Inhibition of LRRK2 Attenuates Depression-Related Symptoms in Mice with Moderate Traumatic Brain Injury

Identification of preventive biomarkers associated with circadian rhythms in traumatic brain injury-mediated depression: Expression of SERPINE1 protein and bioinformatics analysis

Traumatic brain injury (TBI) represents the leading cause of trauma-related mortality, with depression being the most common psychiatric condition following TBI. Although disruptions in circadian rhythms and clock genes have been linked to both conditions, their precise regulatory mechanisms remain unclear. Identifying circadian rhythm-related genes is critical for the prevention and diagnosis of TBI and depression. This study employs Mendelian Randomization (MR) analysis to establish a positive correlation between TBI and depression. Using Weighted Gene Co-expression Network Analysis (WGCNA) on Gene Expression Omnibus (GEO) datasets derived from TBI and depression tissue samples, we identified 99 shared genes functionally linked to circadian rhythms. Furthermore, machine learning algorithms and Receiver Operating Characteristic (ROC) curve analysis identified SERPINE1 as a key diagnostic biomarker for both TBI and depression. In vivo and in vitro experiments further demonstrated that TBI often triggers the development of depression. Suppressing SERPINE1 expression reduced Claudin-1 and BDNF protein levels, alleviating TBI and depressive symptoms. Our findings indicate that SERPINE1 overexpression, which is positively correlated with neutrophil levels, may increase the risk of depression following TBI by disrupting circadian rhythms. This positions SERPINE1 as a critical predictive and diagnostic biomarker for TBI-mediated depression.

The Inhibition of Prolyl Endopeptidase (PREP) by KYP-2047 Treatment to Reduce Myocardial Ischemia/Reperfusion Injury

Myocardial ischemia-reperfusion injury (MI/R) is a negative and adverse cardiovascular outcome following myocardial ischemia, cardiac surgery, or circulatory arrest. Prolyl endopeptidase (PREP) appears to be involved in inflammatory responses, so it could be a possible therapeutic target for counteracting ischemia injury. This study aimed to investigate the role of PREP inhibitor, KYP-2047 (4-phenylbutanoyl-l-prolyl-2(S)-cyanopyrolidine), in the modulation of molecular and biochemical processes involved in MI/R. MI/R was induced through coronary artery occlusion (15 min), followed by reperfusion (2 h). KYP-2047 was intraperitoneally administrated at doses of 2.5 mg/kg and 5 mg/kg 24 h before the surgical procedures. The hearts were removed and processed for analysis. KYP-2047 treatment limited ischemic myocardial-induced histological damage and neutrophil accumulation, limiting inflammation, fibrosis, and apoptosis processes. Additionally, KYP-2047 was able to modulate p-38 and p-ERK expression, suggesting an improving role in recovering cardiac function. These findings highlighted the protective effects of KYP-2047 pretreatment in MI/R injury, suggesting PREP as a potential target therapy for the pathogenesis of MI/R. Although the molecular mechanisms underlying the action of KYP-2047 are still to be explored, these results suggested that the regulation of NF-κB, apoptosis, and MAPK pathways by KYP-2047 treatment could preventatively limit the damage caused by MI/R.

Polysaccharides from Scrophularia ningpoensis Hemsl. improve reserpine-induced depression-like behavior by inhibiting HTR2A/HTR2C mediated AKT/GSK3β/β-catenin/CBP/BDNF signalling

Scrophularia ningpoensis Hemsl. is a traditional Chinese medicine used to regulate blood sugar levels, immunity, etc. We previously isolated polysaccharides from S. ningpoensis Hemsl. (SNPS) and innovatively observed that SNPS exhibit antidepressant properties; however, the underlying mechanism is still unclear. Here, we employed network pharmacology to predict the potential targets and antidepressant mechanism of SNPS. Accordingly, we detected the effects of SNPS on monoamine neurotransmitter synthesis, metabolism, receptor expression and signal transduction in reserpine (RES)-treated mice using ELISA, HPLC-electrochemistry, metabonomics, Golgi-Cox staining and Western blotting. Finally, the mechanism of SNPS on key targets (HTR2A and HTR2C) was verified in vivo and in vitro. Results showed that SNPS ameliorated depression by restoring monoamine neurotransmitter homeostasis and hippocampal neurogenesis. SNPS reversed the depletion of 5-HT, NE and DA by activating the tryptophan (Trp)/5-HT and tyrosine (Tyr)/DA/NE metabolic pathways. SNPS decreased HTR2A and HTR2C contents, leading to the phosphorylation of AKT and GSK3β, followed by increases in β-catenin, CBP and BDNF levels. Mechanistically, SNPS reduced the levels of HTR2A and HTR2C proteins by inhibiting their mRNA transcription, rather than inducing protein degradation. In conclusion, by inhibiting the transcription of HTR2A and HTR2C, SNPS activated the AKT/GSK3β/β-catenin/CBP/BDNF pathway, thereby exerting dose-dependent antidepressant effects.

CK and LRRK2 Involvement in Neurodegenerative Diseases

Neurodegenerative diseases (NDDs) are currently the most widespread neuronal pathologies in the world. Among these, the most widespread are Alzheimer's disease (AD), dementia, Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD)-all characterized by a progressive loss of neurons in specific regions of the brain leading to varied clinical symptoms. At the basis of neurodegenerative diseases, an emerging role is played by genetic mutations in the leucine-rich repeat kinase 2 (LRRK2) gene that cause increased LRRK2 activity with consequent alteration of neuronal autophagy pathways. LRRK2 kinase activity requires GTPase activity which functions independently of kinase activity and is required for neurotoxicity and to potentiate neuronal death. Important in the neurodegeneration process is the upregulation of casein kinase (CK), which causes the alteration of the AMPK pathway by enhancing the phosphorylation of α-synuclein and huntingtin proteins, known to be involved in PD and HD, and increasing the accumulation of the amyloid-β protein (Aβ) for AD. Recent research has identified CK of the kinases upstream of LRRK2 as a regulator of the stability of the LRRK2 protein. Based on this evidence, this review aims to understand the direct involvement of individual kinases in NDDs and how their crosstalk may impact the pathogenesis and early onset of neurodegenerative diseases.

Rebalance of mitophagy by inhibiting LRRK2 improves colon alterations in an MPTP in vivo model

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are common genetic causes of Parkinson's disease (PD). Studies demonstrated that variants in LRRK2 genetically link intestinal disorders to PD. We aimed to evaluate whether the selective inhibitor of LRRK2, PF-06447475 (PF-475), attenuates the PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in central nervous system (CNS) and in the gastrointestinal system. CD1 mice received four intraperitoneal injections of MPTP (20 mg/kg, total dose of 80 mg/kg) at 2 h intervals (day 1). After 24 h PF-475 was administered intraperitoneally at the doses of 2.5, 5, and 10 mg/kg for seven days. LRRK2 inhibition reduced brain α-synuclein and modulated mitophagy pathway and reduced pro-inflammatory markers and α-synuclein aggregates in colonic tissues through the modulation of mitophagy proteins. LRRK2 inhibition suppressed MPTP-induced enteric dopaminergic neuronal injury and protected tight junction in the colon. Results suggested that PF-475 may attenuate gastrointestinal dysfunction associated to PD.

Analysis of MicroRNA-Transcription Factors Co-Regulatory Network Linking Depression and Vitamin D Deficiency

Depression and vitamin D deficiency are often co-occurring pathologies, the common pathogenetic ground of which includes an augmented inflammatory response. However, the molecular details of this relationship remain unclear. Here, we used a bioinformatic approach to analyze GEO transcriptome datasets of major depressive disorder (MDD) and vitamin D deficiency (VDD) to identify the hub genes within the regulatory networks of commonly differentially expressed genes (DEGs). The MDD-VDD shared regulatory network contains 100 DEGs (71 upregulated and 29 downregulated), with six hub genes (PECAM1, TLR2, PTGS2, LRRK2, HCK, and IL18) all significantly upregulated, of which PTGS2 (also known as COX2) shows the highest inference score and reference count. The subsequent analysis of the miRNA-transcription factors network identified COX2, miR-146a-5p, and miR-181c-5p as key co-regulatory actors in the MDD-VDD shared molecular pathogenic mechanisms. Subsequent analysis of published MDD and VDD transcriptome data confirmed the importance of the identified hub genes, further validating our bioinformatic analytical pipeline. Our study demonstrated that PTGS2 was highly upregulated in both depressive patients and patients with low vitamin D plasma levels. Therefore, regulators targeting PTGS2, like miR-146a-5p and miR181c-5p, may have great potential in controlling both diseases simultaneously, accentuating their role in future research.