Conference Agenda

Iron is the most physiologically abundant transition metal in nearly all living organisms and it is required in various fundamental biological processes essential for life. Indeed, iron is critical to physiological cellular homeostasis since it works as a cofactor for proteins involved in essential (ATP production, DNA biosynthesis/repair, cell division) and specialized (oxygen transport, neurotransmission) cellular functions, associated mainly to mitochondria.

In the brain iron is involved in a variety of neurological processes such as myelination of axons, neuronal cells division and dopaminergic neurotransmitters synthesis, especially of monoamines. However, during aging, iron can deposit and accumulate in the nervous tissue inducing neuroinflammation and toxicity, leading to neuronal death by ferroptosis.

Intensive research is ongoing in the field of aging and neurodegenerative disorders to decipher the role of iron and mitochondria in the maintenance of cellular homeostasis and genomic integrity. Indeed, a functional mitochondrial metabolism is known to be essential for the normal physiology of neuronal function. Perturbations of the system due to aging, genetics or environmental factors, induce alterations of the physiological balance and lead to mitochondrial dysfunctions contributing to disease. Interestingly, mitochondrial dysfunctions, oxidative stress and iron dyshomeostasis are some of the earliest neuropathological features observed also in Alzheimer’s disease (AD) which led to the suggestion that it might play a causative role in the disease. We believe that mitochondria and iron homeostasis could represent a new therapeutic targets and potential biomarkers of aging and neurodegeneration, for early diagnosis, to monitor the progression of the disease and, in the future, to test new treatments’ efficacy to prevent and/or cure AD.

In the last years clinical and experimental studies highlight the involvement of ventral tegmental area (VTA) dopaminergic neurons for early pathological alterations during Alzheimer’s disease (AD) progression. Indeed, we described a progressive and selective degeneration of these neurons in the Tg2576 mouse model of AD, long before beta-amyloid plaque deposition. Why VTA dopaminergic neurons are more vulnerable than others is still unclear, although we recently showed that their autophagy machinery is precociously impaired. Autophagy alterations could be the basis for accumulation of damaged mitochondria, leading to Ca²⁺ dishomeostasis and, ultimately, to functional/structural worsening of VTA dopamine neurons.

Deregulated Ca²⁺ homeostasis is associated with aging and neurodegeneration; thus, unravelling the mechanisms underlying Ca²⁺ buffering in dopaminergic neurons may pave the way for possible strategies to prevent or delay neuronal loss.

Indeed, in the VTA dopaminergic neurons of Tg2576 mice, we found accumulation of swollen, damaged mitochondria, associated with translocation of the Apoptosis-Inducing Factor from the mitochondrial inner membrane to the nucleus. These alterations coincide with functional changes in neuronal firing. Interestingly, despite there is a progressive loss of dopaminergic neurons containing Ca²⁺-binding proteins (Calbindin-D28K, Calretinin), the surviving neurons show higher expression of these proteins when compared to dopamine neurons from WT mice. Accordingly, Ca²⁺ microfluorometry revealed reduced free Ca²⁺ levels in Tg2576 dopamine neurons.

Our results demonstrate that overexpression of Ca²⁺-binding proteins in VTA dopaminergic neurons allows their survival from neurodegeneration, increasing the ability of these neurons to buffer free Ca²⁺, thus acting as a neuroprotective agent to reduce neuronal suffering.

The endo-lysosomal system plays a key role in the control of neuronal proteostasis and growing evidence suggest that endo-lysosomal dysfunction or alterations in protein trafficking are involved in neurodegeneration leading to dementia. The three major neurodegenerative dementias, Alzheimer’s disease (AD), frontotemporal dementia (FTD) and dementia with Lewy bodies (DLB) are each characterized by the presence of abnormal protein accumulation in brain: AD by the deposition of beta-amyloid peptides (Aβ) and phosphorylated tau protein; DLB by the presence of α-synuclein in Lewy bodies inclusions; FTD, more heterogenous, by tau, ubiquitin, Fused-in-Sarcoma (FUS), and/or TAR DNA-binding protein 43 (TDP-43) inclusions. Extracellular vesicles (EVs) are membranous particles of endosomal origin (exosomes) or plasma membrane-derived (microvesicles) that are naturally released from cells. EVs have been demonstrated to play a crucial role in intercellular communication, allowing cells to exchange proteins, lipids and genetic material. Therefore, EVs have been suggested as potential carrier of misfolded toxic proteins, such as Aβ peptide and tau in AD and α-synuclein in Parkinson disease (PD)/DLB. In our recent studies we provided evidence that an alteration in EV release is common in AD, genetic and sporadic FTD, and DLB, in particular showing alterations of EV parameters (concentration, size and EV concentration/size ratio) and cargo of circulating EVs, including lysosomal protease Cathepsin D. Moreover, we recently reported that genes involved in the endo-lysosomal pathway, particularly in protein sorting/transport, clathrin-coated vesicle uncoating, and lysosomal enzymatic activity regulation might be involved in neurodegenerative dementias, sharing a genetic variability underlying the pathogenesis or modulation of the disease phenotype.

Alzheimer's disease (AD) is a widespread neurodegenerative disorder, affecting a large number of elderly individuals worldwide. Mitochondrial dysfunction, metabolic alterations, and oxidative stress are believed to contribute to the progression of AD [1]. Metabolic impairment may exacerbate the production of reactive oxygen species (ROS) and lead to Ca²⁺ homeostasis deregulation, which, in turn, can trigger neurodegeneration [2]. The Na⁺/Ca²⁺ exchanger (NCX) proteins are crucial regulators of Ca²⁺ and Na⁺ homeostasis in both the plasma membrane and mitochondria [3]. Our study aimed to explore the role of NCX1 and NCX3 in an in vitro model of retinoic acid (RA) differentiated SH-SY5Y cells exposed to glyceraldehyde (GA), which induces glucose metabolism impairment [4]. By using RNA interference-mediated approach to silence either NCX1 or NCX3 expression, we found that, in GA-treated cells, knocking-down of NCX3 ameliorated cell viability, increased the intracellular ATP production and reduced the oxidative damage. Remarkably, NCX3 silencing also prevented the enhancement of Aβ and pTau levels and normalized the GA-induced decrease of NCX reverse-mode activity. By contrast, knocking-down of NCX1 was totally ineffective in preventing GA-induced cytotoxicity except for the increase in ATP synthesis. These findings highlight the crucial role of NCX3 in setting the conditions to trigger neurodegeneration, providing a potential target for preventing AD.
1. Biochim Biophys Acta. 2010 Jan;1802(1):2-10.
2. J Alzheimers Dis. 2010; 20(2): S413–S426
3. Biochem Pharmacol. 2022 Sep;203:115163.
4. Cell Death Discov. 2022 Sep 20;8(1):391.