibroblast proliferation. Conversely, heparitinase treatment of supernatant samples from heparin-treated cells and the addition of 2-O-desulfated heparin resulted in the generation of active FGF-2, suggesting that the generation of bioinactive FGF-2 was related to binding of FGF-2 by extracellular heparin after its release from cells. These data show that heparin depletes both the cell and surrounding matrix of FGF-2 and suggest that FGF-2 released from cells was mainly derived from a preformed intracellular source. Furthermore, FGF-2 released from epithelial PTCs after the application of heparin was bioinactive. This likely resulted from released FGF-2 binding to an excess of extracellular heparin. Results presented here therefore suggest a mechanism by which heparin, through its effect on depletion of matrix and cells of FGF-2 and its generation in an inactive form, may influence progressive renal interstitial fibrosis.

Coping with the inevitable: how cells repair a torn surface membrane

Disruption of the cell plasma membrane is a commonplace occurrence in many mechanically challenging, biological environments. 'Resealing' is the emergency response required for cell survival. Resealing is triggered by Ca2+ entering through the disruption; this causes vesicles present in cytoplasm underlying the disruption site to fuse rapidly with one another (homotypically) and also with the adjacent plasma membrane (heterotypically/exocytotically). The large vesicular products of homotypic fusion are added as a reparative 'patch' across the disruption, when its resealing requires membrane replacement. The simultaneous activation of the local cytoskeleton supports these membrane fusion events. Resealing is clearly a complex and dynamic cell adaptation, and, as we emphasize here, may be an evolutionarily primitive one that arose shortly after the ancestral eukaryote lost its protective cell wall.

Nuclear accumulation of exogenous DNA fragments in viable cells mediated by FGF-2 and DNA release upon cellular injury

We and others have previously shown that basic fibroblast growth factor (FGF-2 or bFGF) can be used as a targeting molecule to help carry plasmid DNA into cells when the growth factor molecule is physically coupled to the DNA molecule being delivered. Herein we report our observations on the FGF-mediated uptake of exogenous labeled DNA into cultured cells in a manner that is representative of that which may occur under physiological conditions at sites of wounded tissue. Cellular debris at such sites contains nucleic acid fragments released from dead cells, as well as growth factors such as FGF-2 that function early in the wound repair process. Using a cell culture model designed to mimic the local environment of a wound with respect to the presence of soluble FGF-2 and DNA fragments, we have shown that FGF-2 is able to direct the cellular uptake and nuclear localization of fragments of exogenous DNA via the FGF receptor into intact and healthy cells. Furthermore, we can monitor and quantitate this type of FGF-mediated DNA delivery by using indirect immunofluorescence of bromodeoxyuridine-labeled exogenous DNA. Our results suggest that this type of FGF-mediated DNA fragment uptake could allow for the transduction of viable nearest neighbor cells at sites of injury in vivo. Such a phenomenon may lead to mutational aberrations in the recipient cells and enhance the probability of wound carcinogenesis.

Inhibition of angiogenesis in vivo by plasminogen activator inhibitor-1

The process of angiogenesis is important in both normal and pathologic physiology. However, the mechanisms whereby factors such as basic fibroblast growth factor promote the formation of new blood vessels are not known. In the present study, we demonstrate that exogenously added plasminogen activator inhibitor-1 (PAI-1) at therapeutic concentrations is a potent inhibitor of basic fibroblast growth factor-induced angiogenesis in the chicken chorioallantoic membrane. By using specific PAI-1 mutants with either their vitronectin binding or proteinase inhibitor activities ablated, we show that the inhibition of angiogenesis appears to occur via two distinct but apparently overlapping pathways. The first is dependent on PAI-1 inhibition of proteinase activity, most likely chicken plasmin, while the second is independent of PAI-1's anti-proteinase activity and instead appears to act through PAI-1 binding to vitronectin. Together, these data suggest that PAI-1 may be an important factor regulating angiogenesis in vivo.

Activated mesothelial cells produce heparin-binding growth factors: implications for tumour metastases

Curative surgery for gastrointestinal malignancy is commonly thwarted by local tumour recurrence. The heparin-binding growth factors, basic fibroblast growth factor (bFGF), heparin-binding epidermal growth factor-like growth factor (HB-EGF) and vascular epidermal growth factor (VEGF) are all implicated in the metastatic process, but whether or not these essential growth factors are produced by the activated peritoneum is unknown. This study reveals that peritoneal mesothelial cells constitutively express mRNA for bFGF, HB-EGF and two VEGF spliced variants, VEGF121 and VEGF165. Mesothelial activation with interleukin (IL)-1b or tumour necrosis factor (TNF)-a produced an up-regulation of mRNA for HB-EGF and VEGF, but not bFGF expression. IL-6 failed to stimulate growth factor expression, whereas IL-2 produced a marked suppression in HB-EGF and bFGF, but not VEGF expression. Mesothelial cells were shown to predominantly express mRNA for the intermediate affinity (bg(c)) IL-2 receptor. Cytokine-induced growth factor up-regulation was confirmed at the protein level using Western blotting of mesothelial cell lysates for HB-EGF and culture supernatant enzyme-linked immunosorbent assay for VEGF. The production of these growth factors by human mesothelial cells may play a significant role in post-operative peritoneal tumour recurrence. Their common heparin-binding property offers a potential therapeutic target for manipulating the growth factor environment of the human peritoneum.

Histamine induces melanogenesis and morphologic changes by protein kinase A activation via H2 receptors in human normal melanocytes

Hyperpigmentation frequently accompanies chronic or acute inflammation. A number of inflammatory mediators have been shown to stimulate melanin synthesis in human melanocytes. Although histamine is ubiquitous as an inflammatory factor, its involvement in pigmentation remains obscure. In this work, we examined the effects of histamine on cultured human melanocytes. Treatment of human melanocytes with 0.1-10 microM histamine evoked morphologic changes and increases in tyrosinase activity. The concomitant increases in melanin content of the histamine-treated melanocytes indicated an elevation of melanin synthesis by tyrosinase activation. These stimulatory effects of histamine were completely inhibited by an H2 antagonist, famotidine, whereas H1 and H3 antagonists had no inhibitory effect whatsoever. In addition, an H2 agonist, dimaprit, induced the same degree of melanogenesis as histamine at concentrations of 0.1-10 microM. We observed an increase in the intracellular cAMP contents of human melanocytes induced by histamine via the H2 receptors. We know that this cAMP accumulation and subsequent protein kinase A activation plays a critical role in histamine-induced melanogenesis, because a specific protein kinase A inhibitor, H-89, completely suppressed these stimulatory effects of histamine, and because dibutylic cAMP, a specific protein kinase A activator, stimulated human melanocytes as potently as histamine. Taken together, we show here that histamine induces melanogenesis of human cultured melanocytes by protein kinase A activation via H2 receptors.

Production of growth factors by in vitro cultured human endothelial cells after contact with carbon coated polyethylene terephthalate

The release of basic fibroblast growth factor (bFGF) and platelet derived growth factor AB (PDGF-AB) by in vitro cultured human umbilical endothelial cells in contact with carbon and collagen coated polyethylene terephthalate (PET + PC) was assessed by enzyme immunoassay. The same cells cultured on polystyrene without biomaterials were tested as negative control. PET + PC induced a significant increase in the release of bFGF after 72 h and a significative reduction in the release of PDGF-AB after 48 and 72 h, compared to the negative control.

Influence of polyethylene terephthalate on the release of growth factors by human endothelial cells

The influence of polyethylene terephthalate (PET) on the release of platelet derived growth factor AB (PDGF-AB) and basic fibroblast growth factor (bFGF) by in vitro cultured human endothelial cells was assessed by enzyme immunoassay. No significant differences were observed in the production of PDGF-AB with respect to the negative control cultures. A significant increase was observed in the production of bFGF after 48 and 72 h with respect to the negative control cultures. It can be concluded that PET may induce an increase in the production of basic FGF in endothelial cells.

Autocrine FGF-2 is responsible for the cell density-dependent susceptibility to apoptosis of HUVEC : A role of a calpain inhibitor-sensitive mechanism

To elucidate the factors affecting endothelial susceptibility to apoptosis, we studied the effects of cell density on endothelial cell apoptosis induced by deprivation of serum and fibroblast growth factor-2 (FGF-2/basic FGF). On deprivation, more cells became apoptotic in a dense culture (5 x 10(2) cells/mm(2)) than in a sparse culture (1 x 10(2) cells/mm(2)) of human umbilical vein endothelial cells. FGF-2, hepatocyte growth factor, and vascular endothelial cell growth factor, but not insulin-like growth factor-I, decreased apoptosis in the dense culture to a level similar in the sparse culture. An anti-FGF-2 antibody significantly increased the apoptosis in the sparse culture, suggesting that the sparse culture was resistant to apoptosis because of the greater autocrine production of FGF-2. Western blot analysis and metabolic labeling revealed that the sparse culture has, in fact, more FGF-2 than the dense culture. The steady state level of mRNA for FGF-2 was not significantly different between the dense and sparse cultures. Among a panel of inhibitors for 2 major cytoplasmic proteolytic enzymes, calpain inhibitors increased FGF-2 in the dense culture, but proteasome inhibitors did not. Our findings demonstrate that cell density affects endothelial survival by regulating autocrine FGF-2 production through a calpain inhibitor-sensitive mechanism.

Mast cell granule heparin proteoglycan induces lacunae in confluent endothelial cell monolayers

The addition of rat mast cell granules to confluent bovine pulmonary artery endothelial cell monolayers resulted in the formation of numerous lacunae in the cultures. Several lines of evidence identified heparin proteoglycan as the component of the granule matrix responsible for the effect: presence of the activity in the proteoglycan fraction after chromatography of granule extracts, inhibition of granule activity by digestion with heparinase I, the failure of proteolysis of the proteoglycan fraction with proteinase K to significantly diminish its activity, and the failure of chymase and carboxypeptidase inhibitors to inhibit granule activity. The onset of hole formation was delayed for several hours after granule addition to the culture, and maximal hole formation occurred between 8 and 16 hours and was sustained as long as 24 hours. The lacunae formed by the separation of motile endothelial cells within the monolayer and was not attributable to cell contractile activity or cell loss. Time-lapse video recording showed that the holes were dynamic, individual holes expanding and regressing over a period of hours. Formation of lacunae occurred on gelatin and fibronectin surfaces alike. The presence of active chymase in the granules prevented the action of the proteoglycan. Heparin glycosaminoglycan as distinct from the proteoglycan did not similarly affect the endothelial monolayers but did block the action of granules added subsequently, indicating the likelihood of a heparin-reactive receptor or binding site.

Temporary disruption of the plasma membrane is required for c-fos expression in response to mechanical stress

Mechanically stressed cells display increased levels of fos message and protein. Although the intracellular signaling pathways responsible for FOS induction have been extensively characterized, we still do not understand the nature of the primary cell mechanotransduction event responsible for converting an externally acting mechanical stressor into an intracellular signal cascade. We now report that plasma membrane disruption (PMD) is quantitatively correlated on a cell-by-cell basis with fos protein levels expressed in mechanically injured monolayers. When the population of PMD-affected cells in injured monolayers was selectively prevented from responding to the injury, the fos response was completely ablated, demonstrating that PMD is a requisite event. This PMD-dependent expression of fos protein did not require cell exposure to cues inherent in release from cell-cell contact inhibition or presented by denuded substratum, because it also occurred in subconfluent monolayers. Fos expression also could not be explained by factors released through PMD, because cell injury conditioned medium failed to elicit fos expression. Translocation of the transcription factor NF-kappaB into the nucleus may also be regulated by PMD, based on a quantitative correlation similar to that found with fos. We propose that PMD, by allowing a flux of normally impermeant molecules across the plasma membrane, mediates a previously unrecognized form of cell mechanotransduction. PMD may thereby lead to cell growth or hypertrophy responses such as those that are present normally in mechanically stressed skeletal muscle and pathologically in the cardiovascular system.

Dual activities of 22-24 kDA basic fibroblast growth factor: inhibition of migration and stimulation of proliferation

Basic fibroblast growth factor (FGF2) is synthesized as four isoforms with molecular weights of 24, 22.5, 22, and 18 kDa, with each of the three higher molecular weight forms (hmwFGF2) produced by the initiation of translation at one of three upstream CUG codons. We have shown that bovine arterial endothelial cells export the high molecular weight forms of FGF2 (hmwFGF2) in a 17beta-estradiol-dependent manner (Piotrowicz et al., 1997, J Biol Chem 272:7042-7047). To determine whether the hmwFGF2 forms affected cell behavior after release, we evaluated the effect of recombinant hmwFGF2 on the growth and migration of endothelial cells and mammary carcinoma cells (MCF-7). Treatment with the recombinant protein resulted in the inhibition of endothelial cell migration by 45% and MCF-7 cell migration by 70%. HmwFGF2-dependent inhibition was observed when endothelial cell migration was stimulated by 18 kDa FGF2 or vascular endothelial growth, and MCF cell migration was stimulated with insulin-like growth factor. In each case, inclusion of an antibody against the 55 amino acid amino terminal end of 24 kDa FGF2 abrogated the inhibition of migration, while antibodies to the 18 kDa FGF2 domain had no effect. When endothelial cells were cultured under conditions which promoted export of hmwFGF2, a 40% decrease in motility was observed which was reversed by the antibodies to the 24 kDa FGF2. Thus, both recombinant and endogenously produced hmw-FGF2 are capable of inhibiting migration. In contrast to the ubiquitous effect on migration, hmwFGF2 had no effect on endothelial cell growth but stimulated MCF-7 growth equally as well as the 18 kDa FGF2 (threefold). Antibodies to the 18 kDa domain of 24 kDa FGF2 blocked the growth-promoting activity of hmwFGF2, but those to the amino terminal end were ineffective. These data suggest that hmwFGF2 has dual activities, an inhibitory effect on cell migration and a growth-stimulating effect. The two activities can be localized to different parts of hmwFGF2: inhibitory activity to the amino terminal 55 amino acids (which are absent from the 18 kDa FGF2) and growth-promoting activity to the 18 kDa domain. Therefore, the ratio of hmwFGF2 and 18 kDa FGF2 in the extracellular space may provide a mechanism of control for angiogenesis and mammary tumor development.

Development of novel monoclonal antibodies for the analysis of functional sites in FGF-2

Fibroblast growth factor 2 (FGF-2) can function as a potent mitogen, as well as a survival factor for a variety of mammalian cell types. The biological effects of FGF-2 are mediated by its interaction with two types of cellular binding sites: (1) high affinity tyrosine kinase receptors; and (2) low affinity heparan sulfate proteoglycans (HSPGs) on the cell surface. Although numerous FGF-2 antibodies have been used previously to analyze its biological actions, few studies have utilized antibodies to analyze domains within FGF-2 involved in its interactions with the two binding sites. In this report, we describe the generation and use of two monoclonal antibodies against human recombinant FGF-2 (254F1 and 256A12) that inhibit FGF-2 function. However, these antibodies appear to target preferentially different domains within the FGF-2 molecule, and therefore differentially influence the interactions of FGF-2 with its low and high affinity receptors. 254F1 is a more effective inhibitor of the high affinity, receptor tyrosine kinase binding site, whereas 256A12 appears to be a better inhibitor of the low affinity, HSPG interactions. We also demonstrate that the two antibodies are potent inhibitors of FGF-2 stimulated vascular cell proliferation, and as such have potential use in the treatment of vascular hyperproliferative diseases.

RNA and protein interactions modulated by protein arginine methylation

This review summarizes the current status of protein arginine N-methylation reactions. These covalent modifications of proteins are now recognized in a number of eukaryotic proteins and their functional significance is beginning to be understood. Genes that encode those methyltransferases specific for catalyzing the formation of asymmetric dimethylarginine have been identified. The enzyme modifies a number of generally nuclear or nucleolar proteins that interact with nucleic acids, particularly RNA. Postulated roles for these reactions include signal transduction, nuclear transport, or a direct modulation of nucleic acid interactions. A second methyltransferase activity that symmetrically dimethylates an arginine residue in myelin basic protein, a major component of the axon sheath, has also been characterized. However, a gene encoding this activity has not been identified to date and the cellular function for this methylation reaction has not been clearly established. From the analysis of the sequences surrounding known arginine methylation sites, we have determined consensus methyl-accepting sequences that may be useful in identifying novel substrates for these enzymes and may shed further light on their physiological role.

Sodium induces hypertrophy of cultured myocardial myoblasts and vascular smooth muscle cells

The mechanisms of sodium-induced myocardial hypertrophy and vascular hypertrophy are poorly understood. We tested the hypothesis that a high sodium concentration can directly induce cellular hypertrophy. Neonatal rat myocardial myoblasts (MMbs) and vascular smooth muscle cells (VSMCs) were cultured in a 50:50 mixture of DMEM and M199 supplemented with 10% fetal bovine serum. When the monolayers reached approximately 80% confluence, normal sodium medium (146 mmol/L) was replaced with high sodium media (152 mmol/L, 160 mmol/L, and 182 mmol/L) for up to 5 days. Increasing sodium from a baseline concentration of 146 mmol/L to the higher concentrations for 5 days caused dose-related increases in cell mean diameter, cell volume, and cellular protein content in both MMbs and VSMCs. Increasing the sodium concentration by only 4% (from 146 mmol/L to 152 mmol/L) caused the following respective changes in MMbs and VSMCs: 8.5% and 8.7% increase in cell mean diameter, 27.6% and 27.0% increase in cell volume, and 55.7% and 46.7% increase in cellular protein content. The rate of protein synthesis, expressed as [3H]leucine incorporation, increased by 87% and 99% in MMbs after exposure to 152 mmol/L and 160 mmol/L sodium, respectively, compared with the 146-mmol/L sodium control group. Exposure of MMbs to medium with a sodium concentration of 10% above normal, ie, 160 mmol/L, caused a significant decrease (range, 26% to 44%) in the rate of protein degradation at multiple time points over a 48-hour period compared with normal sodium control cells. The increase in cellular protein content caused by 160 mmol/L sodium returned to normal within 3 days after MMbs were returned to a normal sodium medium. These findings support the hypothesis that sodium has a direct effect to induce cellular hypertrophy and may therefore be an important determinant in causing myocardial and/or vascular hypertrophy in subjects with increased sodium concentration in the extracellular fluid.

Macrophage/Microglia regulation of astrocytic tenascin: synergistic action of transforming growth factor-beta and basic fibroblast growth factor

After injury to the CNS, extracellular matrix molecules such as tenascin are upregulated around the injury site and may be involved in inhibition of axon growth. In the present study, astrocytes were investigated to determine which cell types, growth factors, or cytokines are responsible for the injury-induced regulation of tenascin. The addition of activated macrophage- or microglial-conditioned medium increased astrocytic expression of tenascin 2.5-fold, as determined by Northern and Western blot analysis and ELISA. Of the cytokines and growth factors examined, only transforming growth factor-beta1 (TGF-beta1) and basic fibroblast growth factor (bFGF) significantly induced an increase in the production of astrocytic tenascin. Examination of macrophage and microglial supernatants showed the presence of TGF-beta1 but not bFGF; however, the TGF-beta1 concentration in supernatants was lower than that expected to induce an increase in astrocytic tenascin similar to that seen with recombinant TGF-beta1. Western blot analysis of astrocytes showed only the presence of bFGF. Compared with the responses of the individual growth factors, tenascin production by astrocytes was dramatically potentiated when grown in the presence of a combination of both TGF-beta1 and bFGF. A similar synergistic effect was observed after the addition of either TGF-beta1 or bFGF to macrophage-conditioned medium. Northern analysis also showed concomitant increases in TGF-beta1, bFGF, and tenascin after CNS injury to animals 14 d of age or older. These results show that the regulation of astrocytic tenascin is mediated by the synergistic action of TGF-beta1 and bFGF in vitro and after injury in vivo.

Insulin-like growth factor I increases bone formation in old or corticosteroid treated rats

We studied bone induction in subcutaneous implants of demineralized bone matrix with or without insulin-like growth factor I (IGF-I) in aged or corticosteroid-treated rats. Each rat carried one pair of implants, one control and one experiment implant, containing IGF-I dissolved in a hyaluronan solution for slow release. The rats were killed after 3 weeks and the results were evaluated by measuring the calcium content of implants. Young (6-7 weeks) and old (19-27 months) rats were used. A group of young rats was treated for 1 week with subcutaneous injections of 140 micrograms/kg dexamethasone daily. Old rats produced only approximately 1% as much bone as young rats. Local delivery of IGF-I did not increase bone formation in young rats. In old rats, bone formation was increased by IGF-I, 3000 ng/implant. Corticosteroids reduced bone formation in young rats. This effect was partially reversed by local administration of IGF-I.

Basic fibroblast growth factor (bFGF) regulates the expression of the CC chemokine monocyte chemoattractant protein-1 (MCP-1) in autocrine-activated endothelial cells

The CC chemokine monocyte chemoattractant protein (MCP)-1 is induced by inflammatory cytokines and acts as a potent regulator of monocyte trafficking. Monocytes adhere preferentially to migrating endothelial cells in vitro and to endothelial cells at the migration front in vivo after aortic balloon denudation injury. Based on these findings, we analyzed MCP-1 expression in migrating and resting bovine aortic endothelial (BAE) cells and identified prominently upregulated levels of MCP-1 expression in migrating BAE cells. Stimulation of resting BAE cells with 5 ng/mL bFGF resulted in a fourfold induction of MCP-1 mRNA expression. The time course of bFGF-induced MCP-1 mRNA expression indicated a rapid and direct stimulation of MCP-1 expression that was detectable 30 minutes after stimulation. Levels of basal MCP-1 expression, as well as upregulated levels of MCP-1 in migrating BAE cells, were downregulated by addition of a neutralizing anti-bFGF monoclonal antibody (1.0 microgram/mL). Digestion of conditioned media of resting BAE cells with collagenase led to a dose-dependent induction of MCP-1 expression in resting BAE cells, which was inhibited > 50% by addition of neutralizing anti-bFGF antibody. Confirmation of the Northern blot experiments by ELISA-based quantitation of MCP-1 protein levels identified threefold to sixfold higher levels of MCP-1 in the supernatants of bFGF-stimulated BAE cells than in unstimulated resting BAE cells. Finally, analysis of MCP-1 expression by in situ hybridization carried out on en face preparations of aortas demonstrated that MCP-1 expression is dramatically upregulated in regenerating endothelial cells in vivo after balloon denudation. Though not establishing a direct causal relation between the preferential adhesion of monocytes to migrating endothelial cells, these findings strongly suggest that autocrine-activated endothelial cell-derived MCP-1 may play a critical role in recruiting monocytes. They furthermore support the concept that bFGF acts as an autocrine regulator of endothelial cell activity and may imply an involvement of bFGF as a mediator of inflammatory cell trafficking.

Cardiac myocyte membrane wounding in the abruptly pressure-overloaded rat heart under high wall stress

The potential role of transient sarcolemmal membrane wounding as a signal transduction event for cardiomyocyte hypertrophy was evaluated in rats with short-term pressure overload caused by banding of the proximal aorta. This procedure resulted in significant increases in left ventricular systolic (1.5-fold) and end-diastolic (2.6-fold) pressures and wall stresses that were associated with significant wall thinning and cavitary enlargement. Quantitative image analysis of frozen sections of the stressed ventricles obtained 60 minutes after banding demonstrated a 6- to 10-fold increase in cytosolic staining with a horseradish peroxidase-labeled anti-albumin antibody compared with sham-operated controls, indicating that an increase in transient sarcolemmal membrane permeability (wounding) is an early response to an abrupt increase in hemodynamic load in vivo. We conclude that an intense hemodynamic stress in vivo can result in histologically detectable cardiomyocyte wounding.

Ontogeny of epidermal growth factor (EGF), EGF receptor (EGFR) and basic fibroblast growth factor (bFGF) mRNA levels in pancreas, liver, kidney, and skeletal muscle of pig

Epidermal growth factor (EGF), EGF receptor (EGFR), and basic fibroblast growth factor (bFGF) messenger RNA (mRNA) levels were examined by Northern blot analysis in four tissues (pancreas, liver, kidney, and skeletal muscle) of pig from fetal 90 d to postnatal 180 d of age. The present study shows for the first time that EGF mRNA increased with advancing age in the kidney and skeletal muscle of pig. A high level of EGF mRNA was observed in the kidney compared with the liver and skeletal muscle. In the pancreas, high levels of EGF mRNA were found in fetuses and newborns and were low in older pigs. Pancreatic EGFR mRNA level parallelled its EGF mRNA, whereas in the kidney and skeletal muscle, patterns of EGFR mRNA were reversed to their EGF mRNA levels. In the liver, EGFR mRNA was abundant but EGF mRNA was undetected. In the pancreas and skeletal muscle, the highest levels of bFGF mRNA were found in fetuses of 90 d of age and then decreased with advancing age. In the liver and kidney, there were no major changes in bFGF mRNA levels during the examined developmental periods. These results show that EGF, EGFR, and bFGF mRNA levels are developmentally and tissue specifically regulated in pig. In the pancreas, mRNA levels of EGF, EGFR and bFGF were high in fetal and neonatal life and low thereafter. In the kidney and skeletal muscle, EGF mRNA increased with advancing age. EGF may play a role in muscle growth and maintenance in growing pigs during the later stage of development.