Infliximab ameliorates AD-associated object recognition memory impairment

Microglia-mediated neuron death requires TNF and is exacerbated by mutant Huntingtin

Microglia, the resident immune cells of the brain, regulate the balance of inflammation in the central nervous system under healthy and pathogenic conditions. Huntington's disease (HD) is a chronic neurodegenerative disease characterized by activated microglia and elevated concentrations of pro-inflammatory cytokines within the brain. Chronic hyperactivation of microglia is associated with brain pathology and eventual neuron death. However, it is unclear which specific cytokines are required for neuron death and whether HD neurons may be hypersensitive to neuroinflammation. We assessed the profile of microglia-secreted proteins in response to LPS and IFNγ, and a conditioned media paradigm was used to examine the effects of these secreted proteins on cultured neuronal cells. STHdhQ7/Q7 and STHdhQ111/Q111 neuronal cells were used to model wild-type and HD neurons, respectively. We determined that STHdhQ111/Q111 cells were hypersensitive to pro-inflammatory factors secreted by microglia, and that TNF was required to induce neuronal death. Microglia-mediated neuronal death could be effectively halted through the use of JAK-STAT or TNF inhibitors which supported the requirement for TNF as well as IFNγ in the process of secondary neurotoxicity. Further data derived from human HD patients as well as HD mice were suggestive of enhanced receptor density for TNF (TNFR1) and IFNγ (IFNGR) which could sensitize the HD brain to these cytokines. This highlights several potential mechanisms by which microglia may induce neuronal death and suggests that these mechanisms may be upregulated in the brain of HD patients.

Can infliximab serve as a new therapy for neuropsychiatric symptoms?

Neuropsychiatric disorders present a global challenge to public health. Mechanisms associated with neuropsychiatric disorders etiology include apoptosis, oxidative stress, and neuroinflammation. Tumor necrosis factor alpha, an inflammatory cytokine, mediates pathophysiology of neuropsychiatric disorders. Therefore, its inhibition by infliximab might afford a valuable target for intervention. Infliximab is commonly used to treat inflammatory diseases, including ulcerative colitis, Crohn's disease, and rheumatoid arthritis. Recently, it has been shown that infliximab improves cognitive dysfunction, depression, anxiety, and life quality. Here, we review contemporary knowledge supporting the need to further characterize infliximab as a potential treatment for neuropsychiatric disorders.

Mechanisms of damage and therapies for cardiac amyloidosis: a role for inflammation?

The term cardiac amyloidosis (CA) refers to the accumulation of extracellular amyloid deposits in the heart because of different conditions often affecting multiple organs including brain, kidney and liver. Notably, cardiac involvement significantly impacts prognosis of amyloidosis, with cardiac biomarkers playing a pivotal role in prognostic stratification. Therapeutic management poses a challenge due to limited response to conventional heart failure therapies, necessitating targeted approaches aimed at preventing, halting or reversing amyloid deposition. Mechanisms underlying organ damage in CA are multifactorial, involving proteotoxicity, oxidative stress, and mechanical interference. While the role of inflammation in CA remains incompletely understood, emerging evidence suggests its potential contribution to disease progression as well as its utility as a therapeutic target. This review reports on the cardiac involvement in systemic amyloidosis, its prognostic role and how to assess it. Current and emerging therapies will be critically discussed underscoring the need for further efforts aiming at elucidating CA pathophysiology. The emerging evidence suggesting the contribution of inflammation to disease progression and its prognostic role will also be reviewed possibly offering insights into novel therapeutic avenues for CA.

Skin-brain axis in Alzheimer's disease - Pathologic, diagnostic, and therapeutic implications: A Hypothetical Review

The dynamic interaction between the brain and the skin is termed the 'skin-brain axis.' Changes in the skin not only reflect conditions in the brain but also exert direct and indirect effects on the brain. Interestingly, the connection between the skin and brain is crucial for understanding aging and neurodegenerative diseases. Several studies have shown an association between Alzheimer's disease (AD) and various skin disorders, such as psoriasis, bullous pemphigoid, and skin cancer. Previous studies have shown a significantly increased risk of new-onset AD in patients with psoriasis. In contrast, skin cancer may reduce the risk of developing AD. Accumulating evidence suggests an interaction between skin disease and AD; however, AD-associated pathological changes mediated by the skin-brain axis are not yet clearly defined. While some studies have reported on the diagnostic implications of the skin-brain axis in AD, few have discussed its potential therapeutic applications. In this review, we address the pathological changes mediated by the skin-brain axis in AD. Furthermore, we summarize (1) the diagnostic implications elucidated through the role of the skin-brain axis in AD and (2) the therapeutic implications for AD based on the skin-brain axis. Our review suggests that a potential therapeutic approach targeting the skin-brain axis will enable significant advances in the treatment of AD.

Maternal BPAF exposure impaired synaptic development and caused behavior abnormality in offspring

Bisphenol A (BPA) has been widely restricted, leading to a significant increase in the production of bisphenol AF (BPAF), one of the most common bisphenol analogs use as a substitute for BPA. However, there is limit evidence on the neurotoxicity of BPAF, especially the potential effects of maternal exposed to BPAF on offspring. A maternal BPAF exposure model was used to evaluate its effects on long-term neurobehaviors in offspring. We found that maternal BPAF exposure resulted in immune disorders, characterized by abnormal CD4⁺T cell subsets, and their offspring exhibited anxiety- and depression-like behaviors, as well as impairments in learning-memory, sociability and social novelty. Further, brain bulk RNA-sequencing (RNA-seq) and hippocampus single-nucleus RNA-sequencing (snRNA-seq) of offspring showed that differentially expressed genes (DEGs) were enriched in pathways related to synaptic and neurodevelopment. Synaptic ultra-structure of offspring was damaged after maternal BPAF exposure. In conclusion, maternal BPAF exposure induced behavior abnormality in adult offspring, together with synaptic and neurodevelopment defects, which might be related to maternal immune dysfunction. Our results provide a comprehensive insight into the neurotoxicity mechanism of maternal BPAF exposure during gestation. Given the increasing and ubiquitous exposure to BPAF, especially during sensitive periods of growth and development, the safety of BPAF requires urgent attention.

Investigation of Cyclo-Z Therapeutic Effect on Insulin Pathway in Alzheimer's Rat Model: Biochemical and Electrophysiological Parameters

Cyclo (his-pro-CHP) plus zinc (Zn⁺²) (Cyclo-Z) is the only known chemical that increases the production of insulin-degrading enzyme (IDE) and decreases the number of inactive insulin fragments in cells. The aim of the present study was to systematically characterize the effects of Cyclo-Z on the insulin pathway, memory functions, and brain oscillations in the Alzheimer's disease (AD) rat model. The rat model of AD was established by bilateral injection of Aβ42 oligomer (2,5nmol/10μl) into the lateral ventricles. Cyclo-Z (10mg Zn+2/kg and 0.2mg CHP/kg) gavage treatment started seven days after Aβ injection and lasted for 21 days. At the end of the experimental period, memory tests and electrophysiological recordings were performed, which were followed by the biochemical analysis. Aβ42 oligomers led to a significant increase in fasting blood glucose, serum insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and phospho-tau-Ser356 levels. Moreover, Aβ42 oligomers caused a significant decrement in body weight, hippocampal insulin, brain insulin receptor substrate (IRS-Ser612), and glycogen synthase kinase-3 beta (GSK-3β) levels. Also, Aβ42 oligomers resulted in a significant reduction in memory. The Cyclo-Z treatment prevented the observed alterations in the ADZ group except for phospho-tau levels and attenuated the increased Aβ42 oligomer levels in the ADZ group. We also found that the Aβ42 oligomer decreased the left temporal spindle and delta power during ketamine anesthesia. Cyclo-Z treatment reversed the Aβ42 oligomer-related alterations in the left temporal spindle power. Cyclo-Z prevents Aβ oligomer-induced changes in the insulin pathway and amyloid toxicity, and may contribute to the improvement of memory deficits and neural network dynamics in this rat model.

Past, Present and (Foreseeable) Future of Biological Anti-TNF Alpha Therapy

Due to the key role of tumor necrosis factor-alpha (TNF-α) in the pathogenesis of immunoinflammatory diseases, TNF-α inhibitors have been successfully developed and used in the clinical treatment of autoimmune disorders. Currently, five anti-TNF-α drugs have been approved: infliximab, adalimumab, golimumab, certolizumab pegol and etanercept. Anti-TNF-α biosimilars are also available for clinical use. Here, we will review the historical development as well as the present and potential future applications of anti-TNF-α therapies, which have led to major improvements for patients with several autoimmune diseases, such as rheumatoid arthritis (RA), ankylosing spondylitis (AS), Crohn's disease (CD), ulcerative colitis (UC), psoriasis (PS) and chronic endogenous uveitis. Other therapeutic areas are under evaluation, including viral infections, e.g., COVID-19, as well as chronic neuropsychiatric disorders and certain forms of cancer. The search for biomarkers able to predict responsiveness to anti-TNF-α drugs is also discussed.

The relationships between neuroglial and neuronal changes in Alzheimer's disease, and the related controversies II:

Since the original description of Alzheimer´s disease (AD), research into this condition has mainly focused on assessing the alterations to neurons associated with dementia, and those to the circuits in which they are involved. In most of the studies on human brains and in many models of AD, the glial cells accompanying these neurons undergo concomitant alterations that aggravate the course of neurodegeneration. As a result, these changes to neuroglial cells are now included in all the "pathogenic cascades" described in AD. Accordingly, astrogliosis and microgliosis, the main components of neuroinflammation, have been integrated into all the pathogenic theories of this disease, as discussed in this part of the two-part monograph that follows an accompanying article on gliopathogenesis and glioprotection. This initial reflection verified the implication of alterations to the neuroglia in AD, suggesting that these cells may also represent therapeutic targets to prevent neurodegeneration. In this second part of the monograph, we will analyze the possibilities of acting on glial cells to prevent or treat the neurodegeneration that is the hallmark of AD and other pathologies. Evidence of the potential of different pharmacological, non-pharmacological, cell and gene therapies (widely treated) to prevent or treat this disease is now forthcoming, in most cases as adjuncts to other therapies. A comprehensive AD multimodal therapy is proposed in which neuronal and neuroglial pharmacological treatments are jointly considered, as well as the use of new cell and gene therapies and non-pharmacological therapies that tend to slow down the progress of dementia.

Efficacy and Safety of a Brain-Penetrant Biologic TNF-α Inhibitor in Aged APP/PS1 Mice

Tumor necrosis factor alpha (TNF-α) plays a vital role in Alzheimer's disease (AD) pathology, and TNF-α inhibitors (TNFIs) modulate AD pathology. We fused the TNF-α receptor (TNFR), a biologic TNFI that sequesters TNF-α, to a transferrin receptor antibody (TfRMAb) to deliver the TNFI into the brain across the blood-brain barrier (BBB). TfRMAb-TNFR was protective in 6-month-old transgenic APP/PS1 mice in our previous work. However, the effects and safety following delayed chronic TfRMAb-TNFR treatment are unknown. Herein, we initiated the treatment when the male APP/PS1 mice were 10.7 months old (delayed treatment). Mice were injected intraperitoneally with saline, TfRMAb-TNFR, etanercept (non-BBB-penetrating TNFI), or TfRMAb for ten weeks. Biologic TNFIs did not alter hematology indices or tissue iron homeostasis; however, TfRMAb altered hematology indices, increased splenic iron transporter expression, and increased spleen and liver iron. TfRMAb-TNFR and etanercept reduced brain insoluble-amyloid beta (Aβ) 1-42, soluble-oligomeric Aβ, and microgliosis; however, only TfRMAb-TNFR reduced Aβ peptides, Thioflavin-S-positive Aβ plaques, and insoluble-oligomeric Aβ and increased plaque-associated phagocytic microglia. Accordingly, TfRMAb-TNFR improved spatial reference memory and increased BBB-tight junction protein expression, whereas etanercept did not. Overall, despite delayed treatment, TfRMAb-TNFR resulted in a better therapeutic response than etanercept without any TfRMAb-related hematology- or iron-dysregulation in aged APP/PS1 mice.

Targeting Differential Roles of Tumor Necrosis Factor Receptors as a Therapeutic Strategy for Glaucoma

Glaucoma is an irreversible sight-threatening disorder primarily due to elevated intraocular pressure (IOP), leading to retinal ganglion cell (RGC) death by apoptosis with subsequent loss of optic nerve fibers. A considerable amount of empirical evidence has shown the significant association between tumor necrosis factor cytokine (TNF; TNFα) and glaucoma; however, the exact role of TNF in glaucoma progression remains unclear. Total inhibition of TNF against its receptors can cause side effects, although this is not the case when using selective inhibitors. In addition, TNF exerts its antithetic roles via stimulation of two receptors, TNF receptor I (TNFR1) and TNF receptor II (TNFR2). The pro-inflammatory responses and proapoptotic signaling pathways predominantly mediated through TNFR1, while neuroprotective and anti-apoptotic signals induced by TNFR2. In this review, we attempt to discuss the involvement of TNF receptors (TNFRs) and their signaling pathway in ocular tissues with focus on RGC and glial cells in glaucoma. This review also outlines the potential application TNFRs agonist and/or antagonists as neuroprotective strategy from a therapeutic standpoint. Taken together, a better understanding of the function of TNFRs may lead to the development of a treatment for glaucoma.

Potential role of Drug Repositioning Strategy (DRS) for management of tauopathy

Tauopathy is a term that has been used to represent a pathological condition in which hyperphosphorylated tau protein aggregates in neurons and glia which results in neurodegeneration, synapse loss and dysfunction and cognitive impairments. Recently, drug repositioning strategy (DRS) becomes a promising field and an alternative approach to advancing new treatments from actually developed and FDA approved drugs for an indication other than the indication it was originally intended for. This paradigm provides an advantage because the safety of the candidate compound has already been established, which abolishes the need for further preclinical safety testing and thus substantially reduces the time and cost involved in progressing of clinical trials. In the present review, we focused on correlation between tauopathy and common diseases as type 2 diabetes mellitus and the global virus COVID-19 and how tau pathology can aggravate development of these diseases in addition to how these diseases can be a risk factor for development of tauopathy. Moreover, correlation between COVID-19 and type 2 diabetes mellitus was also discussed. Therefore, repositioning of a drug in the daily clinical practice of patients to manage or prevent two or more diseases at the same time with lower side effects and drug-drug interactions is a promising idea. This review concluded the results of pre-clinical and clinical studies applied on antidiabetics, COVID-19 medications, antihypertensives, antidepressants and cholesterol lowering drugs for possible drug repositioning for management of tauopathy.

Biologic TNF-α inhibitors reduce microgliosis, neuronal loss, and tau phosphorylation in a transgenic mouse model of tauopathy

Background

Tumor necrosis factor-α (TNF-α) plays a central role in Alzheimer’s disease (AD) pathology, making biologic TNF-α inhibitors (TNFIs), including etanercept, viable therapeutics for AD. The protective effects of biologic TNFIs on AD hallmark pathology (Aβ deposition and tau pathology) have been demonstrated. However, the effects of biologic TNFIs on Aβ-independent tau pathology have not been reported. Existing biologic TNFIs do not cross the blood–brain barrier (BBB), therefore we engineered a BBB-penetrating biologic TNFI by fusing the extracellular domain of the type-II human TNF-α receptor (TNFR) to a transferrin receptor antibody (TfRMAb) that ferries the TNFR into the brain via receptor-mediated transcytosis. The present study aimed to investigate the effects of TfRMAb-TNFR (BBB-penetrating TNFI) and etanercept (non-BBB-penetrating TNFI) in the PS19 transgenic mouse model of tauopathy.

Methods

Six-month-old male and female PS19 mice were injected intraperitoneally with saline (n = 12), TfRMAb-TNFR (1.75 mg/kg, n = 10) or etanercept (0.875 mg/kg, equimolar dose of TNFR, n = 10) 3 days/week for 8 weeks. Age-matched littermate wild-type mice served as additional controls. Blood was collected at baseline and 8 weeks for a complete blood count. Locomotion hyperactivity was assessed by the open-field paradigm. Brains were examined for phosphorylated tau lesions (Ser202, Thr205), microgliosis, and neuronal health. The plasma pharmacokinetics were evaluated following a single intraperitoneal injection of 0.875 mg/kg etanercept or 1.75 mg/kg TfRMAb-TNFR or 1.75 mg/kg chronic TfRMAb-TNFR dosing for 4 weeks.

Results

Etanercept significantly reduced phosphorylated tau and microgliosis in the PS19 mouse brains of both sexes, while TfRMAb-TNFR significantly reduced these parameters in the female PS19 mice. Both TfRMAb-TNFR and etanercept treatment improved neuronal health by significantly increasing PSD95 expression and attenuating hippocampal neuron loss in the PS19 mice. The locomotion hyperactivity in the male PS19 mice was suppressed by chronic etanercept treatment. Equimolar dosing resulted in eightfold lower plasma exposure of the TfRMAb-TNFR compared with etanercept. The hematological profiles remained largely stable following chronic biologic TNFI dosing except for a significant increase in platelets with etanercept.

Conclusion

Both TfRMAb-TNFR (BBB-penetrating) and non-BBB-penetrating (etanercept) biologic TNFIs showed therapeutic effects in the PS19 mouse model of tauopathy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02332-7.

A Computational Exploration of the Molecular Network Associated to Neuroinflammation in Alzheimer's Disease

Neuroinflammation, as defined by the presence of classically activated microglia, is thought to play a key role in numerous neurodegenerative disorders such as Alzheimer’s disease. While modulating neuroinflammation could prove beneficial against neurodegeneration, identifying its most relevant biological processes and pharmacological targets remains highly challenging. In the present study, we combined text-mining, functional enrichment and protein-level functional interaction analyses to 1) identify the proteins significantly associated to neuroinflammation in Alzheimer’s disease over the scientific literature, 2) distinguish the key proteins most likely to control the neuroinflammatory processes significantly associated to Alzheimer's disease, 3) identify their regulatory microRNAs among those dysregulated in Alzheimer's disease and 4) assess their pharmacological targetability. 94 proteins were found to be significantly associated to neuroinflammation in Alzheimer’s disease over the scientific literature and IL4, IL10 and IL13 signaling as well as TLR-mediated MyD88- and TRAF6-dependent responses were their most significantly enriched biological processes. IL10, TLR4, IL6, AKT1, CRP, IL4, CXCL8, TNF-alpha, ITGAM, CCL2 and NOS3 were identified as the most potent regulators of the functional interaction network formed by these immune processes. These key proteins were indexed to be regulated by 63 microRNAs dysregulated in Alzheimer's disease, 13 long non-coding RNAs and targetable by 55 small molecules and 8 protein-based therapeutics. In conclusion, our study identifies eleven key proteins with the highest ability to control neuroinflammatory processes significantly associated to Alzheimer’s disease, as well as pharmacological compounds with single or pleiotropic actions acting on them. As such, it may facilitate the prioritization of diagnostic and target-engagement biomarkers as well as the development of effective therapeutic strategies against neuroinflammation in Alzheimer’s disease.

Design and characterization of a novel dimeric blood-brain barrier penetrating TNFα inhibitor

Tumor necrosis factor-alpha (TNFα) inhibitors could prevent neurological disorders systemically, but their design generally relies on molecules unable to cross the blood-brain barrier (BBB). This research was aimed to design and characterize a novel TNFα inhibitor based on the angiopeptide-2 as a BBB shuttle molecule fused to the extracellular domain of human TNFα receptor 2 and a mutated vascular endothelial growth factor (VEGF) dimerization domain. This new chimeric protein (MTV) would be able to trigger receptor-mediated transcytosis across the BBB via low-density lipoprotein receptor-related protein-1 (LRP-1) and inhibit the cytotoxic effect of TNFα more efficiently because of its dimeric structure. Stably transformed CHO cells successfully expressed MTV, and its purification by Immobilized-Metal Affinity Chromatography (IMAC) rendered high purity degree. Mutated VEGF domain included in MTV did not show cell proliferation or angiogenic activities measured by scratch and aortic ring assays, which corroborate that the function of this domain is restricted to dimerization. The pairs MTV-TNFα (Kd 279 ± 40.9 nM) and MTV-LRP1 (Kd 399 ± 50.5 nM) showed high affinity by microscale thermophoresis, and a significant increase in cell survival was observed after blocking TNFα with MTV in a cell cytotoxicity assay. Also, the antibody staining in CHOK1 and bEnd3 cells demonstrated the adhesion of MTV to the LRP1 receptor located in the cell membrane. These results provide compelling evidence for the proper functioning of the three main domains of MTV individually, which encourage us to continue the research with this new molecule as a potential candidate for the systemic treatment of neurological disorders.

Astrocyte subtype-specific approach to Alzheimer's disease treatment

Astrocytes respond to any pathological condition in the central nervous system (CNS) including Alzheimer's disease (AD), and this response is called astrocyte reactivity. Astrocyte reaction to a CNS insult is a highly heterogeneous phenomenon in which the astrocytes undergo a set of morphological, molecular and functional changes with a characteristic secretome profile. Such astrocytes are termed as 'reactive astrocytes'. Controversies regarding the reactive astrocytes abound. Recently, a continuum of reactive astrocyte profiles with distinct transcriptional states has been identified. Among them, disease-associated astrocytes (DAA) were uniquely present in AD mice and expressed a signature set of genes implicated in complement cascade, endocytosis and aging. Earlier, two stimulus-specific reactive astrocyte subtypes with their unique transcriptomic signatures were identified using mouse models of neuroinflammation and ischemia and termed as A1 astrocytes (detrimental) and A2 astrocytes (beneficial) respectively. Interestingly, although most of the A1 signature genes were also detected in DAA, as opposed to A2 astrocyte signatures, some of the A1 specific genes were expressed in other astrocyte subtypes, indicating that these nomenclature-based signatures are not very specific. In this review, we elaborate the disparate functions and cytokine profiles of reactive astrocyte subtypes in AD and tried to distinguish them by designating neurotoxic astrocytes as A1-like and neuroprotective ones as A2-like without directly referring to the A1/A2 original nomenclature. We have also focused on the dual nature from a functional perspective of some cytokines depending on AD-stage, highlighting a number of them as major candidates in AD therapy. Therefore, we suggest that promoting subtype-specific beneficial roles, inhibiting subtype-specific detrimental roles or targeting subtype-specific cytokines constitute a novel therapeutic approach to AD treatment.

TNF-α-mediated reduction in inhibitory neurotransmission precedes sporadic Alzheimer's disease pathology in young Trem2R47H rats

Alzheimer's disease (AD) is a neurodegenerative dementia associated with deposition of amyloid plaques and neurofibrillary tangles, formed by amyloid β (Aβ) peptides and phosphor-tau, respectively, in the central nervous system. Approximately 2% of AD cases are due to familial AD (FAD); ∼98% of cases are sporadic AD (SAD). Animal models with FAD are commonly used to study SAD pathogenesis. Because mechanisms leading to FAD and SAD may be distinct, to study SAD pathogenesis, we generated Trem2R47H knock-in rats, which carry the SAD risk factor p.R47H variant of the microglia gene triggering receptor expressed on myeloid cells 2 (TREM2). Trem2R47H rats produce human-Aβ from a humanized-App rat allele because human-Aβ is more toxic than rodent-Aβ and the pathogenic role of the p.R47H TREM2 variant has been linked to human-Aβ-clearing deficits. Using periadolescent Trem2R47H rats, we previously demonstrated that supraphysiological tumor necrosis factor-α (TNF-α) boosts glutamatergic transmission, which is excitatory, and suppresses long-term potentiation, a surrogate of learning and memory. Here, we tested the effect of the p.R47H variant on the inhibitory neurotransmitter γ-aminobutyric acid. We report that GABAergic transmission is decreased in Trem2R47H/R47H rats. This decrease is due to acute and reversible action of TNF-α and is not associated with increased human-Aβ levels and AD pathology. Thus, the p.R47H variant changes the excitatory/inhibitory balance, favoring excitation. This imbalance could potentiate glutamate excitotoxicity and contribute to neuronal dysfunction, enhanced neuronal death, and neurodegeneration. Future studies will determine whether this imbalance represents an early, Aβ-independent pathway leading to dementia and may reveal the AD-modifying therapeutic potential of TNF-α inhibition in the central nervous system.

Insulin resistance: a connecting link between Alzheimer's disease and metabolic disorder

Recent evidence suggests that Alzheimer's disease (AD) is closely linked with insulin resistance, as seen in type 2 diabetes mellitus (T2DM). Insulin signaling is impaired in AD brains due to insulin resistance, ultimately resulting in the formation of neurofibrillary tangles (NFTs). AD and T2DM are connected at molecular, clinical, and epidemiological levels making it imperative to understand the contribution of T2DM, and other metabolic disorders, to AD pathogenesis. In this review, we have discussed various modalities involved in the pathogenesis of these two diseases and explained the contributing parameters. Insulin is vital for maintaining glucose homeostasis and it plays an important role in regulating inflammation. Here, we have discussed the roles of various contributing factors like miRNA, leptin hormone, neuroinflammation, metabolic dysfunction, and gangliosides in insulin impairment both in AD and T2DM. Understanding these mechanisms will be a big step forward for making molecular therapies that may help maintain or prevent both AD and T2DM, thus reducing the burden of both these diseases.

Repositioning of Immunomodulators: A Ray of Hope for Alzheimer's Disease?

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder characterized by cognitive decline and by the presence of amyloid β plaques and neurofibrillary tangles in the brain. Despite recent advances in understanding its pathophysiological mechanisms, to date, there are no disease-modifying therapeutic options, to slow or halt the evolution of neurodegenerative processes in AD. Current pharmacological treatments only transiently mitigate the severity of symptoms, with modest or null overall improvement. Emerging evidence supports the concept that AD is affected by the impaired ability of the immune system to restrain the brain's pathology. Deep understanding of the relationship between the nervous and the immune system may provide a novel arena to develop effective and safe drugs for AD treatment. Considering the crucial role of inflammatory/immune pathways in AD, here we discuss the current status of the immuno-oncological, immunomodulatory and anti-TNF-α drugs which are being used in preclinical studies or in ongoing clinical trials by means of the drug-repositioning approach.

Born to Protect: Leveraging BDNF Against Cognitive Deficit in Alzheimer's Disease

Alzheimer's disease is a chronic neurodegenerative devastating disorder affecting a high percentage of the population over 65 years of age and causing a relevant emotional, social, and economic burden. Clinically, it is characterized by a prominent cognitive deficit associated with language and behavioral impairments. The molecular pathogenesis of Alzheimer's disease is multifaceted and involves changes in neurotransmitter levels together with alterations of inflammatory, oxidative, hormonal, and synaptic pathways, which may represent a drug target for both prevention and treatment; however, an effective treatment for Alzheimer's disease still represents an unmet goal. As neurotrophic factors participate in the modulation of the above-mentioned pathways, they have been highlighted as critical contributors of Alzheimer's disease etiology, whose modulation might be beneficial for Alzheimer's disease. We focused on the neurotrophin brain-derived neurotrophic factor, providing several lines of evidence pointing to brain-derived neurotrophic factor as a plausible endophenotype of cognitive deficits in Alzheimer's disease, illustrating some of the most recent possibilities to modulate the expression of this neurotrophin in the brain in an attempt to ameliorate cognition and delay the progression of Alzheimer's disease. This review shows that otherwise disparate pharmacologic or non-pharmacologic approaches converge on brain-derived neurotrophic factor, providing a means whereby apparently unrelated medical approaches may nevertheless produce similar synaptic and cognitive outcomes in Alzheimer's disease pathogenesis, suggesting that brain-derived neurotrophic factor-based synaptic repair may represent a modifying strategy to ameliorate cognition in Alzheimer's disease.

Targeting TNFR2 as a Novel Therapeutic Strategy for Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia. Accumulating experimental evidence shows the important linkage between tumor necrosis factor-α (TNF) and AD, but the exact role of TNF in AD is still not completely understood. Although TNF-inhibitors are successfully used for treating several diseases, total inhibition of TNF can cause side effects, particularly in neurological diseases. This is attributed to the opposing roles of the two TNF receptors. TNF receptor 1 (TNFR1) predominantly mediates inflammatory and pro-apoptotic signaling pathways, whereas TNF receptor 2 (TNFR2) is neuroprotective and promotes tissue regeneration. Therefore, the specific activation of TNFR2 signaling, either by directly targeting TNFR2 via TNFR2 agonists or by blocking TNFR1 signaling with TNFR1-selective antagonists, seems a promising strategy for AD therapy. This mini-review discusses the involvement of TNFR2 and its signaling pathway in AD and outlines its potential application as therapeutic target. A better understanding of the function of TNFR2 may lead to the development of a treatment for AD.

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

TNF alpha inhibitors in Alzheimer's disease: A systematic review

OBJECTIVES

The objective of this study was to evaluate the effect of tumour necrosis factor-alpha inhibitors (TNF-αI) on Alzheimer's disease-associated pathology.

DESIGN

A literature search of PubMed, Embase, PsychINFO, Web of Science, Scopus, and the Cochrane Library databases for human and animal studies that evaluated the use of TNF-αI was performed on 26 October 2016.

RESULTS

The main outcomes assessed were cognition and behaviour, reduction in brain tissue mass, presence of plaques and tangles, and synaptic function. Risk of bias was assessed regarding blinding, statistical model, outcome reporting, and other biases. Sixteen studies were included, 13 of which were animal studies and 3 of which were human. All animal studies found that treatment with TNF-αI leads to an improvement in cognition and behaviour. None of the studies measured change in brain tissue mass. The majority of studies documented a beneficial effect in other areas, including the presence of plaques and tangles and synaptic function. The amount of data from human studies was limited. Two out of 3 studies concluded that TNF-αI are beneficial in Alzheimer's disease patients, with one being an observational study and the latter being a small pilot study, with a high risk of bias.

CONCLUSION

It was concluded that a large-scale randomized controlled trial assessing the effectiveness of TNF-αI on humans is warranted.

Effects of maternal exposure to bisphenol AF on emotional behaviors in adolescent mice offspring

Exposure to bisphenol A (BPA), one kind of environmental endocrine disruptors (EEDs), exerted significantly detrimental effects on neuro-endocrinological system and related disorders, such as memory dysfunction and depression. Bisphenol AF (BPAF),a newly introduced chemical structurally related to BPA, is used extensively. BPAF has stronger estrogenic activities than BPA. However, the potential neurotoxicological effects of BPAF are still elusive. The present study aimed to investigate the potential effects of maternal BPAF exposure during pregnancy on emotional behaviors of adolescent mice offspring. In male adolescent offspring, maternal exposure to BPAF (0.4, 4.0 mg kg^-1, intragastrically administration) induced significant anxiety- and depressive-like behaviors, assessed by open field test (OFT), novelty-suppressed feeding test (NSF), sucrose preference test (SPT), tail suspension test (TST) and forced swimming test (FST). In female adolescent offspring, BPAF exposure at 0.4 mg kg^-1 dose reduced the latency to feeding in the NSF test, while increased the floating time in the FST. Maternal BPAF exposure decreased the recognition index in the long term memory (LTM) test in both sexes, while only decreased the freezing time of male offspring in the contextual fear conditioning (CFC) task. These results indicate that maternal exposure to BPAF significantly affect emotion-related behaviors in adolescent mice offspring, and the male offspring with a higher probability to develop symptoms of anxiety and depression and to suffer memory impairment after maternal exposure to BPAF.

Chronic sleep restriction promotes brain inflammation and synapse loss, and potentiates memory impairment induced by amyloid-β oligomers in mice

It is increasingly recognized that sleep disturbances and Alzheimer's disease (AD) share a bidirectional relationship. AD patients exhibit sleep problems and alterations in the regulation of circadian rhythms; conversely, poor quality of sleep increases the risk of development of AD. The aim of the current study was to determine whether chronic sleep restriction potentiates the brain impact of amyloid-β oligomers (AβOs), toxins that build up in AD brains and are thought to underlie synapse damage and memory impairment. We further investigated whether alterations in levels of pro-inflammatory mediators could play a role in memory impairment in sleep-restricted mice. We found that a single intracerebroventricular (i.c.v.) infusion of AβOs disturbed sleep pattern in mice. Conversely, chronically sleep-restricted mice exhibited higher brain expression of pro-inflammatory mediators, reductions in levels of pre- and post-synaptic marker proteins, and exhibited increased susceptibility to the impact of i.c.v. infusion of a sub-toxic dose of AβOs (1pmol) on performance in the novel object recognition memory task. Sleep-restricted mice further exhibited an increase in brain TNF-α levels in response to AβOs. Interestingly, memory impairment in sleep-restricted AβO-infused mice was prevented by treatment with the TNF-α neutralizing monoclonal antibody, infliximab. Results substantiate the notion of a dual relationship between sleep and AD, whereby AβOs disrupt sleep/wake patterns and chronic sleep restriction increases brain vulnerability to AβOs, and point to a key role of brain inflammation in increased susceptibility to AβOs in sleep-restricted mice.

Ginsenoside Rb1 ameliorates cisplatin-induced learning and memory impairments

Background

Ginsenoside Rb1 (Rb1), a dominant component from the extract of Panax ginseng root, exhibits neuroprotective functions in many neurological diseases. This study was intended to investigate whether Rb1 can attenuate cisplatin-induced memory impairments and explore the potential mechanisms.

Methods

Cisplatin was injected intraperitoneally with a dose of 5 mg/kg/wk, and Rb1 was administered in drinking water at the dose of 2 mg/kg/d to rats for 5 consecutive wk. The novel objects recognition task and Morris water maze were used to detect the memory of rats. Nissl staining was used to examine the neuron numbers in the hippocampus. The activities of superoxide dismutase, glutathione peroxidase, cholineacetyltransferase, acetylcholinesterase, and the levels of malondialdehyde, reactive oxygen species, acetylcholine, tumor necrosis factor-α, interleukin-1β, and interleukin-10 were measured by ELISA to assay the oxidative stress, cholinergic function, and neuroinflammation in the hippocampus.

Results

Rb1 administration effectively ameliorates the memory impairments caused by cisplatin in both novel objects recognition task and Morris water maze task. Rb1 also attenuates the neuronal loss induced by cisplatin in the different regions (CA1, CA3, and dentate gyrus) of the hippocampus. Meanwhile, Rb1 is able to rescue the cholinergic neuron function, inhibit the oxidative stress and neuroinflammation in cisplatin-induced rat brain.

Conclusion

Rb1 rescues the cisplatin-induced memory impairment via restoring the neuronal loss by reducing oxidative stress and neuroinflammation and recovering the cholinergic neuron functions.

Blood-Brain Barrier Penetrating Biologic TNF-α Inhibitor for Alzheimer's Disease

Tumor necrosis factor alpha (TNF-α) driven processes are involved at multiple stages of Alzheimer's disease (AD) pathophysiology and disease progression. Biologic TNF-α inhibitors (TNFIs) are the most potent class of TNFIs but cannot be developed for AD since these macromolecules do not cross the blood-brain barrier (BBB). A BBB-penetrating TNFI was engineered by the fusion of the extracellular domain of the type II human TNF receptor (TNFR) to a chimeric monoclonal antibody (mAb) against the mouse transferrin receptor (TfR), designated as the cTfRMAb-TNFR fusion protein. The cTfRMAb domain functions as a molecular Trojan horse, binding to the mouse TfR and ferrying the biologic TNFI across the BBB via receptor-mediated transcytosis. The aim of the study was to examine the effect of this BBB-penetrating biologic TNFI in a mouse model of AD. Six-month-old APPswe, PSEN 1dE9 (APP/PS1) transgenic mice were treated with saline (n = 13), the cTfRMAb-TNFR fusion protein (n = 12), or etanercept (non-BBB-penetrating biologic TNFI; n = 11) 3 days per week intraperitoneally. After 12 weeks of treatment, recognition memory was assessed using the novel object recognition task, mice were sacrificed, and brains were assessed for amyloid beta (Aβ) load, neuroinflammation, BBB damage, and cerebral microhemorrhages. The cTfRMAb-TNFR fusion protein caused a significant reduction in brain Aβ burden (both Aβ peptide and plaque), neuroinflammatory marker ICAM-1, and a BBB disruption marker, parenchymal IgG, and improved recognition memory in the APP/PS1 mice. Fusion protein treatment resulted in low antidrug-antibody formation with no signs of either immune reaction or cerebral microhemorrhage development with chronic 12-week treatment. Chronic treatment with the cTfRMAb-TNFR fusion protein, a BBB-penetrating biologic TNFI, offers therapeutic benefits by targeting Aβ pathology, neuroinflammation, and BBB-disruption, overall improving recognition memory in a transgenic mouse model of AD.

Tumor necrosis factor α Inhibition for Alzheimer's Disease

Tumor necrosis factor α (TNF-α) plays a central role in the pathophysiology of Alzheimer's disease (AD). Food and Drug Administration-approved biologic TNF-α inhibitors are thus a potential treatment for AD, but they do not cross the blood-brain barrier. In this short review, we discuss the involvement of TNF-α in AD, challenges associated with the development of existing biologic TNF-α inhibitors for AD, and potential therapeutic strategies for targeting TNF-α for AD therapy.