Theses (MSc. Medical and Health Sciences)

Loss of neurons, excessive accumulation of beta-amyloid (Aβ) peptides in certain brain regions along with accumulation and excessive stimulation of glutamate receptors in the central nervous system (CNS) are common pathological hallmarks of neurodegenerative disease such as Alzheimer’s disease (AD). Although a number of drugs have been approved for the treatment of AD, most of these synthetic drugs have diverse side effects and yield relatively modest benefits. Marine algae have great potential in pharmaceutical and biomedical applications as they are valuable sources of bioactive properties. Hence, this study aimed to provide an overview of potentials of Malaysian seaweeds (Padina australis, Sargassum polycystum, Turbinaria ornata and Caulerpa racemosa) in inhibiting cholinesterase (ChE) enzymes, Aβ-induced and glutamate-induced toxicity. Cholinesterase inhibitory activity was conducted using Ellman’s colorimetric assay while protective effects against Aβ-induced and glutamate-induced toxicity were assessed by determining percentage of viable cells using MTT assay. C. racemosa and S. polycystum showed the most potent anti-acetylcholinesterase activities with the IC50 values ranging from 0.086-0.115 mg/mL. Moreover, C. racemosa and T. ornata were also found to be active against butyrylcholinesterase with IC50 values ranging from 0.118-0.162 mg/mL. Seaweed with dual anti-cholinergic activity is an important finding in this study, as C. racemosa methanol extract and caulerpin exhibited very potent inhibitory activities against both enzymes. Besides that, methanol extract of C. racemosa and caulerpin showed very good neuroprotective effect against beta-amyloid1-42 induced toxicity. In evaluating glutamate-induced toxicity, T. ornata dichloromethane extract had 143.02% viable cells at 0.00030 mg/mL. Moreover, the cell viability continues to increase in the presence of seaweed extracts for other seaweeds extracts except T. ornata extracts. It is extremely noteworthy that the extracts that gave good ChE inhibition activity also gave best protection against Aβ and glutamate induced toxicity. These findings suggest that Malaysian seaweeds have potential to be used as neuroprotective agents in treatment of AD.

Mild Cognitive Impairment (MCI) is a heterogenous neuropsychological syndrome with high risk of progression to various neurodegenerative diseases especially Alzheimer’s disease (AD). Although the late stage of MCI is associated with neuro-modulatory kynurenine pathway (KP) dysregulation, the role of KP-induced neuroinflammation in MCI is still unclear. In addition, the lack of definite therapeutic treatment in MCI brings the concept of using mind-body therapies as alternative treatments to modulate the disease process. This study aimed to investigate the effect of short-term mindfulness meditation practice on the KP metabolites, enzymes and its modifying factors amongst the MCI population. Participants attending the memory clinics at Hospital Tuanku Ja’afar, Malaysia with Monteral Cognitive Assessment test score of 18-25 were randomized into meditation group (n=17, mean age 66.7±6.6 years) undertaking mindfulness practice (30 minutes daily following the audio guided instruction for 21 days) and non-meditation group (n=19, mean age 69.2±8.7 years) which served as control. Mindfulness meditation practice significantly increased serum concentrations of KP inducer, interferon-gamma (IFN-γ), (p<0.05), significantly decreased that of tryptophan (TRP) (p<0.05), and kynurenine (KYN) (p<0.05). Although not significant, higher serum concentrations of neuroprotectant picolinic acid (PIC), and lower concentrations of neurotoxic metabolites, 3-hydroxykynurenine (3-HK) and quinolinic acid (QUIN) were observed after practice. No significant changes were noted for other studied KP modifying factors; perceived negative emotional status assessed by depression, anxiety, stress scores (DASS-21), serum concentrations of cortisol, and brain-derived neurotrophic factor (BDNF). In addition, no changes in cardiovascular parameters (systolic-, diastolic- and mean arterial blood pressures and heart rate) were noted. As for the control group, serum concentrations of cortisol (p<0.01) and IFN-γ (p<0.001) were higher while TRP (p<0.05) were lower at 21 days. However, no significant changes in perceived emotional states, cardiovascular reactivity and KP metabolites were noted with a trend of increase in QUIN concentrations after 21 days. The observed decreasing trends of neurotoxic metabolites, 3-HK and QUIN, and the increasing trend of neuroprotective metabolite (PIC) may potentially ameliorate the neuroinflammatory process of MCI among the meditation group. The preliminary findings in this study highlight the need for longitudinal studies with larger sample sizes of longer interventional periods.

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Alzheimer’s disease (AD), the major cause of dementia, affects elderly population worldwide. Beta amyloid (Aβ) plagues are the main cause in the AD pathology, and removing the plagues is a constant challenge in the treatment of AD. Recently, depletion of receptor interacting protein kinase 1 (RIPK1) activity in murine AD models has been shown to reduce amyloid burden, memory deficits and the levels of inflammatory cytokines. Moreover, inhibition of RIPK1 has been shown to promote microglial degradation of Aβ in vitro. Necroptosis, a programmed form of necrosis, executed by mixed lineage kinase domain-like (MLKL) protein and activated by RIPK1 and RIPK3, has been shown to be involved in AD. However, the role of RIPK1 in Aβ-induced necroptosis is yet to be deciphered. In this study, SH-SY5Y human neuroblastoma cells treated with Aβ 1-40 or Aβ 1-42 was used as an AD model. Caspase activity assay and co-administration with caspase inhibitor or autophagy inhibitor showed that Aβ-induced neuronal cell death was independent of apoptosis and autophagy pathways. Furthermore, immunoblotting assay showed that Aβ-treated cells and cells overexpressing amyloid precursor protein (APP) activated iii RIPK1/MLKL-dependant necroptosis pathway. Moreover, depletion of RIPK1 expression rescued the cells from Aβ-induced neuronal cell death. In addition, ectopic expression of RIPK1 was found to prolong the stability of the endogenous APP. Transcriptomic analysis showed that the expression of RIPK1 was increased in AD patients, particularly in the hippocampus, entorhinal cortex and temporal cortex. Taken together, the present findings show that Aβ is able to activate necroptosis in an RIPK1-MLKL dependent manner, suggesting that RIPK1 plays an important role in the development of AD.

Background Alzheimer's disease (AD) is characterized by progressive cognitive decline in aging, a neurodegenerative disorder marked by amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs), resulting in synaptic dysfunction and neuronal loss. Recent research highlights the intricate interplay between mitochondrial dysfunction and the NLR family pyrin domain-containing 1 (NLRP1) inflammasome in AD pathogenesis, focusing on MIRO1, a mitochondrial Rho GTPase. MIRO1, crucial for mitochondrial transport, orchestrates NLRP1 inflammasome-mediated neuronal cell death in AD. Studies reveal MIRO1's role in activating the NLRP1 inflammasome in response to Aβ. Dysregulated mitochondrial dynamics, due to aberrant MIRO1, contribute to AD pathology, intensifying NLRP1 inflammasome activation, creating a vicious cycle of neuroinflammation and accelerating neuronal demise. This study elucidates MIRO1's functional role in Aβ-induced NLRP1 inflammasome-mediated neuronal pyroptosis and downstream signaling using Multidimensional Protein Identification Technology (MudPIT). Background Alzheimer's disease (AD) is characterized by progressive cognitive decline in aging, a neurodegenerative disorder marked by amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFTs), resulting in synaptic dysfunction and neuronal loss. Recent research highlights the intricate interplay between mitochondrial dysfunction and the NLR family pyrin domain-containing 1 (NLRP1) inflammasome in AD pathogenesis, focusing on MIRO1, a mitochondrial Rho GTPase. MIRO1, crucial for mitochondrial transport, orchestrates NLRP1 inflammasome-mediated neuronal cell death in AD. Studies reveal MIRO1's role in activating the NLRP1 inflammasome in response to Aβ. Dysregulated mitochondrial dynamics, due to aberrant MIRO1, contribute to AD pathology, intensifying NLRP1 inflammasome activation, creating a vicious cycle of neuroinflammation and accelerating neuronal demise. This study elucidates MIRO1's functional role in Aβ-induced NLRP1 inflammasome-mediated neuronal pyroptosis and downstream signaling using Multidimensional Protein Identification Technology (MudPIT). MIRO1 knockout (KO) exacerbated MMP depolarization and tau hyperphosphorylation upon Aβ-induced NLRP1 activation on neuronal cells. However, MIRO1 KO did not elevate but downregulated the caspase-1 activation upon Aβ-induced NLRP1 activation on neuronal cells. MudPIT results showed that PSMC5 as one of the differentially upregulated genes when MIRO1 KO was introduced in Aβ-induced NLRP1-mediated pyroptosis through proteasome pathway in AD. Conclusion Results indicated that MIRO1 modulated MMP, tau production, and caspase-1 activation in response to Aβ-induced NLRP1 activation pyroptosis. PSMC5 was found to regulate MIRO1 through the proteasome pathway in AD, with Carfilzomib, a PSMC5 inhibitor, suggesting a potential therapeutic approach for AD.