Caspase Inhibition Restores NEP Expression and Rescues Olfactory Deficit in Rats Caused by Prenatal Hypoxia

Development of the olfactory system begins early in embryogenesis and is important for the survival of new-borns in postnatal life. Olfactory malfunction in early life disrupts development of behavioural patterns while with ageing manifests development of neurodegenerative disorders. Previously, we have shown that prenatal hypoxia in rats leads to impaired olfaction in the offspring and correlates with reduced expression of a neuropeptidase neprilysin (NEP) in the brain structures involved in processing of the olfactory stimuli. Prenatal hypoxia also resulted in an increased activity of caspases in rat brain and its inhibition restored NEP content in the brain tissue and improved rat memory. In this study, we have analysed effects of intraventricular administration of a caspase inhibitor Ac-DEVD-CHO on NEP mRNA expression, the number of dendritic spines and olfactory function of rats subjected to prenatal hypoxia on E14. The data obtained demonstrated that a single injection of the inhibitor on P20 restored NEP mRNA levels and number of dendritic spines in the entorhinal and parietal cortices, hippocampus and rescued rat olfactory function in food search and odour preference tests. The data obtained suggest that caspase activation caused by prenatal hypoxia contributes to the olfactory dysfunction in developing animals and that caspase inhibition restores the olfactory deficit via upregulating NEP expression and neuronal networking. Because NEP is a major amyloid-degrading enzyme, any decrease in its expression and activity not only impairs brain functions but also predisposes to accumulation of the amyloid-β peptide and development of neurodegeneration characteristic of Alzheimer's disease.

The first tropical sea cucumber caspase-8 from Holothuria leucospilota: Molecular characterization, involvement of apoptosis and inducible expression by immune challenge

In this study, the first tropical sea cucumber caspase-8 named HLcaspase-8 was identified from Holothuria leucospilota. The full-length cDNA of HLcaspase-8 is 2293 bp in size, containing a 245 bp 5'-untranslated region (UTR), a 521 bp 3'-UTR and a 1527 bp open reading frame (ORF) encoding a protein of 508 amino acids with a deduced molecular weight of 57.47 kDa. Besides the common signatures of caspase family including conserved cysteine active site pentapeptide motif QACQG, P20 domain and P10 domain, HLcaspase-8 also contains a characteristic DED domain. The over-expression of HLcaspase-8 in HEK293T cells showed that HLcaspase-8 protein could induce apoptosis and the apoptosis could be promoted by TNF-α, indicating that the apoptosis induced by HLcaspase-8 might also be triggered via a receptor-mediated pathway. Moreover, the expression of HLcaspase-8 in in vitro experiments performed in coelomocytes was significantly up-regulated by lipopolysaccharides (LPS) or polyriboinosinic-polyribocytidylic Acid [poly (I:C)] challenge, suggesting that the sea cucumber caspase-8 might play some important roles in the innate immune defense against bacterial and viral infections.

Cloning and characterization of a novel caspase-8-like gene in Crassostrea gigas

Cysteine-dependent aspartate-directed proteases, or caspases, play key roles in apoptosis and immune defense. In this study, we cloned the first caspase-8-like gene (CgCaspase8-2) identified in the pacific oyster, Crassostrea gigas. The 2572-bp cDNA encodes a putative protein of 714 amino acids that contains two tandem death effector domains (DEDs) at the N-terminal, and P20 and P10 domains at the C-terminal. The conserved pentapeptide motif QACQG was also identified in the deduced CgCaspase8-2 protein. Phylogenetic analysis indicated that CgCaspase8-2 was clustered with initiator caspases in the invertebrate subgroup, but the similarity between CgCaspase8-2 and other invertebrate caspase-8s was low. CgCaspase8-2 protein was localized in the cytoplasm, and over-expression of CgCaspase8-2 in HEK293T cells induced cell death, suggesting a role in apoptosis. Quantitative real-time PCR results demonstrated that CgCaspase8-2 was widely expressed in various tissues and developmental stages, with the highest CgCaspase8-2 expression levels detected in hemolymph and the blastula stage. Furthermore, CgCaspase8-2 transcripts showed no change in response to a bacterial challenge but exhibited notable up-regulation post-poly (I:C) challenge, suggesting that CgCaspase8-2 is specifically involved in immune responses against viruses. In summary, CgCaspase8-2 is involved in both apoptotic and immune function.

Discovery of new candidate genes related to brain development using protein interaction information

Human brain development is a dramatic process composed of a series of complex and fine-tuned spatiotemporal gene expressions. A good comprehension of this process can assist us in developing the potential of our brain. However, we have only limited knowledge about the genes and gene functions that are involved in this biological process. Therefore, a substantial demand remains to discover new brain development-related genes and identify their biological functions. In this study, we aimed to discover new brain-development related genes by building a computational method. We referred to a series of computational methods used to discover new disease-related genes and developed a similar method. In this method, the shortest path algorithm was executed on a weighted graph that was constructed using protein-protein interactions. New candidate genes fell on at least one of the shortest paths connecting two known genes that are related to brain development. A randomization test was then adopted to filter positive discoveries. Of the final identified genes, several have been reported to be associated with brain development, indicating the effectiveness of the method, whereas several of the others may have potential roles in brain development.