The Carnitine Palmitoyltransferase 1A Inhibitor Teglicar Shows Promising Antitumour Activity against Canine Mammary Cancer Cells by Inducing Apoptosis

Canine mammary tumours (CMTs) are the most common cancer in intact female dogs. In addition to surgery, additional targeted and non-targeted therapies may offer survival benefits to these patients. Therefore, exploring new treatments for CMT is a promising area in veterinary oncology. CMT cells have an altered lipid metabolism and use the oxidation of fatty acids for their energy needs. Here we investigated the tumoricidal effects of teglicar, a reversible inhibitor of carnitine palmitoyl transferase 1A (CPT1A), the rate-limiting enzyme for fatty acid import into mitochondria, on two CMT cells, P114 and CMT-U229. Viability and apoptosis were examined in CMT cells using the crystal violet assay, trypan blue assay, and flow cytometry analysis. The expression of mediators of apoptosis signalling (e.g., caspase-9, caspase-8, and caspase-3) was assessed by quantitative real-time polymerase chain reaction and western blot analyses. Teglicar was able to decrease cell viability and induce apoptosis in P114 and CMT-U229 cells. At the molecular level, the effect of teglicar was associated with an upregulation of the mRNA expression levels of caspase-9, caspase-8, and caspase-3 and an increase in their protein levels. In summary, our results show that teglicar has a potential effect against CMTs through the induction of apoptotic cell death, making it a promising therapeutic agent against CMTs.

Metabolic Flexibility in Canine Mammary Tumors: Implications of the Carnitine System

Deregulation of fatty acid catabolism provides an alternative energy source to glycolysis for cancer cell survival and proliferation. The regulator enzymes of the carnitine system (CS), responsible for the transport of fatty acids across mitochondrial membranes for β-oxidation are deregulated in tumorigenesis. Recently, we found that Carnitine Palmitoyl Transferase 1 (CPT1), a crucial regulator of CS components, is expressed and dysregulated in canine mammary tumor (CMT) tissues and cells. In this study, we examined the protein expression of the three remaining enzymes of CS (Carnitine Acylcarnitine Translocase (CACT), Carnitine Palmitoyl Transferase 2 (CPT2), Carnitine O-acetyltransferase (CrAT), in canine mammary cells and tissues by Western blot and immunohistochemistry. Protein expression of the components of CS was found in normal mammary glands and a concomitant deregulation of expression in CMT tissues that inversely correlated with the degree of tumor differentiation. Moreover, the expression and a different deregulation of CS-related proteins was also observed in CF33, CMT-U27, CMT-U309, and P114 cell lines used as in vitro model. These results demonstrate for the first time the expression of CS components in CMT tissues and cancer cells; however, further studies are needed to elucidate their roles in dogs as well.

Carnitine palmitoyltransferase 1 A expression profile in canine mammary tumors

Genetic alterations and/or epigenetic modifications occur frequently in the majority of cancer cells. In addition to playing a crucial role as promoters of tumorigenesis, these processes can also generate metabolic pathways that are different from those in normal cells. Besides the Warburg effect, an alteration in lipid metabolism is also found in cancer cells. Thus, elucidation of the regulators involved in this metabolic reprogramming might provide tools for diagnosis, prognosis, and ultimately treatment of canine mammary tumours (CMTs) in particular. One such regulator is carnitine palmitoyltransferase 1A (CPT1A), which is involved in transportation of long-chain fatty acids into the mitochondrial matrix for beta-oxidation, thereby providing an alternative pathway for the generation of energy for tumour growth and development. In this study, the canine cell lines MDCK, CMT-U309, CMT-U27, and P114 were used as in vitro models for western blot and quantitative real-time polymerase chain reaction (qRT-PCR) analyses. Furthermore, western blot and immunohistochemistry were carried out to evaluate CPT1A protein expression in the CMT specimens. The CPT1A protein and mRNA expression levels were increased in the CMT cell lines relative to their levels in normal epithelial cells. Moreover, increased CPT1A expression levels were found in the CMT tissues, being inversely correlated with the tumour differentiation grade. However, additional studies are required to further specify the role of CPT1A in CMTs.

Ginkgo biloba Prevents Oxidative Stress-Induced Apoptosis Blocking p53 Activation in Neuroblastoma Cells

Oxidative stress has been associated to neuronal cell loss in neurodegenerative diseases. Neurons are post-mitotic cells that are very sensitive to oxidative stress—especially considering their limited capacity to be replaced. Therefore, reduction of oxidative stress, and inhibiting apoptosis, will potentially prevent neurodegeneration. In this study, we investigated the neuroprotective effect of Ginkgo biloba extract (EGb 761) against H₂O₂ induced apoptosis in SK-N-BE neuroblastoma cells. We analysed the molecular signalling pathway involved in the apoptotic cell death. H₂O₂ induced an increased acetylation of p53 lysine 382, a reduction in mitochondrial membrane potential, an increased BAX/Bcl-2 ratio and consequently increased Poly (ADP-ribose) polymerase (PARP) cleavage. All these effects were blocked by EGb 761 treatment. Thus, EGb 761, acting as intracellular antioxidant, protects neuroblastoma cells against activation of p53 mediated pathway and intrinsic mitochondrial apoptosis. Our results suggest that EGb 761, protecting against oxidative-stress induced apoptotic cell death, could potentially be used as nutraceutical for the prevention and treatment of neurodegenerative diseases.

Long-Term Fluoride Release from Dental Resins Affects STRO-1+ Cell Behavior

Fluoride-releasing restorative dental materials can be beneficial to remineralize dentin and help prevent secondary caries. However, the effects of fluoride release from dental materials on the activity of dental pulp stem cells are not known. Here we investigate whether different fluoride release kinetics from dental resins supplemented with modified hydrotalcite (RK-F10) or fluoride-glass filler (RK-FG10) could influence the behavior of a human dental pulp stem cell subpopulation (STRO-1(+) cells) known for its ability to differentiate toward an odontoblast-like phenotype. The 2 resins, characterized by similar physicochemical properties and fluoride content, exhibited different long-term fluoride release kinetics. Our data demonstrate that long-term exposure of STRO-1(+) cells to a continuous release of a low amount of fluoride by RK-F10 increases their migratory response to transforming growth factor β1 (TGF-β1) and stromal cell-derived factor 1 (SDF-1), both important promoters of pulp stem cell recruitment. Moreover, the expression patterns of dentin sialoprotein (dspp), dentin matrix protein 1 (dmp1), osteocalcin (ocn), and matrix extracellular phosphoglycoprotein (mepe) indicate a complete odontoblast-like cell differentiation only when STRO-1(+) cells were cultured on RK-F10. On the contrary, RK-FG10, characterized by an initial fluoride release burst and reduced lifetime of the delivery, did not elicit any significant effect on both STRO-1(+) cell migration and differentiation. Taken together, our results highlight the importance of taking into account fluoride release kinetics in addition to fluoride concentration when designing new fluoride-restorative materials.

High grade glioblastoma is associated with aberrant expression of ZFP57, a protein involved in gene imprinting, and of CPT1A and CPT1C that regulate fatty acid metabolism

The diagnosis of glioblastoma is still based on tumor histology, but emerging molecular diagnosis is becoming an important part of glioblastoma classification. Besides the well-known cell cycle-related circuitries that are associated with glioblastoma onset and development, new insights may be derived by looking at pathways involved in regulation of epigenetic phenomena and cellular metabolism, which may both be highly deregulated in cancer cells. We evaluated if in glioblastoma patients the high grade of malignancy could be associated with aberrant expression of some genes involved in regulation of epigenetic phenomena and lipid metabolism. We measured the mRNA levels of ZFP57, TRIM28, CPT1A, CPT1B, and CPT1C in a cohort of 80 patients divided in two groups: grade II and grade IV. We evidenced that high grade glioblastoma is associated with increased level of ZFP57, a protein involved in gene imprinting, and aberrant expression of CPT1A and CPT1C, regulators of fatty acid oxidation. Our study may pave the way to identify new markers that could be potentially useful for diagnosis and/or prognosis of glioblastoma.

Effect of layered double hydroxide intercalated with fluoride ions on the physical, biological and release properties of a dental composite resin

OBJECTIVES

The aim of this work was the preparation of a new fluoride-releasing dental material characterized by a release of fluoride relatively constant over time without any initial toxic burst effect. This type of delivery is obtained by a matrix controlled elution and elicits the beneficial effect of a low amount of fluoride on human dental pulp stem cells (hDPSCs) towards mature phenotype.

METHODS

The modified hydrotalcite intercalated with fluoride ions (LDH-F), used as filler, was prepared via ion exchange procedure and characterized by X-ray diffraction and FT-IR spectroscopy. The LDH-F inorganic particles (0.7, 5, 10, 20wt.%) were mixed with a photo-activated Bis-GMA/TEGDMA (45/55wt/wt) matrix and novel visible-light cured composites were prepared. The dynamic thermo-mechanical properties were determined by dynamic mechanical analyzer. The release of fluoride ions in physiological solution was determined using a ionometer. Total DNA content was measured by a PicoGreen dsDNA quantification kit to assess the proliferation rate of hDPSCs. Alkaline phosphatase activity (ALP) was measured in presence of fluoride resins.

RESULTS

Incorporation of even small mass fractions (e.g. 0.7 and 5wt.%) of the fluoride LDH in Bis-GMA/TEGDMA dental resin significantly improved the mechanical properties of the pristine resin, in particular at 37°C. The observed reinforcement increases on increasing the filler concentration. The release of fluoride ions resulted very slow, lasting months. ALP activity gradually increased for 28 days in hDPSCs cell grown, demonstrating that low concentrations of fluoride contributed to the cell differentiation.

CONCLUSIONS

The prepared composites containing different amount of hydrotalcite filler showed improved mechanical properties, slow fluoride release and promoted hDPSCs cell proliferation and cell differentiation.

Carnitine-acyltransferase system inhibition, cancer cell death, and prevention of myc-induced lymphomagenesis

BACKGROUND

The metabolic alterations of cancer cells represent an opportunity for developing selective antineoplastic treatments. We investigated the therapeutic potential of ST1326, an inhibitor of carnitine-palmitoyl transferase 1A (CPT1A), the rate-limiting enzyme for fatty acid (FA) import into mitochondria.

METHODS

ST1326 was tested on in vitro and in vivo models of Burkitt's lymphoma, in which c-myc, which drives cellular demand for FA metabolism, is highly overexpressed. We performed assays to evaluate the effect of ST1326 on proliferation, FA oxidation, and FA mitochondrial channeling in Raji cells. The therapeutic efficacy of ST1326 was tested by treating Eµ-myc mice (control: n = 29; treatment: n = 24 per group), an established model of c-myc-mediated lymphomagenesis. Experiments were performed on spleen-derived c-myc-overexpressing B cells to clarify the role of c-myc in conferring sensitivity to ST1326. Survival was evaluated with Kaplan-Meier analyses. All statistical tests were two-sided.

RESULTS

ST1326 blocked both long- and short-chain FA oxidation and showed a strong cytotoxic effect on Burkitt's lymphoma cells (on Raji cells at 72 hours: half maximal inhibitory concentration = 8.6 μM). ST1326 treatment induced massive cytoplasmic lipid accumulation, impairment of proper mitochondrial FA channeling, and reduced availability of cytosolic acetyl coenzyme A, a fundamental substrate for de novo lipogenesis. Moreover, treatment with ST1326 in Eµ-myc transgenic mice prevented tumor formation (P = .01), by selectively impairing the growth of spleen-derived primary B cells overexpressing c-myc (wild-type cells + ST1326 vs. Eµ-myc cells + ST1326: 99.75% vs. 57.5%, difference = 42.25, 95% confidence interval of difference = 14% to 70%; P = .01).

CONCLUSIONS

Our data indicate that it is possible to tackle c-myc-driven tumorigenesis by altering lipid metabolism and exploiting the neoplastic cell addiction to FA oxidation.

Controlled delivery of the heparan sulfate/FGF-2 complex by a polyelectrolyte scaffold promotes maximal hMSC proliferation and differentiation

Growth factors and other regulatory molecules are required to direct differentiation of bone marrow-derived human mesenchymal stem cells (hMSC) along specific lineages. However, the therapeutic use of growth factors is limited by their susceptibility to degradation, and the need to maintain prolonged local release of growth factor at levels sufficient to stimulate hMSC. The aim of this study was to investigate whether a device containing heparan sulfate (HS), which is a co-factor in growth factor-mediated cell proliferation and differentiation, could potentiate and prolong the delivery of fibroblast growth factor-2 (FGF-2) and thus enhance hMSC stimulation. To this aim, we synthesized cationic polyelectrolyte polymers covalently and non-covalently anchored to HS and evaluated their effect on hMSC proliferation. Polymers non-covalently bound to HS resulted in the release of an HS/FGF-2 complex rather than FGF-2 alone. The release of this complex significantly restored hMSC proliferation, which was abolished in serum-free medium and only partially restored by the release of FGF-2 alone as occurred with polymer covalently bound to HS. We also demonstrate that exposure to HS/FGF-2 during early growth but not during post-confluence is essential for hMSC differentiation down the fibroblast lineage, which suggests that both factors are required to establish the correct stem cell commitment that is necessary to support subsequent differentiation. In conclusion, the delivery platform described here is a step towards the development of a new class of biomaterial that enables the prolonged, non-covalent binding and controlled delivery of growth factors and cofactors without altering their potency.

Cationic copolymers nanoparticles for nonviral gene vectors: synthesis, characterization, and application in gene delivery

The major aim of nonviral delivery systems for gene therapy is to mediate high levels of gene expression with low toxicity. Nowadays, one of the most successful synthetic polycations used in gene delivery research is poly(ethylenimine) (PEI) in its high-molecular weight (HMW) branched form. However, PEI is not the ideal transfection agent in vivo because of its overwhelming cytotoxicity. To overcome its toxic effects with a minimal impact on transfection efficiency, PEI has been conjugated with several nonionic biocompatible polymers. Here, we describe the synthesis of nanosized particles consisting of HMW PEI (25 kDa) crosslinked with poly(epsilon-caprolactone) (PCL, 50-60 kDa), a biodegradable aliphatic polyester. PCL was modified by the insertion of glycidyl groups able to condense with the amines of PEI to chemically bind PEI onto PCL. The nanoparticles obtained have been characterized in relation to their physicochemical and biological properties, and the results are extremely promising in terms of low cell toxicity and high transfection efficiency. These biological effects might be related to the peculiar DNA binding to covalently connected polymeric nanoparticles, without the formation of entangled DNA/polymer-soluble aggregates.

Colon OCTN2 gene expression is up-regulated by peroxisome proliferator-activated receptor gamma in humans and mice and contributes to local and systemic carnitine homeostasis

In the large intestine organic cation transporter type-2 (OCTN2) is recognized as a transporter of compounds such as carnitine and colony sporulation factor, promoting health of the colon intestinal epithelium. Recent reports suggest that OCTN2 expression in small intestine is under control of peroxisome proliferator-activated receptor-alpha (PPARalpha). However, PPARalpha contribution to colonic OCTN2 expression remains controversial. Here we examined the transcriptional regulation of colon OCTN2 gene by PPARgamma. To exclude any additional modulation of other PPAR to OCTN2 expression, we used both in vivo and in vitro PPAR-null models and specific PPAR inhibitors. The PPARgamma agonists thiazolidinediones increased both OCTN2 mRNA and protein expression in colonic epithelial cell lines independently by PPARalpha expression. The induction was blocked only by PPARgamma antagonists or by gammaORF4, a PPARgamma isoform with dominant negative activity, suggesting a PPARgamma-dependent mechanism. A conserved noncanonical PPAR-responsive element was found by computational analysis in the first intron of human OCTN2 gene and validated by EMSA assay. Promoter-reporter assays further confirmed transcriptional functionality of the putative PPAR response element, whereas selective mutation caused complete loss of responsiveness to PPARgamma activation. Finally, adenovirus-mediated overexpression of constitutively active PPARgamma mutant increased colon OCTN2 expression in PPARalpha(-/-) mice. Interestingly, animals overexpressing colon PPARgamma showed a significant increase in plasma carnitine, thus demonstrating the functional contribution of large intestine to systemic carnitine homeostasis. This study reveals a PPARgamma-dependent absorption machinery in colon that is likely involved in the health of colon epithelium, in the microbiota-host interactions and in the absorption of nutraceuticals and drugs.

The immunomodulatory protein SV-IV protects serum-deprived cells against apoptosis but not against G0/G1 arrest: Possible implications for the survival of implanting embryo

Serum deprivation induced in human lymphoblastoid Raji cells oxidative stress-associated apoptotic death and G0/G1 cell cycle arrest. Addition into culture medium of the immunomodulatory protein Seminal vesicle protein 4 (SV-IV) protected these cells against apoptosis but not against cycle arrest. The antiapoptotic activity was related to: (1) decrease of endocellular reactive Oxygen species (ROS) (2) increase of mRNAs encoding anti-oxidant enzymes (catalase, G6PD) and antiapoptotic proteins (survivin, cox-1, Hsp70, c-Fos); (3) decrease of mRNAs encoding proapoptotic proteins (c-myc, Bax, caspase-3, Apaf-1). The biochemical changes underlaying these effects were probably induced by a protein tyrosine kinase (PTK) activity triggered by the binding of SV-IV to its putative plasma membrane receptors. The ineffectiveness of SV-IV to abrogate the cycle arrest was accounted for by its downregulating effects on D1,3/E G1-cyclins and CdK2/4 gene expression, ppRb/pRb ratio, and intracellular ROS concentration. In conclusion, these experiments: (1) prove that SV-IV acts as a cell survival factor; (2) suggest the involvement of a PTK in SV-IV signaling; (3) point to cell cycle-linked enzyme inhibition as responsible for cycle arrest; (4) provide a model to dissect the cycle arrest and apoptosis induced by serum withdrawal; (5) imply a possible role of SV-IV in the survival of hemiallogenic implanting embryos.

Experimental colitis: decreased Octn2 and Atb0+ expression in rat colonocytes induces carnitine depletion that is reversible by carnitine-loaded liposomes

Carnitine transporters have recently been implicated in susceptibility to inflammatory bowel disease (IBD). Because carnitine is required for beta-oxidation, it was suggested that decreased carnitine transporters, and hence reduced carnitine uptake, could lead to impaired fatty acid oxidation in intestinal epithelial cells, and to cell injury. We investigated this issue by examining the expression of the carnitine transporters OCTN2 and ATB0+, and butyrate metabolism in colonocytes in a rat model of IBD induced by trinitrobenzene sulfonic acid (TNBS). We found that Octn2 and Atb0+ expression was decreased in inflammatory samples at translational and functional level. Butyrate oxidation, evaluated based on CO2 production and acetyl-coenzyme A synthesis, was deranged in colonocytes from TNBS-treated rats. Treatment with carnitine-loaded liposomes corrected the butyrate metabolic alterations in vitro and reduced the severity of colitis in vivo. These results suggest that carnitine depletion in colonocytes is associated with the inability of mitochondria to maintain normal butyrate beta-oxidation. Our data indicate that carnitine is a rate-limiting factor for the maintenance of physiological butyrate oxidation in colonic cells. This hypothesis could also explain the contradictory therapeutic efficacy of butyrate supplementation observed in clinical trials of IBD.

tBid induces alterations of mitochondrial fatty acid oxidation flux by malonyl-CoA-independent inhibition of carnitine palmitoyltransferase-1

Recent studies suggest a close relationship between cell metabolism and apoptosis. We have evaluated changes in lipid metabolism on permeabilized hepatocytes treated with truncated Bid (tBid) in the presence of caspase inhibitors and exogenous cytochrome c. The measurement of beta-oxidation flux by labeled palmitate demonstrates that tBid inhibits beta-oxidation, thereby resulting in the accumulation of palmitoyl-coenzyme A (CoA) and depletion of acetyl-carnitine and acylcarnitines, which is pathognomonic for inhibition of carnitine palmitoyltransferase-1 (CPT-1). We also show that tBid decreases CPT-1 activity by a mechanism independent of both malonyl-CoA, the key inhibitory molecule of CPT-1, and Bak and/or Bax, but dependent on cardiolipin decrease. Overexpression of Bcl-2, which is able to interact with CPT-1, counteracts the effects exerted by tBid on beta-oxidation. The unexpected role of tBid in the regulation of lipid beta-oxidation suggests a model in which tBid-induced metabolic decline leads to the accumulation of toxic lipid metabolites such as palmitoyl-CoA, which might become participants in the apoptotic pathway.

Differential carnitine/acylcarnitine translocase expression defines distinct metabolic signatures in skeletal muscle cells

Import of acylcarnitine into mitochondrial matrix through carnitine/acylcarnitine-translocase (CACT) is fundamental for lipid catabolism. To probe the effect of CACT down-expression on lipid metabolism in muscle, human myocytes were stably transfected with CACT-antisense construct. In presence of low concentration of palmitate, transfected cells showed decreased palmitate oxidation and acetyl-carnitine content, increased palmitoyl-carnitine level, and reduced insulin-dependent decrease of fatty acylcarnitine-to-fatty acyl-CoA ratio. The augmented palmitoyl-carnitine synthesis, also in the presence of insulin, could be related to an altered regulation of carnitine-palmitoyl-transferase 1 (CPT 1) by malonyl-CoA, whose synthesis is dependent by the availability of cytosolic acetyl-groups. Indeed, all the described effects were completely overcome by CACT neo-expression by recombinant adenovirus vector or by addition of acetyl-carnitine to cultures. Acetyl-carnitine effect was related to an increase of malonyl-CoA and was abolished by down-expression, via antisense RNA strategy, of acetyl-CoA carboxylase-beta, the mitochondrial membrane enzyme involved in the direct CPT 1 inhibition via malonyl-CoA synthesis. Thus, in our experimental model the modulation of CACT expression has consequences for CPT 1 activity, while the biologic effects of acetyl-carnitine are not associated with a generic supply of energy compounds but to the anaplerotic property of the molecule.

Differential expression of multiple transglutaminases in human colon: impaired keratinocyte transglutaminase expression in ulcerative colitis

BACKGROUND AND AIMS

Ulcerative colitis (UC) is characterised by refractory inflammatory ulceration and damage to the colon. The mechanisms underlying impaired healing have yet to be defined. As transglutaminase expression resulting in matrix protein cross linking is associated with increased wound healing in a rat model of colitis, we hypothesised that different types of transglutaminase might also play a role in UC.

PATIENTS AND METHODS

Endoscopic and histological indices were studied in 26 patients with UC (10 active and 16 inactive) and in 20 normal controls undergoing colonoscopy. Transglutaminase activity was evaluated in plasma (factor XIIIa) by a radioenzymatic method. Factor XIIIa, tissue and keratinocyte transglutaminase protein content, and mRNA expression in the colon were evaluated by western blot analysis and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Colonic location of transglutaminases and their reaction products, the epsilon-(gamma-glutamyl)lysine bonds, was evaluated by immunohistochemistry using specific monoclonal antibodies.

RESULTS

Transglutaminase activity was significantly lower in the plasma of patients with active UC (4.2 (2.4) mU/ml; p<0.05 v controls) than in those with inactive UC and controls (10.6 (2.2) and 12.1 (1.7) mU/ml). As shown by western blot, protein levels of tissue transglutaminase and factor XIIIa were unchanged in active UC compared with inactive disease and controls, while the keratinocyte form was reduced in active UC. Tissue transglutaminase and factor XIIIa immunostaining was strongly present in damaged areas colocalising with isopeptide bonds. In contrast, the keratinocyte form was almost absent in active UC and localised in the upper part of the crypts in normal subjects. RT-PCR showed upregulation of tissue transglutaminase mRNA in active UC (320% compared with controls) while keratinocyte transglutaminase gene expression was downregulated in active UC.

CONCLUSIONS

The results of the present study support the concept that, in the damaged colon, transglutaminases are needed in response to chronic injury and underline the key role of these enzymes in mucosal healing.

Skeletal muscle metabolism in physiology and in cancer disease

Skeletal muscle is a tissue of high demand and it accounts for most of daily energy consumption. The classical concept of energy metabolism in skeletal muscle has been profoundly modified on the basis of studies showing the influence of additional factors (i.e., uncoupling proteins (UCPs) and peroxisome proliferator activated receptors (PPARs)) controlling parameters, such as substrate availability, cellular enzymes, carrier proteins, and proton leak, able to affect glycolysis, nutrient oxidation, and protein degradation. This extremely balanced system is greatly altered by cancer disease that can induce muscle cachexia with significant deleterious consequences and results in muscle wasting and weakness, delaying or preventing ambulation, and rehabilitation in catabolic patients.

Cationic polyelectrolyte hydrogel fosters fibroblast spreading, proliferation, and extracellular matrix production: Implications for tissue engineering

Fibrous encapsulation is known to occur to many prosthetic implants and is thought to be due to the cells not adhering adequately to the surface. For developing new materials able to enhance cellular adhesion by mimicking extracellular matrix components, polyelectrolyte polymers, characterized by tunable surface charges, have been proposed. Here we demonstrate that panoply of cell functions over a two-dimensional substratum is influenced by surface charge. We have at first generated structurally related polyelectrolyte substrata varying in their positive surface charge amount and subsequently evaluated a variety of behaviors of human primary fibroblasts seeded on these polymers. The proportion of adherent, spreading, and proliferating cells was increased significantly on cationic hydrophilic surfaces when compared with the neutral base surface. The extent of cell spreading correlated with cytoskeleton organization as assessed using immunofluorescence techniques. In the key experiment, the presence of cationic charges on cell adhesion-resistant neutral surface increased the synthesis of collagen I and III, the release of their metabolites, and the expression of their mRNA by fibroblasts. Interestingly, the scarce collagen deposits on neutral polymer consisted, for the most part, of collagen I while collagen III was present only in traces probably due to the secretion of metalloproteinase-2 by non-adherent fibroblasts. Taken together, these results show that polyelectrolyte films may promote the attachment of fibroblast cells as well as their normal secretory phenotype. Both effects could be potentially useful in integrating soft connective tissue to the implant, decreasing the chance of its fibrous encapsulation.

Hydrothane(R) interactions with biological components: a comparison with Chronoflex(R)

The interaction of a glycol-containing polyurethane, Hydrothane(R), was assessed with respect to protein adsorption and cell and bacterial adhesion. The results obtained were compared with those from a second polyurethane, Chronoflex(R). Dynamic contact angle (DCA) and protein adsorption studies indicated that the overall hydrophilic nature of Hydrothane in physiological environment was affected by the possible presence of hydrophobic domains still exposed at the surface after wetting. Indeed, despite the high degree of hydrophilicity in an aqueous environment, a stronger protein binding was evidenced on Hydrothane when the two serum- and urine-conditioned polyurethane surfaces were selectively washed by isopropanol/water mixtures of increasing concentrations. Furthermore, immunoblotting of the serum proteins adsorbed on Hydrothane demonstrated the presence on its surface of proteins able to establish hydrophobic interactions such as human serum albumin (HSA) and á 1-microglobulin ( á 1-m). The C3 fragment of complement showed an immunoblotting profile different from the control serum suggesting an activation of this fragment. The adhesion of fibroblasts and Pseudomonas aeruginosa on the surface of the two materials was evaluated and the data were related to protein adsorption. In both cases Hydrothane showed levels of adhesion of eukaryotic and prokaryotic cells significantly lower than Chronoflex. These data were related to the absence of a significant binding of proteins such as fibronectin bringing amino acid receptor sequences in their structure. (Journal of Applied Biomaterials & Biomechanics 2003; 1: 67-75).

Decreased mitochondrial carnitine translocase in skeletal muscles impairs utilization of fatty acids in insulin-resistant patients

Insulin resistance (IR) and its health consequences (diabetes, hypertension, cardiovascular disease, obesity etc.) affect between 25 and 35% of Westernized populations. Decreased fatty acid (FA) oxidation in skeletal muscle is implicated in obesity-related IR. Carnitine-acylcarnitine translocase (CACT) transports long-chain FAs both into mitochondria (as carnitine esters for energy-generating processes) and out of mitochondria. To determine whether CACT activity correlates with decreased FA oxidation we measured CACT concentrations in cellular and mitochondrial extracts from the skeletal muscle of 19 obese IR individuals and of 19 lean controls. We also evaluated carnitine transport in skeletal muscle mitochondria in both groups. Mitochondrial CACT was decreased at translational and transductional level, and carnitine-carnitine and acylcarnitine-carnitine exchange rates were significantly lower in IR subjects. Aberrant acylcarnitine flux into mitochondria was not correlated with decreased activity of other components of the mitochondrial carnitine system (i.e., carnitine palmitoyl transferase-I and II). Our data suggest that by restraining entry of FA-coenzyme A into mitochondria, low CACT levels increase cytosolic FA levels and their incorporation into glycerolipids. The low level of CACT in IR muscle may contribute to the elevated muscle concentrations of triglycerides, diacylglycerol, and FA-coenzyme A characteristic of IR muscle.

17-beta estradiol elicits an autocrine leiomyoma cell proliferation: evidence for a stimulation of protein kinase-dependent pathway

The mechanism by which estradiol (E2) acts on cell proliferation is still unclear. In this paper, we report the results of a series of experiments in an attempt to elucidate the effector pathway(s) involved in coupling the E2 receptors binding to cellular growth response in leiomyoma cells (LSMC). Under conditions of E2-dependent growth, E2 treatment of LSMC triggers rapid and transient activation of the MAP-kinase pathway. Interestingly, we demonstrate that the early downstream signal transduction events determined by E2-stimulation in quiescent LSMC, including the rapid protein tyrosine phosphorylation of a subset of intracellular proteins, such GAP, PI-3-K, and PLCgamma, and the concomitant activation of ancillary protein kinases, are related to E2-induced PDGF secretion. Moreover, we identify the PDGF, alone or in association with other growth factors, as the main growth factor involved in the proliferation response of LSMC to E2 stimulation. The addition of neutralizing antibodies anti-PDGF was able to inhibit the mitogenic activity present in LSMC conditioned media samples. On the other hand, E2 did not affect the constitutive expression as well as the ligand affinity of PDGF receptors on LSMC plasmamembrane. Cell treatment with the antiestrogen ICI 182780 correlate both with a perturbation of E2-induced transductional circuit and with the disappearance of the mitogenic factor, PDGF, in LSMC conditioned media; the latter therefore, represents the main autocrine mediator of cell growth modulation, upregulated by E2 and down-regulated by antiestrogenic compound. Our experiments suggest that growth factor secretion is an initial and integral part of the signaling events mediated by the estradiol receptors, not related, at least in part, to E2 transcriptional modulation.

Phenotypic features of alveolar monocytes/macrophages and IL-8 gene activation by IL-1 and TNF-alpha in asthmatic patients

The alveolar macrophage (AM), a major defense cell in the lung, participates in immune and inflammatory reactions through the release of several regulatory and chemotactic cytokines. In particular, macrophages are considered to play a pivotal proinflammatory role in the production and maintenance of airway inflammation and bronchial hyperreactivity. To assess the phenotypic pattern of AM from asthmatic subjects, we performed the following experiments: 1) cytofluorometric analysis of specific phenotypic features (CD11b, CD14, CD16, CD45, HLA-DR, CD71, CD95, and CD44) 2) assessment of the production of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, and the chemotactic regulatory cytokine IL-8 by unstimulated and lipopolysaccharide-stimulated AM. In these patients, we phenotypically characterized the AM, showing their strong proinflammatory activity also in patients with mild asthma. Their activity has been clarified by our biomolecular data that showed a constitutive basal IL-8 production by AM, and also indicated that IL-1 and TNF-alpha were able to upregulate the ability of activated human AM to produce IL-8 at the protein and messenger ribonucleic acid (mRNA) levels.

Increased expression of IGF-binding protein-5 in Duchenne muscular dystrophy (DMD) fibroblasts correlates with the fibroblast-induced downregulation of DMD myoblast growth: an in vitro analysis

In DMD the progressive loss of muscle ability and concomitant increasing fibrosis might originate from, besides other causes, the fibroblast paracrine inhibition of satellite cell "growth." In this study we report that in myoblast/fibroblast coculture experiments, the presence of DMD fibroblasts negatively interfered with DMD myoblast growth to an extent directly proportional to the percentage of DMD fibroblasts present in the mixed-cell cultures. Moreover, the observation that media conditioned with proliferating DMD fibroblasts inhibited the growth of DMD myoblasts more seriously than did control fibroblast-conditioned media suggested a paracrine effect by diffusible factors. IGF-binding proteins could act as such diffusible factors; in fact, IGFBP-5 transcript increased threefold in DMD fibroblasts proliferating in DMD muscle extracts, whereas IGFBP-3 mRNA decreased. In addition, high levels of IGFBP-5 protein were detected in DMD fibroblast-conditioned media. In neutralizing IGFBP-5 in DMD fibroblast-conditioned media by means of specific antibodies, or inhibiting IGFBP-5 gene expression in DMD fibroblasts by means of oligo antisense, the fibroblast-conditioned media lost inhibitory power over DMD myoblast proliferation.

Defective growth in vitro of Duchenne Muscular Dystrophy myoblasts: the molecular and biochemical basis

As the molecular basis of Duchenne Muscular Dystrophy (DMD) was being discovered, increasing focus was placed on the mechanisms of progressive failure of myoregeneration. In this study, we propose a pathogenesis model for DMD, where an autocrine growth factor release of TGF-beta1-from necrotic myofibers-could contribute to the increasing loss of muscle regeneration. In fact, we report evidence that DMD myoblasts reduce their proliferation rate, in time and later cultures; in connection with this, we observed TGF-beta1 increase in conditioned media of DMD myoblasts, able to control the myoblast growth by reducing fusion and differentiation of DMD satellite cells.

Modulation of in vitro myogenesis induced by different polymer substrates

The understanding of substrate dependence of cellular differentiation is important in the surface design of biocompatible artificial devices as well as cell-incorporated tissue engineered devices. In an attempt to understand some of the genetic and epigenetic aspects of the control of cell differentiation in the presence of two different materials, Chronoflex (CH) and plasma treated Chronoflex coated with Hyaluronan (CH-HA), we used primary cultures of human myogenic cells, a model that encompasses cell proliferation, migration, fusion, and differentiation dependent gene activation. By testing both the material samples on the growth of human myoblasts in primary cultures, we demonstrated that both CH and CH-HA substrates were able to support the cell growth since they did not affect cell count and DNA synthesis. On the contrary, the degree of myoblast differentiation, assessed as a function of creatine phosphokinase (CPK) activity on living cells, was completely different on the two biomaterials. Indeed, the amount of CPK increased on CH-HA cultured cells as a result of myotube formation, while CH grown myoblasts remained unfused and displayed no increase on the CPK activity even after 12 days culture. Moreover, the expression level of MyoD and myogenin mRNA, both related to myogenic cell differentiation, appeared extremely low in CH-grown cells, while they were rapidly induced in CH-HA cultured myoblasts.

Role of monocyte/macrophage population in immune response

The central role of macrophages in host defence against infection and malignancy and processes such as atherosclerosis, makes macrophage biology a fascinating area for research in immunology and cell biology. The endocytic and phagocytic machinery of macrophages is particularly potent and their secretory potential is large and diverse. Studies of cell surface receptors and their role in antigen presentation, microbicidal and tumouricidal activity are actively researched and progress is now being made in defining receptors responsible for monocyte/macrophage cell adhesion within the immune system. This short-review highlights the recent advances in macrophage biology.

The differential effects of poly(2-hydroxyethyl methacrylate) and poly(2-hydroxyethyl methacrylate)/poly(caprolactone) polymers on cell proliferation and collagen synthesis by human lung fibroblasts

Because of its chemical versatility and demonstrated biocompatibility, poly(2-hydroxyethyl methacrylate) (pHEMA) has been widely used as a polymer for biomedical applications. Since this hydrophilic material shows a poor interface with cells, blendings with other polymers were done to improve cytocompatibility. In our polymer, the presence of hydrophobic dominions on the material surface, due to the interpenetrating polymerization of pHEMA with poly(caprolactone) (PCL), seems to ameliorate the cytocompatibility in terms of cell adhesion and metabolism. For our experiments, we used IMR-90 human fibroblasts, as these cells strongly regulate DNA, RNA, and protein synthesis as anchorage-dependent variables. Cell attachment on a pHEMA/PCL interpenetrating polymer network was optimal, suggesting a strong adhesion between the cells and the polymer surface. Cell adhesion was weaker on pHEMA, as a significant fraction of the fibroblasts revealed a lack of spreading, with most cells remaining spherical. Moreover, only fibroblasts seeded on pHEMA significantly decreased mRNA synthesis; collagen production and cell shapes ranged from fully flat and proliferating, to minimally spread and nonproliferating. Finally, DNA synthesis, as a measure of cell proliferation, was markedly inhibited in cells cultured on pHEMA but not on pHEMA/PCL. In conclusion, our results suggest that control of cell growth and metabolism by biomedical polymers is based on physicochemical mechanism(s) in which the hydrophilicity/hydrophobicity ratio of the material surfaces may play an important role.

Modulation of cytokine production in activated human monocytes by somatostatin

The immunosuppressor effects of the widely distributed neuropeptide somatostatin were examined on purified peripheral blood human monocytes. Somatostatin, at concentrations thought to be physiologic (10(-10)-10(-7) M), regulated monocyte/macrophage responses to (LPS) stimulation, as reflected by interleukin production. In particular, somatostatin had direct inhibitory effects on TNF-alpha, IL-1 beta, and IL-6 secretion by LPS-activated monocytes, while the decrease on IL-8 synthesis was modulated mainly by the action of somatostatin on TNF-alpha and IL-1 beta. In fact, the addition of these two inflammatory cytokines to the monocyte culture medium was able to induce IL-8 expression, as demonstrated by mRNA analysis, also in presence of the neuropeptide. Although somatostatin affected IL-8 production in an indirect way, it suppressed directly the chemotactic response of neutrophils to IL-8. Finally, somatostatin downregulation of monocyte activation was confirmed by the decrease of HLA-DR expression on cell plasma membranes (52% versus 33%). Our results confirm that somatostatin exerts preferential effects on the suppression of immunoreactions by modulating cytokine production and activity.

Chitosan-mediated stimulation of macrophage function

According to the modern definition of biocompatibility, a biocompatible material need not be inert but be bioactive. A benign reactivity implies that the reactivity has to be appropriate for the intended use. Chitosan, a non-acetylated or partially deacetylated chitin (a linear homopolymer of beta (1-4)-linked N-acetylglucosamine) has been proposed as a biomaterial because of its apparent satisfactory biocompatibility. The present investigation demonstrates that chitosan has an in vitro stimulatory effect on both macrophage nitric oxide (NO) production and chemotaxis. The macrophage NO secretion is attributed to the N-acetylglucosamine unit of the chitosan molecule rather than to the glucosamine residue (28 and 15 microM NO respectively). Moreover, the immune stimulatory effect of chitosan was very specific since other glycosaminoglycans, such as N-acetyl-D-mannosamine and N-acetyl-D-galactosamine, had no effects on NO production (5 and 8 respectively). In vivo experiments strengthen this hypothesis. Transmission electron microscopy analysis identifies the presence of many leucocytes in the specimens after 14 d post-implantation, showing poor healing processes (i.e. fibroblast proliferation and collagen deposition) that characterize the tissue repair at this time in our animal model.

In vivo induction of macrophage Ia antigen (MHC class II) expression by biomedical polymers in the cage implant system

Examination of the cellular components in the inflammatory exudate, which infiltrates subcutaneous cages, can be used to monitor the progress of an inflammatory response to an implanted material. Of particular interest is the study of monocyte/macrophage infiltration into the implanted cages containing biomaterials, as macrophages may initiate a wide spectrum of responses upon interaction with a foreign material. In this study, the authors propose a technique using subcutaneous tissue cages in conjunction with cytofluorimetric analysis of exudate leukocytes to evaluate the monocyte/macrophage cell activation in response to different materials. The studies reported here used several materials (thermoplastic and elastomeric polymers) as the challenging agent, to demonstrate whether polymers, chemically different from each other, could differentially activate macrophages to carry out their proinflammatory role more effectively. The materials tested included: poly(etherurethane ureas) (PEUU A'), poly(etherurethane ureas) with a surface active additive, Methacrol, (PEUU C'), polymethylsiloxane (PDMS), polyetherimide, (PEI), and polyetheretherketone, (PEEK). For all tested materials, the maximum numbers of exudate cells and of Ia-positive macrophages were found on day 7, although the entity of the cell increase was associated with the material used for the implant. Similarly, the percentage of Ia-positive macrophages varied according to the specific polymer present in the cages after 7 days. By day 14, the percentage of Ia-positive macrophages decreased with individual exudates showing 19-32% Ia-positive cells depending on the different type of material. Only in the case of PDMS did the percentage of Ia-positive macrophages remain the same as compared with control empty cage macrophages.