Lysosomal dysfunction in neurodegeneration

Neuronal homeostasis and survival critically depend on an efficient autophagy-lysosomal degradation pathway, especially since neurons cannot reduce the concentration of misfolded proteins and damaged organelles by cell division. While increasing evidence implicates lysosomal dysfunction in the pathogenesis of neurodegenerative disorders, the molecular underpinnings of the role of lysosomes in neurodegeneration remain largely unknown. To this end, studies of neurodegenerative disorders caused by mutations in lysosomal proteins offer an opportunity to elucidate such mechanisms and potentially identify specific therapeutic targets. One of these disorders is Kufor-Rakeb syndrome, caused by mutations in the lysosomal protein ATP13A2/PARK9 and characterized by early-onset Parkinsonism, pyramidal degeneration and dementia. We found that loss of ATP13A2 function results in impaired lysosomal function and, consequently, accumulation of SNCA/α-synuclein and neurotoxicity. Our results suggest that targeting of ATP13A2 to lysosomes to enhance lysosomal function may result in neuroprotection in Kufor-Rakeb syndrome. From a broader perspective, these findings, together with other recent studies of lysosomal dysfunction in neurodegeneration, suggest that strategies to upregulate lysosomal function in neurons represent a promising therapeutic approach for neurodegenerative disorders.     

Programmed cell death 1 positive lymphocytes at palate tonsils in the elder patients with chronic tonsillitis

Circulating lymphocytes infiltrate into local foci at the inflammatory phase of acute wound healing for activation of the immune system and express an immune checkpoint protein programmed cell death 1 (PD-1) at the resolution phase for inactivation of the immune system. Conversely, the PD-1 expression was still found even on circulating lymphocytes of the elder patients with chronic tonsillitis at the palliative stage. Recently, an adhesion G protein coupled receptor 56 (GPR56) was reported to at least work as a proliferation factor for infiltrated lymphocytes into local foci at the resolution phase of acute wound healing. To preliminary examine a similar role of PD-1 and GPR56 at local foci at chronic inflammation, palate tonsils were prepared from small amounts of patients with chronic tonsillitis and tonsillar hypertrophy. A positive relationship of RNA expression might be observed between PD-1 and GPR56 in the elder patients with chronic tonsillitis. In regard to immunohistopathological findings, there were huge and small amounts of PD-1 and GPR56 expression at the marginal zone of lymphoid follicles of palate tonsils with chronic tonsillitis. Moreover, the positive relationship of RNA expression between PD-1 and GPR56 confirmed in large numbers of the elder patients with chronic tonsillitis. Probably, GPR56 participates in a supplement of PD-1⁺ lymphocytes to circulating bloods of the elder patients with chronic tonsillitis through a lymphocyte cell maintenance system at the marginal zone of the lymphoid follicles of palate tonsils.     

Synthesis of 5- and 7-hydroxy indolizidin-2-one prostaglandin-F2α modulators and activity on myometrial contractility towards development of agents for delaying preterm birth

In pursuit of more effective-labor delaying tocolytic agents, the prostaglandin F2α (PGF2α) receptor (FP) modulator PDC113.824 [(6S)- 2 ] represents a potent lead for developing therapy to treat preterm birth. Derivatives of FP modulator (6S)- 2 were synthesized, possessing respectively 5- and 7-hydroxyl groups on the indolizidin-2-one amino acid (I²aa) residue. The effects of the alcohol substituents were examined in a PGF2α-induced myometrial contraction assay. Based on knowledge of dihedral angle values of model I²aa peptides from X-ray analyses, the results of the study indicate respectively encouraging and limited potential for creating improved tocolytic agents by modifications at the 5- and 7-positions.     

Elevation in liver enzymes is associated with increased IL-2 and predicts severe outcomes in clinically apparent dengue virus infection

The objective of the present study was to assess the circulating TNF-α and IL-2 levels in dengue virus (DENV) infected patients and to correlate these with clinical severity of DENV infections. A single analyte quantitative immunoassay was used to detect TNF-α and IL-2 in 24 dengue fever (DF) and 43 dengue haemorrhagic fever (DHF) patients, 15 healthy adults and 6 typhoid patients. The mean TNF-α and IL-2 levels of DENV- infected patients were higher than that of healthy adults and typhoid patients. No significant difference in TNF-α levels was noted between DF and DHF patients (p = 0.5) but a significant increase in IL-2 levels was observed in DHF compared with DF patients (mean of DF = 59.7 pg/mL, mean of DHF = 166.9 pg/mL; p = 0.02). No significant association of TNF-α or IL-2 levels was noted with packed cell volume (>45), thrombocytopenia, leucopenia or the presence of viraemia. The liver function tests measuring AST (aspartate aminotransferase) (p = 0.01) and ALT (alanine aminotransferase) (p = 0.02) levels were significantly elevated in DENV-infected patients. AST:ALT was significantly elevated in DHF/DSS (dengue shock syndrome) compared with DF patients. A significant positive linear correlation was noted between AST and IL-2 (r = 0.31; p = 0.01) and ALT and IL-2 elevations (r = 0.2; p = 0.02). Thus, AST and ALT levels correlate with both disease severity and circulating IL-2 levels. We suggest a role for circulating IL-2 in liver dysfunction and propose that a combined assessment of AST/ALT in conjunction with IL-2 at the early stages of symptomatic DENV infection may be useful to predict the severe forms of dengue.     

Co-occurrence of c-24 epimeric 24-ethyl-Δ7 -sterols in the roots of Trichosanthes japonica

¹³C NMR spectroscopy has demonstrated that the major components (～80%) of 24 - ethyl - 5α -cholest - 7 - en - 3β - ol and 24 - ethyl - 5α - cholesta - 7,trans - 22 - dien - 3β - ol isolated from the roots of Trichosanthes japonica are the 24α-epimers, 22-dihydrospinasterol and spinasterol, accompanied by minor amounts (～20%) of their 24β-epimers, 22-dihydrochondrillasterol and chondrillasterol, respectively. The possible biosynthetic pathway leading to these sterols is discussed. This seems to be the first instance of the detection of 22-dihydrochondrillasterol in a higher plant.     

Common Mechanisms Underlying α-Synuclein-Induced Mitochondrial Dysfunction in Parkinson’s Disease

Parkinson’s disease (PD) is the most common neurological movement disorder characterized by the selective and irreversible loss of dopaminergic neurons in substantia nigra pars compacta resulting in dopamine deficiency in the striatum. While most cases are sporadic or environmental, about 10% of patients have a positive family history with a genetic cause. The misfolding and aggregation of α-synuclein (α-syn) as a casual factor in the pathogenesis of PD has been supported by a great deal of literature. Extensive studies of mechanisms underpinning degeneration of the dopaminergic neurons induced by α-syn dysfunction suggest a complex process that involves multiple pathways, including mitochondrial dysfunction and increased oxidative stress, impaired calcium homeostasis through membrane permeabilization, synaptic dysfunction, impairment of quality control systems, disruption of microtubule dynamics and axonal transport, endoplasmic reticulum/Golgi dysfunction, nucleus malfunction, and microglia activation leading to neuroinflammation. Among them mitochondrial dysfunction has been considered as the most primary target of α-syn-induced toxicity, leading to neuronal cell death in both sporadic and familial forms of PD. Despite reviewing many aspects of PD pathogenesis related to mitochondrial dysfunction, a systemic study on how α-syn malfunction/aggregation damages mitochondrial functionality and leads to neurodegeneration is missing in the literature. In this review, we give a detailed molecular overview of the proposed mechanisms by which α-syn, directly or indirectly, contributes to mitochondrial dysfunction. This may provide valuable insights for development of new therapeutic approaches in relation to PD. Antioxidant-based therapy as a potential strategy to protect mitochondria against oxidative damage, its challenges, and recent developments in the field are discussed.     

Cellular phosphatidic acid sensor, α-synuclein N-terminal domain,detects endogenous phosphatidic acid in macrophagic phagosomes and neuronal growth cones

Phosphatidic acid (PA) is the simplest phospholipid and is involved in the regulation of various cellular events. Recently, we developed a new PA sensor, the N-terminal region of α-synuclein (α-Syn-N). However, whether α-Syn-N can sense physiologically produced, endogenous PA remains unclear. We first established an inactive PA sensor (α-Syn-N-KQ) as a negative control by replacing all eleven lysine residues with glutamine residues. Using confocal microscopy, we next verified that α-Syn-N, but not α-Syn-N-KQ, detected PA in macrophagic phagosomes in which PA is known to be enriched, further indicating that α-Syn-N can be used as a reliable PA sensor in cells. Finally, because PA generated during neuronal differentiation is critical for neurite outgrowth, we investigated the subcellular distribution of PA using α-Syn-N. We found that α-Syn-N, but not α-Syn-N-KQ, accumulated at the peripheral regions (close to the plasma membrane) of neuronal growth cones. Experiments using a phospholipase D (PLD) inhibitor strongly suggested that PA in the peripheral regions of the growth cone was primarily produced by PLD. Our findings provide a reliable sensor of endogenous PA and novel insights into the distribution of PA during neuronal differentiation.