The ral exchange factor rgl2 promotes cardiomyocyte survival and inhibits cardiac fibrosis

Cardiomyocytes compensate to acute cardiac stress by increasing in size and contractile function. However, prolonged stress leads to a decompensated response characterized by cardiomyocyte death, tissue fibrosis and loss of cardiac function. Identifying approaches to inhibit this transition to a decompensated response may reveal important targets for treating heart failure. The Ral guanine nucleotide disassociation (RalGDS) proteins are Ras-interacting proteins that are upregulated by hypertrophic stimuli. The Ral guanine nucleotide dissociation stimulator-like 2 (Rgl2) is a member of the RalGDS family that modulates expression of hypertrophic genes in cardiomyocytes. However, the pathophysiologic consequence of increased Rgl2 expression in cardiomyoctyes remains unclear. To evaluate the effect of increasing Rgl2 activity in the heart, transgenic mice with cardiac-targeted over-expression of Rgl2 were generated. Although Ral activation was increased, there were no apparent morphologic or histological differences between the hearts of Rgl2 transgenic and nontransgenic mice indicating that increased Rgl2 expression had no effect on basal cardiac phenotype. To determine if Rgl2 modulates the cardiac response to stress, mice were infused with the ß-adrenergic receptor agonist, isoproterenol. Isoproterenol infusion increased heart mass in both Rgl2 transgenic and nontransgenic mice. However, unlike nontransgenic mice, Rgl2 transgenic mice showed no morphologic evidence of cardiomyocyte damage or increased cardiac fibrosis following isoproterenol infusion. Increased Rgl2 expression in cultured cardiomyocytes stimulated Ral activation and inhibited staurosporine-induced apoptosis via increased activation of PI3-kinase. Activation of the PI3-kinase signaling pathway was confirmed in hearts isolated from Rgl2 transgenic mice. Increased expression and function of Rgl2 in cardiomyocytes promotes activation of the PI3-kinase signaling cascade and protects from carciomyocyte death and pathologic cardiac fibrosis. Taken further, these results suggest that Rgl2 upregulation in hypertrophic hearts may be a protetive mechanism, and that Rgl2 may be a novel therapeutic target in treating heart disease

Persistent Penumbra in a Rabbit Stroke Model: Incidence and Histologic Characteristics

Duration and extent of penumbra determine the window and brain volume in which interventions may save injured tissue after stroke. Understanding the penumbra in animals is necessary in order to design models that translate to effective clinical therapies. New Zealand white rabbits were embolized with aged autologous clot (n = 23) or insoluble microspheres (n = 21). To examine effects of treatment on penumbra, sphere-stroked animals were treated with 3 μm microbubbles plus ultrasound (n = 19). Rabbits were euthanized at 4 or 24 hr. Infarct volume was measured following triphenyltetrazolium chloride (TTC) staining of brain sections. Penumbra was visualized using immunostaining of pimonidazole injected fifteen minutes prior to euthanasia. Potentially reversible penumbra was present in 14.3% stroked rabbits at 4 hours and 15.7% at 24 hours after embolic stroke and represented up to 35% of total lost tissue. Intervention at up to 24 hours may benefit a significant patient population

Desmoglein 2 is a substrate of kallikrein 7 in pancreatic cancer

<p>Abstract</p> <p>Background</p> <p>In a previous report we have demonstrated that the chymotryptic-like serine protease kallikrein 7 (<it>KLK7</it>/hK7) is overexpressed in pancreatic cancer. In normal skin, hK7 is thought to participate in skin desquamation by contributing in the degradation of desmosomal components, such as desmogleins. Thus, the ability of hK7 to degrade desmogleins was assessed and the effect of hK7 expression on desmoglein 2 was examined in cultured pancreatic cancer cells.</p> <p>Methods</p> <p>The expression of Dsg1, Dsg2, and Dsg3 in pancreatic tissues was examined by immunohistochemistry and their expression in two pancreatic cancer cell lines, BxPC-3 and Panc-1, was determined by western blot analysis. The ability of hK7 to degrade Dsg1 and Dsg2 was investigated using <it>in vitro </it>degradation assays. BxPC-3 cells stably transfected to overexpress hK7 were used to examine the effect of hK7 on cell-surface resident Dsg2.</p> <p>Results</p> <p>The levels of immunoreactive Dsg1 and Dsg2 were reduced in pancreatic adenocarcinomas compared with both normal pancreatic and chronic pancreatitis tissues. Among the desmosomal proteins examined, Dsg2 exhibited robust expression on the surface of BxPC-3 cells. When hK7 was overexpressed in this cell line, there was a significant increase in the amount of soluble Dsg2 released into the culture medium compared with vector-transfected control cells.</p> <p>Conclusion</p> <p>A reduction in the amount of the cell adhesion components Dsg1 and Dsg2 in pancreatic tumors suggests that loss of these desmosomal proteins may play a role in pancreatic cancer invasion. Using <it>in vitro </it>degradation assays, both Dsg1 and Dsg2 could be readily proteolyzed by hK7, which is overexpressed in pancreatic adenocarcinomas. The enforced expression of hK7 in BxPC-3 cells that express significant amounts of Dsg2 resulted in a marked increase in the shedding of soluble Dsg2, which is consistent with the notion that aberrant expression of hK7 in pancreatic tumors may result in diminished cell-cell adhesion and facilitate tumor cell invasion.</p

Lack of efficacy of blueberry in nutritional prevention of azoxymethane-initiated cancers of rat small intestine and colon

<p>Abstract</p> <p>Background</p> <p>Blueberries may lower relative risk for cancers of the gastrointestinal tract. Previous work indicated an inhibitory effect of consumed blueberry (BB) on formation of aberrant crypt foci (ACF) in colons of male Fisher F344 rats (inbred strain). However, effects of BB on colon tumors and in both genders are unknown.</p> <p>Methods</p> <p>We examined efficacy of BB in inhibition of azoxymethane (AOM)-induced colon ACF and intestine tumors in male and female Sprague-Dawley rats (outbred strain). Pregnant rats were fed a diet with or without 10% BB powder; progeny were weaned to the same diet as their dam and received AOM as young adults.</p> <p>Results</p> <p>Male and female rats on control diet had similar numbers of ACF at 6 weeks after AOM administration. BB increased (<it>P </it>< 0.05) ACF numbers within the distal colon of female but not male rats. There was a significant (<it>P </it>< 0.05) diet by gender interaction with respect to total colon ACF number. Colon and duodenum tumor incidences were less in females than males at 17 weeks after AOM. BB tended (0.1 > <it>P </it>> 0.05) to reduce overall gastrointestinal tract tumor incidence in males, however, tumor incidence in females was unaffected (<it>P </it>> 0.1) by BB. There was a tendency (0.1 > <it>P </it>> 0.05) for fewer adenocarcinomas (relative to total of adenomatous polyps plus adenocarcinomas) in colons of female than male tumor-bearing rats; in small intestine, this gender difference was significant (<it>P </it>< 0.05). BB favored (<it>P </it>< 0.05) fewer adenocarcinomas and more adenomatous polyps (as a proportion of total tumor number) in female rat small intestine.</p> <p>Conclusion</p> <p>Results did not indicate robust cancer-preventive effects of BB. Blueberry influenced ACF occurrence in distal colon and tumor progression in duodenum, in gender-specific fashion. Data indicate the potential for slowing tumor progression (adenomatous polyp to adenocarcinoma) by BB.</p

The ral exchange factor rgl2 promotes cardiomyocyte survival and inhibits cardiac fibrosis.

Cardiomyocytes compensate to acute cardiac stress by increasing in size and contractile function. However, prolonged stress leads to a decompensated response characterized by cardiomyocyte death, tissue fibrosis and loss of cardiac function. Identifying approaches to inhibit this transition to a decompensated response may reveal important targets for treating heart failure. The Ral guanine nucleotide disassociation (RalGDS) proteins are Ras-interacting proteins that are upregulated by hypertrophic stimuli. The Ral guanine nucleotide dissociation stimulator-like 2 (Rgl2) is a member of the RalGDS family that modulates expression of hypertrophic genes in cardiomyocytes. However, the pathophysiologic consequence of increased Rgl2 expression in cardiomyoctyes remains unclear. To evaluate the effect of increasing Rgl2 activity in the heart, transgenic mice with cardiac-targeted over-expression of Rgl2 were generated. Although Ral activation was increased, there were no apparent morphologic or histological differences between the hearts of Rgl2 transgenic and nontransgenic mice indicating that increased Rgl2 expression had no effect on basal cardiac phenotype. To determine if Rgl2 modulates the cardiac response to stress, mice were infused with the ß-adrenergic receptor agonist, isoproterenol. Isoproterenol infusion increased heart mass in both Rgl2 transgenic and nontransgenic mice. However, unlike nontransgenic mice, Rgl2 transgenic mice showed no morphologic evidence of cardiomyocyte damage or increased cardiac fibrosis following isoproterenol infusion. Increased Rgl2 expression in cultured cardiomyocytes stimulated Ral activation and inhibited staurosporine-induced apoptosis via increased activation of PI3-kinase. Activation of the PI3-kinase signaling pathway was confirmed in hearts isolated from Rgl2 transgenic mice. Increased expression and function of Rgl2 in cardiomyocytes promotes activation of the PI3-kinase signaling cascade and protects from carciomyocyte death and pathologic cardiac fibrosis. Taken further, these results suggest that Rgl2 upregulation in hypertrophic hearts may be a protetive mechanism, and that Rgl2 may be a novel therapeutic target in treating heart disease