Non-antioxidant molecular functions of alpha-tocopherol (vitamin E)

alpha-Tocopherol (the major vitamin E component) regulates key cellular events by mechanisms unrelated with its antioxidant function. Inhibition of protein kinase C (PKC) activity and vascular smooth muscle cell growth by alpha-tocopherol was first described by our group. Later, alpha-tocopherol was shown to inhibit PKC in various cell types with consequent inhibition of aggregation in platelets, of nitric oxide production in endothelial cells and of superoxide production in neutrophils and macrophages. alpha-Tocopherol diminishes adhesion molecule, collagenase and scavenger receptor (SR-A and CD36) expression and increases connective tissue growth factor expression.     

Effect of surfactant on pulmonary expression of type IIA PLA(2) in an animal model of acute lung injury

We previously showed that the seminatural surfactant Curosurf inhibits the in vitro synthesis of secretory type IIA phospholipase A(2) (sPLA(2)-IIA) in alveolar macrophages (AM). These cells are the main source of sPLA(2)-IIA in a guinea pig model of lipopolysaccharide (LPS)-induced acute lung injury (ALI). Here, we investigate the effect of Curosurf on the pulmonary synthesis of sPLA(2)-IIA in this ALI model. Our results showed that intratracheal administration of LPS (330 microg/kg) induced an increase in pulmonary expression of sPLA(2)-IIA, which was inhibited when animals received Curosurf (16 mg/guinea pig) 30 min or 8 h after LPS instillation. When AM were isolated from LPS-treated animals and cultured in conditioned medium, they expressed higher levels of sPLA(2)-IIA than AM from saline-treated animals. This ex vivo sPLA(2)-IIA expression was significantly reduced when guinea pigs received Curosurf 30 min after LPS instillation. Finally, we examined the effect of Curosurf on pulmonary inflammation measured 8 or 24 h after LPS administration. Curosurf instillation 30 min or 8 h after LPS reversed the increase in tumor necrosis factor-alpha expression, polymorphonuclear cell extravasation, and protein concentration in bronchoalveolar lavage fluids. Curosurf also decreased the bronchial reactivity induced by LPS. We conclude that Curosurf inhibits the pulmonary expression of sPLA(2)-IIA and exhibits palliative anti-inflammatory effects in an animal model of ALI.     

Fragile X related protein 1 isoforms differentially modulate the affinity of fragile X mental retardation protein for G-quartet RNA structure

Fragile X syndrome, the most frequent form of inherited mental retardation, is due to the absence of expression of the Fragile X Mental Retardation Protein (FMRP), an RNA binding protein with high specificity for G-quartet RNA structure. FMRP is involved in several steps of mRNA metabolism: nucleocytoplasmic trafficking, translational control and transport along dendrites in neurons. Fragile X Related Protein 1 (FXR1P), a homologue and interactor of FMRP, has been postulated to have a function similar to FMRP, leading to the hypothesis that it can compensate for the absence of FMRP in Fragile X patients. Here we analyze the ability of three isoforms of FXR1P, expressed in different tissues, to bind G-quartet RNA structure specifically. Only the longest FXR1P isoform was found to be able to bind specifically the G-quartet RNA, albeit with a lower affinity as compared to FMRP, whereas the other two isoforms negatively regulate the affinity of FMRP for G-quartet RNA. This result is important to decipher the molecular basis of fragile X syndrome, through the understanding of FMRP action in the context of its multimolecular complex in different tissues. In addition, we show that the action of FXR1P is synergistic rather than compensatory for FMRP function.     

Comparative profiling of primary colorectal carcinomas and liver metastases identifies LEF1 as a prognostic biomarker

Purpose

We sought to identify genes of clinical significance to predict survival and the risk for colorectal liver metastasis (CLM), the most common site of metastasis from colorectal cancer (CRC).

Patients and Methods

We profiled gene expression in 31 specimens from primary CRC and 32 unmatched specimens of CLM, and performed Significance Analysis of Microarrays (SAM) to identify genes differentially expressed between these two groups. To characterize the clinical relevance of two highly-ranked differentially-expressed genes, we analyzed the expression of secreted phosphoprotein 1 (SPP1 or osteopontin) and lymphoid enhancer factor-1 (LEF1) by immunohistochemistry using a tissue microarray (TMA) representing an independent set of 154 patients with primary CRC.

Results

Supervised analysis using SAM identified 963 genes with significantly higher expression in CLM compared to primary CRC, with a false discovery rate of <0.5%. TMA analysis showed SPP1 and LEF1 protein overexpression in 60% and 44% of CRC cases, respectively. Subsequent occurrence of CLM was significantly correlated with the overexpression of LEF1 (chi-square p = 0.042), but not SPP1 (p = 0.14). Kaplan Meier analysis revealed significantly worse survival in patients with overexpression of LEF1 (p<0.01), but not SPP1 (p = 0.11). Both univariate and multivariate analyses identified stage (p<0.0001) and LEF1 overexpression (p<0.05) as important prognostic markers, but not tumor grade or SPP1.

Conclusion

Among genes differentially expressed between CLM and primary CRC, we demonstrate overexpression of LEF1 in primary CRC to be a prognostic factor for poor survival and increased risk for liver metastasis.     

Bcl-2 and Bax exert opposing effects on Ca2+ signaling, which do not depend on their putative pore-forming region

Recent work has shown that Bcl-2 and other anti-apoptotic proteins partially deplete the endoplasmic reticulum (ER) Ca(2+) store and that this alteration of Ca(2+) signaling reduces cellular sensitivity to apoptotic stimuli. We expressed in HeLa cells Bcl-2, Bax, and Bcl-2/Bax chimeras in which the putative pore-forming domains of the two proteins (alpha 5-alpha 6) were mutually swapped, comparing the effects on Ca(2+) signaling of the two proteins and relating them to defined molecular domains. The results showed that only Bcl-2 reduces ER Ca(2+) levels and that this effect does not depend on the alpha 5-alpha 6 helices of this oncoprotein. Soon after its expression, Bax increased ER Ca(2+) loading, with ensuing potentiation of mitochondrial Ca(2+) responses. Then the cells progressed into an apoptotic phenotype (which included drastic reductions of cytosolic and mitochondrial Ca(2+) responses and alterations of organelle morphology). These results provide a coherent scenario that high-lights a primary role of Ca(2+) signals in deciphering apoptotic stimuli.