Biomolecular changes at ventrolateral medulla and respiratory deficit in an experimental model of Parkinson's disease
Authors: Fernandes Silvio Araujo , Junior  , Czeisler Catherine , Mo Xiaokui , Sashwati Roy , Somogyi Arpad , Zhang Liwen , dos Santos Moreira Thiago , Otero Jose Javier , Takakura Ana Carolina 
Published: June 2021

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor and non‐motor symptoms, and caused by degeneration of dopaminergic neurons of substantia nigra pars compacta (SNpc). Prior studies showed that in animal model of PD there is a decrease in the resting and hypercapnia‐induced respiratory rate and in the number of phox2b‐expressing RTN neurons. The aim of this study was to identify the extent to which RTN pharmacological rescue restores respiratory function and determine the extent of biomolecular changes following PD‐induction. Adult male Wistar rats with bilateral injections of 6‐hydroxy‐dopamine (6‐OHDA, 24 μg/μl) or vehicle into the striatum were used. For proteomic analyzes, laser capture and pressure catapulting was used for microdissection of the brain cuts. We also performed comparative proteomic studies followed by Ingenuity Pathway Analysis (IPA®) of the RTN region in PD‐induced rats. Stainless steel canullas were implanted into RTN region and injections of N‐methyl D‐aspartate (NMDA, 50 nl) were performed to verify the pharmacological activation of these neurons. Respiratory parameters were evaluated by whole body plethysmography. The results showed that sixty days after injection of 6‐OHDA, the number of SNpc catecholaminergic and RTN phox2b neurons reduced (73.1± 2 and 55.9 ± 17%, respectively). In PD‐animals, there is a reduction in basal ventilation, hypercapnia, hypoxia and maximal chemoreflex stimulation (MCS) (basal: 357 ± 19, vs. vehicle: 917 ± 22 ml/kg/min; hypercapnia: 1064 ± 35, vs. vehicle: 1921 ± 108 ml/kg/min; hypoxia: 711 ± 6, vs. vehicle: 1851 ± 102 ml/kg/min; MCS: 1195 ± 17, vs. vehicle: 2727 ± 26 ml/kg/min, p<0.05). However, the activation of RTN by NMDA injection showed similar respiratory responses between PD and control animals (respiratory frequency: 149 ± 12, vs. control 155 ± 12 breaths/min; ventilation: 1028 ± 191, vs. vehicle: 985 ± 199 ml/kg/min; tidal volume: 6.9 ± 0.7, vs. vehicle: 6.4 ± 0.5 ml/kg, p>0.05). The proteomic analyses of the RTN showed a biomolecular profile indicative of ongoing cell remodeling in PD‐induced animals. In PD‐group, some proteins showed a decreased fold change in quantity, such as MYH9 (cytoskeleton reorganization), CAMK2D (regulation of Ca2+ homeostasis), RAB6A (protein transport), whereas Dnah5 (cellular movement) and Rnh1 (ribonuclease inhibitor) were increased. In addition, other genes were functionally inhibited, such as ADORA‐2A (g‐protein receptor), IGF‐1 (growth factor) and SRF (transcription regulation) or activated, as RICTOR (kinases mediate responses to stress), MAP4K4 (kinase) and CAMK2A (NMDAR signaling complex). Our data suggest, therefore, that despite the fact that biomolecular changes occur at the RTN level, there may be persistence of an NMDA‐specific compensatory mechanism provided by the surviving neurons.Support or Funding InformationNIH/NHLBI, FAPESP, CNPq and CAPESThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.