Synthesis and photothermal conversion properties of sandwich N-fused porphyrin rhodium-μ-dichloride dimer complexes: π-extended analog of pentamethylcyclopentadienyl dirhodium(III)-μ-dichloride dimer

Anionic cyclopentadienyl (Cp) and its pentamethyl-substituted derivative (Cp*) serve as crucial ligands for creating stable π-coordinated materials, including catalysts. From a structural perspective, the π-extended analog of Cp, known as an N-fused porphyrin (NFP), is recognized as an intriguing 18π aromatic chromophore, offering near-infrared (NIR) optical properties that can be fine-tuned through metal complexation. When coordinated with rhodium at the central NFP core, it forms a sandwich binuclear rhodium(III) complex along with terminal and bridging chloride ligands, denoted as Rh-1, and its bromo derivative, Rh-1-Br. In contrast to the bis-NFP complex of iron(II) reported previously by our team, both Rh-1 and Rh-1-Br complexes exhibit strong NIR optical properties and narrow HOMO-LUMO energy gaps, attributed to minimal orbital interactions between the two co-facial NFP ligands. Leveraging these NIR absorption properties, we assessed the photothermal conversion properties of Rh-1 and ligand 1, revealing high conversion efficiency. This suggests their potential application as photothermal agents for use in photothermal therapy.

Cohort profile: the ESC EURObservational Research Programme Non-ST-segment elevation myocardial infraction (NSTEMI) Registry

AIMS

The European Society of Cardiology (ESC) EURObservational Research Programme (EORP) Non-ST-segment elevation myocardial infarction (NSTEMI) Registry aims to identify international patterns in NSTEMI management in clinical practice and outcomes against the 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without ST-segment-elevation.

METHODS AND RESULTS

Consecutively hospitalised adult NSTEMI patients (n = 3620) were enrolled between 11 March 2019 and 6 March 2021, and individual patient data prospectively collected at 287 centres in 59 participating countries during a two-week enrolment period per centre. The registry collected data relating to baseline characteristics, major outcomes (in-hospital death, acute heart failure, cardiogenic shock, bleeding, stroke/transient ischaemic attack, and 30-day mortality) and guideline-recommended NSTEMI care interventions: electrocardiogram pre- or in-hospital, pre-hospitalization receipt of aspirin, echocardiography, coronary angiography, referral to cardiac rehabilitation, smoking cessation advice, dietary advice, and prescription on discharge of aspirin, P2Y12 inhibition, angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB), beta-blocker, and statin.

CONCLUSION

The EORP NSTEMI Registry is an international, prospective registry of care and outcomes of patients treated for NSTEMI, which will provide unique insights into the contemporary management of hospitalised NSTEMI patients, compliance with ESC 2015 NSTEMI Guidelines, and identify potential barriers to optimal management of this common clinical presentation associated with significant morbidity and mortality.

Iridium Complex of N-Fused Bilatrienone: Oxidative Cleavage of N-Fused Porphyrin Induced by Iridium-Cyclooctadiene Complexation

N-fused porphyrin (NFP) is a unique class of photostable near-infrared dyes with an 18π aromatic tetrapyrrole macrocyclic skeleton containing a tri-fused pentacyclic moiety. Here, the synthesis of an iridium complex of N-fused bilatrienone is reported as the degradation product of Ir-cyclooctadiene (cod)-induced oxidative cleavage of NFP under aerobic conditions. Similar to the native bilin chromophores, the ring-opened complex featured a broken π-conjugation circuit and exhibited a broad visible absorption band. In contrast, metalation of NFP using an iridium(I)(cod) complex under an inert atmosphere resulted in the formation of a cod-isomerized (κ¹ ,η³ -C₈ H₁₂ )-Ir complex.

Tungsten(VI) Complex of N-Fused Porphyrin Absorbing Near-Infrared Light beyond 1000 nm

Incorporating tungsten into the N3 core of a N-fused porphyrin (NFP; 1) affords high-valent tungsten(VI)-NFP complexes, WClO₂ -1 and 21-chlorinated WClO₂ -3. The X-ray structure of WClO₂ -1 reveals a distorted octahedral geometry with sitting atop metal coordination. The absorption spectrum of WClO₂ -1 displays bathochromically shifted Q-like bands beyond 1000 nm, indicating an inherently narrow HOMO-LUMO energy gap. DFT calculations show that the degeneracy of the LUMO and LUMO+1 pair of 1 is significantly resolved by the tungsten(VI) coordination. Conclusively, magnetic circular dichroism (MCD) spectroscopy and cyclic voltammetry provide a rationale for the narrow HOMO-LUMO energy gap in the "16-electron" d⁰ tungsten(VI)-NFP complexes.

Vascular endothelial growth factor (VEGF121) protects rats from renal infarction in thrombotic microangiopathy

BACKGROUND

Renal thrombotic microangiopathy, typified by the hemolytic uremic syndrome, is associated with endothelial cell injury in which the presence of cortical necrosis, extensive glomerular involvement, and arterial occlusive lesions correlates with a poor clinical outcome. We hypothesized that the endothelial survival factor vascular endothelial growth factor (VEGF) may provide protection.

METHOD

Severe, necrotizing, thrombotic microangiopathy was induced in rats by the renal artery perfusion of antiglomerular endothelial antibody, followed by the administration of VEGF or vehicle, and renal injury was evaluated.

RESULTS

Control rats developed severe glomerular and tubulointerstitial injury with extensive renal necrosis. The administration of VEGF significantly reduced the necrosis, preserved the glomerular endothelium and arterioles, and reduced the number of apoptotic cells in glomeruli (at 4 hours) and in the tubulointerstitium (at 4 days). The prosurvival effect of VEGF for endothelium may relate in part to the ability of VEGF to protect endothelial cells from factor-induced apoptosis, as demonstrated for tumor necrosis factor-alpha (TNF-alpha), which was shown to be up-regulated through the course of this model of renal microangiopathy. Endothelial nitric oxide synthase expression was preserved in VEGF-treated rats compared with its marked decrease in the surviving glomeruli and interstitium of the antibody-treated rats that did not receive VEGF.

CONCLUSIONS

VEGF protects against renal necrosis in this model of thrombotic microangiopathy. This protection may be mediated by maintaining endothelial nitric oxide production and/or preventing endothelial cell death.

VEGF(121)- and bFGF-induced increase in collateral blood flow requires normal nitric oxide production

The angiogenic proteins basic fibroblast growth factor (bFGF; FGF-2) and vascular endothelial growth factor 121 (VEGF(121)) are each able to enhance the collateral-dependent blood flow after bilateral femoral artery ligation in rats. To study the effect of nitric oxide (NO) synthase (NOS) inhibition on bFGF- or VEGF(121)-induced blood flow expansion, the femoral arteries of male Sprague-Dawley rats were ligated bilaterally, and the animals were given tap water [non-N(G)-nitro-L-arginine methyl ester (L-NAME) group; n = 36] or water that contained L-NAME (L-NAME group; 2 mg/ml, n = 36). Animals from each group were further divided into three subgroups: vehicle (n = 12), bFGF (5 microg x kg(-1) x day(-1), n = 12), or VEGF(121) (10 microg x kg(-1) x day(-1), n = 12). Growth factors were delivered via intra-arterial infusion with osmotic pumps over days 1-14. On day 16, after a 2-day delay to permit clearance of bFGF and VEGF from the circulation, maximal collateral blood flow was determined by (85)Sr- and (141)Ce-labeled microspheres during treadmill running. L-NAME (approximately 137 mg x kg(-1) x day(-1)) for 18 days increased systemic blood pressure (approximately 26%, P<0.001). In the absence of L-NAME, collateral-dependent blood flows to the calf muscles were greater in the VEGF(121)- and bFGF-treated subgroups (85 +/- 4.5 and 80 +/- 2.9 ml x min(-1) x 100 g(-1), respectively) than in the vehicle subgroup (49 +/- 3.0 ml x min(-1) x 100 g(-1), P<0.001). In the presence of NOS inhibition by L-NAME, blood flows to the calf muscles were essentially equivalent among the three subgroups (54 +/- 3.0, 56 +/- 5.1, and 47 +/- 2.0 ml x min(-1) x 100 g(-1) in the bFGF-, VEGF(121)-, and vehicle-treated subgroups, respectively) and were not different from the blood flow in the non-L-NAME vehicle subgroup. Our results therefore indicate that normal NO production is essential for the enhanced vascular remodeling induced by exogenous bFGF or VEGF(121) in this rat model of experimental peripheral arterial insufficiency. These results imply that a blunted endothelial NO production could temper vascular remodeling in response to these angiogenic growth factors.

Insulin-like growth factor-binding protein-3 induces fetalization in neonatal rat cardiomyocytes

We employed cDNA microarrays representing 4000 distinct sequences to profile changes in gene expression in a rodent model of heart disease, namely, progression to heart failure after myocardial infarction. Differential gene expression in the left ventricle was examined at 4-week intervals over a 12-week period after coronary artery ligation in rats. Over this time course, insulin-like growth factor-binding protein-3 (IGFBP-3) was found to have a greater expression than in nondiseased tissues. We then employed quantitative real-time PCR to analyze gene expression in neonatal rat cardiac myocytes that had been treated with recombinantly expressed IGFBP-3 to examine a number of transcriptional responses designed to reflect the heart failure phenotype. The IGFBP-3 protein was shown to induce transcription of atrial natriuretic factor (ANF) and beta-myosin heavy chain (B-MHC). Analysis of conditioned media taken from IGFBP-3-treated cardiac myocyte cultures demonstrated an increase in ANF protein as well as in protein synthesis, as determined by metabolic incorporation of a radiolabeled amino acid. However, transcriptional changes of troponin-1, endothelin-1, or angiotensin-II by IGFBP-3 were not observed.

CTGF expression is induced by TGF- beta in cardiac fibroblasts and cardiac myocytes: a potential role in heart fibrosis

Connective tissue growth factor (CTGF) is a cysteine-rich protein induced by transforming growth factor beta (TGF- beta) in connective tissue cells. CTGF can trigger many of the cellular processes underlying fibrosis, such as cell proliferation, adhesion, migration and the synthesis of extracellular matrix; however, its role in acute and chronic cardiac injury is not fully understood. Here, we show that TGF- beta is a specific inducer of CTGF expression in both cardiac fibroblasts and cardiac myocytes. The activity of a CTGF promoter-based reporter construct correlated with endogenous CTGF expression, suggesting that TGF- beta induces CTGF expression most likely by activating its promoter. Upregulation of CTGF coincided with an increase in fibronectin, collagen type I and plasminogen activator inhibitor-1 production. Forskolin, a stimulator of cyclic AMP, blocked TGF- beta induced CTGF expression and reduced the basal level of CTGF, whereas an inhibitor that blocks the MAP kinase signaling pathway (PD 98059) significantly enhanced TGF- beta induced CTGF expression. Furthermore, we found that both TGF- beta and CTGF mRNAs were significantly elevated in the left ventricles and septa of rat hearts 2-16 weeks following myocardial infarction. This correlated well with concomitant increases in fibronectin, and type I and type III collagen mRNA levels in these animal hearts. Significant upregulation of CTGF was also detected in human heart samples derived from patients diagnosed with cardiac ischemia. Based on these findings, we propose that CTGF is an important mediator of TGF- beta signaling in the heart and abnormal expression of this gene could be used as a diagnostic marker for cardiac fibrosis.

Heparin blockade of thrombin-induced smooth muscle cell migration involves inhibition of epidermal growth factor (EGF) receptor transactivation by heparin-binding EGF-like growth factor

Agonists of G protein-coupled receptors, such as thrombin, act in part by transactivating the epidermal growth factor (EGF) receptor (EGFR). Although at first a ligand-independent mechanism for EGFR transactivation was postulated, it has recently been shown that this transactivation by various G protein-coupled receptor agonists can involve heparin-binding EGF-like growth factor (HB-EGF). Because thrombin stimulation of vascular smooth muscle cell migration is blocked by heparin and because heparin can displace HB-EGF, we investigated the possibility that thrombin stimulation of smooth muscle cells (SMCs) depends on EGFR activation by HB-EGF. In rat SMCs, EGFR phosphorylation and extracellular signal-regulated kinase (ERK) activation in response to thrombin are inhibited not only by the EGFR inhibitor AG1478 and by EGFR blocking antibody but also by heparin and by neutralizing HB-EGF antibody. HB-EGF-dependent signaling induced by thrombin is inhibited by batimastat, which suggests a requirement for pro-HB-EGF shedding by a metalloproteinase. We further demonstrate that this novel pathway is required for the migration of rat and baboon SMCs in response to thrombin. We conclude from these data that the inhibitory effect of heparin on SMC migration induced by thrombin relies, at least in part, on a blockade of HB-EGF-mediated EGFR transactivation.

Heparin-binding EGF-like growth factor contributes to reduced glomerular filtration rate during glomerulonephritis in rats

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the epidermal growth factor (EGF) family, is expressed during inflammatory and pathological conditions. We have cloned the rat HB-EGF and followed the expression of HB-EGF in rat kidneys treated with anti- glomerular basement membrane (anti-GBM) antibody (Ab) to induce glomerulonephritis (GN). We observed glomerular HB-EGF mRNA and protein within 30 minutes of Ab administration and showed by in situ hybridization that glomerular HB-EGF mRNA expression was predominantly in mesangial and epithelial cells. Expression of HB-EGF correlated with the onset of decreased renal function in this model. To test the direct effect of HB-EGF on renal function, we infused the renal cortex with active rHB-EGF, prepared from transfected Drosophila melanogaster cells. This treatment induced a significant decrease in single nephron GFR (SNGFR), single nephron plasma flow, and glomerular ultrafiltration coefficient and an increase in the glomerular capillary hydrostatic pressure gradient. In addition, anti-HB-EGF Ab administered just before anti-GBM Ab blocked the fall in SNGFR and GFR at 90 minutes without any change in the glomerular histologic response. These studies suggest that HB-EGF expressed early in the anti-GBM Ab GN model contributes to the observed acute glomerular hemodynamic alterations.

Production of heparin binding epidermal growth factor-like growth factor in the early phase of regeneration after acute renal injury. Isolation and localization of bioactive molecules

We have recently reported that heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA is induced in the rat kidney after acute ischemic injury. The present studies were designed to investigate whether bioactive HB-EGF protein is also produced in response to renal injury induced by either ischemia/reperfusion or aminoglycosides. Heparin-binding proteins were purified from kidney homogenates by heparin affinity column chromatography using elution with a 0.2-2.0 M gradient of NaCl. A single peak of proteins that eluted at 1.0-1.2 M NaCl was detected in the postischemic kidney within 6 h of injury. This eluate fraction stimulated DNA synthesis in quiescent Balb/c3T3, RIE, and NRK-52E cell lines, all of which are responsive to the epidermal growth factor family of mitogenic proteins. The EGF receptor of A431 cells was also tyrosine phosphorylated by this eluate peak. Furthermore, immunoblotting with a polyclonal antibody against rat HB-EGF indicated that the eluate peak contained immunoreactive proteins of 22 and 29 kD mol wt, consistent with the reported sizes of the secreted form and membrane anchored form of HB-EGF, respectively. Immunohistochemical studies revealed that HB-EGF was produced predominantly in distal tubules in kidneys injured either by ischemia/reperfusion or aminoglycoside administration. We also found that during metanephric development immunoreactive HB-EGF was detected in the ureteric bud as early as E14.5 and persisted in structures arising from the ureteric bud throughout embryogenesis. These results suggest that in response to acute injury, HB-EGF is produced predominantly in distal tubules and that endogenous HB-EGF may be an important growth factor involved in renal epithelial cell repair, proliferation, and regeneration in the early stages of recovery after acute renal injury, as well as in nephrogenesis.

Heparin-binding EGF-like growth factor is a mitogen for rat alveolar type II cells

Alveolar type II cells proliferate and differentiate into type I epithelial cells to restore the alveolar epithelium after lung injury. Since mitogens that bind the epidermal growth factor (EGF), EGF, receptor and transforming growth factor alpha (TGF alpha) have been shown to stimulate type II cell proliferation, studies were undertaken to determine whether the recently described protein, heparin-binding EGF-like growth factor (HB-EGF), was a mitogen for rat alveolar type II cells in primary culture. In addition, since HB-EGF is produced by macrophages, it was of interest to determine whether mitogenic activity for type II cells present in macrophage conditioned medium was due to HB-EGF. Rat and human recombinant HB-EGF stimulated thymidine incorporation into rat type II cells in a concentration-dependent manner up to 10-50 ng/ml then became inhibitory. The nuclear labeling index of type II cells increased from 2% to 16% with 10 ng/ml HB-EGF. However, HB-EGF induced only a small increase in cell number after 48 h and did not support low-density proliferation of alveolar type II cells. Conditioned medium from the human monocytic cell line, U937, stimulated type II cell DNA synthesis, and stimulatory activity could be partially purified by S-sepharose and heparin-sepharose chromatography. The growth-promoting activity from U937 cells that bound to heparin-sepharose was inhibited by a neutralizing antibody to human HB-EGF. Immunoblot analysis of active fractions also verified the presence of HB-EGF. However, the neutralizing antibody to rat HB-EGF did not inhibit mitogenic activity for type II cells found in rat bronchoalveolar lavage fluid. HB-EGF mRNA was found to be expressed in human alveolar macrophages to similar levels as differentiated U937 cells but was not detected in rat alveolar macrophages by Northern analysis of total mRNA. There was no difference in the level of HB-EGF mRNA expression in human alveolar macrophages from patients with interstitial lung disease compared with macrophages from normal subjects. The results demonstrate that HB-EGF is a mitogen for rat alveolar type II cells but appears to show species-specific differences with regard to its production by macrophages. Leslie, C. C., K. McCormick-Shannon, J. M. Shannon, B. Garrick, D. Damm, J. A. Abraham, and R. J. Mason. 1997. Heparin-binding EGF-like growth factor is a mitogen for rat alveolar type II cells. Am. J. Respir. Cell Mol. Biol. 16:379-387.

Involvement of wound-associated factors in rat brain astrocyte migratory response to axonal injury: in vitro simulation

The poor ability of mammalian central nervous system (CNS) axons to regenerate has been attributed, in part, to astrocyte behavior after axonal injury. This behavior is manifested by the limited ability of astrocytes to migrate and thus repopulate the injury site. Here, the migratory behavior of astrocytes in response to injury of CNS axons in vivo was simulated in vitro using a scratch-wounded astrocytic monolayer and soluble substances derived from injured rat optic nerves. The soluble substances, applied to the scratch-wounded astrocytes, blocked their migration whereas some known wound-associated factors such as transforming growth factor-beta 1 (TGF-beta 1), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and heparin-binding epidermal growth factor in combination with insulin-like growth factor-1 (HB-EGF + IGF-1) stimulated intensive migration with consequent closure of the wound. Migration was not dominated by proliferating cells. Both bFGF and HB-EGF + IGF-1, but not TGF-beta 1, could overcome the blocking effect of the optic nerve-derived substances on astrocyte migration. The induced migration appeared to involve proteoglycans. It is suggestive that appropriate choice of growth factors at the appropriate postinjury period may compensate for the endogenous deficiency in glial supportive factors and/or presence of glial inhibitory factors in the CNS.

Rapid induction of heparin-binding epidermal growth factor/diphtheria toxin receptor expression by Raf and Ras oncogenes

We have used differential display PCR to search for mRNAs induced by delta Raf-1:ER, an estradiol-dependent form of Raf-1 kinase. Through this approach the gene encoding heparin-binding epidermal growth factor (HB-EGF) was identified as an immediate-early transcriptional target of oncogenic Raf kinases. Activation of delta Raf-1:ER and a conditional oncogenic form of B-Raf, delta B-RAF:ER, resulted in rapid and sustained induction of HB-EGF mRNA expression and secretion of mature HB-EGF from cells. Neutralizing anti-HB-EGF antisera prevented the delayed activation of the c-Jun amino-terminal kinases that is observed in cells transformed by delta Raf-1:ER. These results demonstrate that distinct signaling pathways can cross talk via the secretion of polypeptide growth factors. Furthermore, cells transformed by oncogenic Ras, which also induced HB-EGF expression, demonstrated a marked increase in sensitivity to the cytotoxic action of diphtheria toxin, for which the membrane anchored HB-EGF precursor acts as a cell-surface receptor.

Carboxyl-terminal truncation of leucine76 converts heparin-binding EGF-like growth factor from a heparin-enhancible to a heparin-suppressible growth factor

Previous studies have indicated that heparin differentially regulates heparin-binding EGF-like growth factor (HB-EGF) and amphiregulin (AR) mitogenic activity. To further explore this phenomenon, these mitogens were compared under identical cell culture conditions in two different assays. The results of our present investigation demonstrated that AR-mediated mitogenic activity in the murine AKR-2B fibroblast-like cell line was inhibited by heparin, while HB-EGF activity was enhanced. However, the absolute effect of heparin appeared to be cell type specific since HB-EGF mitogenic activity was not dramatically affected by coincubation with heparin when tested on human dermal fibroblasts. Several studies have indicated that mutation of a conserved leucine in the carboxyl-terminal region of both EGF and transforming growth factor-alpha results in decreased affinity for EGF receptors. Since this leucine is present in the analogous position of HB-EGF, but absent in AR, we examined the effect of deleting this residue by carboxyl-terminal truncation of HB-EGF. Analysis of recombinant forms of HB-EGF demonstrated that HB-EGF can be converted to a heparin-inhibited growth factor if the putative mature form of the protein is truncated by two residues (leucine76 and proline77) at the carboxyl terminus. Further analysis demonstrated that only leucine76 appears to be required for heparin-dependent enhancement of HB-EGF-mediated mitogenic activity, indicating that this amino acid may play a pivotal role in controlling the response of HB-EGF to heparin or related glycosaminoglycan sulfates. Our results also suggest that expression of different HB-EGF forms in vivo could result in the production of HB-EGFs with divergent responses to sulfated glycosaminoglycans and proteoglycans.

Purification and characterization of transmembrane forms of heparin-binding EGF-like growth factor

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), whose cDNA has a predicted 208-codon open reading frame, is synthesized as a membrane-spanning precursor that is processed to release mature mitogenic proteins of approximately 73-87 amino acids in length. Previous work has focused on the structural and biological properties of secreted HB-EGF. In this study, human recombinant transmembrane HB-EGF, produced by expression of HB-EGF1-208 cDNA in a baculovirus system, has been isolated, purified, and characterized structurally and biologically. Two isoforms of transmembrane HB-EGF (HB-EGFTM) were purified from membrane fractions of infected insect cells by a combination of heparin affinity chromatography and reversed-phase high performance liquid chromatography. The isoform designated as HB-EGFTM-1, a 21.5-kDa protein, yielded no N-terminal sequence, suggesting that it is N-terminally blocked. However, HB-EGFTM-II, a 24-kDa protein, was N-terminally sequenced and found to be initiated at Asp63 in the 208-amino acid residue primary translation product. This N terminus is the same as that determined for a 18-kDa isoform of secreted HB-EGF purified from the conditioned medium of insect cells expressing HB-EGF1-149 cDNA and is also identical to the N terminus of the longest form of secreted HB-EGF initially purified from human macrophage-like U-937 cell conditioned medium. HB-EGFTM-II cross-reacted on a Western blot with an antibody directed against the 16 C-terminal amino acids of the cytoplasmic tail of HB-EGF, indicating that it contains a putative transmembrane domain. HB-EGFTM-II was bioactive and stimulated the proliferation of BALB/c 3T3 cells and smooth muscle cells and the motility of smooth muscle cells, albeit with approximately 10-25% of the specific activity of secreted HB-EGF isoforms. We concluded that transmembrane HB-EGF is bioactive when isolated, consistent with the possibility of its functioning as a juxtacrine growth factor when still tethered to the cell.

Biosynthesis and processing by phorbol ester of the cells surface-associated precursor form of heparin-binding EGF-like growth factor

Human MDA MB 231 cells were found to synthesize mostly the cell surface-associated precursor form of heparin-binding EGF-like growth factor (HB-EGF), a 27-kDa protein. Evidence for this form of HB-EGF included increased fluorescence intensity when cells were analyzed by flow cytometry using anti-HB-EGF antibodies, lack of HB-EGF in conditioned medium, and sensitivity to diphtheria toxin, for which HB-EGF is the receptor. Phorbol ester treatment of cells resulted, within 30 minutes, in loss of cell surface 27 kDA HB-EGF, lack of interaction with anti-HB-EGF antibodies, accumulation of active 21 kDa HB-EGF in conditioned medium, and the acquisition of diphtheria toxin resistance. It was concluded that cell surface-associated HB-EGF is the precursor of a bioactive growth factor, is biologically active as the receptor for diphtheria toxin, and is susceptible to rapid processing.

Differential regulation of heparin-binding epidermal growth factor-like growth factor in the adult ovariectomized mouse uterus by progesterone and estrogen

Expression of heparin-binding epidermal growth factor-like growth factor (HB-EGF) was studied in the adult ovariectomized mouse uterus in response to progesterone (P4) and/or 17 beta-estradiol (E2) using Northern blotting, in situ hybridization, and immunohistochemistry. A 2.5-kilobase transcript of HB-EGF messenger RNA (mRNA) was detected in total uterine RNA samples. Although low levels of this mRNA were detected in uterine samples of oil-treated ovariectomized mice (control), an injection of E2 promptly up-regulated the levels. The mRNA levels peaked at 2 h and returned to basal levels after 12 h. Injection of P4 alone did not influence the basal levels; however, coinjection of E2 with P4 caused a rapid, but transient, up-regulation of the mRNA. The levels peaked between 2-4 h and declined 6 h after the hormone injections. Coinjection of E2 with P4 after 1 day of P4 priming also resulted in peak levels of HB-EGF mRNA at 2 h; however, the levels were not sustained thereafter. Because P4 and E2 differentially regulate heterogeneous uterine cell types, in situ hybridization was performed to determine cell-specific expression of HB-EGF mRNA in the ovariectomized uterus before and after steroid treatments. In the oil-treated uterine sections, very low levels of autoradiographic signals were observed in the luminal epithelium. In contrast, an injection of E2 resulted in a marked accumulation of HB-EGF mRNA primarily in uterine epithelial cells within 2 h. Although specific hybridization signals could not be detected in any uterine cell types after P4 treatment, combined treatment with P4 and E2 resulted in an accumulation of HB-EGF mRNA in stromal cells. To determine whether uterine HB-EGF mRNA was translated, cellular distribution of HB-EGF protein was investigated by immunohistochemistry. In oil-treated uterine sections, an overall weak immunostaining was noted, whereas no staining could be detected in uterine sections after P4 treatment. In contrast, positive immunostaining was noted in epithelial cells after E2 treatment. Coinjection of P4 with E2 caused immunostaining in the stroma. These results are consistent with those of in situ hybridization. The present investigation establishes that in the adult ovariectomized mouse uterus, E2 regulates HB-EGF expression in the epithelium, whereas expression of HB-EGF in the stroma is regulated by P4 and E2.

Heparin-binding EGF-like growth factor gene is induced in the mouse uterus temporally by the blastocyst solely at the site of its apposition: a possible ligand for interaction with blastocyst EGF-receptor in implantation

Heparin-binding EGF-like growth factor (HB-EGF) is a newly discovered member of the EGF family of growth factors. HB-EGF can bind to two loci on cell surfaces, heparan sulphate proteoglycans and EGF-receptor (EGF-R), and either one or both of these interactions could play a role in cell-cell interactions. In the rodent, increased endometrial vascular permeability at the site of blastocyst apposition is considered to be an earliest discernible prerequisite event in the process of implantation and this event coincides with the initial attachment reaction between the blastocyst trophectoderm and uterine luminal epithelium. This investigation demonstrates that the HB-EGF gene is expressed in the mouse uterine luminal epithelium surrounding the blastocyst 6–7 hours before the attachment reaction that occurs at 2200–2300 hours on day 4 of pregnancy. It was further demonstrated that this gene is not expressed in the luminal epithelium at the site of the blastocyst apposition during the progesterone-maintained delayed implantation, but is readily induced in the luminal epithelium surrounding an activated blastocyst after termination of the delay by an estrogen injection. In vitro studies showed that HB-EGF induced blastocyst EGF-R autophosphorylation, and promoted blastocyst growth, zona-hatching and trophoblast outgrowth. These results suggest possible interactions between the uterine HB-EGF and blastocyst EGF-R very early in the process of implantation, earlier than any other embryo-uterine interactions defined to date at the molecular level.

Lysophosphatidylcholine upregulates the level of heparin-binding epidermal growth factor-like growth factor mRNA in human monocytes

Lysophosphatidylcholine is increased in the plasma of hypercholesterolemic patients, is a component of oxidatively modified low-density lipoprotein, and, as such, may play an important role in atherosclerosis. Here we demonstrate that in human monocytes, lysophosphatidylcholine increases the level of mRNA encoding the heparin-binding epidermal growth factor-like growth factor (HB-EGF), a potent smooth muscle mitogen. Lysophosphatidylcholine treatment also enhances the release of heparin-binding mitogenic activity by these cells in culture. The anti-inflammatory glucocorticoid dexamethasone inhibits the upregulation of HB-EGF mRNA induced by either lysophosphatidylcholine or bacterial lipopolysaccharide in cultured monocytes. However, the responses induced by lysophosphatidylcholine and by lipopolysaccharide differ in their kinetics. In addition, the response to lysophosphatidylcholine is resistant to the action of cycloheximide, whereas the response to lipopolysaccharide is not, suggesting that the activation mechanisms induced by these two stimuli are different. Since a nuclear run-on assay showed no effect of lysophosphatidylcholine on the transcription of the HB-EGF gene, we speculate that lysophosphatidylcholine may increase the level of HB-EGF mRNA by altering the processing or degradation of primary or mature transcripts. Lysophosphatidylcholine enhancement of monocyte production of HB-EGF may represent an important result of the interactions among oxidized low-density lipoprotein and monocyte-derived macrophages and may play a role in initiation of smooth muscle proliferation in atherogenesis.

Heparin-binding EGF-like growth factor is a potent mitogen for rat hepatocytes

We examined the hepatotrophic activity of heparin-binding EGF-like growth factor (HB-EGF), a recently identified potent mitogen for vascular smooth muscle cells and fibroblasts. HB-EGF stimulated DNA synthesis of rat hepatocytes in primary culture in a dose-dependent manner up to 30 ng/ml. The maximal stimulation by HB-EGF represented more than 80% of that induced by HGF. In normal rat liver, the transcript of HB-EGF gene was detected in the non-parenchymal cells and very low level in the hepatocytes. In the regenerating liver on the 3rd day after 70% hepatectomy, the HB-EGF mRNA increased in the non-parenchymal cells, suggesting that HB-EGF may contribute to liver regeneration through a paracrine mechanism.

Heparin-binding EGF-like growth factor synthesis by smooth muscle cells

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been previously demonstrated to be a potent mitogen for smooth muscle cells. Evidence is now presented that these cells synthesize HB-EGF as well. Cultured fetal human vascular smooth muscle cells express 2.5-kb HB-EGF mRNA. These cells also release an HB-EGF-like activity that (i) stimulates smooth muscle cell and BALB/c 3T3 cell but not endothelial cell proliferation; (ii) binds to TSK heparin affinity columns and is eluted with 0.9-1.2 M NaCl, and (iii) triggers phosphorylation of a protein with the same molecular weight as the 170-kD EGF receptor. In addition, 125I-HB-EGF can be cross-linked to the EGF receptor on fetal human vascular smooth muscle cells. These results suggest that smooth muscle cells can both synthesize and respond to HB-EGF, and that HB-EGF may therefore be involved in autocrine regulation of these cells.

Glucocorticoid inhibits thrombin-induced expression of platelet-derived growth factor A-chain and heparin-binding epidermal growth factor-like growth factor in human aortic smooth muscle cells

Proliferation of smooth muscle cells (SMCs) in atherosclerosis may be modulated by several growth regulatory molecules. At least two mitogens for SMCs, platelet-derived growth factor (PDGF) A-chain and heparin-binding epidermal growth factor-like growth factor (HB-EGF), can be produced by SMCs themselves and may stimulate smooth muscle proliferation in an autocrine or paracrine fashion. We examined the effects of thrombin, which may be generated at the site of vascular injury during atherogenesis, and the potent anti-inflammatory glucocorticoid, dexamethasone (DEX), on the expression of the genes encoding these two growth factors. Since both PDGF A-chain and HB-EGF have affinity for heparin, we also examined the effect of thrombin and DEX on the release of heparin binding mitogenic activity from SMCs. Treatment of SMCs with thrombin resulted in increases both in the level of the PDGF-A and HB-EGF transcripts in the cells, as well as in released heparin-binding growth factor activity. DEX inhibits the thrombin-stimulated release of mitogenic activity in a dose-dependent manner. An enzyme-linked immunoadsorbent assay showed that DEX inhibits both constitutive and thrombin-stimulated release of PDGF-AA. DEX also decreases both constitutive and thrombin-stimulated mRNA levels for PDGF A-chain and HB-EGF and destabilizes the transcripts for both growth factors. A nuclear run-on assay revealed that DEX acts, in addition, to inhibit constitutive and thrombin-stimulated transcription of the PDGF A-chain and HB-EGF genes. Thus, these findings indicate that expression of PDGF A-chain and HB-EGF may be regulated by thrombin and glucocorticoid at the transcription level. Our results are consistent with the involvement of thrombin-induced growth factor expression in neointimal SMC proliferation and suggest the possibility that intimal proliferation may be attenuated by glucocorticoids.

Eosinophils expressing heparin-binding EGF-like growth factor mRNA localize around lung microvessels in pulmonary hypertension

In pulmonary hypertension, induced in rats breathing high oxygen at normobaric pressure, vascular cell hypertrophy and hyperplasia thicken the walls of lung microvessels (15-100 microns in diameter). Over a 28-day time course, new contractile cells develop from intimal precursor smooth muscle cells, which include intermediate cells and interstitial fibroblasts. Cell labeling studies in vivo have shown that these cells proliferate more than other vascular cells and that most of this activity occurs between 4 and 7 days of hyperoxia. The growth factors responsible for this proliferation are unknown. In the present study, we investigate the expression of mRNA for the epidermal growth factor (EGF)-related protein, heparin-binding EGF-like growth factor (HB-EGF), a newly discovered mitogen for fibroblasts and smooth muscle cells. Northern analysis shows HB-EGF mRNA levels to be low in normal lung but increased 100-fold by day 7 of hyperoxia. In situ hybridization identifies a select group of cells expressing HB-EGF mRNA. In normal lung, hybridizing cells are randomly distributed in the alveolar wall and space. By day 7, they increase in number and cluster around the microvessels. Histochemical techniques identify cells expressing HB-EGF mRNA as eosinophils.

Heparin-binding epidermal growth factor-like growth factor expression in cultured fetal human vascular smooth muscle cells. Induction of mRNA levels and secretion of active mitogen

Heparin-binding EGF-like growth factor (HB-EGF) is a recently identified potent mitogen for smooth muscle cells (SMC). To explore whether SMC can also synthesize HB-EGF, cultured fetal human vascular SMC (FHVSMC) were analyzed for the production of HB-EGF mRNA and active growth factor. It was found that in FHVSMC, HB-EGF has the characteristics of an early response gene in that (i) the addition of fresh 10% fetal calf serum to serum-starved FHVSMC led to a rapid and transient rise in HB-EGF mRNA levels with a maximal induction of 12-14-fold occurring within 2-4 h, (ii) the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) also elevated HB-EGF mRNA levels rapidly and transiently with a maximal induction of 7-8-fold occurring at 2-4 h, and (iii) cyclohexamide at 40 micrograms/ml markedly increased basal, serum-, and TPA-induced HB-EGF mRNA levels. In addition, HB-EGF mRNA levels were increased 7-11-fold by addition of either HB-EGF itself, platelet-derived growth factor, or basic fibroblast growth factor, all potent SMC mitogens. Besides synthesizing HB-EGF mRNA, FHVSMC were found to release into conditioned medium a bioactive HB-EGF-like protein that cross-reacted with anti-HB-EGF antibody.

Heparin-binding EGF-like growth factor stimulation of smooth muscle cell migration: dependence on interactions with cell surface heparan sulfate

Heparin-binding EGF-like growth factor (HB-EGF), but not EGF, binds to cell surface heparan sulfate proteoglycan (HSPG). This was demonstrated in (a) the binding of 125I-HB-EGF to mutant CHO cells deficient in HS production was diminished by 70% compared to wild-type CHO cells, (b) the binding of 125I-HB-EGF to CHO cells and bovine aortic smooth muscle cells (BASMC) was diminished 80% by heparitinase or chlorate treatment, and (c) 125I-EGF did not bind to CHO cells and its binding to BASMC was not diminished at all by heparitinase and only slightly by chlorate treatment. Accordingly, the role of HB-EGF interactions with HSPG in modulating bioactivity was examined. Heparitinase or chlorate treatment of BASMC diminished the ability of HB-EGF to stimulate BASMC migration by 60-80%. A similar inhibition of migration occurred when BASMC were treated with a synthetic peptide (P21) corresponding to the sequence of the putative heparin-binding domain of HB-EGF. As a control for BASMC viability, and for specificity, it was found that heparitinase and P21 did not inhibit at all and chlorate inhibited only slightly the stimulation of BASMC migration by PDGF AB. Since heparitinase, chlorate, and P21 treatment also diminished by 70-80% the cross-linking of 125I-HB-EGF to the EGF receptor, it was concluded that the interaction of HB-EGF, via its heparin-binding domain, with cell surface HSPG was essential for its optimal binding to the EGF receptor on BASMC and hence for its optimal ability to stimulate migration.

Heparin-binding EGF-like growth factor: characterization of rat and mouse cDNA clones, protein domain conservation across species, and transcript expression in tissues

Clones were obtained that encode the rat and mouse forms of heparin-binding EGF-like growth factor (HB-EGF), a potent mitogen for smooth muscle cells, fibroblasts and keratinocytes that is proposed to be derived from a transmembrane precursor. Within the HB-EGF precursor sequences predicted from these cDNAs, the region corresponding to the secreted ("mature") factor was found to represent one of the least well conserved areas when compared to human or monkey HB-EGF (73-76% sequence identity). Regions of high sequence conservation included the proposed juxtamembrane and transmembrane domains, as well as a proposed heparin-binding region within the "mature" factor. Northern blotting experiments using the HB-EGF clones as probes revealed HB-EGF transcript expression in multiple tissues, particularly lung, skeletal muscle, brain, and heart.

Structure of heparin-binding EGF-like growth factor. Multiple forms, primary structure, and glycosylation of the mature protein

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a newly described member of the epidermal growth factor (EGF) family that is mitogenic for BALB/c 3T3 cells, inhibits the binding of 125I-EGF to its receptor, and triggers autophosphorylation of the EGF receptor. HB-EGF was purified from the conditioned medium of U-937 cells using cation exchange, copper affinity, heparin affinity, and two rounds of C4 reversed phase liquid chromatography. The elution profile of the first round of C4 column chromatography contained four growth factor activity peaks with similar specific biological activities. N-terminal and tryptic fragment microsequencing demonstrated that these peaks contained different structural forms of the HB-EGF protein. Some of the differences in the various forms of HB-EGF were found to be due to N-terminal heterogeneity. Microsequencing of tryptic fragments indicated that the mature HB-EGF polypeptide can contain at least 86 of the 208 amino acids predicted by nucleotide sequence to be the HB-EGF precursor molecule. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that the various forms of HB-EGF have apparent molecular masses of 19-23 kDa. Further analysis of the most predominant form of HB-EGF found in U-937 cell conditioned medium indicated that it has a pI of 7.2-7.8 and is O-glycosylated.

The human gene for vascular endothelial growth factor. Multiple protein forms are encoded through alternative exon splicing

Vascular endothelial growth factor (VEGF) is an apparently endothelial cell-specific mitogen that is structurally related to platelet-derived growth factor. By Northern blot and protein analyses, we show that VEGF is produced by cultured vascular smooth muscle cells. Analysis of VEGF transcripts in these cells by polymerase chain reaction and cDNA cloning revealed three different forms of the VEGF coding region, as had been reported in HL60 cells. The three forms of the human VEGF protein chain predicted from these coding regions are 189, 165, and 121 amino acids in length. Comparison of cDNA nucleotide sequences with sequences derived from human VEGF genomic clones indicates that the VEGF gene is split among eight exons and that the various VEGF coding region forms arise from this gene by alternative splicing: the 165-amino-acid form of the protein is missing the residues encoded by exon 6, whereas the 121-amino-acid form is missing the residues encoded by exons 6 and 7. Analysis of the VEGF gene promoter region revealed a single major transcription start, which lies near a cluster of potential Sp1 factor binding sites. The promoter region also contains several potential binding sites for the transcription factors AP-1 and AP-2; consistent with the presence of these sites, Northern blot analysis demonstrated that the level of VEGF transcripts is elevated in cultured vascular smooth muscle cells after treatment with the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate.

A heparin-binding growth factor secreted by macrophage-like cells that is related to EGF

Macrophage-like U-937 cells secrete a 22-kilodalton heparin-binding growth factor that is mitogenic for BALB-3T3 fibroblasts and smooth muscle cells, but not endothelial cells. The amino acid sequence predicted from complementary DNA clones indicates that the mitogen is a new member of the epidermal growth factor (EGF) family. This heparin-binding EGF-like growth factor (HB-EGF) binds to EGF receptors on A-431 epidermoid carcinoma cells and smooth muscle cells, but is a far more potent mitogen for smooth muscle cells than is EGF. HB-EGF is also expressed in cultured human macrophages and may be involved in macrophage-mediated cellular proliferation.

Basic fibroblast growth factor stimulation of epidermal wound healing in pigs

Basic fibroblast growth factor (bFGF) has recently been shown to be a mitogen for keratinocytes. This observation has now been extended in a porcine model of epidermal wound healing. A single application of recombinant human bFGF given at the time of injury to healthy animals accelerated the rate of epithelialization by 20%; multiple applications gave no greater effect than the single application. Histologic analysis of biopsies of these partial-thickness wounds taken during bFGF-mediated healing supported the assessment of an enhanced rate of epithelialization and an earlier onset of dermal healing. Because no histologic abnormalities were observed, bFGF induced an acceleration of what appears to be the normal healing process.

Vascular endothelial growth factor: a new member of the platelet-derived growth factor gene family

Using applications of the polymerase chain reaction (PCR) technique, cDNA clones have been isolated encoding bovine vascular endothelial growth factor (VEGF), a mitogen with specificity for vascular endothelial cells. Analysis of the clones indicates that VEGF can exist in two forms, probably due to alternative RNA splicing. The amino acid sequences predicted from the clones also show that VEGF shares homologies of about 21% and 24% respectively with the A and B chains of human platelet-derived growth factor (PDGF), and has complete conservation of the eight cysteine residues found in both mature PDGF chains. The homology is not reflected in function, however, since the cell types responsive to VEGF are distinct from those responsive to homo- and heterodimers of the PDGF chains.

Structural analysis of the gene for human acidic fibroblast growth factor

Genomic clones derived from the gene for human acidic fibroblast growth factor (aFGF) have been isolated. Nucleotide sequence analysis of these clones revealed that the coding region of the human aFGF gene is interrupted by two introns, located at precisely homologous locations to introns in four other members of the FGF gene family, strongly indicating a common evolutionary origin for these genes. Northern blot analyses of the multiple aFGF transcripts found in serum-stimulated human foreskin fibroblasts indicated that the aFGF gene also contains a third intron, lying in the 5' untranslated region.

Isolation and characterization of a vascular endothelial cell mitogen produced by pituitary-derived folliculo stellate cells

A growth factor with specificity for vascular endothelial cells has been identified in conditioned medium of pituitary-derived folliculo stellate cells. This factor, named folliculo stellate-derived growth factor (FSdGF), was purified to homogeneity by a combination of heparin-Sepharose affinity chromatography, Bio-Gel P-60 exclusion chromatography, Mono S ion-exchange chromatography, and hydrophobic chromatography on a C4 reverse-phase HPLC column. FSdGF was characterized as a homodimer composed of two subunits with a molecular mass of 23 kDa. FSdGF was a potent mitogen for vascular endothelial cells with activity detectable at 25 pg/ml and saturation at 500 pg/ml. It did not stimulate the proliferation of other cell types such as bovine vascular smooth muscle cells, corneal endothelial cells, adrenal cortex cells, granulosa cells, BALB/MK cells, or BHK-21 cells. Microsequencing revealed an N-terminal sequence having no significant homology to any known protein. The release of FSdGF by pituitary cells and its target cell specificity raise the possibility that FSdGF may play a role in angiogenesis.

The presence of fibroblast growth factor in the frog egg: its role as a natural mesoderm inducer

A complementary DNA clone corresponding to a 4.2-kilobase transcript that is present in the Xenopus oocyte and newly transcribed in the neurula stages of development has been isolated. This messenger RNA encodes a 155-amino acid protein that is 84% identical to the human basic fibroblast growth factor (bFGF). When expressed in Escherichia coli and purified, the Xenopus FGF induced mesoderm in animal cell blastomeres as measured by muscle actin expression. Immunoblots with an antibody to a Xenopus FGF peptide show that the oocyte and early embryo contain a store of the FGF polypeptide at high enough concentrations to induce mesoderm. The presence of FGF in the oocyte, together with the apparent lack of a secretory signal sequence in the protein, suggest that the regulation of mesoderm induction may involve novel mechanisms that occur after the translation of FGF.

Addition of growth hormone secretion signal to basic fibroblast growth factor results in cell transformation and secretion of aberrant forms of the protein

Basic fibroblast growth factor (bFGF) is a potent mitogen for a wide variety of cell types. Unlike most growth factors, the primary translation product for bFGF appears to lack a secretory signal peptide. To explore the normal mode of bFGF release, as well as to investigate the growth factor's oncogenic potential, expression vectors were created for a bFGF cDNA and for a chimeric molecule in which the bFGF coding sequence was linked to the human growth hormone signal peptide sequence. Transfection of NIH3T3 cells with the bFGF cDNA vectors caused the synthesis of high levels of biologically active, cell-associated bFGF, but no evidence of transformation was detected. In contrast, the chimeric bFGF-signal peptide expression vector induced foci of transformation at a very high frequency. The transformed cells grew in soft agar and were tumorigenic in nude mice. The majority of the immunoreactive bFGF species made by the transformed cells was found in the conditioned medium and appeared to be posttranslationally modified, indicating that the chimeric bFGF-signal peptide molecule was processed through the secretory pathway. The secreted bFGF exhibited little mitogenic activity, suggesting that interaction of bFGF with its receptor likely occurs while the fusion protein is being processed along the secretory pathway.

Basic fibroblast growth factor: production and growth stimulation in cultured adrenal cortex cells

Cultured bovine adrenal cortex cells express the basic fibroblast growth factor (bFGF) gene and contain, but under normal conditions apparently do not release, bFGF. However, once released, bFGF can stimulate proliferation of the cells, indicating that it could act as a self-stimulating growth factor for adrenal cortex cells. It is conceivable that the intracellular bFGF is released upon injury of the adrenal cortex and that it may be involved in the subsequent tissue repair mechanisms by stimulating the proliferation of adrenal cortical and vascular endothelial cells.

Basic fibroblast growth factor in human rhabdomyosarcoma cells: implications for the proliferation and neovascularization of myoblast-derived tumors

Cultured human embryonal rhabdomyosarcoma cells express the basic fibroblast growth factor (bFGF) gene and they produce bFGF, which is apparently composed of two microheterogenous forms with Mrs of 16,500 and 17,200, respectively. bFGF derived from the rhabdomyosarcoma cells stimulates their own proliferation and that of human or bovine vascular endothelial cells. It is conceivable that the rhabdomyosarcoma-derived bFGF stimulates the growth and neovascularization of human rhabdomyosarcomas and that it may thereby contribute to the development of these tumors.

Capillary endothelial cells express basic fibroblast growth factor, a mitogen that promotes their own growth

Angiogenesis, the formation of new capillaries, which is observed in embryonic and injured tissue and is particularly prominent in the vicinity of solid tumours, involves the migration and proliferation of capillary endothelial cells. It is probably triggered by agents, such as basic fibroblast growth factor (bFGF), thought to be released from tissues adjacent to proliferating capillaries. As well as being a potent inducer of cell division in capillary endothelial cells in vitro, bFGF can act as an angiogenic agent in vivo. It is present in a wide variety of richly vascularized tissues including brain, pituitary, retina, adrenal gland, kidney, corpus luteum, placenta and various tumours. So far, however, the normal bFGF-producing cell species in these tissues have not been identified. We report here that capillary endothelial cells express the bFGF gene, that they produce and release bFGF and that bFGF derived from them can stimulate the proliferation of capillary endothelial cells. We conclude that bFGF can act as a self-stimulating growth factor for capillary endothelial cells, and that it is possible that the formation of new capillaries is induced by capillary endothelial cells themselves.

Human basic fibroblast growth factor: nucleotide sequence and genomic organization

Clones encoding the angiogenic endothelial cell mitogen, basic fibroblast growth factor (FGF), have been isolated from human cDNA libraries made from kidney, fetal heart, fetal liver, term placenta, and a breast carcinoma. Basic FGF cDNA clones are present in these libraries at very low levels when compared to the quantity of the growth factor in the tissues. This observation, combined with the fact that several of the clones represent unspliced transcripts, suggests that cytoplasmic basic FGF mRNA is unstable and that the protein is stored in tissues. The amino acid sequence of human basic FGF, deduced from the sequence of these cDNAs and from genomic clones, is 99% homologous to that of bovine basic FGF, implying a strong selection pressure for maintenance of function and structure. As with the bovine factor, human basic FGF does not appear to have a signal peptide sequence. Southern blot analysis of human genomic DNA and mapping of the cloned gene shows that there is only one basic FGF gene. All of the basic, heparin-binding endothelial cell mitogens of similar amino acid composition that have been described must therefore be products of this single gene.

Nucleotide sequence of a bovine clone encoding the angiogenic protein, basic fibroblast growth factor

Basic and acidic fibroblast growth factors (FGF's) are potent mitogens for capillary endothelial cells in vitro, stimulate angiogenesis in vivo, and may participate in tissue repair. An oligonucleotide probe for bovine basic FGF was designed from the nucleotide sequence of the amino-terminal exon of bovine acidic FGF, taking into account the 55 percent amino acid sequence homology between the two factors. With this oligonucleotide probe, a full length complementary DNA for basic FGF was isolated from bovine pituitary. Basic FGF in bovine hypothalamus was shown to be encoded by a single 5.0-kilobase messenger RNA; in a human hepatoma cell line, both 4.6- and 2.2-kilobase basic FGF messenger RNA's were present. Both growth factors seem to be synthesized with short amino-terminal extensions that are not found on the isolated forms for which the amino acid sequences have been determined. Neither basic nor acidic FGF has a classic signal peptide.

The genes for basic and acidic fibroblast growth factors are on different human chromosomes

Basic and acidic fibroblast growth factor (FGF) are related both structurally and functionally. A bovine basic FGF cDNA and a human acidic FGF genomic fragment were used as hybridization probes in Southern blot analysis of DNAs isolated from a panel of 30 mouse-human cell hybrids. The gene encoding basic FGF was assigned to human chromosome 4, and the gene for acidic FGF to human chromosome 5. The two growth factors which are presumed to have a common evolutionary ancestor are therefore not linked. A HindIII restriction fragment length polymorphism was detected for human basic FGF.

Expression and secretion of biologically active human atrial natriuretic peptide in Saccharomyces cerevisiae

A hybrid gene was constructed containing a fusion between the DNA sequences encoding the secretory precursor of the yeast mating pheromone alpha-factor and a synthetic sequence encoding a biologically active 24-amino acid carboxyl-terminal portion of the human atrial natriuretic peptide (hANP) precursor. Transformation of Saccharomyces cerevisiae with the hybrid gene resulted in the yeast cells secreting biologically active hANP into the extracellular medium. The secreted hANP was purified and found to be accurately processed at the junction in the chimeric alpha-factor/hANP protein, producing the desired mature hANP amino terminus. The secreted product was also folded correctly with respect to the single disulfide bond. However, the carboxyl terminus of the secreted hANP material was heterogeneous such that the major form lacked the last two amino acids of the peptide while the minor form was the full length material. The observed processing at the carboxyl terminus of the secreted hANP may reflect a normal processing event involved in alpha-factor peptide maturation.

Involvement of double-strand chromosomal breaks for mating-type switching in Saccharomyces cerevisiae

The yeast S. cerevisiae switches a and alpha cell types by a transposition mechanism that replaces genetic information residing at the mating-type locus (MAT) with information copied from either of the two donor loci, HML and HMR. The donor HML and HMR loci contain the same genetic information as the MATa and MAT alpha alleles, yet they do not switch. Additionally, Strathern et al. (1982) have described an in vivo double-strand DNA break found at subgenomic levels (approximately 2% of MAT DNA) within the MAT locus but not within HML and HMR. We have examined the role of this double-strand DNA break in the switching process. Cell lineage studies show that strains containing deletions of the donor HML and HMR loci produce lethal progeny in the exact pattern described for MAT switching in standard strains. Our interpretation is that the double-strand MAT break in the deletion strains cannot be repaired because of the lack of the donor loci, resulting in cell death. We suggest that the double-strand DNA break is an initiating event for switching and that this event is lethal in the absence of the donor loci. MAT mutants isolated as survivors from this "pedigree of death" define a site required for switching where the double-strand break occurs. We have also examined marl mutant strains in which the donor loci are expressed and observed to switch (Klar et al. 1981a). The double-strand DNA cut appears at the HM loci in these strains. Thus, there is a strong correlation between the presence or absence of the double-strand break at each cassette and its ability or inability to switch as observed at the single cell level.