Mitochondrial DNA damage triggers spread of Parkinson's disease-like pathology.

In the field of neurodegenerative diseases, especially sporadic Parkinson's disease (sPD) with dementia (sPDD), the question of how the disease starts and spreads in the brain remains central. While prion-like proteins have been designated as a culprit, recent studies suggest the involvement of additional factors. We found that oxidative stress, damaged DNA binding, cytosolic DNA sensing, and Toll-Like Receptor (TLR)4/9 activation pathways are strongly associated with the sPDD transcriptome, which has dysregulated type I Interferon (IFN) signaling. In sPD patients, we confirmed deletions of mitochondrial (mt)DNA in the medial frontal gyrus, suggesting a potential role of damaged mtDNA in the disease pathophysiology. To explore its contribution to pathology, we used spontaneous models of sPDD caused by deletion of type I IFN signaling (Ifnb-/-/Ifnar-/- mice). We found that the lack of neuronal IFNß/IFNAR leads to oxidization, mutation, and deletion in mtDNA, which is subsequently released outside the neurons. Injecting damaged mtDNA into mouse brain induced PDD-like behavioral symptoms, including neuropsychiatric, motor, and cognitive impairments. Furthermore, it caused neurodegeneration in brain regions distant from the injection site, suggesting that damaged mtDNA triggers spread of PDD characteristics in an "infectious-like" manner. We also discovered that the mechanism through which damaged mtDNA causes pathology in healthy neurons is independent of Cyclic GMP-AMP synthase and IFNß/IFNAR, but rather involves the dual activation of TLR9/4 pathways, resulting in increased oxidative stress and neuronal cell death, respectively. Our proteomic analysis of extracellular vesicles containing damaged mtDNA identified the TLR4 activator, Ribosomal Protein S3 as a key protein involved in recognizing and extruding damaged mtDNA. These findings might shed light on new molecular pathways through which damaged mtDNA initiates and spreads PD-like disease, potentially opening new avenues for therapeutic interventions or disease monitoring.

Effects of buprenorphine and meloxicam analgesia on induced cerebral ischemia in C57BL/6 male mice.

Laboratory mice constitute an extensively used model to study the pathologic and functional outcomes of cerebral ischemic stroke. The middle cerebral artery occlusion (MCAO) model requires surgical intervention, which potentially can result in postsurgical pain and stress. In the present study, we investigated whether buprenorphine and meloxicam, at clinically relevant doses provided pain relief without altering infarct volume in male C57BL/6 mice. Common known side-effects of buprenorphine, including decreased food consumption, were noted after surgery in buprenorphine-treated mice, but these effects were brief and seen only during the treatment period. Fecal corticosterone metabolites did not differ significantly between the groups. In the present study, buprenorphine treatment did not alter infarction volume when compared with that of mice that did not receive analgesia. In contrast, meloxicam treatment significantly reduced infarct volume and may be a confounder if used as an analgesic during MCAO surgery. Furthermore, investigation of behavioral profiles by using an automated behavioral scoring system showed that rearing and sniffing behaviors decreased as infarct volume increased. This suggests that studies of exploratory behavior may aid in developing new markers of short-term stroke-related behavioral deficiencies in laboratory mice.

The effect of voluntarily ingested buprenorphine on rats subjected to surgically induced global cerebral ischaemia.

The effect of perioperatively administered buprenorphine analgesia on rats subjected to surgically induced global ischaemia was assessed. Rats supplied with buprenorphine, mixed in nut paste for voluntary ingestion, displayed significant reductions in postoperative excretions of faecal corticosterone, in both magnitude and variance. This is indicative of lowered stress levels and less inter-animal metabolic variation. Although corticosterone has been reported to modulate the extent of cerebral damage, histology of coronal sections exhibited no differences in the extent of the ischaemia in buprenorphine-treated and untreated animals. A part from a slightly higher hyperthermia immediately after surgery and typical opiate-associated behaviour, the buprenorphine treatment had no apparent adverse effects on the experimental model. In contrast, the analgesic treatment improved the model by minimizing stress-associated confounding variables in the experimental animals.