Neuroinflammation and inhibitory synaptic control of cultured premotor circuits

My PhD project is focused on the impact of neuroinflammation processes in the mouse spinal cord, with particular attention to cytokines and their functional role. In particular, I have used as model the organotypic spinal cultures, which allowed me to investigate: i. spinal network activity changes induced by pro-inflammatory cytokines; ii. resident microglia and astrocytes response to inflammatory stress; iii. mechanisms by which pro-inflammatory cytokines modulate the inhibitory transmission. The principal aim of my work was to understand the crosstalk between neuroinflammation and the spinal pre-motor network. For this purpose, I combined electrophysiological and immunofluorescence methods to assess the interneurons synaptic activity especially localized in the ventral organotypic cultures from embryonic mouse spinal cord. I investigated a specific cytokines cocktail (TNF-α, IL-1β, and GM-CSF; CKs) and their effects on spontaneous and inhibitory postsynaptic currents (sPSCs and IPSCs). In cultured spinal networks, I have observed a progressive increase in the frequency of PSCs and IPSCs accompanied by a fastening of GABAergic currents, due to a reduction in the decay time constant (τ). This difference in the GABAergic PSCs kinetic properties is maintained in miniature PSCs (mPSCs) recorded after CKs treatments, suggesting mechanisms strictly associated with post-synaptic modification. The specific CKs modulation of GABAergic currents is strengthened by the absence of such a regulation by another danger signal as LPS. In this work, I evaluated and compared resident neuroglial cells response to CKs and LPS. Microglia and astrocytes show a different activation in the spinal slices. In particular, CKs induce an increase of microglia proliferation and astrogliosis followed by decreasing of microglia ramification. On the other hand, LPS increases only microglia ramification maintaining unaffected the other properties. Regardless the cell morphology, the activation of an inflammatory status was confirmed by the presence of cytokines and chemokines release in the supernatants in both conditions. I investigated the mechanisms by which cytokines speeded up the GABAAR-mediated currents, and pharmacologically based electrophysiological experiments strongly indicated the presence of a modulation of GABAAR subunit, in particular of α-subunit.