Acute injury to central nervous system (CNS) triggers neurodegenerative processes that can result in serious damage or complete loss of function. After injury, production of transforming growth factor β1 (TGFβ1) increases and initiates creation of a fibrotic scar that prevents normal growth, plasticity, and recovery of damaged neurons. Administration of TGFβ1 antagonists can prevent its pathological effects. To define consequences of increased TGFβ1 release on calcium signaling, neuronal plasticity, excitability, and mitochondrial dynamics in CNS neurons we directly exposed a rat primary culture of cerebellar granule neurons to TGFβ1. We focused on changes in expression of intracellular calcium transporters, especially inositol-1,4,5-trisphosphate receptor (IP3R) type 1, mitochondrial dynamics, and membrane excitability. TGFβ1 significantly decreased the gene and protein expression of inositol-1,4,5-trisphosphate receptor type 1 and the gene expression of additional intracellular Ca transporters such as IP3R2, ryanodine receptor type 1 (RyR1), RyR2, and SERCA2. Altered calcium signaling suppressed neurite outgrowth and significantly decreased the length of the mitochondria and the frequency of mitochondrial fusion. The resting membrane potential of cerebellar granule neurons was hyperpolarized and slow after depolarization of single action potential was suppressed. LY364947, a blocker of TGFβ1 receptor I, prevented these effects, and IP3 receptor blocker 2-aminoethoxydiphenyl borate (2APB) mimicked them. After CNS injury TGFβ1 downregulates intracellular Ca levels and alters Ca signaling within injured neurons. We suggest that in our model TGFβ1 may trigger both neurodegenerative and neuroprotective events through IP3-induced Ca signaling.

Abstract. Neurodegeneration comprises assembly of pathophysiological events that gives rise to a progressive loss of neuronal structure and function including cellular damage, diseases development or cellular death. Neurons respond by adjusting signaling pathways, from gene expression to morphological changes. In most of these processes, Ca 2+ signaling plays a pivotal role. By increasing the Ca 2+ concentration, the cell responds to neuronal, neurotrophic and other growth factor stimuli, however, the molecular mechanism of Ca 2+ -dependent neurite outgrowth and development yet requires further elucidation.Here we focus on the role of Ca 2+ and selected Ca 2+ transporters involved in processes of CNS neurodegeneration -inositol 1,4,5-trisphosphate (IP 3 Rs) and ryanodine receptors (RyRs), considering the fact that these receptors may be important "sensors" of disturbed intracellular calcium homeostasis. We propose that in vitro cellular models could serve as suitable experimental systems for the determination of the role that these receptors play in neuropathological conditions.Recognition of the principles, key players and regulatory processes may elucidate the role of Ca 2+ in the regulation of neuronal proliferation, development and differentiation, growth and axon navigation in neurodegenerative and regenerative processes. This may provide a new insight and also discovery of novel therapeutic-targeting possibilities for severe neurological disorders and pathophysiological changes.