Overexpression of the Pdx-1 homeodomain transcription factor impairs glucose metabolism in cultured rat hepatocytes.

The Pdx-1 transcription factor plays crucial functions both during pancreas development and in the adult beta cells. Previous studies have indicated that ectopic Pdx-1 expression in liver or intestinal primary and immortalized cells is sufficient to promote activation of insulin gene expression. This work is focused on the molecular and physiological consequences of Pdx-1 overexpression in liver cells. We present evidence that Pdx-1 affects the level of expression of one of the four mammalian hexokinase isozymes. These are glucose phosphorylating enzymes involved in essential cellular functions such as glucose sensing, metabolic energy production and apoptosis. Specifically, our data show that over-expression of Pdx-1 in cultured hepatocytes is able to repress the expression of hexokinase 2 (Hxk 2) and the phenomenon is mediated via binding of Pdx-1 to a specific sequence on the Hxk 2 gene promoter. As a consequence, liver cells over-expressing Pdx-1 present interesting alterations concerning glucose metabolism.

Stability of Drugs of Abuse in Urine Samples at Room Temperature by Use of a Salts Mixture.

BACKGROUND: It has long been recognized that ensuring analyte stability is of crucial importance in the use of any quantitative bioanalytical method. As analyses are usually not performed directly after collection of the biological samples, but after these have been processed and stored, it is essential that analyte stability can be maintained at storage conditions to ensure that the obtained concentration results adequately reflect those directly after sampling. The conservation of urine samples in refrigerated/ frozen conditions is strongly recommended; but not always feasible. The aim of this study was to assess the stability of some well-known drugs of abuse methamphetamine (MA), 11-nor-9-carboxy-Δ9- tetrahydrocannabinol (THC-COOH), benzoylecgonine (BE), and morphine (MOR) in urine samples kept at room temperature by adding a salt mixture (sodium citrate, sodium ascorbate, borax). METHODS: Two different urine samples were prepared with and without salt mixture, stored at room temperature and then analyzed by gas chromatography-mass spectrometry at 0, 1, 7, 15, and 30 days after collection/preparation to look for eventual analyte degradation. RESULTS: Methamphetamine showed no significant changes with respect to the time of collection/ preparation (T0) up to 7 days later (T7), with or without salt mixture addiction. Then a significant degradation occurred in both salted and non salted urine. BE decrease was observed starting from day 1 after sample collection in salted and not salted samples, respectively. Salt addition seemed to reduce at least the initial BE degradation, with a significant difference (p<0.001) at 7 and 15 days of storage. However, the degradation was not more prevented in salted samples at 30 days of storage. A 20% decrease of MOR concentration was observed starting from day 1 after collection/preparation, both in salted and not salted samples with no subsequent decrease. With regard to THCCOOH, a significant decrease was observed starting from 7 days after collection/preparation, with of without adding the salt mixture. However, when comparing salted versus non salted samples at each time point, a statistically significant difference was observed at 7 and 30 days of storage. CONCLUSION: The results obtained indicate that the degradation of MA, THC-COOH and BE in urine samples kept at room temperature can be slowed by the addition of the salt mixture, whereas it seems to be ineffective in samples containing MOR. This evidence has to be taken into account, in the eventuality of using salted urine to prevent in a certain extent abuse of above-reported drugs of abuse.

Biomolecular Modulation of Neurodegenerative Events during Ageing.

The objective is to assess the modulation of retinal and optic nerve degenerative events induced by the combination of α-lipoic acid (ALA) and superoxide dismutase (SOD) in an animal model of ageing. For this study, 24 male Wistar-Harlan strain rats were left to age for up to 24 months. One group of rats was subjected to a diet supplemented with ALA and SOD for 8 weeks, while another group was used as a positive control and not subjected to any dietary treatment. To assess the cytoprotective effects of the antioxidants, a morphological analysis was carried out on sections of retina and optic nerve head, stained with haematoxylin-eosin, followed by an analysis of the modifications to nuclear DNA detected by the TUNEL technique. The lipid peroxidation assay was used to assess the damage induced by oxidative stress at cell membrane level. The molecules involved in apoptosis mediated by oxidative stress, such as caspase-3 and inducible nitric oxide synthase, were also assayed by immunolocalization and western blot. ALA and SOD are able to counteract senile neurodegenerative deterioration to the retina and optic nerve. Indeed, the combination of these antioxidant molecules can reduce oxidative stress levels and thus prevent both nuclear degradation and subsequent cell death.

Cataract surgery complications: an in vitro model of toxic effects of ropivacaine and lidocaine.

BACKGROUND: Intraoperative lidocaine is widely used in controlling discomfort during cataract surgery. However, recent studies have confirmed the toxic effect of lidocaine on ganglion cells. Ropivacaine is an anesthetic recently introduced in clinical practice that couples a long anesthetic effect with a mild vasoconstrictive action. OBJECTIVE: The aim of this study was an in vitro evaluation of the efficacy of ropivacaine in reducing the degenerative effects usually observed during lidocaine treatment. METHODS: Ropivacaine and lidocaine toxicity has been evaluated in murine fibroblasts 3T6 by measuring percentage of cell death, cell growth inhibition, and DNA degradation. The choice of this cellular line is motivated by the presence of a complete apoptotic system that can be assimilated to the endothelium precursor cells. RESULTS: We observed that lidocaine 0.25% decreases cell viability and causes DNA degradation in murine fibroblasts 3T6, whereas ropivacaine 0.5% does not cause any cellular or molecular degenerative effect. CONCLUSIONS: Our in vitro studies confirm that ropivacaine is less toxic than lidocaine to these cells. Therefore, in vivo studies in the anterior chamber could be useful to evaluate the effects of ropivacaine versus lidocaine in intracameral anesthesia in cataract surgery.

Regeneration and DNA demethylation do not trigger PDX-1 expression in rat hepatocytes.

AIM: To explore the possibility that PDX-1 gene is reactivated as a consequence of molecular events that occur during liver regeneration. METHODS: Rat hepatocytes were maintained in DMEM-F12, 10% fetal bovine serum (FBS), penicillin/streptomycin and geneticin when applicable. Rat insulinoma RIN 1046-38 cells were maintained in M-199-10% FBS and penicillin/streptomycin. The final concentration of glucose was 11.1 mmol/L. During regeneration, lateral and medial liver lobes of adult male Wistar rats were surgically removed, with up 70% loss of liver mass. In methylation experiments, 5-aza-deoxycytidine (5-aza-dC) was used. Primer3 software was used for polymerase chain reaction (PCR). Quantitative real time PCR (qRT-PCR) was performed using SYBR Green technology; primers were designed by Beacon Designer 6 software. Western blotting and SDS-PAGE were performed according to standard procedures. Antibodies were purchased from commercial suppliers. RESULTS: We explored the possibility that liver regeneration could trigger PDX-1 expression, and hence insulin production. Twenty-four hours after surgical liver removal, regeneration was active as demonstrated by the increased proliferating cell nuclear antigen; however, all the other checked genes (involved in insulin gene expression): PC-1, Ngn3, NeuroD1, Btc, PDX-1 and Ins-1, were not related to the molecular events caused by this process. The only marker detected in regenerating liver was E47: a transcription factor of the the basic helix-loop-helix family known to be expressed ubiquitously in mammalian cells. In the rat pancreas, almost all of the tested genes were expressed as shown by RT-PCR, except for Ngn3, which was silenced 2 d after birth. Therefore, the molecular events in liver regeneration are not sufficient to promote PDX-1 expression. DNA methylation is a known mechanism to achieve stable repression of gene expression in mammals: Hxk 2 gene is silenced through this mechanism in normal hepatocytes. The administration of 5-aza-dC to cultured cells is in fact able to upregulate Hxk 2 mRNA. We investigated whether PDX-1 silencing in liver cells could be exerted through methylation of CpG islands in both the promoter and the gene coding regions. The results show that the drug increased the expression level of the Hxk 2 control gene but failed to rescue the expression of PDX-1, thus DNA demethylation is not sufficient to override repression of the PDX-1 gene. CONCLUSION: During liver regeneration, PDX-1 gene is not reactivated. Demethylation does not de-repress PDX-1 gene expression. Therefore gene silencing is not achieved through this epigenetic mechanism.

Degenerative and apoptotic events at retinal and optic nerve level after experimental induction of ocular hypertension.

Ocular hypertension is a symptom of a glaucomatous condition characterized by a severe vision decrease. Blindness caused by the apoptotic death of the retinal ganglion cells and of the astrocytes of the optic nerve may eventually result. Experimental hypertension was induced by inoculation of methylcellulose in the anterior chamber. Chromatin staining, TUNEL assay, and inter-nucleosomal DNA fragmentation observed in retina and optic nerve strongly suggest that hypertension causes apoptosis. Immunolocalization of the fibrillary acidic glial protein, specific of cell stress, and caspase-3 in the same tissues, further support this mode of cell death. Activation of the ubiquitin dependent proteolytic system was also observed. Protection from apoptosis exerted by administration of the peroxide scavenger trolox, suggests that the apoptotic pathway is activated by an oxidative stress. The data presented here show that the experimental hypertensive insult induces degenerative and apoptotic events comparable to those observed in human glaucoma.

Cytotoxic and antiproliferative effects induced by a non terpenoid polar extract of A. indica seeds on 3T6 murine fibroblasts in culture.

Neem oil is a natural product obtained from the seeds of the tree Azadirachta indica. Its composition is very complex and the oil exhibits a number of biological activities. The most studied component is the terpenoid azadirachtin which is used for its insecticidal and putative antimicrobial properties. In this report we investigate the biological activity of partially purified components of the oil obtained from A. indica. We show that the semi-purified fractions have moderate to strong cytotoxicity. However, this is not attributable to azadirachtin but to other active compounds present in the mixture. Each fraction was further purified by appropriate extraction procedures and we observed a differential cytotoxicity in the various sub-fractions. This led us to investigate the mode of cell death. After treatment with the oil fractions we observed positivity to TUNEL staining and extensive internucleosomal DNA degradation both indicating apoptotic death. The anti-proliferative properties of the neem oil-derived compounds were also assayed by evaluation of the nuclear PCNA levels (Proliferating Cell Nuclear Antigen). PCNA is significantly reduced in cells treated with a specific fraction of neem oil. Finally, our results strongly suggest a possible involvement of the mitochondrial pathway in the apoptotic death.

Reduction of apoptosis through the mitochondrial pathway by the administration of acetyl-L-carnitine to mouse fibroblasts in culture.

It is shown in literature that stress, such as deprivation of trophic factors and hypoxia, induces apoptosis in cultured cells and in tissues. In light of these results, we explored the possibility of protecting cells from programmed death by improving the metabolism of the mitochondrion. To this end, acetyl-L-carnitine was administered at various concentrations under conditions of serum deprivation. The choice of this drug was based on the accepted notion that acetyl-L-carnitine is able to stabilize mitochondrial membranes and to increase the supply of energy to the organelle. The results presented here indicate that the drug protects cells from apoptotic death: this is demonstrated by a lower positivity to the TUNEL reaction and by a strong reduction of the apoptotic DNA ladder in serum-deprived cells. The involvement of the mitochondrial apoptotic pathway was assessed by cytochrome C release and immunoreactivity to caspase 3. Moreover, acetyl-L-carnitine stimulates cell proliferation.

Acute ischemia/hypoxia in rat hippocampal neurons activates nuclear ubiquitin and alters both chromatin and DNA.

We investigated early alterations in rat neurons after experimental ischemic stress. Transient ischemia was generated by bilateral occlusion of the carotids after hypoxia. Data show a relevant increase of the nuclear level of ubiquitin 2 h post-stress as evaluated by immuno-cytolocalization. Ubiquitin returns to normal levels after 6 h. The increase in ischemic/hypoxic rats was localized preferentially in nuclei of hippocampal neurons, although some augmentation was also shown essentially in dendrites. The activation of ubiquitin system is related to a defective homeostasis and might trigger different degenerative processes. With respect to this, we observed chromatin alterations by densitometric analysis. The shown extensive DNA degeneration is consistent with the occurrence of necrotic phenomena at an early stage. However the parallel internucleosomal specific DNA fragmentation, strongly suggests that apoptotic events also occur. In any case both necrosis and apoptosis are likely to occur at same time, although apoptosis is less extensive, and the two phenomena take place in different neural cells.

Effects of the plasticiser DEHP on lung of newborn rats: catalase immunocytochemistry and morphometric analysis.

Experimental administration of di-(2-ethylexyl)-phthalate (DEHP), a plasticiser employed in the fabrication of polyvinyl chloride (PVC), causes increases in lipid metabolising enzymes along with marked peroxisomal proliferation. The effects are found in several mammalian tissues, of which the rodent liver is the most responsive target. Leakage of DEHP from PVC devices is favoured by high temperature and contact with lipid-containing biological fluids. Since preterm babies are currently ventilated through endotracheal PVC tubes, it seemed worthwhile to investigate DEHP effects on immature mammalian lung. In this research, female rats were fed with DEHP in the last week of pregnancy and after delivery, and lungs were excised from 2-day-old pups. At this age, in fact, rat lung histological features closely resemble those found in 24- to 36-week-old human fetuses. In treated animals, morphometric analysis of histological parameters revealed a dramatic decrease in the number of parenchymal airspaces, together with significant increases in their mean size. Moreover, cytochemical detection of the peroxisomal marker catalase revealed an increase in the number of type II pneumocytes. Our findings closely resemble abnormal histological features observed in autoptic lung specimens from children affected with chronic lung diseases.