Crocus sativus L. natural compounds have been extensively used in traditional medicine for thousands of years. Recent research evidence is now emerging in support of its therapeutic potential for different pathologies including neurodegenerative diseases. Herein, the C. sativus L. natural compounds trans -crocin 4 and trans -crocetin were selected for in depth molecular characterization of their potentially protective effects against Alzheimer’s Disease (AD), utilizing two AD neuronal cell culture models (SH-SY5Y overexpressing APP and PC12 expressing hyperphosphorylated tau). Biologically relevant concentrations, ranging from 0.1 μM to 1 mM, applied for 24 h or 72 h, were well tolerated by differentiated wild type SH-SY5Y and PC12 cells. When tested on neuronally differentiated SH-SY5Y-APP both trans -crocin 4 and trans -crocetin had significant effects against amyloidogenic pathways. Trans -crocin 4 significantly decreased of β-secretase, a key enzyme of the amyloidogenic pathway, and APP-C99, while it decreased γ-secretases that generate toxic beta-amyloid peptides. Similarly, trans -crocetin treatment led to a reduction in β- and γ-secretases, as well as to accumulation of cellular AβPP. When tested on the neuronally differentiated PC12-htau cells, both compounds proved effective in suppressing the active forms of GSK3β and ERK1/2 kinases, as well as significantly reducing total tau and tau phosphorylation. Collectively, our data demonstrate a potent effect of trans -crocin 4 and trans -crocetin in suppressing key molecular pathways of AD pathogenesis, rendering them a promising tool in the prevention and potentially the treatment of AD.

These findings suggest that C. spinosum and S. scardica could have a notable potential in the prevention and/or treatment of AD, and merit further investigations at the in vivo level.

L-Dopa decarboxylase (DDC) catalyses the decarboxylation of L-Dopa. It has been shown that the DDC gene undergoes alternative splicing within its 5'-untranslated region (UTR), in a tissue-specific manner, generating identical protein products. The employment of two alternative 5'UTRs is thought to be responsible for tissue-specific expression of the human DDC mRNA. In this study, we focused on the investigation of the nature of the mRNA expression in human cell lines of neural and non-neural origin. Our results show the expression of a neural-type DDC mRNA splice variant, lacking exon 3 in all cell lines studied. Co-expression of the full length non-neural DDC mRNA and the neural-type DDC splice variant lacking exon 3 was detected in all cell lines. The alternative DDC protein isoform, Alt-DDC, was detected in SH-SY5Y and HeLa cells. Our findings suggest that the human DDC gene undergoes complex processing, leading to the formation of multiple mRNA isoforms. The study of the significance of this phenomenon of multiple DDC mRNA isoforms could provide us with new information leading to the elucidation of the complex biological pathways that the human enzyme is involved in.

No abstract

L-Dopa Decarboxylase is a pyridoxal 5-phosphate (PLP)-dependent enzyme that catalyses the decarboxylation of L-Dopa to dopamine. In this study, we investigated the cellular topology of the active human enzyme. Fractionation of membranes from human cell lines, of neural and non-neural origin, by temperature-induced phase separation in Triton X-114 resulted in the detection of DDC molecules in all separation phases. Solubilization of membrane-associated DDC was observed in a pH and time-dependent manner and was affected by divalent cations and protease inhibitors, suggesting the involvement of a possible release mechanism. The study of the biological properties and function of the solubilization phenomenon described here, as well as, the study of the membrane-associated enzyme could provide us with new information about the participation of the human L-Dopa decarboxylase in physiological and aberrant processes.