CALRETININ IMMUNOREACTIVITY IN NERVE CELLS OF THE HUMAN MIDBRAIN AND THEIR POTENTIAL ROLE IN NEURODEGENERATIVE DISORDERS

Flace P¹, Caporusso C², Galletta D³, Stolfa M², Cacciola A^4,5, Scarcella VS², Branca JJV⁶, Gulisano M⁶, Milardi D⁷, Gradini R⁸, Livrea P⁹ and Marzullo A² | ¹Medical School, University of Bari Aldo Moro, Bari, Italy; ²Department of Precision and Regenerative Medicine and Ionian Area, Pathology Unit, University of Bari Aldo Moro, Bari, Italy; ³Specialization School Neuropsychology, University of Campania Luigi Vanvitelli, Caserta, Italy; ⁴IRCCS Humanitas Research Hospital, Milan, Italy; ⁵Department of Biomedical Sciences, Humanotas University, Milan, Italy; ⁶Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy; ⁷Brain Mapping Lab, Department of Biomedical, Dental Sciences and Morphological and Functional Imaging, University of Messina, Messina, Italy; ⁸Department of Experimental Medicine, Sapienza University, Roma, Italy; ⁹University of Bari Aldo Moro, Bari, Italy

Calretinin (CR) is an intracellular calcium binding protein of the EF-hand family, firstly described in the chick retina. CR is composed by 261-271 amino acids, with a MW of 29 kDa .CR and calbindin D-28k present 58% of identical amino acids residues. CR is widely expressed in the neuronal cell bodies and processes and in synaptic specializations on spines, dendrites and cell bodies. Although, studies suggest a role of CR in midbrain dopaminerelated disorders (e.g. schizophrenia, autism spectrum disorders, Parkinson’s disease), currently not exist in the human midbrain a morphofunctional analyses of the nerve cells (neurons and glia) immunoreactive to CR. Therefore, the aim of this study is to carry out, using an immunohistochemical approach, a detailed analysis of CR immunoreactivity (ir) in the adult human midbrain. The study was carried out on postmortem human midbrain fragments taken from human brains with no clinical history of neuropsychiatric disorders. The midbrain were fixed in neutral buffered formalin, embedded in paraffin, cut into 4 μm sections and subjected to light microscopic immunohistochemistry with CR mouse polyclonal antibody. For CR positive controls were used fragments of human mesothelioma subjected to the same experimental procedure. In the midbrain, CR immunoreactivity (ir) in the neuropil (puncta and tracts of processes) and in neuronal cell bodies and processes of the substantia nigra pars compacta and (SNpc), and pars reticulata (SNpr), ventral tegmental area (VTA), in the reticular formation and in other areas has been detected. In addition, CR-ir in cell bodies and processes of glial cells (astrocytes; oligodendrocytes, microgliocytes) has been also detected. Therefore, in the midbrain CR is not only involved in excitatory and inhibitory neurotransmission mechanisms but, also in gliotransmission and in immunitary mechanisms. Furthermore, in previous studies the absence in the midbrain of others calcium binding proteins (e.g. calbindin D-28k) in vulnerability for dopamine-related brain disorders has been suggested. In addition, we do not exclude the pathophysiological role of CR in the midbrain dopamine-related disorders. Moreover, although these results overall constitute a novelty, we subsequently aim to compare CR data between normal and pathological midbrain. Finally, based on CR functions do not exclude the preparation of therapies, by means of a combined use of pharmacological approach and transcranial stimulation.