Ketone bodies mediate alterations in brain energy metabolism and biomarkers of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common form of dementia. AD is a progressive neurodegenerative disorder characterized by cognitive dysfunction, including learning and memory deficits, and behavioral changes. Neuropathology hallmarks of AD such as amyloid beta (Aβ) plaques and neurofibrillary tangles containing the neuron-specific protein tau is associated with changes in fluid biomarkers including Aβ, phosphorylated tau (p-tau)-181, p-tau 231, p-tau 217, glial fibrillary acidic protein (GFAP), and neurofilament light (NFL). Another pathological feature of AD is neural damage and hyperactivation of astrocytes, that can cause increased pro-inflammatory mediators and oxidative stress. In addition, reduced brain glucose metabolism and mitochondrial dysfunction appears up to 15 years before the onset of clinical AD symptoms. As glucose utilization is compromised in the brain of patients with AD, ketone bodies (KBs) may serve as an alternative source of energy. KBs are generated from the β-oxidation of fatty acids, which are enhanced following consumption of ketogenic diets with high fat, moderate protein, and low carbohydrate. KBs have been shown to cross the blood brain barrier to improve brain energy metabolism. This review comprehensively summarizes the current literature on how increasing KBs support brain energy metabolism. In addition, for the first time, this review discusses the effects of ketogenic diet on the putative AD biomarkers such as Aβ, tau (mainly p-tau 181), GFAP, and NFL, and discusses the role of KBs on neuroinflammation, oxidative stress, and mitochondrial metabolism

The Protective Role of Protein Disulphide Isomerase (PDI) against DNA damage in Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration and death of motor neurons in the brain, brainstem, and spinal cord. Previous studies from our group have established that a chaperone usually associated with the endoplasmic reticulum (ER), protein disulphide isomerase (PDI) is protective against dysfunction to proteostasis mechanisms in vitro in ALS. However, it remains unclear if PDI is also protective in vivo, or against other processes in ALS, particularly DNA damage, which is increasingly implicated as a disease mechanism. We have also recently established that Tar DNA binding protein 43 (TDP-43) is involved in DNA repair but ALS-associated mutant TDP-43 lacks this activity, resulting in DNA damage. In the studies described in this thesis, it was examined whether PDI is protective in vivo and against DNA damage (both in vivo and in vitro). In neuronal cells, PDI was found to be protective against DNA damage induced by etoposide, H2O2 or ALS-associated mutant TDP-43. In addition, it was demonstrated that PDI translocates into the nucleus following induction of DNA damage. PDI displays two main activities; it is a general protein chaperone and it also functions as an oxidoreductase. The latter activity is mediated by redox active cysteine residues in its active site. Using a mutant in which all four redox active site cysteines were removed (‘quad’ mutant), it was also demonstrated that the oxidoreductase activity mediates its protective activity against DNA damage. Proteomics analysis using wildtype PDI and the quad mutant identified the Nrf2 pathway as a possible mediator of this protective function. The oxidoreductase activities of PDI and several PDI family members were also examined in vitro using three different methods. This study also demonstrates a protective activity for PDI in vivo. PDI was also found to be protective in zebrafish against DNA damage induced by H2O2 and in two ALS-associated models, expressing either A4V mutant superoxide dismutase 1 (SOD1A4V) or S621G mutant cyclin F (CCNFS621G). Moreover, knockdown of PDI in C. elegans was found to shorten the lifespan and reduce the fecundity of these animals, implying that PDI has an important protective activity against ageing and viability in C. elegans. These results therefore demonstrate the protective role of PDI against DNA damage both in vivo and in vitro. They also reveal that PDI has a much broader protective role than previously recognised. This study therefore has implications for future therapeutic studies based on PDI.</p

The Complex Mechanisms by Which Neurons Die Following DNA Damage in Neurodegenerative Diseases

Human cells are exposed to numerous exogenous and endogenous insults every day. Unlike other molecules, DNA cannot be replaced by resynthesis, hence damage to DNA can have major consequences for the cell. The DNA damage response contains overlapping signalling networks that repair DNA and hence maintain genomic integrity, and aberrant DNA damage responses are increasingly described in neurodegenerative diseases. Furthermore, DNA repair declines during aging, which is the biggest risk factor for these conditions. If unrepaired, the accumulation of DNA damage results in death to eliminate cells with defective genomes. This is particularly important for postmitotic neurons because they have a limited capacity to proliferate, thus they must be maintained for life. Neuronal death is thus an important process in neurodegenerative disorders. In addition, the inability of neurons to divide renders them susceptible to senescence or re-entry to the cell cycle. The field of cell death has expanded significantly in recent years, and many new mechanisms have been described in various cell types, including neurons. Several of these mechanisms are linked to DNA damage. In this review, we provide an overview of the cell death pathways induced by DNA damage that are relevant to neurons and discuss the possible involvement of these mechanisms in neurodegenerative conditions

Biochemical properties and microbial analysis of honey from North-Western regions of Iran: Seasonal effects on physicochemical properties of honey

In the present study, physicochemical properties (pH, ash, commercial glucose, starch, reducing sugars and moisture) and microbial (yeast and enterobacterial) contaminations of 263 honey samples from North-western regions of Iran were evaluated in a 2 year period in different seasons of 2010 and 2011. Levels of reducing sugars and sucrose showed significant seasonal differences, with the highest levels observed in summer samples. No commercial glucose or starch was detected in any of the samples; but levels of reducing sugars and sucrose content of 1.52 and 6.84% samples were unacceptable, respectively. Moisture, ash content (0.4 ± 0.01%) and pH values (4.44 ± 0.02) of all samples were in the required standard range and did not significantly vary in different seasons. Of all the samples evaluated, only seven samples (2.66%) contained yeast, and two samples (0.76%) were contaminated with bacteria from family Enterobacteriaceae (2 samples with both contaminations). None of the isolates were found to be of major pathogenic importance.Keywords: Honey, physicochemical, microbial, north-western, Ira

Enhanced neuroinflammatory responses after systemic LPS injection in IL-32β transgenic mice

IL-32 is a proinflammatory cytokine, and involved in various diseases including infection, inflammation, and cancer. However, effects of IL-32 on neuroinflammation remain obscure. Herein, we examined the effects of IL-32β on systemic LPS-induced neuroinflammation using IL-32β transgenic (Tg) mice. IL-32β wild type (WT) and Tg mice received LPS injection (5 mg/kg, i.p.), and then neuroinflammatory responses were evaluated. Systemic LPS caused remarkable gliosis in the brain at 12 h regardless of genotypes. The gliosis in WT mice was sustained by 24 h, whereas it became more severe in Tg mice by 24 h. Proinflammatory cytokines and proteins were increased at 12 h both in WT and Tg brains. The elevated levels of TNFα and VCAM-1were not altered over time, while levels of IL-6, IL-1β and iNOS were dropped in WT mice. In contrast, elevated levels IL-6, IL-1β, iNOS and VCAM-1 were sustained, and level of TNFα was augmented in Tg brains by 24 h. Interestingly, level of IL-10 mRNA in Tg mice was remarkably higher than in WT mice at 0 h, which was decreased at 12 h and maintained by 24 h. In WT brain, mRNA level of IL-10 was raised at 12 h after LPS injection, and further increased at 24 h. Activation of NF-κB signaling pathway was detected in glia cells after LPS injection which was exaggerated at 24 h in Tg mice in comparison to WT mice. These results indicate that IL-32β enhances neuroinflammatory responses caused by systemic LPS, and this might be attributable to prolonged activation of NF-κB signaling pathway

Neuroprotective effects of antidepressants via upregulation of neurotrophic factors in the MPTP model of Parkinson's disease

Neurotrophic factors are essential for neuronal survival, plasticity, and development and have been implicated in the action mechanism of antidepressants. In this study, we assessed the neurotrophic factor-inducing and neuroprotective properties of antidepressants. In the first part of the study, we found that fluoxetine, imipramine, and milnacipran (i.p., 20 mg/kg/day for 1 week or 3 weeks) upregulated brain-derived neurotrophic factor in the striatum and substantia nigra both at 1 week and 3 weeks. In contrast, an increase in the glial-derived neurotrophic factor was more obvious at 3 weeks after the antidepressants treatment. Specifically, it was found that fluoxetine and imipramine are more potent in raising the levels of neurotrophic factors than milnacipran. Furthermore, antidepressants elevated the phosphorylation of extracellular signal-regulated-protein kinase (ERK1/2) and the serine/threonine kinase Akt. In the second part of the study, we compared the neuroprotective effects of fluoxetine, imipramine, and milnacipran in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease. Pretreament with fluoxetine, imipramine or milnacipran for 3 weeks reduced MPTP-induced dopaminergic neurodegeneration and microglial activation in the nigrostriatal pathway. Neurochemical analysis by HPLC exhibited that antidepressants attenuated the depletion of striatal dopamine. In consistent, beam test showed that behavioral impairment was ameliorated by antidepressants. Neuroprotective effects were more prominent in the fluoxetine or imipramine treatment group than in milnacipran treatment group. Finally, we found that neuroprotection of the antidepressants against 1-methyl-4-phenylpyridinium neurotoxicity in SH-SY5Y cells was attenuated by ERK or Akt inhibitor. These results indicate that neuroprotection by antidepressants might be associated with the induction of neurotrophic factors, and antidepressant could be a potential therapeutic intervention for treatment of Parkinson's disease

Enhanced dopaminergic neurotoxicity mediated by MPTP in IL-32β transgenic mice

Parkinson's disease (PD) is a neurodegenerative disorder characterized by prominent loss of the nigral dopaminergic neurons and motor symptoms, such as resting tremor and bradykinesia. Evidence suggests that neuroinflammation may play a critical role in PD pathogenesis. Interleukin (IL)-32 is a newly-identified proinflammatory cytokine, which regulates innate and adaptive immune responses by activating p38 MAPK and NF-κB signaling pathways. The cytokine has been implicated in cancers and autoimmune, inflammatory, and infectious diseases. In this study, we attempted to identify the effects of IL-32β on dopaminergic neurotoxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), using IL-32β transgenic mice. Male wild type and IL-32β transgenic mice received intraperitoneal injections of vehicle or MPTP (15\ua0mg/kg\ua0×\ua04). Immunohistochemistry showed that overexpression of IL-32β significantly increased MPTP-mediated loss of dopaminergic neurons in the substantia nigra and deletion of tyrosine hydroxylase-positive fibers in the striatum. Dopamine depletion in the striatum and deficit in locomotor activity were enhanced in IL-32β transgenic mice. These results were accompanied by higher neuroinflammatory responses in the brains of transgenic mice. Finally, we found that IL-32β exaggerated MPTP-mediated activation of p38 MAPK and JNK pathways, which have been shown to be involved in MPTP neurotoxicity. These results suggest that IL-32β exacerbates MPTP neurotoxicity through enhanced neuroinflammatory responses

ALS/FTD-associated mutation in cyclin F inhibits ER-Golgi trafficking, inducing ER stress, ERAD and Golgi fragmentation

Abstract Amyotrophic lateral sclerosis (ALS) is a severely debilitating neurodegenerative condition that is part of the same disease spectrum as frontotemporal dementia (FTD). Mutations in the CCNF gene, encoding cyclin F, are present in both sporadic and familial ALS and FTD. However, the pathophysiological mechanisms underlying neurodegeneration remain unclear. Proper functioning of the endoplasmic reticulum (ER) and Golgi apparatus compartments is essential for normal physiological activities and to maintain cellular viability. Here, we demonstrate that ALS/FTD-associated variant cyclin FS621G inhibits secretory protein transport from the ER to Golgi apparatus, by a mechanism involving dysregulation of COPII vesicles at ER exit sites. Consistent with this finding, cyclin FS621G also induces fragmentation of the Golgi apparatus and activates ER stress, ER-associated degradation, and apoptosis. Induction of Golgi fragmentation and ER stress were confirmed with a second ALS/FTD variant cyclin FS195R, and in cortical primary neurons. Hence, this study provides novel insights into pathogenic mechanisms associated with ALS/FTD-variant cyclin F, involving perturbations to both secretory protein trafficking and ER-Golgi homeostasis