Nocardia cyriacigeorgica Elicits Gut Disturbances in a Leaky Gut Model of Colitis, but Not the Harmful Cascade Leading to Gut-First Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative disorder with an unknown cause. Recent research has highlighted the importance of the gut in neuronal and immune maturation through the exchange of nutrients and cellular signals. This has led to the "gut-first PD" hypothesis, which aims to explain many of the sporadic cases and their prodromal intestinal symptoms, such as constipation and intestinal α-synuclein (aSyn) aggregation. The link between mitochondrial dysfunction and aSyn deposition is central to PD pathophysiology, since they can also trigger pro-inflammatory signals associated with aSyn deposition, potentially contributing to the onset of PD. As mitochondria are derived from ancestral alpha-proteobacteria, other bacteria may specifically target this organelle. We sought to use Nocardia cyriacigeorgica, a bacterium previously associated with parkinsonism, and dextran sulfate sodium (DSS) as pro-inflammatory modulators to gain further insight into the onset of PD. This study indicates that aSyn aggregation plus mitochondrial dysfunction without intestinal barrier leakage are not sufficient to trigger gut-first PD.