Routine experimental system for defining conditions used in photodynamic therapy and fluorescence photodetection of (non-) neoplastic epithelia

A common method to induce enhanced short-term endogenous porphyrin synthesis and accumulation in cell is the topical, systemic application of 5-aminolevulinic acid or one of its derivatives. This circumvents the intravenous administration of photosensitizers normally used for photodynamic therapy (PDT) of fluorescence photodetection. However, in the majority of potential medical indications, optimal conditions with respect to the porphyrin precursor or its pharmaceutical formulation have not yet been found. Due to ethical restrictions and animal right directives, the number of available test objects is limited. Hence, definition and use of nonanimal test methods are needed. Tissue and organ cultures are a promising approach in replacing cost intensive animal models in early stages of drug development. In this paper, we present a tissue culture, which can among others be used routinely to answer specific questions emerging in the field of photodynamic therapy and fluorescence photodetection. This technique uses mucosae excised from sheep paranasal sinuses or pig bladder, which is cultured under controlled conditions. It allows quasiquantitative testing of different protoporphyrin IX precursors with respect to dose-response curves and pharmacokinetics, as well as the evaluation of different incubation conditions and/or different drug formulations. Furthermore, this approach, when combined with the use of electron microscopy and fluorescence-based methods, can be used to quantitatively determine the therapeutic outcome following protoporphyrin IX-mediated PDT.

Changes in UCP mRNA expression levels in brown adipose tissue and skeletal muscle after feeding a high-energy diet and relationships with leptin, glucose and PPARgamma

Brown adipose tissue and skeletal muscle are known to be important sites for nonshivering thermogenesis. In this context, it is accepted that uncoupling proteins (UCPs) are involved in such process, but little is known about the physiological regulation of these proteins as affected by the intake of a high-energy (cafeteria) diet inducing fat deposition. In this study, the UCP messenger RNA (mRNA) expression in interscapular brown adipose tissue (iBAT) and skeletal muscle was assessed to evaluate the influence of a dietary manipulation on energy homeostasis regulation. We report a statistically significant increase in mRNA levels of iBAT UCP1 and UCP3 and a statistical marginal rise in skeletal muscle UCP3 mRNA expression after feeding a high-energy diet, whereas no changes in UCP2 expression were found in either tissue. Furthermore, significant positive associations between iBAT UCP1 and UCP3 mRNA levels with serum leptin were found. Although the expression of the beta(3) adrenoceptor (beta(3)AR) was about 50% in the lean controls compared with the obese group in iBAT, no statistically significant changes were observed concerning peroxisome proliferator-activated receptor gamma2 (PPARgamma2) mRNA levels in muscle or iBAT. We conclude that feeding a diet inducing weight and fat gain produces different outcomes on iBAT and skeletal muscle UCP mRNA expression, revealing a tissue-dependent response for the three UCPs. Results suggest that the regulation of UCP expression in both tissues under these specific dietary conditions may be related to leptin circulating levels.

Caspases: decoders of apoptotic signals during mammary involution. Caspase activation during involution

At weaning most of the alveolar epithelial cells in the mammary gland die by apoptosis and are removed by phagocytosis. Caspases are a family of aspartate specific cysteine proteases. Activation of caspases is generally thought to represent a major and irreversible event in the apoptotic process. We analyzed caspase expression and activation during mammary gland involution. A quantitative RT-PCR based approach revealed that levels of mRNA expression of several caspases are induced during involution. Using an antibody that specifically recognizes activated caspases we measured a transient induction of caspase activity in situ and found a maximal activation at days two and three of involution. These data were corroborated by monitoring caspase-3 like activity in mammary extracts with a synthetic DEVD-afc peptide as caspase-3 substrate. Using Fas-deficient mice we present evidence that the Fas signaling pathway is not essential for caspase activation and apoptosis during mammary gland involution. In summary, signaling pathways during involution seem to involve activation of caspases as intraepithelial triggers of mammary epithelial cell apoptosis.

Role of Fas ligand expression in promoting escape from immune rejection in a spontaneous tumor model

Tumors escape immune-mediated rejection by a variety of mechanisms during tumor progression. The elucidation of these mechanisms in vivo suffers from a lack of suitable models of spontaneous tumor formation escaping active specific immunotherapy (ASI). In a rat neu transgenic (rNeu-TG) mouse model of spontaneous breast tumor formation, we showed that rNeu-TG mice developed late escape tumors despite the presence of a persistent rNeu-specific immune response after ASI. Cell suspensions derived from these escape tumors grew in vaccinated tumor-free mice, whereas injected spontaneous tumor cells were rejected. Escape tumors retained rNeu or MHC class I expression but significantly upregulated Fas (CD95, Apo-1) ligand. We further demonstrated that Fas-L on escape tumor cells correlated with apoptosis of infiltrating T lymphocytes. Thus, our results provide evidence that spontaneous breast tumors upregulate Fas-L expression after vaccination that may promote tumor escape in vivo after ASI.

UCP2 muscle gene transfer modifies mitochondrial membrane potential

OBJECTIVE

The aim of this work was to evaluate the effect of uncoupling protein 2 (UCP2) muscle gene transfer on mitochondrial activity.

DESIGN

Five week-old male Wistar rats received an intramuscular injection of plasmid pXU1 containing UCP2 cDNA in the right tibialis anterior muscles. Left tibialis anterior muscles were injected with vehicle as control. Ten days after DNA injection, tibialis anterior muscles were dissected and muscle mitochondria isolated and analyzed.

RESULTS

There were two mitochondrial populations in the muscle after UCP2 gene transfer, one of low fluorescence and complexity and the other, showing high fluorescence and complexity. UCP2 gene transfer resulted in a 3.6 fold increase in muscle UCP2 protein levels compared to control muscles assessed by Western blotting. Furthermore, a significant reduction in mitochondria membrane potential assessed by spectrofluorometry and flow cytometry was observed. The mitochondria membrane potential reduction might account for a decrease in fluorescence of the low fluorescence mitochondrial subpopulation.

CONCLUSION

It has been demonstrated that UCP2 muscle gene transfer in vivo is associated with a lower mitochondria membrane potential. Our results suggest the potential involvement of UCP2 in uncoupling respiration. International Journal of Obesity (2001) 25, 68-74

Cobalt-base alloys used in bone surgery

Cobalt-base alloys may be generally described as non magnetic, wear, corrosion and heat-resistant (high strength even at elevated temperature). Many properties of the alloy originate from the crystallographic nature of cobalt, the solid-solution-strengthening effect of chromium and molybdenum, the formation of extremely hard carbides and the corrosion resistance imparted by chromium. Cobalt-base alloys are difficult to fabricate which is why their use has been limited, but continuous work led to the development of specialized casting methods. Due to its excellent resistance to degradation in the oral environment, the first medical use of cobalt-base alloys was in the cast of dental implants. Various in vitro and in vivo tests have shown that the alloys are biocompatible and suitable for use as surgical implants. Today, the use of Co alloys for surgical applications is mainly related to orthopaedic prostheses for the knee, shoulder and hip as well as to fracture fixation devices. Joint endoprostheses are typical long-term implants and the applied implant material must therefore meet extremely high requirements with regard to biocompatibility with the surrounding body tissue material and corrosion resistance to body fluids.

Inert bioceramics (Al2O3, ZrO2) for medical application

Ceramics is defined as the art and science of making and using solid articles having as essential components inorganic non-metallic materials and which are composed largely of them (Kingery et al., 1976). The inherent brittleness of traditional ceramics has limited their ability to compete with ductile metals and polymers for technical applications. However, over the last 100 years innovative techniques in the fabrication of ceramics have led to their use as high-tech materials. Inert bioceramics, such as Al2O3 and ZrO2, have inherently low levels of reactivity compared with other materials such as polymers and metals as well as surface reactive or resorbable ceramics. In a human body, they are expected to be non-toxic, non-allergenic, and non-carcinogenic for a life-time, which leads to a corresponding range of engineering design philosophies for medical application. Due to their excellent frictional properties technical ceramics are nowadays mainly used in endoprosthetics.

A new NPY-antagonist strongly stimulates apoptosis and lipolysis on white adipocytes in an obesity model

Neuropeptide Y (NPY) is a 36 amino acid peptide released in central and peripheral mammalian neurons, which appears to contribute to adiposity regulation by increasing food intake, thus promoting weight gain on animals. Nevertheless, little is known about NPY direct actions on white adipocytes. This trial, which was designed to test the possible effects of a new NPY antagonist, S.A.0204, on white adipose tissue, revealed that the administration of this novel molecule strongly ex vivo stimulates apoptosis and lipolysis in animals fed on a high-fat diet.

Desmoplastic non-infantile ganglioglioma. Case report

Desmoplastic gangliogliomas are rare mixed glial and neuronal cerebral tumors, especially described in infants below 4 years of age but exceptional cases have been reported in young adults. These tumors are generally localised in parietal or temporal lobes, present as a large cystic lesion with peripheral contrast enhancement. They also have characteristic histological features: extensive desmoplasia and tumoral cells of variable size exhibiting immunohistochemical and ultrastructural features of glial and neuronal differentiation. Total surgical removal is sufficient for the treatment of these tumors and no radiotherapy or chemotherapy are indicated if complete resection is achieved. We report a case of desmoplastic ganglioglioma in a 19-year-old male. This tumor presented as a large parieto- temporal cystic lesion with rimmed contrast enhancement. At histological examination, this tumor exhibited extensive desmoplasia and comprised 2 types of tumoral cells: small cells with round nuclei, positive for NSE, neurofilaments and synaptophysin and sometimes presenting typical morphological features of neuronal differentiation, and large cells with abundant eosinophilic strongly staining for GFAP. This observation emphazises on the fact that desmoplastic ganglioglioma can no more be considered as a specific entity of infancy and must be well recognised even in young adults because it may be misdiagnosed as malignant glioma.

Caspase-3 is essential for procaspase-9 processing and cisplatin-induced apoptosis of MCF-7 breast cancer cells

In this study, we sought to investigate in more detail the role of caspase-3 in apoptotic processes in cultured cells and in cell-free extracts of breast cancer cells. We present evidence that apoptosis of caspase-3-deficient MCF-7 breast cancer cells is defective in response to cisplatin treatment, as determined by chromatin condensation, nuclear fragmentation, DNA fragmentation, and release of cytochrome c from the mitochondria. Reconstitution of MCF-7 cells by stable transfection of CASP-3 cDNA restores all these defects and results in an extensive apoptosis after cisplatin treatment. We further show that in extracts from caspase-3-deficient MCF-7 cells, procaspase-9 processing is strongly impaired after stimulation with either cytochrome c or recombinant caspase-8. Reconstitution of MCF-7 cell extracts with procaspase-3 corrects this defect, resulting in an efficient and complete processing of procaspase-9. Together, our data define caspase-3 as an important integrator of the apoptotic process in MCF-7 breast cancer cells and reveal an essential function of caspase-3 for procaspase-9 processing.

Methodological approaches to assess body-weight regulation and aetiology of obesity

Obesity, which is becoming one of the major health hazards in developed and developing societies, results from a long-term positive energy balance. Body-weight regulation and stability depend on an axis with three interrelated components: food intake, energy expenditure and adipogenesis, although there are still many unknown features concerning fuel homeostasis and energy balance. Biochemical processes are interconnected, and a separate consideration of each component is often useful for methodological purposes and to achieve a better understanding of the whole system. Thus, many different experimental approaches can be applied by using laboratory animals, cell culture or human subjects to unravel the molecular mechanisms which participate in body-weight regulation. Thus, both in vitro (cellular and subcellular models) and in vivo methods have dramatically increased our knowledge of weight control. Several strategies in obesity research are reported here, exploiting the opportunities of the molecular era as well as novel whole-body approaches, which will impact on the development of new targets for obesity management and prevention.

The mouse ERG before and after light damage is independent of p53

Death of retinal photoreceptors by apoptosis is observed under many physiological and pathological conditions such as histogenesis, retinal dystrophies and light-induced photoreceptor degeneration. To date, little is known about regulatory mechanisms for apoptosis in the retina. The tumor suppressor gene p53 is a regulator of apoptosis in a number of systems, however, p53-independent apoptosis has also been described. We have therefore investigated whether the lack of p53 influences the dark-adapted ERG in C57BL/6 p53-/- mice compared to p53+/+ control littermates under physiological (regular light-dark cycle) conditions. We also recorded ERGs at 12 to 14 h in darkness following diffuse bright light exposure to 8,000 or 15,000 lux for 2 h. ERG analysis over a range of 6 logarithmic units of light intensity revealed normal and virtually identical a-, b-, c-waves and oscillatory potentials in dark-adapted p53+/+ and p53-/- mice. After exposure to diffuse white fluorescent light strong decreases of all ERG components were found to be very similar in both genotypes. These data support the notion that the p53 protein is neither essential for normal retinal function nor for processes involved in light-induced depression of the ERG in mice.

Nuclear localization of procaspase-9 and processing by a caspase-3-like activity in mammary epithelial cells

Caspases are aspartate-specific proteases that are specifically activated by numerous death stimuli. Caspase activation is thought to play a major role for the execution of apoptosis. Inactive caspase-9 zymogen is known to be localized within the mitochondrial intermembrane space where it is involved in monitoring mitochondrial damage-associated cytochrome c release and subsequent activation of procaspase-3. Here we show that in mammary epithelial cell lines a significant fraction of caspase-9 proform is associated with discrete structures in the nucleus. Stimulation of cells with chemotherapeutic agents leads to the processing of nuclear procaspase-9 and to the accumulation of nuclear and cytoplasmic caspase activity. Using cell-free extracts from caspase-3-deficient MCF-7 cells we show that caspase-8-mediated processing of nuclear procaspase-9 requires caspase-3. In caspase-3-expressing breast cancer cells, cytochrome c-induced processing of nuclear procaspase-9 is blocked by the caspase inhibitors z-VAD and DEVD but not by YVAD. Purified active caspase-3 is sufficient to cleave nuclear caspase-9 zymogen. These results suggest that, in addition to the mitochondrial localization, caspase-9 proform is found within the nucleus and its processing can be regulated by caspase-3.

Over-expression of erbB-2/neu is paralleled by inhibition of mouse-mammary-epithelial-cell differentiation and developmental apoptosis

The erbB-2/neu oncogene is frequently over-expressed in many different tumors in humans, including those of breast and ovary. The oncogene encodes a receptor tyrosine kinase closely related to the epidermal-growth-factor receptor. We studied effects on differentiation and cell death of erbB-2/neu during mammary-gland development in transgenic mice expressing an activated, oncogenic rat erbB-2/neu gene controlled by the mammary-gland-specific promoter from mouse-mammary-tumor virus (MMTV-LTR). Transgenic animals develop mammary cancer after repeated pregnancies and lactation. We present evidence that over-expression of erbB-2/neu in these mice is restricted to tumor cells. Tumor cells fail to differentiate and express milk proteins such as beta-casein and whey acidic protein (WAP) during lactation. Epithelial-cell apoptosis during normal involution is characterized by non-random DNA degradation into oligonucleosomal fragments. Tumor cells were mostly refractory to this developmentally controlled programmed cell death. Distinct areas within tumors, however, showed spontaneous cell death as measured by in situ TUNEL staining that co-localized with caspase-3-like activity. Our results indicate that the control of developmental cell death during involution is disturbed in erbB-2/neu-induced tumors although cell death and caspase activation can take place.

Up-regulation of muscle UCP2 gene expression by a new beta3-adrenoceptor agonist, trecadrine, in obese (cafeteria) rodents, but down-regulation in lean animals

OBJECTIVE

The anti-obesity properties of a new beta3-adrenergic agonist (Trecadrine) were examined in a diet-induced obesity model, including the effects on OB and uncoupling protein (UCP-1 and -2) gene expression.

MEASUREMENTS

Control rats and cafeteria-fed rats were treated with placebo or Trecadrine for 35 days. Leptin and UCP (1 and 2) mRNA levels were determined by reverse transcription-polymerase chain reaction (RT-PCR) methodology in adipose tissue and gastrocnemius muscle.

RESULTS

Animals fed a cafeteria diet increased body weight, fat content, white adipose tissue (WAT), brown adipose tissue (BAT) weights and oxygen consumption in relation to lean controls. A rise in plasma leptin, WAT OB gene expression as well as circulating free fatty acids levels was found in obese rats as compared with lean controls. Trecadrine administration to cafeteria-fed animals decreased fat content, WAT weight, circulating leptin and fatty acids concentrations, and WAT OB gene expression, reaching comparable values to lean controls, while WAT O2 consumption was increased in these animals. Also, an increase in BAT UCP1 mRNA levels was found through a two-way analysis of variance in control and obese animals after Trecadrine administration. Gastrocnemius muscle UCP2 gene expression was reduced in lean Trecadrine-treated and diet-induced obese animals as compared to controls, while an increase was found in cafeteria-fed animals after Trecadrine administration. A negative correlation between WAT O2 consumption and UCP2 expression was found in control animals, but not in the cafeteria-fed groups, suggesting a differential response to the beta3-adrenergic compound in lean and obese animals, which is in agreement with the reported statistical interactions between obesity and Trecadrine administration found for WAT O2 consumption and muscle UCP2 expression, as well as for plasma leptin and WAT leptin expression.

CONCLUSION

The new beta3-adrenergic agonist, Trecadrine, decreases fat content and increases gastrocnemius muscle UCP2 gene expression in a diet-induced obesity model. This sheds additional light on the action mechanism of compounds with affinity for beta3-adrenoceptors and other potential anti-obesity agents.

c-fos controls the "private pathway" of light-induced apoptosis of retinal photoreceptors

White light (5 klux for 2 hr) induces apoptosis of rod photoreceptors in wild-type mice (c-fos(+/+)) within 24 hr, whereas rods of c-fos knock-out mice (c-fos(-/-)) are protected (). The range of this protection was tested by analyzing retinas of c-fos(+/+) and c-fos(-/-) mice up to 10 d after exposure to threefold increased light intensities (15 klux for 2 hr). In c-fos(-/-) mice, rods were unaffected, whereas they were destroyed in c-fos(+/+) mice. After light exposure, mitochondrial damage in rods was observed exclusively in c-fos(+/+) mice. Electroretinograms recorded 48 hr after exposure revealed a decrease of all components in c-fos(+/+) mice but indicated no light-induced loss of function in c-fos(-/-) mice. Thus, in c-fos(-/-) mice, light-induced apoptosis is blocked or its threshold is elevated more than threefold. Increased activity of the transcription factor activator protein-1 (AP-1) in retinas of light-exposed c-fos(+/+) mice indicated an acute contribution of AP-1 to apoptosis induction. AP-1 activity increased already during exposure and peaked approximately 6 hr thereafter, coinciding with the appearance of major morphological signs of apoptosis. Activated AP-1 mainly consisted of c-Fos/Jun heterodimers. In c-fos(-/-) mice, AP-1 activity remained unchanged, indicating that no other Jun- or Fos-family member could substitute for c-Fos. Like damaging light, N-methyl-N-nitrosourea (MNU) induced AP-1 containing c-Fos in c-fos(+/+) mice and did not induce AP-1 in c-fos(-/-) mice. In contrast to light, however, MNU induced apoptosis in rods of c-fos(-/-) mice. Thus, c-Fos is essential for a specific premitochondrial "private apoptotic pathway" induced by light but not for the execution of apoptosis induced by other stimuli.

Physiological apoptosis in hormone-dependent tissues: involvement of caspases

Physiological apoptosis in mammals is a type of programmed cell death, an important element in the developmental repertoire ensuring tissue homeostasis and proper disposal of cells that are no longer needed, such as milk-producing epithelial cells in the mammary gland after lactation, luteal cells in the post partum Corpus luteum or secretory cells in the prostate after castration. Although incompletely described, apoptosis in hormone-dependent tissues is apparently initiated and executed using common biochemical strategies. These include survival pathways governed by local and systemic factors and hormones, diverse regulatory pathways and caspase-dependent execution pathways. Using an antibody that recognizes processed effector caspases or a fluorogenic caspase substrate, we present for the first time evidence that caspases are activated in the mammary gland, in the prostate and in the ovary at the time when apoptosis occurs. Most likely phagocytosis of apoptotic cells by neighboring cells may represent an important step, since only a modest involvement of professional phagocytes is apparent. Here, we will summarize and discuss recent data and will attempt to draw a generalized picture of how physiological apoptosis may occur in these organs.

[Leptin and body weight regulation]

The discovery of leptin, besides causing a revolution in physiological knowledge about the regulation of body weight, awakes an interest in fat tissue as an endocrine organ and its active contribution to the establishment of energy deposits. Leptin, principally secreted by the adipocytes, interacts with hypothalamic receptors, and is capable of activating diverse neuroendocrinal routes responsible for controlling the balance between energy intake and expenditure. Like other cytokines, leptin is also able to play a role in the complex regulation of diverse metabolic aspects. Since the discovery that the placenta, gastric mucous or the star-shaped cells of the liver (Kupffer cells), are places that produce leptin, a great range of functions have been attributed to this hormone; since it appears to favour foetal development and can act as a factor of satiety in the stomach or participate in the afferent signals mediated by the vagus. Besides, leptin participates es in the immune and inflammatory responses, in reproduction, in processes related to angiogenesis, control of arterial pressure, lipolysis, etc. This paper reviews the role of leptin in the regulation of body weight, as well as different aspects related to obesity.

Molecular tools for identification of Penicillium starter cultures used in the food industry

The main goal of this work was to develop rapid and accurate molecular tools to discriminate species of white industrial Penicillia. We applied three different polymerase chain reaction (PCR) based techniques. Sequences of the ITS region of the rRNA gene unit and of the 5' end of the beta tubulin gene yielded 1.2% and 5.8% nucleotide variability respectively, between Penicillium camembertii and Penicillium nalgiovense. Polymorphic restriction sites were found in both sequences. These may be used in diagnostic PCR-RFLP analysis to rapidly distinguish between the two Penicillium species. Random amplified polymorphic DNA (RAPD) markers were also useful to differentiate these two species, but no polymorphism was found at the subspecific level, which evidenced a high level of homogeneity of the isolates studied. By means of these three techniques, the real identity of industrial strains of Penicillium chrysogenum and P. nalgiovense could be demonstrated. The comparison of these isolates with type strains of the two species suggested that the former corresponds to P. nalgiovense. The genetic relatedness between P. naglovense and Penicillium dipodomyis was also confirmed.

Optimisation of the formation and distribution of protoporphyrin IX in the urothelium: an in vitro approach

PURPOSE

To optimize conditions for photodynamic detection (PDD) and photodynamic therapy (PDT) of bladder carcinoma, urothelial accumulation of protoporphyrin IX (PpIX) and conditions leading to cell photodestruction were studied.

MATERIALS AND METHODS

Porcine and human bladder mucosae were superfused with derivatives of 5-aminolevulinic acid (ALA). PpIX accumulation and distribution across the mucosa was studied by microspectrofluorometry. Cell viability and structural integrity were assessed by using vital dyes and microscopy.

RESULTS

ALA esters, especially hexyl-ALA, accelerated and regularized urothelial PpIX accumulation and allowed for necrosis upon illumination.

CONCLUSIONS

hexyl-ALA used at micromolar concentrations is the most efficient PpIX precursor for PDD and PDT.

p45SKP2 promotes p27Kip1 degradation and induces S phase in quiescent cells

The F-box protein p45SKP2 is the substrate-targeting subunit of the ubiquitin-protein ligase SCFSKP2 and is frequently overexpressed in transformed cells. Here we report that expression of p45SKP2 in untransformed fibroblasts activates DNA synthesis in cells that would otherwise growth-arrest. Expression of p45SKP2 in quiescent fibroblasts promotes p27Kip1 degradation, allows the generation of cyclin-A-dependent kinase activity and induces S phase. Coexpression of a degradation-resistant p27Kip1 mutant suppresses p45SKP2-induced cyclin-A-kinase activation and S-phase entry. We propose that p45SKP2 is important in the progression from quiescence to S phase and that the ability of p45SKP2 to promote p27Kip1 degradation is a key aspect of its S-phase-inducing function. In transformed cells, p45SKP2 may contribute to deregulated initiation of DNA replication by interfering with p27Kip1 function.

Differential DNA binding activities of the transcription factors AP-1 and Oct-1 during light-induced apoptosis of photoreceptors

The activity of transcription factors like AP-1 and Oct-1 is critical for the regulation of gene expression. Whereas Oct-1 mainly regulates the expression of housekeeping genes, AP-1 is often involved in cellular responses to external stimuli and plays an essential role in the regulation of light-induced apoptosis of mouse retinal photoreceptors. In this study, we investigated AP-1 and Oct-1 DNA binding activity and AP-1 complex composition in the mouse retina during light-induced photoreceptor apoptosis. AP-1 DNA binding activity was low in dark-adapted animals but was transiently elevated within 12 h after exposure of mice to apoptosis-inducing levels of white fluorescent light. Maximal AP-1 activity was found 6 h after light-exposure. Antibody interference analysis at 6 h after damaging light exposure and under normal light conditions revealed that the major fraction of AP-1 consists of c-Fos/JunD heterodimers in both situations. In contrast to AP-1, Oct-1 DNA binding activity was maximal in dark-adapted animals and was reduced during photoreceptor apoptosis. Transient induction of AP-1 (c-Fos/JunD) and inactivation of Oct-1 may be crucial events for light-mediated apoptosis of retinal photoreceptors.

High-fat feeding reduced muscle uncoupling protein 3 expression in rats

Uncoupling Protein 3 (UCP3), largely expressed in skeletal muscle, is modulated by cold, thyroid hormones, leptin, fasting-refeeding and exercise training among other factors in a tissue-specific manner. In brown adipose tissue, there is an increase in UCP3 levels after high-fat feeding and beta3-adrenergic agonist treatment. Controversial effects of these agents have been reported in skeletal muscle. The aim of this experimental trial was to evaluate the effect of high-fat feeding and beta3-adrenergic agent treatment on skeletal muscle UCP3 expression levels. Lean rats were fed a cafeteria diet for 30 days and found to have significantly higher fat stores and body weight than control rats at the end of the experimental period. When cafeteria-diet rats were daily i.p. injected with Tertatolol for 30 days; a decrease in total fat mass and body weight was found. Such an effect was not observed in fa/fa rats. Interestingly, gastrocnemius muscle UCP3 mRNA levels were significantly reduced in cafeteria-diet rats when compared to lean animals. Likewise, mitochondrial O2 consumption in gastrocnemius muscle was also significantly decreased (-31%) in cafeteria-diet rats as compared to the control group. It is suggested that the down-regulation of UCP3 gene expression together with the lower O2 consumption observed in high fat fed rats may be linked to lower fatty oxidation, which would promote triglyceride accumulation.

Interaction between ubiquitin-protein ligase SCFSKP2 and E2F-1 underlies the regulation of E2F-1 degradation

The transcription factor E2F-1 is important in the control of cell proliferation. Its activity must be tightly regulated in a cell-cycle-dependent manner to enable programs of gene expression to be coupled closely with cell-cycle position. Here we show that, following its accumulation in the late G1 phase of the cell cycle, E2F-1 is rapidly degraded in S/G2 phase. This event is linked to a specific interaction of E2F-1 with the F-box-containing protein p45SKP2, which is the cell-cycle-regulated component of the ubiquitin-protein ligase SCFSKP2 that recognizes substrates for this ligase. Disruption of the interaction between E2F-1 and p45SKP2 results in a reduction in ubiquitination of E2F-1 and the stabilization and accumulation of transcriptionally active E2F-1 protein. These results indicate that an SCFSKP2-dependent ubiquitination pathway may be involved in the downregulation of E2F-1 activity in the S/G2 phase of the cell cycle, and suggest a link between SCFSKP2 and cell-cycle-dependent gene control.