Spectrum of abnormalities of sympathetic tyrosine hydroxylase and alpha-synuclein in chronic autonomic failure

Lewy body forms of primary chronic autonomic failure (CAF) such as incidental Lewy body disease (ILBD), Parkinson's disease (PD), and pure autonomic failure evolving into dementia with Lewy bodies (PAF+DLB) feature cardiac sympathetic denervation, whereas multiple system atrophy (MSA) in most cases does not. What links Lewy bodies with cardiac sympathetic denervation in CAF? In familial PD, abnormalities of the alpha-synuclein (AS) gene cause CAF and cardiac sympathetic denervation; and in sporadic PD, brainstem Lewy bodies contain AS co-localized with tyrosine hydroxylase (TH), a marker of catecholaminergic neurons. Cytotoxicity from AS deposition within sympathetic neurons might explain noradrenergic denervation in Lewy body forms of CAF. We used immunofluorescence microscopy (IM) to explore this possibility in sympathetic ganglia obtained at autopsy from CAF patients. Immunoreactive AS and TH were imaged in sympathetic ganglion tissue from 6 control subjects (2 with ILBD), 5 PD patients (1 with concurrent PSP), and 3 patients with CAF (2 PAF + DLB, 1 MSA). MSA involved normal ganglionic TH and no AS deposition. In ILBD TH was variably decreased, and TH and AS were co-localized in Lewy bodies. In PD TH was substantially decreased, and TH and AS were co-localized in Lewy bodies. In PAF + DLB TH was virtually absent, but AS was present in Lewy bodies. The PD + PSP patient had AS co-localized with tau but not TH. Sympathetic denervation and intraneuronal AS deposition are correlated across CAF syndromes, consistent with a pathogenic contribution of synucleinopathy to cardiac noradrenergic deficiency in Lewy body diseases.