Amyloid-β pathology is attenuated by tauroursodeoxycholic acid treatment in APP/PS1 mice after disease onset

GSK3: A Kinase Balancing Promotion and Resolution of Inflammation

GSK3 has been implicated for years in the regulation of inflammation and addressed in a plethora of scientific reports using a variety of experimental (disease) models and approaches. However, the specific role of GSK3 in the inflammatory process is still not fully understood and controversially discussed. Following a detailed overview of structure, function, and various regulatory levels, this review focusses on the immunoregulatory functions of GSK3, including the current knowledge obtained from animal models. Its impact on pro-inflammatory cytokine/chemokine profiles, bacterial/viral infections, and the modulation of associated pro-inflammatory transcriptional and signaling pathways is discussed. Moreover, GSK3 contributes to the resolution of inflammation on multiple levels, e.g., via the regulation of pro-resolving mediators, the clearance of apoptotic immune cells, and tissue repair processes. The influence of GSK3 on the development of different forms of stimulation tolerance is also addressed. Collectively, the role of GSK3 as a kinase balancing the initiation/perpetuation and the amelioration/resolution of inflammation is highlighted.

Non-polyphenolic natural inhibitors of amyloid aggregation

Protein misfolding diseases (PMDs) are chronic and progressive, with no effective therapy so far. Aggregation and misfolding of amyloidogenic proteins are closely associated with the onset and progression of PMDs, such as amyloid-β (Aβ) in Alzheimer's disease, α-Synuclein (α-Syn) in Parkinson's disease and human islet amyloid polypeptide (hIAPP) in type 2 diabetes. Inhibiting toxic aggregation of amyloidogenic proteins is regarded as a promising therapeutic approach in PMDs. The past decade has witnessed the rapid progresses of this field, dozens of inhibitors have been screened and verified in vitro and in vivo, demonstrating inhibitory effects against the aggregation and misfolding of amyloidogenic proteins, together with beneficial effects. Natural products are major sources of small molecule amyloid inhibitors, a number of natural derived compounds have been identified with great bioactivities and translational prospects. Here, we review the non-polyphenolic natural inhibitors that potentially applicable for PMDs treatment, along with their working mechanisms. Future directions are proposed for the development and clinical applications of these inhibitors.

Alzheimer's disease: The derailed repair hypothesis

A lot of research has been done on Alzheimer's disease, especially focused on factors like amyloid beta, ApoE and tau-protein. However, a complete theory on the disease mechanism of AD, including and connecting all known pathological elements of AD in a conceivable context and order of occurrence, is still lacking. In this article I describe a hypothesis on the entire pathophysiology of Alzheimer's disease, based on the most wellknown pathological elements in AD, filling the gaps with hypothetical mechanisms. This proposed mechanism of derailed repair starts with an insufficiently increased level of injury signalling in the axon by ApoE, DLK, APP, BACE-1, Aβ and iPLA2β, followed by an excessive repair response induced by opening of the mitochondrial permeability transition pore, release of mitochondrial CoA and activation of palmitoylation and massive endocytosis. Excessive compounds, associated with injury signalling and repair, start to accumulate, adding to axonal injury. This increased activation of the repair mechanism causes exhaustion of the repair response by lack of mitochondrial CoA. A vicious circle of increased injury signalling and insufficient repair ensues. Based on this hypothesis, I propose possible markers for early diagnosis and disease-modifying treatments for Alzheimer's disease.

Increased ileal bile acid binding protein and galectin-9 are associated with mild cognitive impairment and Alzheimer's disease

Enterocyte damage and subsequent microbial translocation drive neuroinflammation in the pathogenesis of Alzheimer's disease (AD). Human ileal bile acid binding protein (I-BABP) and intestinal fatty acid binding proteins (I-FABP) are the indicators of enterocyte damage. Lipopolysaccharide-binding protein (LBP) is an indirect marker of microbial translocation. The activation of peripheral innate immune cells plays a crucial role in modulating AD progression. Galectin-9 is a versatile immunomodulatory molecule. The purpose of this study was to determine I-FABP, I-BABP, LBP, and galectin-9 levels in MCI and AD and investigate the relationship between I-FABP, I-BABP, LBP and galectin-9. In this study, I-FABP, I-BABP, LBP, and galectin-9 levels were measured using ELISA assay in 115 AD patients, 115 MCI patients, and 115 non-demented control subjects. Increased I-BABP and galectin-9 were observed in MCI and AD patients. Furthermore, AD patients had higher I-BABP and galectin-9 levels compared with MCI patients. However, I-FABP and LBP in three groups had no difference. I-BABP levels were positively correlated with galectin-9, after adjusting confounding factors (r = 0.409, p < 0.001). In addition, multivariate analysis revealed that increased I-BABP and galectin-9 levels were significantly associated with reduced mini-mental state examination (MMSE) score. In conclusion, galectin-9 is correlated with I-BABP after adjusting confounding covariates. Moreover, increased I-BABP and galectin-9 in MCI and AD are significant factors for reduced MMSE score. Further studies are needed.

Ursodeoxycholic acid: a promising therapeutic target for inflammatory bowel diseases?

The secondary bile acid ursodeoxycholic acid (UDCA) has long been known to have medicinal properties. As the therapeutically active component of bear bile, it has been used for centuries in traditional Chinese medicine to treat a range of conditions, while manufactured UDCA has been used for decades in Western medicine to treat cholestatic liver diseases. The beneficial qualities of UDCA are thought to be due to its well-established cytoprotective and anti-inflammatory actions. In addition to its established role in treating liver diseases, UDCA is now under investigation for numerous conditions associated with inflammation and apoptosis, including neurological, ocular, metabolic, and cardiovascular diseases. Here, we review the growing evidence base from in vitro and in vivo models to suggest that UDCA may also have a role to play in the therapy of inflammatory bowel diseases.

Gut Microbiota and Microbiota-Related Metabolites as Possible Biomarkers of Cognitive Aging

Gut microbiota composition and functionality can influence the pathophysiology of age-related cognitive impairment and dementia, according to a large number of animal studies. The translation of this concept to humans is still uncertain, due to the relatively low number of clinical studies focused on fecal microbiota and large number of environmental factors that influence the microbiota composition. However, the fecal microbiota composition of older patients with dementia is deeply different from that of healthy active controls, conditioning a different metabolic profile. The possible use of fecal microbiota-related parameters and microbiota-derived metabolites as biomarkers of cognitive performance and dementia is critically reviewed in this paper, focusing on the most promising areas of research for the future.

A cell-based high-throughput screening method to directly examine transthyretin amyloid fibril formation at neutral pH

Transthyretin (TTR) is a major amyloidogenic protein associated with hereditary (ATTRm) and nonhereditary (ATTRwt) intractable systemic transthyretin amyloidosis. The pathological mechanisms of ATTR-associated amyloid fibril formation are incompletely understood, and there is a need for identifying compounds that target ATTR. C-terminal TTR fragments are often present in amyloid-laden tissues of most patients with ATTR amyloidosis, and on the basis of in vitro studies, these fragments have been proposed to play important roles in amyloid formation. Here, we found that experimentally-formed aggregates of full-length TTR are cleaved into C-terminal fragments, which were also identified in patients' amyloid-laden tissues and in SH-SY5Y neuronal and U87MG glial cells. We observed that a 5-kDa C-terminal fragment of TTR, TTR81-127, is highly amyloidogenic in vitro, even at neutral pH. This fragment formed amyloid deposits and induced apoptosis and inflammatory gene expression also in cultured cells. Using the highly amyloidogenic TTR81-127 fragment, we developed a cell-based high-throughput screening method to discover compounds that disrupt TTR amyloid fibrils. Screening a library of 1280 off-patent drugs, we identified two candidate repositioning drugs, pyrvinium pamoate and apomorphine hydrochloride. Both drugs disrupted patient-derived TTR amyloid fibrils ex vivo, and pyrvinium pamoate also stabilized the tetrameric structure of TTR ex vivo in patient plasma. We conclude that our TTR81-127-based screening method is very useful for discovering therapeutic drugs that directly disrupt amyloid fibrils. We propose that repositioning pyrvinium pamoate and apomorphine hydrochloride as TTR amyloid-disrupting agents may enable evaluation of their clinical utility for managing ATTR amyloidosis.

Nutritional Modulation of Immune and Central Nervous System Homeostasis: The Role of Diet in Development of Neuroinflammation and Neurological Disease

The gut-microbiome-brain axis is now recognized as an essential part in the regulation of systemic metabolism and homeostasis. Accumulating evidence has demonstrated that dietary patterns can influence the development of metabolic alterations and inflammation through the effects of nutrients on a multitude of variables, including microbiome composition, release of microbial products, gastrointestinal signaling molecules, and neurotransmitters. These signaling molecules are, in turn, implicated in the regulation of the immune system, either promoting or inhibiting the production of pro-inflammatory cytokines and the expansion of specific leukocyte subpopulations, such as Th17 and Treg cells, which are relevant in the development of neuroinflammatory and neurodegenerative conditions. Metabolic diseases, like obesity and type 2 diabetes mellitus, are related to inadequate dietary patterns and promote variations in the aforementioned signaling pathways in patients with these conditions, which have been linked to alterations in neurological functions and mental health. Thus, maintenance of adequate dietary patterns should be an essential component of any strategy aiming to prevent neurological pathologies derived from systemic metabolic alterations. The present review summarizes current knowledge on the role of nutrition in the modulation of the immune system and its impact in the development of neuroinflammation and neurological disease.

Tauroursodeoxycholic acid (TUDCA) abolishes chronic high salt-induced renal injury and inflammation

AIM

Chronic high salt intake exaggerates renal injury and inflammation, especially with the loss of functional ET_B receptors. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and bile salt that is approved for the treatment of hepatic diseases. Our aim was to determine whether TUDCA is reno-protective in a model of ET_B receptor deficiency with chronic high salt-induced renal injury and inflammation.

METHODS

ET_B -deficient and transgenic control rats were placed on normal (0.8% NaCl) or high salt (8% NaCl) diet for 3 weeks, receiving TUDCA (400 mg/kg/d; ip) or vehicle. Histological and biochemical markers of kidney injury, renal cell death and renal inflammation were assessed.

RESULTS

In ET_B -deficient rats, high salt diet significantly increased glomerular and proximal tubular histological injury, proteinuria, albuminuria, excretion of tubular injury markers KIM-1 and NGAL, renal cortical cell death and renal CD4⁺ T cell numbers. TUDCA treatment increased proximal tubule megalin expression as well as prevented high salt diet-induced glomerular and tubular damage in ET_B -deficient rats, as indicated by reduced kidney injury markers, decreased glomerular permeability and proximal tubule brush border restoration, as well as reduced renal inflammation. However, TUDCA had no significant effect on blood pressure.

CONCLUSIONS

TUDCA protects against the development of glomerular and proximal tubular damage, decreases renal cell death and inflammation in the renal cortex in rats with ET_B receptor dysfunction on a chronic high salt diet. These results highlight the potential use of TUDCA as a preventive tool against chronic high salt induced renal damage.

Altered bile acid profile associates with cognitive impairment in Alzheimer's disease-An emerging role for gut microbiome

INTRODUCTION

Increasing evidence suggests a role for the gut microbiome in central nervous system disorders and a specific role for the gut-brain axis in neurodegeneration. Bile acids (BAs), products of cholesterol metabolism and clearance, are produced in the liver and are further metabolized by gut bacteria. They have major regulatory and signaling functions and seem dysregulated in Alzheimer's disease (AD).

METHODS

Serum levels of 15 primary and secondary BAs and their conjugated forms were measured in 1464 subjects including 370 cognitively normal older adults, 284 with early mild cognitive impairment, 505 with late mild cognitive impairment, and 305 AD cases enrolled in the AD Neuroimaging Initiative. We assessed associations of BA profiles including selected ratios with diagnosis, cognition, and AD-related genetic variants, adjusting for confounders and multiple testing.

RESULTS

In AD compared to cognitively normal older adults, we observed significantly lower serum concentrations of a primary BA (cholic acid [CA]) and increased levels of the bacterially produced, secondary BA, deoxycholic acid, and its glycine and taurine conjugated forms. An increased ratio of deoxycholic acid:CA, which reflects 7α-dehydroxylation of CA by gut bacteria, strongly associated with cognitive decline, a finding replicated in serum and brain samples in the Rush Religious Orders and Memory and Aging Project. Several genetic variants in immune response-related genes implicated in AD showed associations with BA profiles.

DISCUSSION

We report for the first time an association between altered BA profile, genetic variants implicated in AD, and cognitive changes in disease using a large multicenter study. These findings warrant further investigation of gut dysbiosis and possible role of gut-liver-brain axis in the pathogenesis of AD.

Translating the biology of aging into novel therapeutics for Alzheimer disease

Aging is the leading risk factor for most chronic illnesses of old age, including Alzheimer disease (AD), a progressive neurodegenerative disease with currently no therapies that prevent, slow, or halt disease progression. Like other chronic diseases of old age, the progressive pathology of AD begins decades before the onset of symptoms. Many decades of research in biological gerontology have revealed common processes that are relevant to understanding why the aging brain is vulnerable to AD. In this review, we frame the development of novel therapeutics for AD in the context of biological gerontology. The many therapies currently in development based on biological gerontology principles provide promise for the development of a new generation of therapeutics to prevent and treat AD.

Ursodeoxycholic Acid Improves Mitochondrial Function and Redistributes Drp1 in Fibroblasts from Patients with Either Sporadic or Familial Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia worldwide. Mitochondrial abnormalities have been identified in many cell types in AD, with deficits preceding the development of the classical pathological aggregations. Ursodeoxycholic acid (UDCA), a treatment for primary biliary cirrhosis, improves mitochondrial function in fibroblasts derived from Parkinson's disease patients as well as several animal models of AD and Parkinson's disease. In this paper, we investigated both mitochondrial function and morphology in fibroblasts from patients with both sporadic and familial AD. We show that both sporadic AD (sAD) and PSEN1 fibroblasts share the same impairment of mitochondrial membrane potential and alterations in mitochondrial morphology. Mitochondrial respiration, however, was decreased in sAD fibroblasts and increased in PSEN1 fibroblasts. Morphological changes seen in AD fibroblasts include reduced mitochondrial number and increased mitochondrial clustering around the cell nucleus as well as an increased number of long mitochondria. We show here for the first time in AD patient tissue that treatment with UDCA increases mitochondrial membrane potential and respiration as well as reducing the amount of long mitochondria in AD fibroblasts. In addition, we show reductions in dynamin-related protein 1 (Drp1) level, particularly the amount localized to mitochondria in both sAD and familial patient fibroblasts. Drp1 protein amount and localization were increased after UDCA treatment. The restorative effects of UDCA are abolished when Drp1 is knocked down. This paper highlights the potential use of UDCA as a treatment for neurodegenerative disease.

Ellagic acid ameliorates learning and memory impairment in APP/PS1 transgenic mice via inhibition of β-amyloid production and tau hyperphosphorylation

β-amyloid (Aβ) aggregation and tau hyperphosphorylation are considered to be the primary pathological hallmarks of Alzheimer's disease (AD). Targeted inhibition of these pathological processes may provide effective treatments for AD. Accumulating evidence has demonstrated that ellagic acid (EA) exerts neuroprotective effects in several diseases. The present study investigated the effects of EA on AD-associated learning and memory deficits on APP/PS1 double transgenic mice and the underlying mechanisms. APP/PS1 mice or wild-type C57BL/6 mice were intragastrically administered EA (50 mg/kg/day) or vehicle for 60 consecutive days. The learning and memory abilities of mice were investigated using the Morris water maze test. Hippocampal regions were examined for the presence of amyloid plaques, neuronal apoptosis and tau phosphorylation. Expression levels of APP, Aβ, RAC-αserine/threonine-protein kinase and glycogen synthase kinase (GSK)3β in the hippocampus were determined by western blot analysis and ELISA. The results demonstrated that EA treatment ameliorated spatial learning and memory impairment in APP/PS1 mice and significantly reduced neuronal apoptosis and Aβ deposition in the hippocampus (P<0.05 and P<0.01). In addition, EA significantly inhibited the hyperphosphorylation of tau and significantly decreased the activity of glycogen synthase kinase (GSK)3β (P<0.01), which is involved in tau phosphorylation. Overall, these findings indicated that the beneficial effects of EA on AD-associated cognitive impairments may be attributed to the inhibition of Aβ production and tau hyperphosphorylation, and its beneficial action may be mediated in part, by the RAC-α serine/threonine-protein kinase/GSK3β signaling pathway.

Next-generation biomarker discovery in Alzheimer's disease using metabolomics - from animal to human studies

Alzheimer's disease (AD) is a complex disease driven mainly by neuronal loss due to accumulation of intracellular neurofibrillary tangles and amyloid β aggregates in the brain. The diagnosis of AD currently relies on clinical symptoms while the disease can only be confirmed at autopsy. The few available biomarkers allowing for diagnosis are typically detected many years after the onset of the disease. New diagnostic approaches, particularly in easily-accessible biofluids, are essential. By providing an exhaustive information of the phenotype, metabolomics is an ideal approach for identification of new biomarkers. This review investigates the current position of metabolomics in the field of AD research, focusing on animal and human studies, and discusses the improvements carried out over the past decade.

The neuroprotective effect of deep brain stimulation at nucleus basalis of Meynert in transgenic mice with Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common type of dementia and mainly treated by drugs, while the therapeutic outcomes are very limited. This study aimed to determine the optimized parameters of deep brain stimulation (DBS) which was applied to the treatment of AD and propose the involved mechanisms.

METHODS

Amyloid-β precursor protein/Presenilin1 (APP/PS1) transgenic mice were used and received DBS at nucleus basalis of Meynert (NBM). The optimized parameters of DBS were determined by using different stimulation frequencies, durations and ages of mice under Morris water maze test. The involved mechanisms and the possible signal pathways were also investigated.

RESULTS

The optimized parameters for DBS were high frequency (100 Hz) for 21 days starting from early age (4 months old). Under the above parameters, the soluble Aβ40 and Aβ42 in the hippocampus and cortex were down-regulated significantly. DBS increased survival neurons and reduced apoptotic cells in the hippocampus and cortex. Meanwhile, the apoptosis-related proteins caspase-3, caspase-8 and Bid were down-regulated. Moreover, DBS caused a significant increase of superoxide dismutase, glutathione peroxidase and choline acetyltransferase activity as well as a decrease of methane dicarboxylic aldehyde content and acetylcholine esterase activity. Phosphorylation of Akt (p-Akt)/total Akt (t-Akt) was up-regulated while p-extracellular signal-regulated kinase 1/2 (ERK1/2)/t-ERK1/2 was down-regulated. The neuroprotective effect of DBS was attenuated by their inhibitors.

CONCLUSIONS

NBM-DBS starting from 4 months of age for 21 days at a high frequency (100 Hz) has therapeutic effects on AD through activating phosphatidylinositol 3'-kinase (PI3K)/Akt pathway and inhibiting ERK1/2 pathway.

MALDI Mass Spectral Imaging of Bile Acids Observed as Deprotonated Molecules and Proton-Bound Dimers from Mouse Liver Sections

Bile acids (BAs) play two vital roles in living organisms, as they are involved in (1) the secretion of cholesterol from liver, and (2) the lipid digestion/absorption in the intestine. Abnormal bile acid synthesis or secretion can lead to severe liver disorders. Even though there is extensive literature on the mass spectrometric determination of BAs in biofluids and tissue homogenates, there are no reports on the spatial distribution in the biliary network of the liver. Here, we demonstrate the application of high mass resolution/mass accuracy matrix-assisted laser desorption/ionization (MALDI)-Fourier-transform ion cyclotron resonance (FTICR) to MS imaging (MSI) of BAs at high spatial resolutions (pixel size, 25 μm). The results show chemical heterogeneity of the mouse liver sections with a number of branching biliary and blood ducts. In addition to ion signals from deprotonation of the BA molecules, MALDI-MSI generated several further intense signals at larger m/z for the BAs. These signals were spatially co-localized with the deprotonated molecules and easily misinterpreted as additional products of BA biotransformations. In-depth analysis of accurate mass shifts and additional electrospray ionization and MALDI-FTICR experiments, however, confirmed them as proton-bound dimers. Interestingly, dimers of bile acids, but also unusual mixed dimers of different taurine-conjugated bile acids and free taurine, were identified. Since formation of these complexes will negatively influence signal intensities of the desired [M - H]^- ions and significantly complicate mass spectral interpretations, two simple broadband techniques were proposed for non-selective dissociation of dimers that lead to increased signals for the deprotonated BAs. Graphical Abstract ᅟ.

Harnessing Gut Microbes for Mental Health: Getting From Here to There

There has been an explosion of interest in the study of microorganisms inhabiting the gastrointestinal tract (gut microbiota) and their impact on host health and physiology. Accumulating data suggest that altered communication between gut microbiota and host systems could participate in disorders such as obesity, diabetes mellitus, and autoimmune disorders as well as neuropsychiatric disorders, including autism, anxiety, and major depressive disorders. The conceptual development of the microbiome-gut-brain axis has facilitated understanding of the complex and bidirectional networks between gastrointestinal microbiota and their host, highlighting potential mechanisms through which this environment influences central nervous system physiology. Communication pathways between gut microbiota and the central nervous system could include autonomic, neuroendocrine, enteric, and immune systems, with pathology resulting in disruption to neurotransmitter balance, increases in chronic inflammation, or exacerbated hypothalamic-pituitary-adrenal axis activity. However, uncertainty remains regarding the generalizability of controlled animal studies to the more multifaceted pattern of human pathophysiology, especially with regard to the therapeutic potential for neuropsychiatric health. This narrative review summarizes current understanding of gut microbial influence over physiological function, with an emphasis on neurobehavioral and neurological impairment based on growing understanding of the gut-brain axis. Experimental and clinical data regarding means of therapeutic manipulation of gut microbiota as a novel treatment option for mental health are described, and important knowledge gaps are identified and discussed.

Alzheimer's disease pathology and the unfolded protein response: prospective pathways and therapeutic targets

Many vital interdependent cellular functions including proteostasis, lipogenesis and Ca homeostasis are executed by the endoplasmic reticulum (ER). Exogenous insults can impair ER performance: this must be rapidly corrected or cell death will ensue. Protective adaptations can boost the functional capacity of the ER and form the basis of the unfolded protein response (UPR). Activated in response to the accumulation of misfolded proteins, the UPR can halt protein translation while increasing protein-handling chaperones and the degradation of erroneous proteins through a conserved three-tier molecular cascade. However, prolonged activation of the UPR can result in the maladaptation of the system, resulting in the activation of inflammatory and apoptotic effectors. Recently, UPR and its involvement in neurodegenerative disease has attracted much interest and numerous potentially 'drugable' points of crosstalk are now emerging. Here, we summarize the functions of the ER and UPR, and highlight evidence for its potential role in the pathogenesis of Alzheimer's disease, before discussing several key targets with therapeutic potential.

Emerging roles of ER stress in the etiology and pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by synaptic dysfunction and accumulation of abnormal aggregates formed by amyloid-β peptides or phosphorylated tau proteins. Accumulating evidence suggests that alterations in the buffering capacity of the proteostasis network are a salient feature of AD. The endoplasmic reticulum (ER) is the main compartment involved in protein folding and secretion and is drastically affected in AD neurons. ER stress triggers the activation of the unfolded protein response (UPR), a signal transduction pathway that enforces adaptive programs to recover homeostasis or trigger apoptosis of irreversibly damaged cells. Experimental manipulation of specific UPR signaling modules in preclinical models of AD has revealed a key role of this pathway in regulating protein misfolding and neurodegeneration. Recent studies suggest that the UPR also influences synaptic plasticity and memory through ER stress-independent mechanisms. Consequently, targeting of the UPR in AD is emerging as an interesting therapeutic approach to modify the two pillars of AD, protein misfolding and synaptic failure. Here, we review the functional role of ER stress signaling in AD, discussing the complex involvement of the pathway in controlling neuronal survival, the amyloid cascade, neurodegeneration and synaptic function. Recent intervention efforts to target the UPR with pharmacological and gene therapy strategies are also discussed.

Targeting the enhanced ER stress response in Marinesco-Sjögren syndrome

BACKGROUND AND OBJECTIVE

Marinesco-Sjögren syndrome (MSS) is an autosomal recessive infantile-onset disorder characterized by cataracts, cerebellar ataxia, and progressive myopathy caused by mutation of SIL1. In mice, a defect in SIL1 causes endoplasmic reticulum (ER) chaperone dysfunction, leading to unfolded protein accumulation and increased ER stress. However, ER stress and the unfolded protein response (UPR) have not been investigated in MSS patient-derived cells.

METHODS

Lymphoblastoid cell lines (LCLs) were established from four MSS patients. Spontaneous and tunicamycin-induced ER stress and the UPR were investigated in MSS-LCLs. Expression of UPR markers was analyzed by western blotting. ER stress-induced apoptosis was analyzed by flow cytometry. The cytoprotective effects of ER stress modulators were also examined.

RESULTS

MSS-LCLs exhibited increased spontaneous ER stress and were highly susceptible to ER stress-induced apoptosis. The inositol-requiring protein 1α (IRE1α)-X-box-binding protein 1 (XBP1) pathway was mainly upregulated in MSS-LCLs. Tauroursodeoxycholic acid (TUDCA) attenuated ER stress-induced apoptosis.

CONCLUSION

MSS patient-derived cells exhibit increased ER stress, an activated UPR, and susceptibility to ER stress-induced death. TUDCA reduces ER stress-induced death of MSS patient-derived cells. The potential of TUDCA as a therapeutic agent for MSS could be explored further in preclinical studies.

Tauroursodeoxycholic bile acid arrests axonal degeneration by inhibiting the unfolded protein response in X-linked adrenoleukodystrophy

The activation of the highly conserved unfolded protein response (UPR) is prominent in the pathogenesis of the most prevalent neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), which are classically characterized by an accumulation of aggregated or misfolded proteins. This activation is orchestrated by three endoplasmic reticulum (ER) stress sensors: PERK, ATF6 and IRE1. These sensors transduce signals that induce the expression of the UPR gene programme. Here, we first identified an early activator of the UPR and investigated the role of a chronically activated UPR in the pathogenesis of X-linked adrenoleukodystrophy (X-ALD), a neurometabolic disorder that is caused by ABCD1 malfunction; ABCD1 transports very long-chain fatty acids (VLCFA) into peroxisomes. The disease manifests as inflammatory demyelination in the brain or and/or degeneration of corticospinal tracts, thereby resulting in spastic paraplegia, with the accumulation of intracellular VLCFA instead of protein aggregates. Using X-ALD mouse model (Abcd1⁻ and Abcd1⁻/Abcd2^−/− mice) and X-ALD patient’s fibroblasts and brain samples, we discovered an early engagement of the UPR. The response was characterized by the activation of the PERK and ATF6 pathways, but not the IRE1 pathway, showing a difference from the models of AD, PD or ALS. Inhibition of PERK leads to the disruption of homeostasis and increased apoptosis during ER stress induced in X-ALD fibroblasts. Redox imbalance appears to be the mechanism that initiates ER stress in X-ALD. Most importantly, we demonstrated that the bile acid tauroursodeoxycholate (TUDCA) abolishes UPR activation, which results in improvement of axonal degeneration and its associated locomotor impairment in Abcd1⁻/Abcd2^−/− mice. Altogether, our preclinical data provide evidence for establishing the UPR as a key drug target in the pathogenesis cascade. Our study also highlights the potential role of TUDCA as a treatment for X-ALD and other axonopathies in which similar molecular mediators are implicated.

Effects of bile acids on neurological function and disease

Bile acids are synthesized from cholesterol and are known to be involved with the emulsification and digestion of dietary lipids and fat-soluble vitamins. Outside of this role, bile acids can act as cell signaling effectors through binding and activating receptors on both the cell membrane and nucleus. Numerous reports have investigated these signaling pathways in conditions where the liver is damaged. More recently, effort has been made to investigate the role of bile acids in diseases outside of those associated with liver damage. This review summarizes recent findings on the influences that bile acids can exert in normal neurological function and their contribution to diseases of the nervous system, with the intent of highlighting the role of these metabolites as potential players in neurological disorders.-McMillin, M., DeMorrow, S. Effects of bile acids on neurological function and disease.

Protection of tauroursodeoxycholic acid on high glucose-induced human retinal microvascular endothelial cells dysfunction and streptozotocin-induced diabetic retinopathy rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tauroursodeoxycholic acid (TUDCA), one of the main ingredients from bear gall which hold "Clearing heat and detoxification, Removing liver fire for improving eyesight" functions, is formed by the conjugation of ursodeoxycholic acid (UDCA) with taurine. However, the limited information of TUDCA on protecting diabetic retinopathy (DR) has been known. The present study was conducted to evaluate the protection of TUDCA on high glucose-induced human retinal microvascular endothelial cells (HRMECs) dysfunction and streptozotocin (STZ)-induced diabetic retinopathy (DR) rats and the possible mechanism underlying was also explored.

MATERIALS AND METHODS

The proliferation of high glucose-induced HRMECs was determined by MTT assay. DR rats' model was established by an administration of high-glucose-fat diet and an intraperitoneal injection of STZ (30mg/kg). The cell supernatant and rats' serum were collected for the assays of NO content by ELISA kits. Retinas were stained with hematoxylin and eosin (HE) to observe pathological changes. Immunohistochemical assay was applied to examine the protein expression of ICAM-1, NOS, NF-κB p65 and VEGF in rat retinas. Furthermore, western blot analysis was carried out to examine the protein expression of ICAM-1, NOS, NF-κB p65 and VEGF in high glucose-induced HRMECs.

RESULTS

After treating with TUDCA, high glucose-induced HRMECs proliferation could be significantly inhibited. TUDCA (5.0μM, 25.0μM and 125.0μM) could decrease NO content in high glucose-induced HRMECs. Furthermore, TUDCA (500mg/kg/d and 250mg/kg/d) also decrease NO content in serum of DR rats. Additionally, both immunocytochemistry analysis and western blot analysis showed that the over-expression of ICAM-1, NOS, NF-κB p65 and VEGF were significantly decreased by TUDCA.

CONCLUSION

The data indicated that TUDCA could ameliorate DR by decreasing NO content and down-regulating the protein expression of ICAM-1, NOS, NF-κB p65 and VEGF. Thus, our experimental results suggested that TUDCA might be a potential drug for the prevention and treatment of DR.

Atorvastatin ameliorates cognitive impairment, Aβ1-42 production and Tau hyperphosphorylation in APP/PS1 transgenic mice

Amyloid-beta (Aβ) interacts with the serine/threonine protein kinase AKT (also known as protein kinase B)/glycogen synthase kinase 3β (GSK3β) pathway and deactivates GSK3β signaling, which result in microtubule protein tau phosphorylation. Atorvastatin, a HMG-CoA reductase inhibitor, has been proven to improve learning and memory performance, reduce Aβ and phosphorylated tau levels in mouse model of Alzheimer's disease (AD). However, it still remains unclear whether atorvastatin is responsible for regulation of AKT/GSK3β signaling and contributes to subsequent down-regulation of Aβ1-42 and phosphorylated tau in APP/PS1 transgenic (Tg APP/PS1) mice. Herein, we aimed to investigate the possible impacts of atorvastatin (10 mg/kg, p.o.) on the memory deficit by behavioral tests and changes of AKT/GSK3β signaling in hippocampus and prefrontal cortex by western blot test in Tg APP/PS1 mice. The results showed that treatment with atorvastatin significantly reversed the memory deficit in the Tg APP/PS1 mice in a novel object recognition and the Morris water maze tests. Moreover, atorvastatin significantly attenuated Aβ1-42 accumulation and phosphorylation of tau (Ser396) in the hippocampus and prefrontal cortex of Tg APP/PS1 mice. In addition, atorvastatin treatment also increased phosphorylation of AKT, inhibited GSK3β activity by increasing phosphorylation of GSK3β (Ser9) and decreasing the beta-site APP cleaving enzyme 1 (BACE1) expression. These results indicated that the memory ameliorating effect of atorvastatin may be, in part, by regulation the AKT/GSK3β signaling which may contribute to down-regulation of Aβ1-42 and tau hyperphosphorylation.

Neuroprotective effect of β-asarone against Alzheimer's disease: regulation of synaptic plasticity by increased expression of SYP and GluR1

Aim

β-asarone, an active component of Acori graminei rhizome, has been reported to have neuroprotective effects in Alzheimer’s disease. As the underlying mechanism is not known, we investigated the neuroprotective effects of β-asarone in an APP/PS1 double transgenic mouse model and in NG108 cells.

Materials and methods

APPswe/PS1dE9 double transgenic male mice were randomly assigned to a model group, β-asarone treatment groups (21.2, 42.4, or 84.8 mg/kg/d), or donepezil treatment group (2 mg/kg/d). Donepezil treatment was a positive control, and background- and age-matched wild-type B6 mice were an external control group. β-asarone (95.6% purity) was dissolved in 0.8% Tween 80 and administered by gavage once daily for 2.5 months. Control and model animals received an equal volume of vehicle. After 2.5 months of treatment, behavior of all animals was evaluated in a Morris water maze. Expression of synaptophysin (SYP) and glutamatergic receptor 1 (G1uR1) in the hippocampus and cortex of the double transgenic mice was assayed by Western blotting. The antagonistic effects of β-asarone against amyloid-β peptide (Aβ) were investigated in vitro in the NG108-15 cell line. After 24 hours of incubation, cells were treated with 10 μm Aβ with or without β-asarone at different concentrations (6.25, 12.5, or 25 μM) for an additional 36 hours. The cytotoxicity of β-asarone was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay of cell viability, and cell morphology was evaluated by bright-field microscopy after 24 hours of treatment. The expression of SYP and GluR1 in cells was detected by Western blot assay in the hippocampus and brain cortex tissues of mice.

Results

β-asarone at a high dose reduced escape latency and upregulated SYP and GluR1 expression at both medium and high doses. Cell morphology evaluation showed that β-asarone treatment did not result in obvious cell surface spots and cytoplasmic granularity. β-asarone had a dose-dependent effect on cell proliferation.

Conclusion

β-asarone antagonized the Aβ neurotoxicity in vivo, improved the learning and memory ability of APP/PS1 mice, and increased the expression of SYP and GluR1 both in vivo and in vitro. Thus, β-asarone may be a potential drug for the treatment of Alzheimer’s disease.

Brain endoplasmic reticulum stress mechanistically distinguishes the saline-intake and hypertensive response to deoxycorticosterone acetate-salt

Endoplasmic reticulum stress has become an important mechanism in hypertension. We examined the role of endoplasmic reticulum stress in mediating the increased saline-intake and hypertensive effects in response to deoxycorticosterone acetate (DOCA)-salt. Intracerebroventricular delivery of the endoplasmic reticulum stress-reducing chemical chaperone tauroursodeoxycholic acid did not affect the magnitude of hypertension, but markedly decreased saline-intake in response to DOCA-salt. Increased saline-intake returned after tauroursodeoxycholic acid was terminated. Decreased saline-intake was also observed after intracerebroventricular infusion of 4-phenylbutyrate, another chemical chaperone. Immunoreactivity to CCAAT homologous binding protein, a marker of irremediable endoplasmic reticulum stress, was increased in the subfornical organ and supraoptic nucleus of DOCA-salt mice, but the signal was absent in control and CCAAT homologous binding protein-deficient mice. Electron microscopy revealed abnormalities in endoplasmic reticulum structure (decrease in membrane length, swollen membranes, and decreased ribosome numbers) in the subfornical organ consistent with endoplasmic reticulum stress. Subfornical organ-targeted adenoviral delivery of GRP78, a resident endoplasmic reticulum chaperone, decreased DOCA-salt-induced saline-intake. The increase in saline-intake in response to DOCA-salt was blunted in CCAAT homologous binding protein-deficient mice, but these mice exhibited a normal hypertensive response. We conclude that (1) brain endoplasmic reticulum stress mediates the saline-intake, but not blood pressure response to DOCA-salt, (2) DOCA-salt causes endoplasmic reticulum stress in the subfornical organ, which when attenuated by GRP78 blunts saline-intake, and (3) CCAAT homologous binding protein may play a functional role in DOCA-salt-induced saline-intake. The results suggest a mechanistic distinction between the importance of endoplasmic reticulum stress in mediating effects of DOCA-salt on saline-intake and blood pressure.

Stress signaling in mammalian oocytes and embryos: a basis for intervention and improvement of outcomes

Oocytes and early stage embryos are highly sensitive to variation in diverse exogenous factors such as temperature, osmolarity, oxygen, nutrient restriction, pH, shear stress, toxins, amino acid availability, and lipids. It is becoming increasingly apparent that many such factors negatively affect the endoplasmic reticulum, protein synthesis and protein processing, initiating ER stress and unfolded protein responses. As a result, ER stress signaling serves as a common mediator of cellular responses to diverse stressors. In oocytes and embryos, this leads to developmental arrest and epigenetic changes. Recent studies have revealed that preventing ER stress or inhibiting ER stress signaling can preserve or even enhance oocyte and embryo developmental potential. This review examines ER stress signaling, how it arises, how it affects oocytes and embryos, and how its occurrence can be managed or prevented.

Novel therapeutic targets in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic immune-mediated liver disease characterized by progressive cholestasis, biliary fibrosis and eventually cirrhosis. It results in characteristic symptoms with marked effects on life quality. The advent of large patient cohorts has challenged the view of PBC as a benign condition treated effectively by the single licensed therapy-ursodeoxycholic acid (UDCA). UDCA nonresponse or under-response has a major bearing on outcome, substantially increasing the likelihood that liver transplantation will be required or that patients will die of the disease. In patients with high-risk, treatment-unresponsive or highly symptomatic disease the need for new treatment approaches is clear. Evolution in our understanding of disease mechanisms is rapidly leading to the advent of new and re-purposed therapeutic agents targeting key processes. Notable opportunities are offered by targeting what could be considered as the 'upstream' immune response, 'midstream' biliary injury and 'downstream' fibrotic processes. Combination therapy targeting several pathways or the development of novel agents addressing multiple components of the disease pathway might be required. Ultimately, PBC therapeutics will require a stratified approach to be adopted in practice. This Review provides a current perspective on potential approaches to PBC treatment, and highlights the challenges faced in evaluating and implementing those treatments.