The novel hydroxylamine derivative NG-094 suppresses polyglutamine protein toxicity in Caenorhabditis elegans

Abalone peptide increases stress resilience and cost-free longevity via SKN-1-governed transcriptional metabolic reprogramming in C. elegans

A major goal of healthy aging is to prevent declining resilience and increasing frailty, which are associated with many chronic diseases and deterioration of stress response. Here, we propose a loss-or-gain survival model, represented by the ratio of cumulative stress span to life span, to quantify stress resilience at organismal level. As a proof of concept, this is demonstrated by reduced survival resilience in Caenorhabditis elegans exposed to exogenous oxidative stress induced by paraquat or with endogenous proteotoxic stress caused by polyglutamine or amyloid-β aggregation. Based on this, we reveal that a hidden peptide ("cryptide")-AbaPep#07 (SETYELRK)-derived from abalone hemocyanin not only enhances survival resilience against paraquat-induced oxidative stress but also rescues proteotoxicity-mediated behavioral deficits in C. elegans, indicating its capacity against stress and neurodegeneration. Interestingly, AbaPep#07 is also found to increase cost-free longevity and age-related physical fitness in nematodes. We then demonstrate that AbaPep#07 can promote nuclear localization of SKN-1/Nrf, but not DAF-16/FOXO, transcription factor. In contrast to its effects in wild-type nematodes, AbaPep#07 cannot increase oxidative stress survival and physical motility in loss-of-function skn-1 mutant, suggesting an SKN-1/Nrf-dependent fashion of these effects. Further investigation reveals that AbaPep#07 can induce transcriptional activation of immune defense, lipid metabolism, and metabolic detoxification pathways, including many SKN-1/Nrf target genes. Together, our findings demonstrate that AbaPep#07 is able to boost stress resilience and reduce behavioral frailty via SKN-1/Nrf-governed transcriptional reprogramming, and provide an insight into the health-promoting potential of antioxidant cryptides as geroprotectors in aging and associated conditions.

Moderate Fever Cycles as a Potential Mechanism to Protect the Respiratory System in COVID-19 Patients

Mortality in COVID-19 patients predominantly results from an acute respiratory distress syndrome (ARDS), in which lungs alveolar cells undergo programmed cell death. Mortality in a sepsis-induced ARDS rat model is reduced by adenovirus over-expression of the HSP70 chaperone. A natural rise of body temperature during mild fever can naturally accumulate high cellular levels of HSP70 that can arrest apoptosis and protect alveolar lung cells from inflammatory damages. However, beyond 1-2 h of fever, no HSP70 is being further produced and a decreased in body temperature required to the restore cell's ability to produce more HSP70 in a subsequent fever cycle. We suggest that antipyretics may be beneficial in COVID-19 patients subsequent to several hours of mild (<38.8°C) advantageous fever, allowing lung cells to accumulate protective HSP70 against damages from the inflammatory response to the virus SARS-CoV-2. With age, the ability to develop fever and accumulate HSP70 decreases. This could be ameliorated, when advisable to do so, by thermotherapies and/or physical training.

Heat Shock Proteins and Autophagy Pathways in Neuroprotection: from Molecular Bases to Pharmacological Interventions

Neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease and Huntington's disease (HD), amyotrophic lateral sclerosis, and prion diseases are all characterized by the accumulation of protein aggregates (amyloids) into inclusions and/or plaques. The ubiquitous presence of amyloids in NDDs suggests the involvement of disturbed protein homeostasis (proteostasis) in the underlying pathomechanisms. This review summarizes specific mechanisms that maintain proteostasis, including molecular chaperons, the ubiquitin-proteasome system (UPS), endoplasmic reticulum associated degradation (ERAD), and different autophagic pathways (chaperon mediated-, micro-, and macro-autophagy). The role of heat shock proteins (Hsps) in cellular quality control and degradation of pathogenic proteins is reviewed. Finally, putative therapeutic strategies for efficient removal of cytotoxic proteins from neurons and design of new therapeutic targets against the progression of NDDs are discussed.

The central role of heat shock factor 1 in synaptic fidelity and memory consolidation

Networks of neuronal synapses are the fundamental basis for making and retaining memory. Reduced synapse number and quality correlates with loss of memory in dementia. Heat shock factor 1 (HSF1), the major transcription factor regulating expression of heat shock genes, plays a central role in proteostasis, in establishing and sustaining synaptic fidelity and function, and in memory consolidation. Support for this thesis is based on these observations: (1) heat shock induces improvements in synapse integrity and memory consolidation; (2) synaptic depolarization activates HSF1; (3) activation of HSF1 alone (independent of the canonical heat shock response) augments formation of essential synaptic elements-neuroligands, vesicle transport, synaptic scaffolding proteins, lipid rafts, synaptic spines, and axodendritic synapses; (4) HSF1 coalesces and activates memory receptors in the post-synaptic dendritic spine; (5) huntingtin or α-synuclein accumulation lowers HSF1 while HSF1 lowers huntingtin and α-synuclein aggregation-a potential vicious cycle; and (6) HSF1 agonists (including physical activity) can improve cognitive function in dementia models. Thus, via direct gene expression of synaptic elements, production of HSPs that assure high protein fidelity, and activation of other neuroprotective signaling pathways, HSF1 agonists could provide breakthrough therapy for dementia-associated disease.

Using C. elegans to discover therapeutic compounds for ageing-associated neurodegenerative diseases

Age-associated neurodegenerative disorders such as Alzheimer's disease are a major public health challenge, due to the demographic increase in the proportion of older individuals in society. However, the relatively few currently approved drugs for these conditions provide only symptomatic relief. A major goal of neurodegeneration research is therefore to identify potential new therapeutic compounds that can slow or even reverse disease progression, either by impacting directly on the neurodegenerative process or by activating endogenous physiological neuroprotective mechanisms that decline with ageing. This requires model systems that can recapitulate key features of human neurodegenerative diseases that are also amenable to compound screening approaches. Mammalian models are very powerful, but are prohibitively expensive for high-throughput drug screens. Given the highly conserved neurological pathways between mammals and invertebrates, Caenorhabditis elegans has emerged as a powerful tool for neuroprotective compound screening. Here we describe how C. elegans has been used to model various human ageing-associated neurodegenerative diseases and provide an extensive list of compounds that have therapeutic activity in these worm models and so may have translational potential.

Unraveling protein misfolding diseases using model systems

Experimental model systems have long been used to probe the causes, consequences and mechanisms of pathology leading to human disease. Ideally, such information can be exploited to inform the development of therapeutic strategies or treatments to combat disease progression. In the case of protein misfolding diseases, a wide range of model systems have been developed to investigate different aspects of disorders including Huntington's disease, Parkinson's disease, Alzheimer's disease as well as amyotrophic lateral sclerosis. Utility of these systems broadly correlates with evolutionary complexity: small animal models such as rodents and the fruit fly are appropriate for pharmacological modeling and cognitive/behavioral assessment, the roundworm Caenorhabditis elegans allows analysis of tissue-specific disease features, and unicellular organisms such as the yeast Saccharomyces cerevisiae and the bacterium Escherichia coli are ideal for molecular studies. In this chapter, we highlight key advances in our understanding of protein misfolding/unfolding disease provided by model systems.

Membrane lipid therapy: Modulation of the cell membrane composition and structure as a molecular base for drug discovery and new disease treatment

Nowadays we understand cell membranes not as a simple double lipid layer but as a collection of complex and dynamic protein-lipid structures and microdomains that serve as functional platforms for interacting signaling lipids and proteins. Membrane lipids and lipid structures participate directly as messengers or regulators of signal transduction. In addition, protein-lipid interactions participate in the localization of signaling protein partners to specific membrane microdomains. Thus, lipid alterations change cell signaling that are associated with a variety of diseases including cancer, obesity, neurodegenerative disorders, cardiovascular pathologies, etc. This article reviews the newly emerging field of membrane lipid therapy which involves the pharmacological regulation of membrane lipid composition and structure for the treatment of diseases. Membrane lipid therapy proposes the use of new molecules specifically designed to modify membrane lipid structures and microdomains as pharmaceutical disease-modifying agents by reversing the malfunction or altering the expression of disease-specific protein or lipid signal cascades. Here, we provide an in-depth analysis of this emerging field, especially its molecular bases and its relevance to the development of innovative therapeutic approaches.

Medical implications of understanding the functions of human small heat shock proteins

Small heat shock proteins (sHsps) are ubiquitous molecular chaperones that are implicated in a variety of diseases. Upon stress, they stabilize unfolding proteins and prevent them from aggregating. However, under physiological conditions without severe stress, some sHsps interact with other proteins. In a perspective view, their ability to bind specific client proteins might allow them to fine-tune the availability of the client for other, client-dependent cellular processes. Additionally, some sHsps seem to interact with specific co-chaperones. These co-chaperones are usually part of large protein machineries that are functionally modulated upon sHsps interaction. Finally, secreted human sHsps seem to interact with receptor proteins, potentially as signal molecules transmitting the stress status from one cell to another. This review focuses on the mechanistic description of these different binding modes for human sHsps and how this might help to understand and modulate the function of sHsps in the context of disease.

The biology of proteostasis in aging and disease

Loss of protein homeostasis (proteostasis) is a common feature of aging and disease that is characterized by the appearance of nonnative protein aggregates in various tissues. Protein aggregation is routinely suppressed by the proteostasis network (PN), a collection of macromolecular machines that operate in diverse ways to maintain proteome integrity across subcellular compartments and between tissues to ensure a healthy life span. Here, we review the composition, function, and organizational properties of the PN in the context of individual cells and entire organisms and discuss the mechanisms by which disruption of the PN, and related stress response pathways, contributes to the initiation and progression of disease. We explore emerging evidence that disease susceptibility arises from early changes in the composition and activity of the PN and propose that a more complete understanding of the temporal and spatial properties of the PN will enhance our ability to develop effective treatments for protein conformational diseases.

Metabotropic glutamate receptor 5 as a potential therapeutic target in Huntington's disease

INTRODUCTION

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a polyglutamine expansion in the amino-terminal region of the huntingtin (htt) protein, which underlies the loss of striatal and cortical neurons. Glutamate has been implicated in a number of neurodegenerative diseases, and several studies suggest that the metabotropic glutamate receptor 5 (mGluR5) may represent a target for the treatment of HD.

AREAS COVERED

The main goal of this review is to discuss the current data in the literature regarding the role of mGluR5 in HD and evaluate the potential of mGluR5 as a therapeutic target for the treatment of HD. mGluR5 is highly expressed in the brain regions affected in HD and is involved in movement control. Moreover, mGluR5 interacts with htt and mutated htt profoundly affects mGluR5 signaling. However, mGluR5 stimulation can activate both neuroprotective and neurotoxic signaling pathways, depending on the context of activation.

EXPERT OPINION

Although the data published so far strongly indicate that mGluR5 plays a major role in HD-associated neurodegeneration, htt aggregation and motor symptoms, it is not clear whether mGluR5 stimulation can diminish or intensify neuronal cell loss and HD progression. Thus, future experiments will be necessary to further investigate the outcome of drugs acting on mGluR5 for the treatment of neurodegenerative diseases.

Therapeutic inducers of the HSP70/HSP110 protect mice against traumatic brain injury

Traumatic brain injury (TBI) induces severe harm and disability in many accident victims and combat-related activities. The heat-shock proteins Hsp70/Hsp110 protect cells against death and ischemic damage. In this study, we used mice deficient in Hsp110 or Hsp70 to examine their potential requirement following TBI. Data indicate that loss of Hsp110 or Hsp70 increases brain injury and death of neurons. One of the mechanisms underlying the increased cell death observed in the absence of Hsp110 and Hsp70 following TBI is the increased expression of reactive oxygen species-induced p53 target genes Pig1, Pig8, and Pig12. To examine whether drugs that increase the levels of Hsp70/Hsp110 can protect cells against TBI, we subjected mice to TBI and administered Celastrol or BGP-15. In contrast to Hsp110- or Hsp70i-deficient mice that were not protected following TBI and Celastrol treatment, there was a significant improvement of wild-type mice following administration of these drugs during the first week following TBI. In addition, assessment of neurological injury shows significant improvement in contextual and cued fear conditioning tests and beam balance in wild-type mice that were treated with Celastrol or BGP-15 following TBI compared to TBI-treated mice. These studies indicate a significant role of Hsp70/Hsp110 in neuronal survival following TBI and the beneficial effects of Hsp70/Hsp110 inducers toward reducing the pathological consequences of TBI. Our data indicate that loss of Hsp110 or Hsp70 in mice increases brain injury following TBI. (a) One of the mechanisms underlying the increased cell death observed in the absence of these Hsps following TBI is the increased expression of ROS-induced p53 target genes known as Pigs. In addition, (b) using drugs (Celastrol or BGP-15) to increase Hsp70/Hsp110 levels protect cells against TBI, suggesting the beneficial effects of Hsp70/Hsp110 inducers to reduce the pathological consequences of TBI.

Animal models of neurodegenerative diseases

The prevalence of neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD), increases with age, and the number of affected patients is expected to increase worldwide in the next decades. Accurately understanding the etiopathogenic mechanisms of these diseases is a crucial step for developing disease-modifying drugs able to preclude their emergence or at least slow their progression. Animal models contribute to increase the knowledge on the pathophysiology of neurodegenerative diseases. These models reproduce different aspects of a given disease, as well as the histopathological lesions and its main symptoms. The purpose of this review is to present the main animal models for AD, PD, and Huntington's disease.

Geldanamycin attenuates 3‑nitropropionic acid‑induced apoptosis and JNK activation through the expression of HSP 70 in striatal cells

Although selective striatal cell death is a characteristic hallmark in the pathogenesis of Huntington's disease (HD), the underlying mechanism of striatal susceptibility remains to be clarified. Heat shock proteins (HSPs) have been reported to suppress the aggregate formation of mutant huntingtin and concurrent striatal cell death. In a previous study, we observed that heat shock transcription factor 1 (HSF1), a major transcription factor of HSPs, significantly attenuated 3‑nitropropionic acid (3NP)‑induced reactive oxygen species (ROS) production and apoptosis through the expression of HSP 70 in striatal cells. To investigate the differential roles of HSPs in 3NP‑induced striatal cell death, the effect of geldanamycin (GA), an HSP 90 inhibitor, was examined in 3NP‑stimulated striatal cells. GA significantly attenuated 3NP‑induced striatal apoptosis and ROS production with an increased expression of HSP 70. Triptolide (TL), an HSP 70 inhibitor, abolished GA‑mediated protective effects in 3NP‑stimulated striatal cells. To understand the underlying mechanism by which GA‑mediated HSP 70 protects striatal cells against 3NP stimulation, the involvement of various signaling pathways was examined. GA significantly attenuated 3NP‑induced c‑Jun N‑terminal kinase (JNK) phosphorylation and subsequent c‑Jun phosphorylation in striatal cells. Taken together, the present study demonstrated that GA exhibits protective properties against 3NP‑induced apoptosis and JNK activation via the induction of HSP 70 in striatal cells, suggesting that expression of HSP 70 may be a valuable therapeutic target in the treatment of HD.

Fluorodeoxyuridine improves Caenorhabditis elegans proteostasis independent of reproduction onset

Protein homeostasis (proteostasis) networks are dynamic throughout the lifespan of an organism. During Caenorhabditis elegans adulthood, the maintenance of metastable proteins and the activation of stress responses are inversely associated with germline stem cell proliferation. Here, we employed the thymidylate synthase inhibitor 5-fluoro-2'-deoxyuridine (FUdR) to chemically inhibit reproduction, thus allowing for examination of the interplay between reproduction and somatic proteostasis. We found that treatment with FUdR modulates proteostasis decline both before and after reproduction onset, such that effective induction of the heat shock response was maintained during adulthood and that metastable temperature-sensitive mutant phenotypes were rescued under restrictive conditions. However, FUdR treatment also improved the folding capacity of germline- and gonadogenesis-defective mutants, suggesting that proteostasis modulation by FUdR is independent of germline stem cell proliferation or inhibition of reproduction. Our data, therefore, indicate that FUdR converges on alternative regulatory signals that modulate C. elegans proteostasis capacity during development and adulthood.

Pharmacological protein targets in polyglutamine diseases: mutant polypeptides and their interactors

Polyglutamine diseases are a group of pathologies affecting different parts of the brain and causing dysfunction and atrophy of certain neural cell populations. These diseases stem from mutations in various cellular genes that result in the synthesis of proteins with extended polyglutamine tracts. In particular, this concerns huntingtin, ataxins, and androgen receptor. These mutant proteins can form oligomers, aggregates, and, finally, aggresomes with distinct functions and different degrees of cytotoxicity. In this review, we analyze the effects of different forms of polyQ proteins on other proteins and their functions, which are considered as targets for therapeutic intervention.

Pharmacological lifespan extension of invertebrates

There is considerable interest in identifying small, drug-like compounds that slow aging in multiple species, particularly in mammals. Such compounds may prove to be useful in treating and retarding age-related disease in humans. Just as invertebrate models have been essential in helping us understand the genetic pathways that control aging, these model organisms are also proving valuable in discovering chemical compounds that influence longevity. The nematode Caenorhabditis elegans has numerous advantages for such studies including its short lifespan and has been exploited by a number of investigators to find compounds that impact aging. Here, we summarize the progress being made in identifying compounds that extend the lifespan of invertebrates, and introduce the challenges we face in translating this research into human therapies.

Heat shock transcription factor-1 suppresses apoptotic cell death and ROS generation in 3-nitropropionic acid-stimulated striatal cells

Striatal neuronal cell death is one of the pathological features of Huntington's disease (HD). Overexpression of some heat shock proteins (HSPs) has been reported to suppress the aggregate formation of mutant huntingtin and concurrent cell death. Heat shock transcription factor-1 (HSF 1), a major transcription factor of HSPs, has also been reported to be increased in HD models. However, the exact role of HSF 1 in the pathogenesis of HD has not been clearly elucidated. 3-Nitropropionic acid (3NP), an irreversible inhibitor of the mitochondrial complex II, induces selective damage to the striatum in animals and produces clinical features of HD. To investigate roles of HSF 1 on 3NP-induced oxidative stress, HSF 1 was transiently overexpressed in striatal cells. Expression of HSF 1 significantly attenuated 3NP-induced apoptotic striatal cell death and resulted in increased expression of HSP 70. Furthermore, expression of HSF 1 significantly attenuated 3NP-induced intracellular reactive oxygen species (ROS) generation. Taken together, the present study clearly demonstrates that HSF 1 attenuates 3NP-induced apoptotic striatal cell death and ROS generation, possibly through HSP70 expression, suggesting that HSF 1 might be a valuable therapeutic target in the treatment of HD.

HSPBs: small proteins with big implications in human disease

Although initially somewhat ignored, recent studies have now clearly established that the diverse members of the human family of small HSPs (HSPB1-HSPB10) play crucial roles in a wide range of cell types to maintain the integrity and function of tissues, in particular that of nervous and muscular tissue. The 10 human HSPBs clearly have overlapping and non-overlapping functional characteristics. Their ability to self- and hetero-oligomerise provides the cells with a large array of potentially different, specific functions. Single HSPB members can have a multitude of functions (moonlighting) and act on different "clients", thus affecting a wide range of different processes or structures that can ultimately affect the rate of aging of tissues and entire organisms. This is underscored by the findings that some inherited diseases involve mutations in several HSPB members that cause premature (mostly muscle and neuronal) tissue degeneration. Inversely, cancer cell resistance to different anticancer therapies is associated with elevated expression of several HSPBs. Still, many unanswered questions exist about the precise functioning of HSPBs, their collaboration with other HSPB members as well as their functions within the entire cellular chaperone network. Also, better insight in the regulation of expression of the various members and how their function is modulated post-translationally is needed. Such may be crucially important to develop means to intervene with their function for therapeutic purposes, which would require functional down-regulation in cancer but up-regulation in, for instance, cardiac or degenerative neuro/neuromuscular diseases. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Pharmacological maintenance of protein homeostasis could postpone age-related disease

Over the last 10 years, various screens of small molecules have been conducted to find long sought interventions in aging. Most of these studies were performed in invertebrates but the demonstration of pharmacological lifespan extension in the mouse has created considerable excitement. Since aging is a common risk factor for several chronic diseases, there is a reasonable expectation that some compounds capable of extending lifespan will be useful for preventing a range of age-related diseases. One of the potential targets is protein aggregation which is associated with several age-related diseases. Genetic studies have long indicated that protein homeostasis is a critical component of longevity but recently a series of chemicals have been identified in the nematode Caenorhabditis elegans that lead to the maintenance of the homeostatic network and extend lifespan. Herein we review these interventions in C. elegans and consider the potential of improving health by enhancing protein homeostasis.

Membrane-lipid therapy in operation: the HSP co-inducer BGP-15 activates stress signal transduction pathways by remodeling plasma membrane rafts

Aging and pathophysiological conditions are linked to membrane changes which modulate membrane-controlled molecular switches, causing dysregulated heat shock protein (HSP) expression. HSP co-inducer hydroxylamines such as BGP-15 provide advanced therapeutic candidates for many diseases since they preferentially affect stressed cells and are unlikely have major side effects. In the present study in vitro molecular dynamic simulation, experiments with lipid monolayers and in vivo ultrasensitive fluorescence microscopy showed that BGP-15 alters the organization of cholesterol-rich membrane domains. Imaging of nanoscopic long-lived platforms using the raft marker glycosylphosphatidylinositol-anchored monomeric green fluorescent protein diffusing in the live Chinese hamster ovary (CHO) cell plasma membrane demonstrated that BGP-15 prevents the transient structural disintegration of rafts induced by fever-type heat stress. Moreover, BGP-15 was able to remodel cholesterol-enriched lipid platforms reminiscent of those observed earlier following non-lethal heat priming or membrane stress, and were shown to be obligate for the generation and transmission of stress signals. BGP-15 activation of HSP expression in B16-F10 mouse melanoma cells involves the Rac1 signaling cascade in accordance with the previous observation that cholesterol affects the targeting of Rac1 to membranes. Finally, in a human embryonic kidney cell line we demonstrate that BGP-15 is able to inhibit the rapid heat shock factor 1 (HSF1) acetylation monitored during the early phase of heat stress, thereby promoting a prolonged duration of HSF1 binding to heat shock elements. Taken together, our results indicate that BGP-15 has the potential to become a new class of pharmaceuticals for use in ‘membrane-lipid therapy’ to combat many various protein-misfolding diseases associated with aging.