p53 activates ICAM-1 (CD54) expression in an NF-kappaB-independent manner

Intercellular adhesion molecule-1 (ICAM-1) is a crucial receptor in the cell-cell interaction, a process central to the reaction to all forms of injury. Its expression is upregulated in response to a variety of inflammatory/immune mediators, including cellular stresses. The NF-kappaB signalling pathway is known to be important for activation of ICAM-1 transcription. Here we demonstrate that ICAM-1 induction represents a new cellular response to p53 activation and that NF-kappaB inhibition does not prevent the effect of p53 on ICAM-1 expression after DNA damage. Induction of ICAM-1 is abolished after treatment with the specific p53 inhibitor pifithrin-alpha and is abrogated in p53-deficient cell lines. Furthermore, we map two functional p53-responsive elements to the introns of the ICAM-1 gene, and show that they confer inducibility to p53 in a fashion similar to other p53 target genes. These results support an NF-kappaB-independent role for p53 in ICAM-1 regulation that may link p53 to ICAM-1 function in various physiological and pathological settings.

Letrozole as a potent inhibitor of cell proliferation and expression of metalloproteinases (MMP-2 and MMP-9) by human epithelial breast cancer cells

P450 aromatase catalyzes the conversion of androgens to estrogens and plays a key role in the cell growth of hormone-dependent breast cancer in postmenopausal women. On the other hand, matrix metalloproteinases (MMPs), which can degrade almost all components of the extracellular matrix, play a crucial role in tumor cell invasion and cancer metastasis. In the present study the effect of letrozole on cell proliferation of estrogen receptor (ER)-positive MCF-7 human epithelial breast cancer and MCF-12A human mammary epithelial cells was studied. The effect of letrozole on the in vitro release of MMPs, particularly type IV collagenases (MMP-2 and MMP-9), by the ER-positive MCF-7 cells was also investigated, using a solid-phase method of high sensitivity and accuracy. Using RNA isolates from cell lines MCF-7 and MCF-12A, reverse transcriptase-polymerase chain reaction analysis revealed that only MCF-7 cells express the P450 aromatase gene. Study of the effects of letrozole alone and the hormones 17-beta-estradiol, testosterone and 4-androstene-3, 17-dione in the presence and absence of letrozole on cell growth at the DNA synthesis level showed that letrozole significantly suppressed the endogenous aromatase-induced proliferation of MCF-7 cells. The majority of MMPs secreted by MCF-7 cells were identified in their pro-forms, which was in accordance with the low metastatic potential determined for these cells. After treatment of cells with letrozole (10 nM) for 24 and 48 h, significant inhibition of MMP levels was obtained. Furthermore, concurrent treatment of MCF-7 cells with 17-beta-estradiol in the presence of letrozole significantly suppressed the estradiol-induced stimulation of MMP levels. The data obtained suggest that letrozole is a potent in vitro inhibitor of cell proliferation and of type IV collagenases expressed by ER-positive MCF-7 cells and may be of value for suppressing breast tumor growth and invasiveness.

Developmental and age-related alterations of calcium homeostasis in human fibroblasts

Calcium homeostasis, in terms of both cytosolic calcium concentration ([Ca(2+)](i)) and capacitative calcium entry, has been investigated in human skin and lung fibroblasts at different developmental and ageing stages by employing the Fura-2 based measurements. [Ca(2+)](i) in foetal lung or skin cells were nearly similar. However, significant changes were observed between foetal and adult fibroblasts and interestingly in opposite directions depending on the tissue of origin. In particular, in adult lung cells [Ca(2+)](i) was more than three-fold higher compared to adult skin fibroblasts, a difference which may contribute to tissue-specific functions. Capacitative Ca(2+) entry, i.e. the transient [Ca(2+)](i) increase induced by re-addition of extracellular calcium after depletion of thapsigargin-sensitive calcium stores, was found to exhibit the same pattern of differences during foetal-to-adult transition (it is two-fold higher in adult lung cells than in adult skin cells). At variance, we found capacitative Ca(2+) entry to be significantly attenuated during in vivo or in vitro ageing of fibroblasts; while minor alterations of [Ca(2+)](i) were observed. These findings indicate that capacitative calcium entry rather than [Ca(2+)](i), is mainly affected during the ageing process.

The complement inhibitor CD59 and the lymphocyte function-associated antigen-3 (LFA-3, CD58) genes possess functional binding sites for the p53 tumor suppressor protein

p53 is an oncosuppressor protein, which acts via transcriptional and non-transcriptional mechanisms. The transcriptional function of p53 is mediated by specific responsive elements. In the present study we found active responsive elements, specific for the p53 within the 5'flanking region and within the first intron of the gene encoding for the CD59 membrane inhibitor of reactive lysis, and within the first intron of the gene encoding for the CD58 membrane protein (LFA-3). The results suggest that p53 may enhance the transcription of both CD59 and CD58 and imply a novel role for p53 as a direct regulator of the immune response.

Transcription factor E2F-1 acts as a growth-promoting factor and is associated with adverse prognosis in non-small cell lung carcinomas

Numerous upstream stimulatory and inhibitory signals converge to the pRb/E2F pathway, which governs cell-cycle progression, but the information concerning alterations of E2F-1 in primary malignancies is very limited. Several in vitro studies report that E2F-1 can act either as an oncoprotein or as a tumour suppressor protein. In view of this dichotomy in its functions and its critical role in cell cycle control, this study examined the following four aspects of E2F-1 in a panel of 87 non-small cell lung carcinomas (NSCLCs), previously analysed for defects in the pRb-p53-MDM2 network: firstly, the status of E2F-1 at the protein, mRNA and DNA levels; secondly, its relationship with the kinetic parameters and genomic instability of the tumours; thirdly, its association with the status of its transcriptional co-activator CBP, downstream target PCNA and main cell cycle regulatory and E2F-1-interacting molecules pRb, p53 and MDM2; and fourthly, its impact on clinical outcome. The protein levels of E2F-1 and its co-activator CBP were significantly higher in the tumour area than in the corresponding normal epithelium (p<0.001). E2F-1 overexpression was associated with increased E2F-1 mRNA levels in 82% of the cases examined. The latter finding, along with the low frequency of E2F-1 gene amplification observed (9%), suggests that the main mechanism of E2F-1 protein overexpression in NSCLCs is deregulation at the transcriptional level. Mutational analysis revealed only one sample with asomatic mutation at codon 371 (Glu-->Asp) and one carrying a polymorphism at codon 393 (Gly-->Ser). Carcinomas with increased E2F-1 positivity demonstrated a significant increase in their growth indexes (r=0.402, p=0.001) and were associated with adverse prognosis (p=0.033 by Cox regression analysis). The main determinant of the positive association with growth was the parallel increase between E2F-1 staining and proliferation (r=0.746, p<0.001), whereas apoptosis was not influenced by the status of E2F-1. Moreover, correlation with the status of the pRb-p53-MDM2 network showed that the cases with aberrant pRb expression displayed significantly higher E2F-1 indexes (p=0.033), while a similar association was noticed in the group of carcinomas with deregulation of the p53-MDM2 feedback loop. In conclusion, the results suggest that E2F-1 overexpression may contribute to the development of NSCLCs by promoting proliferation and provide evidence that this role is further enhanced in a genetic background with deregulated pRb-p53-MDM2 circuitry.

Chronic in vivo exposure to glucocorticoids prolongs cellular lifespan: the case of Cushing's syndrome-patients' fibroblasts

Glucocorticoid (GC) hypersecretion constitutes the major hormonal response to stress. In an effort to investigate the impact of a long-lasting exposure to high GC levels in vivo on cellular longevity, we have studied the lifespan of skin fibroblasts from patients suffering from Cushing's syndrome, who are characterised by chronic endogenous GC excess. Interestingly, we have observed that these cells exhibit a significant increase in their proliferative lifespan when cultured in vitro, under standard conditions, compared to fibroblasts from normal donors. In parallel, these cells secrete lower levels of transforming growth factor-beta, known to be implicated in stress-induced premature senescence. Furthermore, they also exhibit an intense stress reaction (near 2-fold, compared to normal cells) in terms of heat-shock protein-70 induction. These results support the hypothesis that stress response may have beneficial consequences in cellular longevity, as well as in tissue homeostasis.

Human fibroblast alterations induced by low power laser irradiation at the single cell level using confocal microscopy

Low power laser irradiation is regarded to have a significant role in triggering cellular proliferation and in treating diseases of diverse etiologies. The present work contributes to the understanding of the mechanisms of action by studying low power laser effects in human fibroblasts. Confocal laser scanning microscopy is used for irradiation and observation of the same area of interest allowing the imaging of laser effects at the single cell level and in real time. Coverslip cultures were placed in a small incubation chamber for in vivo microscopic observation. Laser stimulation of the cells was performed using the 647 nm line of the confocal laser through the objective lens of the microscope. Mitochondrial membrane potential (delta psi(m)), intracellular pH, calcium alterations and generation of reactive oxygen species (ROS) were monitored using specific fluorescent vital probes. The induced effects were quantified using digital image processing techniques. After laser irradiation, a gradual alkalinization of the cytosolic pH and an increase in mitochondrial membrane potential were observed. Recurrent spikes of intracellular calcium concentration were also triggered by laser. Reactive oxygen species were generated as a result of biostimulation. No such effects were monitored in microscopic fields other than the irradiated ones.

The bone-specific transcriptional regulator Cbfa1 is a target of mechanical signals in osteoblastic cells

A primary goal of bone research is to understand the mechanism(s) by which mechanical forces dictate the cellular and metabolic activities of osteoblasts, the bone-forming cells. Several studies indicate that osteblastic cells respond to physical loading by transducing signals that alter gene expression patterns. Accumulated data have documented the fundamental role of the osteoblast-specific transcription factor Cbfa1 (core-binding factor) in osteoblast differentiation and function. Here, we demonstrate that low level mechanical deformation (stretching) of human osteoblastic cells directly up-regulates the expression and DNA binding activity of Cbfa1. This effect seems to be fine tuned by stretch-triggered induction of distinct mitogen-activated protein kinase cascades. Our novel finding that activated extracellular signal-regulated kinase mitogen-activated protein kinase physically interacts and phosphorylates endogenous Cbfa1 in vivo (ultimately potentiating this transcription factor) provides a molecular link between mechanostressing and stimulation of osteoblast differentiation. Elucidation of the specific modifiers and cofactors that operate in this mechanotranscription circuitry will contribute to a better understanding of mechanical load-induced bone formation which may set the basis for nonpharmacological intervention in bone loss pathologies.

Ageing research in Greece

Ageing research in Greece is well established. Research groups located in universities, research institutes or public hospitals are studying various and complementary aspects of ageing. These research activities include (a) functional analysis of Clusterin/Apolipoprotein J, studies in healthy centenarians and work on protein degradation and the role of proteasome during senescence at the National Hellenic Research Foundation; (b) regulation of cell proliferation and tissue formation, a nationwide study of determinants and markers of successful ageing in Greek centenarians and studies of histone gene expression and acetylation at the National Center for Scientific Research, Demokritos; (c) work on amyloid precursor protein and Presenilin 1 at the University of Athens; (d) oxidative stress-induced DNA damage and the role of oncogenes in senescence at the University of Ioannina; (e) studies in the connective tissue at the University of Patras; (f) proteomic studies at the Biomedical Sciences Research Center Alexander Fleming; (g) work on Caenorhabditis elegans at the Foundation for Research and Technology; (h) the role of ultraviolet radiation in skin ageing at Andreas Sygros Hospital; (i) follow-up studies in healthy elderly at the Athens Home for the Aged; and (j) socio-cultural aspects of ageing at the National School of Public Health. These research activities are well recognized by the international scientific community as it is evident by the group's very good publication records as well as by their direct funding from both European Union and USA. This article summarizes these research activities and discuss future directions and efforts towards the further development of the ageing field in Greece.

Effect of protein kinase inhibitors on the stretch-elicited c-Fos and c-Jun up-regulation in human PDL osteoblast-like cells

Osteoblastic cells transduce signals of mechanical loading that plays a key role in maintaining bone formation. In an attempt to elucidate the biochemical events associated with the conversion of mechanical stress to biological outcome, we examined cultured human periodontal ligament (hPDL) osteoblastic cells exposed to continuous stretch, in terms of cellular parameters correlating known signaling cascades to the initial phase of osteoblast-specific transcriptional control. Time-course experiments revealed that mechanical stretch-loaded hPDL cells exhibit a very rapid and relatively sustained increase in the abundance of the immediate-early gene products, c-Fos and c-Jun, components of the activator protein-1 (AP-1) transcription factor. Moreover, this increase in protein levels was accompanied by hyperphosphorylation and thereby potentiation of c-Jun, the principal modulator of AP-1 activity. Importantly, these inductive effects were partly or completely abolished by pre-incubating the cells with SB 203580, PD 098059, and the novel compound Y-27632, inhibitors of p38 mitogen-activated protein kinase (MAPK), MAPK kinase (MEK), and Rho-associated protein kinase (RhoK), respectively. These results consolidate AP-1 as the pivotal downstream effector in the early response of hPDL cells to continuous mechanical stretching, via the coordinate stimulation of de novo synthesis and post-translational regulation of AP-1 proteins. This "integrating" function of AP-1 is mediated through a mechanotransduction circuit that incorporates elements of well-defined upstream signaling protein kinase systems.

Relationship of the K-ras/c-mos expression patterns with angiogenesis in non-small cell lung carcinomas

BACKGROUND

Neo-angiogenesis is an acquired capability vital for a tumor to grow and metastasize. Evidence has shown that the mitogen-activated protein (MAP) kinase pathway is involved in this process. Alterations of K-ras and c-mos, two pivotal components of this pathway, have been implicated in non-small cell lung carcinogenesis. In the present report, we examine, in a series of non-small cell lung carcinomas (NSCLCs), the status of K-ras and c-mos oncoproteins in correlation with the tumor neo-angiogenesis state and the major angiogenic factor, vascular endothelial growth factor (VEGF).

MATERIALS AND METHODS

c-mos and p-ERK1/2 status was evaluated immunohistochemically in a total of 65 NSCLCs, whereas the presence of K-ras mutations was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) restriction fragment length polymorphism (RFLP) in available matched normal tumor material from 56 cases. Microvessel density (MVD) was estimated by immunodetection of CD3, endothelial marker, and VEGF expression was assessed by immunohistochemistry. All possible associations were examined by a series of statistical methods.

RESULTS

Expression of oncogenic activated K-ras and c-mos overexpression was observed in 12 of 49 (25%) and in 16 of 61 (26%) informative cases, respectively. Only 1 of the 25 deregulated for K-ras or c-mos cases exhibited both alterations, suggesting a mutually exclusive relationship between activated K-ras and c-mos overexpression (p = 0.074) in a subset of NSCLCs. In these cases, the MAPK kinase kinase/MEK/ERK pathway was found to be activated. MVD and VEGF expression were 36.9 +/- 10.6 mv/mm2 and 73.1 +/- 20.0%, respectively. The most intriguing finding was that the [K-ras(No)/c-mos(P)] profile was significantly associated with low MVD levels compared to normal cases (p = 0.004); by contrast, no correlation was found between the other K-ras/c-mos patterns and MVD. Furthermore, the former group exhibited the lowest VEGF levels.

CONCLUSIONS

The mutually exclusive relationship between mutated K-ras and c-mos overexpression in a subset of NSCLCs implies a common signal transduction pathway in lung carcinogenesis. The effect of this pathway on NSCLC neo-angiogenesis seems to depend upon the status of c-mos, which acts as a molecular "switch," possibly exerting a negative selective pressure on tumor progression.

Platelet-derived growth factor and transforming growth factor-beta in invertebrate immune and neuroendocrine interactions: another sign of conservation in evolution

Growth factor-like molecules have been found in various invertebrate species. In particular, we have reported the presence of platelet-derived growth factor (PDGF)-AB and transforming growth factor-beta (TGF-beta)1 immunoreactive molecules in molluscs, insects and annelids. Moreover, PDGF-AB and TGF-beta1 affect the main immune functions, such as phagocytosis, chemotaxis and cell motility. Changes in cell shape are induced via interactions of growth factors with their respective specific receptors. The extracellular signals are transduced by the activation of classical signal transduction pathways, such as those involving PKA and PKC, and pivotal transcription regulators, i.e. the Fos, Jun and SMAD proteins. The two growth factors intervene in stress responses by activating the CRH-ACTH-biogenic amine axis. Exogenous administration of PDGF-AB and TGF-beta1 in a molluscan wound provokes an accelerated migration of immunocytes and fibroblasts to the injured area, stimulating granulation tissue formation and wound re-epithelialization. These findings suggest that these molecules are ancestral and that their function is well conserved and crucial in the maintenance of invertebrate homeostasis.

Low levels of p27 in association with deregulated p53-pRb protein status enhance tumor proliferation and chromosomal instability in non-small cell lung carcinomas

BACKGROUND

Down-regulation or overexpression of the cyclin-dependent kinase inhibitor p27 have been observed in a range of malignancies, including lung cancer. To further elucidate the role of the molecule in tumor growth regulation, we evaluated p27 expression in a series of non-small cell lung carcinomas (NSCLCs), and examined its relation with histology, kinetic parameters, ploidy, and overall survival. We extended our investigation into the association of p27 levels with the presence of Ki-ras mutations, as well as with the expression status of p53 and pRb in tumor cells.

MATERIAL AND METHODS

p27, p53, and pRb status were immunohistochemically evaluated in a total of 69 NSCLCs. In situ assays were employed to assess the kinetic parameters (Ki-67 immunohistochemistry for proliferation index, Tdt-mediated dUTP nick end labeling assay for apoptotic index). The ploidy status of the tumors was assessed after staining nuclei with the Feulgen procedure, and the presence of Ki-ras mutations was examined by restriction fragment length polymorphisms. All possible associations were assessed with a series of statistical methods.

RESULTS

Immunoreactivity for p27 was observed in the entire series of specimens, with the mean percentage of positive cells being 33%. Adenocarcinomas (AdCs) exhibited higher p27 levels compared to squamous cell carcinomas (SqCCs) (p < 0.01). An inverse correlation was established between p27 expression and proliferation index (PI) (r = -0.834, p < 0.01) but not with apoptotic index (AI), whereas aneuploid tumors were characterized by lower p27 levels than diploid ones (p < 0.01). No difference in p27 immunostaining was observed with regard to the presence of Ki-ras mutations, whereas aberrant p53 and/or pRb expression patterns were associated with p27 underexpression (p < 0.01 for p53 status, p < 0.05 regarding pRb levels, and p < 0.01 for a combined deregulation of both proteins). Two or more alterations in the p27/p53/pRb protein network (i.e., p27 levels lower than the estimated mean value, overexpressed p53, and/or aberrant pRb) were associated with increased PI and aneuploidy (p < 0.001 and p < 0.01, respectively). A powerful trend was found between p27 expression and overall survival (p = 0.066).

CONCLUSIONS

Our findings confirm the heterogeneity between AdCs and SqCCs, and are suggestive of an increased proliferative activity in NSCLCs underexpressing p27. Furthermore, our analysis supports the concept of p27 forming a functionally compact network with p53 and pRb, which is actively involved in the regulation of cellular proliferation and chromosomal stability.

Involvement of PI 3-kinase, PKA and PKC in PDGF- and TGF-beta-mediated prevention of 2-deoxy-D-ribose-induced apoptosis in the insect cell line, IPLB-LdFB

Activation of phosphatidylinositol (PI) 3-kinase, protein kinase A (PKA) and protein kinase C (PKC) is associated with the survival effect elicited by PDGF-AB and TGF-beta1 against the apoptotic inducer 2-deoxy-D-ribose (dRib) in the fat body cell line, IPLB-LdFB, from the insect Lymantria dispar. dRib induces apoptosis and provokes mitochondrial membrane depolarization (MMD). The antioxidant N -acetyl-L-cysteine annuls only the first effect. These findings suggest that apoptosis and MMD are provoked by two different mechanisms, and that dRib induces apoptosis by oxidative stress.

Food-dependent androgen and cortisol secretion by a gastric inhibitory polypeptide-receptor expressive adrenocortical adenoma leading to hirsutism and subclinical Cushing's syndrome: in vivo and in vitro studies

Aberrant gastric inhibitory polypeptide (GIP) receptor expression in bilaterally hyperplastic adrenals or unilateral adrenal adenomas is a rare form of adrenal hyperfunction. So far, only few cases have been described. In all these cases, cortisol was the predominant steroid released in a food-dependent manner, leading to the development of non-ACTH-dependent Cushing's syndrome. In the present study, we describe a novel case of a GIP receptor-expressive adrenocortical adenomatous nodule, detected incidentally by computed tomography scanning in a 41-yr-old lady with hirsutism but no clinical signs of Cushing's syndrome, on physical examination. Hormonal investigations in morning fasting samples showed slightly elevated androgen levels, low-normal baseline cortisol, normal suppression of cortisol after dexamethasone administration, and ACTH levels that were not suppressed and did stimulate after CRH administration. The elevated urinary free cortisol excretion, in conjunction with an atypical cortisol diurnal rhythm, raised the possibility of an aberrant stimulation of cortisol production by the adrenal tumor. Further studies demonstrated food-dependent secretion of cortisol, which was abolished by prior octreotide administration. Notably, substantial amounts of adrenal androgens were also secreted after food consumption. Removal of the tumor resulted in undetectable cortisol and androgen levels that did not respond to food consumption. Histological examination of the excised tumor revealed an adrenocortical adenomatous nodule originating from the inner zona reticularis, consisting mainly of compact cells. A steroidogenic secretory pattern, indicating the concomitant release of adrenal androgens and cortisol, was also observed in vitro from tumor cells cultured in the presence of GIP. The in vitro secretory response to GIP was higher for the adrenal androgen DHEA, compared with cortisol. The expression of the GIP receptor in tumor cells, but not in the adjacent normal adrenal, was demonstrated by RT-PCR), using specific oligonucleotide probes for this receptor. In summary, we describe a patient with a GIP-expressive cortisol and androgen oversecreting adrenocortical nodule with the unusual presentation of hirsutism and not the typical clinical signs of Cushing's syndrome. It is of note that food intake in this patient provoked a substantial increase in both adrenal androgen and cortisol levels that, together with the histological appearance of this nodule, was compatible with a zona reticularis-derived tumor. Thus, aberrant expression of the GIP receptor does not exclusively involve cells of a zona fasciculata phenotype, as previously reported, but may also occur in other types of differentiated adrenocortical cells.

Deregulated expression of c-mos in non-small cell lung carcinomas: relationship with p53 status, genomic instability, and tumor kinetics

Little is known about the status of the mitogen-activating protein kinase pathways in lung cancer. One of the key molecules taking part in these pathways is the product of the c-mos proto-oncogene, which plays an important role in oocyte maturation. In vitro investigations in somatic cells have shown that c-mos expression has opposing effects on the cell cycle, which suggests that this proto-oncogene may represent an important determinant of aberrant cell function (genomic instability and altered kinetics). A recent study suggests that these effects may be p53 dependent. In view of the apparent link between c-mos and p53, we investigated in a series of 56 non-small cell lung carcinomas: a) the status of c-mos; b) its relationship to genomic instability (aneuploidy) and two kinetic parameters of the tumors, proliferation and apoptotic indexes (AI); and c) its association with p53 alterations and their concomitant relationship with the above parameters. We found c-mos overexpression in 27% of the tumors. Expression was higher in stages II/III (34%) than in stage I (17%; P = 0.018). Complete concordance was observed between c-mos overexpression and elevated c-mos mRNA levels. Because c-mos gene amplification was not detected, its deregulated expression may be attributable to increased transcription. Of the c-mos positive [c-mos(P)] cases, 77% were associated with aneuploidy. Sequencing showed two silent mutations and one missense (R-->L) at codon 22, located in a region critical for c-mos stability. In contrast to the findings of some in vitro studies, c-mos(P) tumors had a lower mean AI score than the c-mos negative [c-mos(N)] tumors had, implying that induction of apoptosis may have been defective. Indeed, 86% of the tumors overexpressing c-mos showed p53 alterations. The carcinomas with concomitant alterations of c-mos and p53 [c-mos(P)/p53 positive] had significantly lower AI values (P < 0.001) and were more frequently associated with aneuploidy (P = 0.015) than the c-mos(N)/p53 negative tumors but not the c-mos(N)/p53 positive tumors, which suggests that p53 status is the main determinant of ploidy status and apoptosis in our series. This finding also strengthens the concept that wild-type p53 plays a "safeguard" role in preventing oncogene-mediated activation.

Autocrine regulation of proliferation and extracellular matrix homeostasis in human fibroblasts

In the late stages of the tissue repair process, as well as during normal tissue turnover, tissue homeostasis may rely mostly on autocrine mechanisms. Accordingly, we have cultured normal human fibroblasts on plastic surfaces and within three-dimensional collagen gels in order to study, in this environment, the action of autologous medium conditioned by the same cells. We have observed that inside collagen gels the autologous medium strongly restrains cell proliferation, due to fibroblast-secreted growth factors, whose inhibitory effect can be annulled by suramin. Furthermore, concerning extracellular matrix formation, conditioned medium has no effect on novel collagen synthesis, while it up-regulates collagenase MMP-1 only in cultures on plastic. On the other hand, it strongly inhibits the secretion of the collagenase inhibitor TIMP-1, irrespective of the substratum. This effect is completely blocked by SB 203580, an inhibitor of the p38 MAP kinase. The above suggest the presence of an autoregulatory mechanism involved in tissue homeostasis.

Neutral endopeptidase-24.11 (NEP) deactivates PDGF- and TGF-beta-induced cell shape changes in invertebrate immunocytes

Using a cytofluorimetric assay, we found that immunocytes of the mollusc, Mytilus galloprovincialis, express CD10, a surface antigen known to be identical to neutral endopeptidase-24.11 (NEP). The spectrofluorimetric analysis demonstrates that the growth factors PDGF-AB and TGF-beta1 provoke an increase in NEP-like activity in membrane preparations from the immunocytes, but have no effect on the soluble form in the serum. On the other hand, computer-assisted microscopic image analysis reveals that NEP deactivates the PDGF-AB- and TGF-beta1-induced shape changes in immunocytes. However, Western blots show that, in solution, NEP does not cleave PDGF-AB or TGF-beta1, indicating that the inactivation is not due to proteolysis. These results suggest a functional interplay in invertebrate immunocytes between growth factors and NEP, as previously shown in vertebrate cells.

Fibroblast responses to exogenous and autocrine growth factors relevant to tissue repair. The effect of aging

The aging process is often associated with impaired wound healing, but the cellular and molecular mechanisms implicated are not completely understood. Accordingly, we have investigated the response of human fibroblasts from donors of various ages to platelet-derived and autocrine growth factors, in terms of mitogenicity as well as extracellular matrix synthesis and degradation. Our data indicate that fibroblast responses persist during aging, suggesting the involvement of systemic factors in the regulation of the healing process. In this context, we have found that neutral endopeptidase-24.11, a metalloproteinase controlling the action of neuroendocrine peptides and also of immunocyte chemotaxis, is overexpressed during aging. Finally, the connection between these data and those from in vitro aging studies is discussed.

p53, p21(WAF1/CIP1), and MDM2 involvement in the proliferation and apoptosis in an in vitro model of conditionally immortalized human vascular smooth muscle cells

Using an in vitro model of a conditionally immortalized cell line, we have investigated how human vascular smooth muscle cells (VSMCs) are affected by the expression of simian virus 40 (SV40) large T antigen (LT antigen), which binds to cell cycle regulators such as the tumor suppressor protein p53. Cells were obtained after infection of saphenous vein-derived VSMCs with a nonreplicative retroviral vector containing a temperature-sensitive mutant of SV40 LT antigen and were shown to have maintained some characteristics and responses of VSMCs. Under permissive-temperature conditions (36 degrees C), the increased rate of cell proliferation was shown to be associated with expression of LT antigen and with LT antigen binding to and inactivation of p53. p53 inactivation failed to block apoptosis induced by serum withdrawal or UV irradiation. Downregulation of LT antigen expression at a nonpermissive temperature (39 degrees C) was shown to be associated with growth arrest, increased expression of the cell cycle inhibitor p21(WAF1/CIP1), increased murine double minute-2 promoter activity, and differential expression of murine double minute-2 gene products, suggesting that p53-induced transcription/transactivation may be involved in VSMC cycle control but not necessarily in apoptosis. The established SMC line HVTs-SM1 may be a useful model for study of the processes involved in myointimal hyperplasia and cellular aging, as well as for the study of cell cycle control in general.

p53, p21(WAF1/CIP1), and MDM2 involvement in proliferation and apoptosis in an in vitro model of conditionally immortalized human vascular smooth muscle cells

Using an in vitro model of a conditionally immortalized cell line, we investigated how human vascular smooth muscle cells (VSMCs) are affected by the expression of simian virus 40 (SV40) large T antigen (LT antigen), which binds to cell cycle regulators, such as the tumor suppressor protein p53. Cells were obtained after infection of saphenous vein-derived VSMCs with a nonreplicative retroviral vector containing a temperature-sensitive (ts) mutant of SV40 LT antigen and were shown to have maintained some characteristics and responses of VSMCs. Under permissive temperature conditions (36 degrees C), the increased rate of cell proliferation was shown to be associated with expression of LT antigen and with LT-antigen binding to and inactivation of p53. p53 inactivation failed to block apoptosis induced by serum withdrawal or by UV irradiation. Downregulation of LT-antigen expression at the nonpermissive temperature (39 degrees C) was shown to be associated with growth arrest, increased expression of the cell cycle inhibitor p21(WAF1/CIP1), increased MDM2-promoter activity, and differential expression of MDM2 gene products, suggesting that p53-induced transcription/transactivation may be involved in VSMC cell cycle control but not necessarily apoptosis. The established SMC line HVTs-SM1 may be a useful model for the study of processes involved in myointimal hyperplasia and cellular aging, as well as for the study of cell cycle control in general.

PDGF and TGF-beta partially prevent 2-deoxy-D-ribose-induced apoptosis in the fat body cell line IPLB-LdFB from the insect Lymantria dispar

The IPLB-LdFB cell line from the fat body of the insect Lymantria dispar shows the presence of immunoreactive, platelet-derived growth factor (PDGF)-AB and transforming growth factor (TGF)-beta1 molecules, as well as the corresponding plasma membrane-like receptors, i.e. PDGFR-alpha, PDGFR-beta and TGFR-beta type II. Cytofluorimetric and morphological studies reveal that the reducing sugar 2-deoxy-D-ribose (dRib), an apoptotic agent for human cells, induces apoptosis in a concentration- and time-dependent manner even in IPLB-LdFB cells. PDGF-AB and TGF-beta1 partially counteract the effect of dRib, indicating a survival role of these factors in this apoptotic model of insect cells.

Mechanical stress induces DNA synthesis in PDL fibroblasts by a mechanism unrelated to autocrine growth factor action

Periodontal regeneration is thought to require the proliferation of stress-sensitive periodontal ligament (PDL) fibroblast cells. The influence of physiological amounts of mechanical stretching on the DNA synthesis potential of human PDL fibroblasts was examined by means of an established, simple in vitro system of stretch application. A significant increase in the relative levels of incorporation of tritiated thymidine was observed in cultures stretched for 1-6 h. Neutralising antibodies for platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) did not blunt the DNA synthesis induction. This mitogenic response to stretch appears to be independent of an autocrine mechanism involving growth factors in general, because stretch-conditioned medium, when transferred to non-stretched fibroblasts, did not mimic the mitogenic effect of stretch.

The CRH-ACTH-biogenic amine axis in invertebrate immunocytes activated by PDGF and TGF-beta

In immunocytes from the mollusc Mytilus galloprovincialis, the major pathway followed by platelet-derived growth factor (PDGF)-AB and transforming growth factor (TGF)-beta1 in provoking the release of norepinephrine, epinephrine and dopamine into cell-free hemolymph (serum) is mediated by a corticotropin-releasing hormone-adrenocorticotropin hormone (CRH-ACTH) biogenic amine axis. This axis not only annulled the inhibiting properties of PDGF-AB, it even reversed the latter's effect, while the inducing effect of TGF-beta1 was amplified. These findings show that non-classical immune-neuroendocrine molecules, such as PDGF-AB and TGF-beta1, are involved in building stress response, using the same conserved mechanisms present from invertebrates to vertebrates.

Neutral endopeptidase-24.11 (NEP) activity in human fibroblasts during development and ageing

Neutral endopeptidase-24.11 (NEP, EC 3.4.24.11) is a cell surface Zn metallopeptidase that hydrolyzes bioactive regulatory peptides. Using a spectrofluorimetric procedure, we assessed NEP activity in plasma membranes of normal human skin and lung fibroblasts. We found a considerable increase in NEP activity during fetal-to-adult transition. Adult skin fibroblasts from an old donor exhibited significantly higher levels of NEP activity than cells from young donors. Interestingly, however, the NEP activity of fibroblasts from a centenarian donor was similar to that of cells from young donors. Increased levels of NEP activity were also found in in vitro aged lung fibroblasts. Finally, adrenocorticotropin hormone (ACTH (1-24)), a regulatory peptide that can be cleaved by NEP, provoked an increase in enzymic activity in fetal and young adult donor fibroblasts and a decrease in this activity in fibroblasts from adult and old donors. This finding suggests that ageing may affect NEP activity.

PDGF and TGF-beta induce cell shape changes in invertebrate immunocytes via specific cell surface receptors

The presence of PDGF receptor-alpha- and -beta- and TGF-beta-receptor (type II)-like molecules on the plasma membranes of the immunocytes of the mollusc Mytilus galloprovincialis was demonstrated by an immunocytochemical procedure. Furthermore, the present study provides evidence that PDGF-AB and TGF-beta1 provoke cell shape changes in immunocytes via interactions with the respective receptors and that these extracellular signals are transduced along the phosphoinositide signaling pathway.

The highly reducing sugar 2-deoxy-D-ribose induces apoptosis in human fibroblasts by reduced glutathione depletion and cytoskeletal disruption

2-deoxy-D-Ribose (dRib), the most reducing sugar, induces apoptosis in normal human fibroblasts, as judged by cytoplasmic shrinkage, chromatin condensation, DNA fragmentation and mitochondrial depolarization. This effect is independent from culture conditions, such as cell density and the presence or absence of serum in the culture milieu, suggesting that dRib-induced apoptosis is cell cycle-independent. dRib was found also to provoke disruption of the actin filament network and detachment from the substratum, while at the same time, interestingly, it increases the expression of several integrins and cell adhesion molecules. Furthermore, dRib was found to reduce the intracellular levels of reduced glutathione (GSH). The apoptotic process was not affected by the macromolecular-synthesis inhibitors cycloheximide and actinomycin D. On the contrary, the antioxidant N-acetyl-L-cysteine (NAC) fully blocks the dRib-induced apoptosis by preventing GSH depletion, while it also inhibits actin-filament-network disruption and mitochondrial depolarization. The above indicate that dRib induces apoptosis in human fibroblasts by a mechanism involving glutathione metabolism and oxidative stress, as well as disturbance of cytoskeletal integrity and cell adhesion.

Interactions of signaling pathways in ACTH (1-24)-induced cell shape changes in invertebrate immunocytes

ACTH (1-24) induces cell shape changes in the immunocytes of the bivalve mollusc, Mytilus galloprovincialis. Using computer-assisted microscopic image analysis, we have found that the G protein antagonist suramin sodium, the adenylate cyclase inhibitor 2',5'-dideoxyadenosine, and the protein kinase inhibitor staurosporine inhibit this effect. The highly specific inhibitors H-89 (for protein kinase A) and calphostin C (for protein kinase C) only inhibited partially the morphological alterations. In contrast, the simultaneous action of H-89 and calphostin C completely blocked these changes. The above findings indicate that ACTH (1-24) induces cell shape changes in molluscan immunocytes via adenylate cyclase/cAMP/protein kinase A pathway, as well as the activation of protein kinase C.

PDGF- and TGF-beta-induced changes in cell shape of invertebrate immunocytes: effect of calcium entry blockers

The cellular activity of hemocytes from the marine mollusc Mytilus galloprovincialis was studied using computer-assisted microscopic image analysis. PDGF-AB and TGF-beta 1 caused changes in cellular shape and induced the immunocytes to migrate in a chemotactic manner. The effect of PDGF-AB was more potent than that of TGF-beta 1, and the responses were dose-correlated for PDGF-AB, while they were dose-dependent up to 5 pg/ml for TGF-beta 1. Moreover, the PDGF-AB response was extracellular Ca(2+)-independent, while TGF-beta 1 was Ca(2+)-dependent.

Autocrine growth regulation in fetal and adult human fibroblasts

Medium conditioned (CM) by human fetal fibroblasts stimulates proliferation in sparse cultures. This effect is inhibited by suramin and staurosporine, indicating the presence of autocrine growth factors in CM. On the contrary, CM inhibits DNA synthesis in confluent cultures, suggesting a regulatory role for the secreted factors. The growth regulatory profile of CM persists during in vitro ageing. However, it changes dramatically during the fetal-to-adult transition, as adult human fibroblasts are stimulated by CM, regardless of the culture density. These effects are similar to those that TGF-beta is known to have on fetal and adult human fibroblasts. Indeed TGF-beta is present in media conditioned by human fibroblasts, but CM-activity cannot be ascribed solely to this factor. Fibroblasts originating from different tissues exhibit the same autocrine regulatory features, suggesting the general character of this mechanism.

Effect of PDGF and TGF-beta on the release of biogenic amines from invertebrate immunocytes and their possible role in the stress response

PDGF-AB and TGF-beta 1 intervene in molluscan stress response, the former inhibiting and the latter inducing the release of norepinephrine and epinephrine from hemocytes. These amines are down-regulated even when TGF-beta 1 is added to hemolymph pre-incubated with PDGF-AB. The opposite behaviour is observed if the growth factors are reversed. The dopamine response is not affected in either case, even after the addition of CRH or ACTH. After pre-incubation with PDGF-AB or TGF-beta 1 in the presence of CRH or ACTH, norepinephrine and epinephrine release falls. These findings suggest that when the interaction is between growth factors, the order of combination is crucial, while in cases where the interaction is between growth factors and other peptides, such as CRH and ACTH, the order is of no importance.

Immunocytochemical evidence of PDGF- and TGF-beta-like molecules in invertebrate and vertebrate immunocytes: an evolutionary approach

Immunoreactive platelet-derived growth factor-AB and transforming growth factor-beta 1 were demonstrated in invertebrate and vertebrate immunocytes by an immunocytochemical procedure. These factors are only present in phagocytic cells among invertebrate immunocytes, whereas in vertebrate immunocytes they are found in monocytes, granulocytes, lymphocytes, thrombocytes and platelets. These results, in agreement with previous reports, represent further evidence in favour of the hypothesis that Nature has followed a conservative strategy in using a common pool of signal molecules that have been highly conserved throughout evolution.

The growth-inhibitory block of TGF-beta is located close to the G1/S border in the cell cycle

Transforming growth factor-beta (TGF-beta) inhibits DNA synthesis in dense cultures of young human embryonic fibroblasts and antagonizes the mitogenic action of platelet-derived growth factor (PDGF). The inhibition of the PDGF-BB action by TGF-beta was independent of the induction of mRNAs for the PDGF-A chain and PDGF-beta receptor, the predominant types of PDGF receptor in human fibroblasts. The TGF-beta-mediated inhibition did not influence the expression of various genes that are involved in the transition from the arrested (GO) state to the S phase of the cell cycle. Indeed, TGF-beta upregulated the "early" genes c-myc, c-fos, and junB and downregulated the growth arrest-specific (gas) genes. These results suggest that the inhibition of DNA synthesis by TGF-beta in human fibroblasts is independent of modulation of expression of early and gas genes, placing the TGF-beta block comparatively late in the GO to S transition. In cultures of senescent human fibroblasts TGF-beta stimulated DNA synthesis but, nevertheless, had the same effect as in young cells on the expression of PDGF chains and receptor genes, as well as on early and gas genes, with the exception of a significantly lower induction of c-fos.

Restoration of down-regulated PDGF receptors by TGF-beta in human embryonic fibroblasts. Enhanced response during cellular in vitro aging

The study of [125I]PDGF-BB binding to normal human embryonic lung fibroblasts, quiescent when cultured at sparsity in the presence of minute concentrations of homologous PDS, reveals approximately 2 x 10(5) binding sites for PDGF per cell; this number significantly increases during prolonged quiescence of the culture. As late as 48 h after down-regulation of PDGF receptors, the cells restore only partially their capacity to bind PDGF, with aged cells (above CPD 45) responding more rapidly and efficiently than younger ones. TGF-beta significantly enhances restoration of PDGF receptors and, in aged cells in particular, its presence results in total receptor recovery within 24 h, suggesting a concerted action of PDGF and TGF-beta regulating the proliferation of human fibroblasts in tissue regeneration.

Stimulation of human embryonic lung fibroblasts by TGF-beta and PDGF acting in synergism. The role of cell density

The concerted action of TGF-beta and PDGF on a diploid human embryonic lung fibroblast cell strain (Flow 2002) grown in an homologous environment is investigated here. In sparse cultures, TGF-beta stimulates DNA synthesis over a broad concentration range (0.1-10 ng/ml). Furthermore, it acts in synergism with PDGF, a phenomenon which persists also during in vitro aging of the cells. Preincubation of TGF-beta with the fibroblasts up to 12 hours reduces the subsequent PDGF binding to the cells, while prolonged preincubation restores PDGF binding to control levels. Finally, in cultures of higher cell densities, TGF-beta ceases to stimulate DNA synthesis, whereas PDGF continues even at cell confluency, retains its stimulatory activity suggesting different roles for the two growth factors during the wound healing process.

Quiescence and proliferative response of normal human embryonic fibroblasts in homologous environment. Effect of aging

A cell culture system for the study of human serum growth factors is described. It is based on a diploid human embryonic lung fibroblast cell strain (Flow 2002) with a finite life span (60 +/- 3 CPDs). When maintained in homologous (human) plasma-derived serum (PDS) at concentrations as low as 0.05%, the cells attain quiescence. Under these conditions, they remain viable for at least 14 days and they readily respond when stimulated to proliferate by human serum or human PDS, as well as by growth factors, such as PDGF, EGF, FGF. During in vitro aging, the cells retain their responsiveness to these growth stimuli, although the net proliferative effect decreases as they approach senescence.