Relationship of Mcl-1 isoforms,ratio p21WAF1/cyclin A,and Jun kinase phosphorylation to apoptosis in human breast carcinomas

Full length Mcl-1 is an anti-apoptotic protein consisting of two closely migrating 42/40kDa species. We now investigated the relationship of these isoforms to the expression of cell cycle stimulatory (cyclin A) and inhibitory (p21WAF1) proteins and to the induction of apoptosis in wt p53 MCF-7 and mutant p53 SKBR3 human breast carcinomas. The latter cells exhibited lower 42kDa Mcl-1, higher expression of cyclin A relative to that of p21WAF1, and apoptosis in response to okadaic acid, a phosphatase 1/2A inhibitor. The proteasome inhibitor MG-115 selectively increased expression of the 40kDa Mcl-1 isoform and induced p21WAF1, but also promoted preferential apoptosis in SKBR3 cells. Neither okadaic acid nor MG-115 caused comparable effects in MCF-7 cells. However, vanadate or acetyl furanonaphthoquinone induced the 40kDa Mcl-1 and greater Jun kinase (JNK) phosphorylation without apoptosis-associated PARP fragmentation in MCF-7 cells. Our data suggest that the higher susceptibility of SKBR3 cells to undergo apoptosis may be partly due to their greater proliferative potential (cyclin A), low expression of the anti-apoptotic 42kDa Mcl-1 isoform, and suboptimal JNK activation in response to stress.     

Participation of CaMKII in neuronal plasticity and memory formation

1. The unique biochemical properties of Ca²⁺/calmodulin (CaM)-dependent protein kinase II have made this enzyme one of the paradigmatic models of the forever searched memory molecule.2. In particular, the central participation of CaMKII as a sensor of the Ca²⁺ signals generated by activation of NMDA receptors after the induction of long-term plastic changes, has encouraged the use of pharmacological, genetic, biochemical, and imaging tools to unveil the role of this kinase in the acquisition, consolidation, and expression of different types of memories.3. Here we review some of the more exciting discoveries related to the mechanisms involved in CaMKII activation and synaptic plasticity.     

Molecular pharmacological dissection of short- and long-term memory

1. It has been discussed for over 100 years whether short-term memory (STM) is separate from, or just an early phase of, long-term memory (LTM). The only way to solve this dilemma is to find out at least one treatment that blocks STM while keeping LTM intact for the same task in the same animal.2. The effect of a large number of treatments infused into the hippocampus, amygdala, and entorhinal, posterior parietal or prefrontal cortex on STM and LTM of a one-trial step-down inhibitory avoidance task was studied. The animals were tested at 1.5 h for STM, and again at 24 h for LTM. The treatments were given after training.3. Eleven different treatments blocked STM without affecting LTM. Eighteen treatments affected the two memory types differentially, either blocking or enhancing LTM alone. Thus, STM is separate from, and parallel to the first hours of processing of, LTM of that task.4. The mechanisms of STM are different from those of LTM. The former do not include gene expression or protein synthesis; the latter include a double peak of cAMP-dependent protein kinase activity, accompanied by the phosphorylation of CREB, and both gene expression and protein synthesis.5. Possible cellular and molecular events that do not require mRNA or protein synthesis should account for STM. These might include a hyperactivation of glutamate AMPA receptors, ribosome changes, or the exocytosis of glycoproteins that participate in cell addition.     

Signaling mechanisms mediating BDNF modulation of memory formation in vivo in the hippocampus

Given that brain-derived neutrophic factor (BDNF) modulates both short-term synaptic function and activity-dependent synaptic plasticity in the adult hippocampus, here we examined signaling mechanisms in vivo in the hippocampus mediating BDNF modulation of long-term memory (LTM) formation of a one-trial fear-motivated learning task in rats. Bilateral infusions of function-blocking anti-BDNF antibody into the CA1 region of the dorsal hippocampus decreased extracellular-signal regulated kinase 2 (ERK2) and CREB activation and impaired LTM retention scores. Inhibition of ERK1/2 activation by PD098059 produced similar effects and also reduced CREB phosphorylation. In contrast, intrahippocampal administration of recombinant human BDNF increased ERK1/2 and CREB activation and facilitated LTM. Activated-p38, activated-PKC isoforms, and activated-AKT were unaltered after BDNF or anti-BDNF infusion. In addition, no changes were found on PKA and PKA catalytic subunits in nuclear samples. Thus, our results suggest that BDNF exerts its role in LTM formation in vivo in CA1 region of the hippocampus, at least in part, via CREB activation. Moreover, BDNF-induced CREB activation appears to be mediated mainly through the activation of ERK1/2 signaling pathway.     

8-(Hydroxymethyl)-3,N(4)-etheno-C, a potential carcinogenic glycidaldehyde product, miscodes in vitro using mammalian DNA polymerases

8-(Hydroxymethyl)-3,N(4)-etheno-C (8-HM-epsilonC) is an exocyclic adduct resulting from the reaction of dC with glycidaldehyde, a mutagen and animal carcinogen. This compound has now been synthesized and its phosphoramidite incorporated site-specifically into a defined 25-mer oligonucleotide. In this study, the mutagenic potential of this adduct in the 25-mer oligonucleotide was investigated in an in vitro primer-template extension assay using four mammalian DNA polymerases. The miscoding potentials were also compared to those of an analogous derivative, 3,N(4)-etheno C (epsilonC), in the same sequence. Both adducts primarily blocked replication by calf thymus DNA polymerase alpha at the modified base, while human polymerase beta catalyzed measurable replication synthesis through both adducts. Nucleotide insertion experiments showed that dA and dC were incorporated by pol beta opposite either adduct, which would result in a C --> T transition or C --> G transversion. Human polymerase eta, a product of the xeroderma pigmentosum variant (XP-V) gene, catalyzed the most efficient bypass of the two lesions with 25% and 32% for 8-HM-epsilonC and epsilonC bypassed after 15 min. Varying amounts of all four bases opposite the modified bases resulted with pol eta. Human polymerase kappa primarily blocked synthesis at the base prior to the adduct. However, some specific misincorporation of dT resulted, forming an epsilonC.T or 8-HM-epsilonC.T pair. From these data, we conclude that the newly synthesized glycidaldehyde-derived adduct, 8-HM-epsilonC, is a miscoding lesion. The bypass efficiency and insertion specificity of 8-HM-epsilonC and epsilonC were similar for all four polymerases tested, which could be attributed to the similar planarity and sugar conformations for these two derivatives as demonstrated by molecular modeling studies.     

Changes in gluconic acid, polyols and major volatile compounds in sherry wine during aging with submerged flor yeast cultures

The traditional biological process by which sherry wines are aged can be accelerated by using submerged Saccharomyces cerevisiae var. capensis (G1) strain cultures previously grown in glycerol. The used controlled shaking conditions raise the acetaldehyde, acetoin, and meso 2,3-butanediol contents in the wine, and increases the consumption of gluconic acid by flor yeast relative to traditional biological aging under flor yeast velum.     

Pulmonary bioavailability of ascorbic acid in an ascorbate-synthesising species,the horse

Vitamin C (ascorbic acid) is a non-enzymatic antioxidant important in protecting the lung against oxidative damage and is decreased in lung lining fluid of horses with airway inflammation. To examine possible therapeutic regimens in a species with ascorbate-synthesising capacity, we studied the effects of oral supplementation of two forms of ascorbic acid, (each equivalent to 20 mg ascorbic acid per kg body weight) on the pulmonary and systemic antioxidant status of six healthy ponies in a 3 x 3 Latin square design. Two weeks supplementation with ascorbyl palmitate significantly increased mean plasma ascorbic acid concentrations compared to control (29 +/- 5 and 18 +/- 7 micromol/l, respectively; p < 0.05). Calcium ascorbyl-2-monophosphate, a more stable form of ascorbic acid, also increased mean plasma ascorbic acid concentrations, but not significantly (23 +/- 1 micromol/l; p = 0.07). The concentration of ascorbic acid in bronchoalveolar lavage fluid increased in five out of six ponies following supplementation with either ascorbyl palmitate or calcium ascorbyl-2-monophosphate compared with control (30 +/- 10, 25 +/- 4 and 18 +/- 8 micromol/l, respectively; p < 0.01). Neither supplement altered the concentration of glutathione, uric acid or alpha-tocopherol in plasma or bronchoalveolar lavage fluid. In conclusion, the concentration of lung lining fluid ascorbic acid is increased following ascorbic acid supplementation (20 mg/kg body weight) in an ascorbate-synthesising species.     

Increased activity and expression of matrix metalloproteinase-9 in a rat model of distal colitis

Matrix metalloproteinases may play a role in tissue remodelling and destruction associated with inflammation. We investigated activity and expression of matrix metalloproteinases in a rat model of colitis and tested the therapeutic potential of a synthetic inhibitor (CGS-27023-A). Colitis was induced by dextran sulphate sodium (at 5% in drinking water for 5 days) in a group of eight rats, whereas a matched control group received plain water. Activity and expression of matrix metalloproteinases were measured in colonic tissue homogenates using zymography and Western blot on days 3 and 5 after induction of colitis. In another set of experiments, two groups of colitic rats (20 per group) were treated with CGS-27023-A (20 mg/kg) or vehicle, respectively. On days 5 and 14, colonic mucosal lesions were blindly scored by microscopic examination. Induction of colitis led to a significant upregulation of matrix metalloproteinase-9 protein and its activity, but no change in matrix metalloproteinase-2 activity was observed. Treatment with CGS-27023-A significantly decreased the extent and severity of epithelial injury but did not influence mucosal repair. We conclude that increased activity of matrix metalloproteinases may contribute to epithelial damage in this model of colitis.     

Decreased activity of lecithin:cholesterol acyltransferase and hepatic lipase in chronic hypothyroid rats: Implications for reverse cholesterol transport

Chronic hypothyroidism is frequently associated with atherosclerosis due to increased cholesterol plasma levels; nevertheless, the contribution of impaired reverse cholesterol transport (RCT) in this process has not been completely elucidated. The aim of this study was to evaluate the effect of thyroidectomy (Htx) upon the main stages of RCT in rats. Plasma lipid alterations induced by thyroidectomy showed a slight, but significant, reduction of total plasma triglycerides, a 300% increase of LDL-cholesterol and a 25% decrease in HDL-cholesterol compared to control rats. We evaluated the first stage of RCT determining ₃H-cholesterol efflux in Fu5AH cells. The capacity of HDL obtained from Htx rats to promote cholesterol efflux was similar to that of controls. Lecithin:cholesterol acyltransferase (LCAT) activity, the second stage and the driving force of RCT was 30% lower in Htx animals compared to controls, as determined by reconstituted HDL used as an external substrate. Lipoproteins are remodeled by hepatic lipase; the mean activity of this enzyme in postheparin plasma of Htx animals was reduced by 30% compared to controls, thus suggesting an impaired HDL remodeling by this enzyme in the hypothyroid status. In contrast, lipoprotein lipase activity in the Htx group was unchanged. In summary, this study demonstrates that chronic hypothyroidism in the rat induced an impaired RCT mainly at the cholesterol esterification, and HDL remodeling mediated by hepatic lipase. The latter probably results in an abnormal HDL structure, i.e. phospholipid enrichment, which contributes to decrease HDL-apo AI fractional catabolic rates.