Multifactorial Attenuation of the Murine Heat Shock Response With Age

HDAC6 modulates the cognitive behavioral function and hippocampal tissue pathological changes of APP/PS1 transgenic mice through HSP90-HSF1 pathway

The aim of this study was to investigate histone deacetylase 6 (HDAC6) modifies the heat shock protein 90 (HSP90) and heat shock transcription factor 1 (HSF1) affect the levels of pathological markers such as Aβ oligomers (Aβo) and Tau phosphorylation (p-Tau) in APP/PS1 double transgenic mice hippocampal tissues or HT22 neurons as well as the changes in cognitive behavioral functions of mice. (1) APP/PS1 transgenic mice (6 months old, 25 ~ 30 g) were randomly assigned to 5 experimental groups, C57BL/6J mice (6 months old, 25 ~ 30 g) were used as 4 control groups, with 8 mice in each group. All mice underwent intracerebroventricular (i.c.v.) cannulation, and the experimental groups were administered with normal saline (APP + NS group), HDAC6 agonist tubastatin A hydrochloride (TSA) (APP + TSA group) or HDAC6 agonist theophylline (Theo) (APP + Theo group), HSP90 inhibitor Ganetespib (Gane) (APP + Gane group), or a combination of pre-injected Gane by TSA (APP + Gane + TSA group); the control group received i.c.v. injections of Gane (Gane group), TSA (TSA group), Theo (Theo group) or NS (NS group), respectively. (2) Mouse hippocampal neurons HT22 were randomly divided into a control group (Control) and an Aβ1-42 intervention group (Aβ). Within the Aβ group, further divisions were made for knockdown HSP90 (Aβ + siHSP90 group), overexpression HSP90 (Aβ + OE-HSP90 group), knockdown HSF1(Aβ + siHSF1 group) and knockdown HSF1 followed by overexpression HSP90 (Aβ + siHSF1 + OE-HSP90 group), resulting in a total of 6 groups. Morris water maze test was used to evaluate the cognitive behavior of the mice. Western blot and immunohistochemistry or immunofluorescence were performed to detect the levels of HDAC6, HSP90, HSF1, Aβ1-42, Tau protein, and p-Tau in the hippocampal tissue or HT22 cells. qRT-PCR was used to measure the levels of hdac6, hsp90, and hsf1 mRNA in the hippocampus or nerve cells. (1) The levels of HDAC6, Aβ1-42 and p-Tau were elevated, while HSP90 and HSF1 were decreased in the hippocampal tissue of APP/PS1 transgenic mice (all P < 0.01). Inhibiting HDAC6 upregulated the expressions of HSP90 and HSF1 in the hippocampal tissue of APP/PS1 mice, while decreasing the levels of Aβ1-42 and p-Tau as well as improving the spatial cognitive behavior in mice (P < 0.05 or P < 0.01). The opposite effects were observed upon HDAC6 activation. However, inhibiting HSP90 reduced the expression of HSF1 (P < 0.01) and increased the levels of Aβ1-42 and p-Tau (P < 0.05 or P < 0.01) but did not significantly affect the expression of HDAC6 (P > 0.05). No significant changes were observed in the aforementioned indicators in the 4 control groups (P > 0.05). (2) In the Aβ1-42 intervention group, HDAC6 and Aβ1-42, p-Tau expression levels were elevated, while HSP90 and HSF1 expressions were all decreased, and cell viability was reduced (P < 0.05 or P < 0.01). Overexpression of HSP90 upregulated HSF1 expression, decreased the levels of Aβ1-42 and p-Tau, and increased cell viability (P < 0.05 or P < 0.01). Knocking down HSP90 had the opposite effect; and knocking down HSF1 increased the levels of Aβ1-42 and p-Tau and decreased cells viability (all P < 0.01), but did not result in significant changes in the expression levels of HSP90 (P > 0.05). Inhibiting HDAC6 can upregulate the expressions of HSP90 and HSF1 but reduce the levels of Aβ1-42 and p-Tau in the hippocampus of APP/PS1 mice and improvement of cognitive behavioral function in mice; Overexpression of HSP90 can increase HSF1 but decrease Aβ1-42 and p-Tau levels in the hippocampal neurons and increase cell activity. It is suggested that HDAC6 may affect the formation of Aβ oligomers and the changes in Tau protein phosphorylation levels in the hippocampus of AD transgenic mouse as well as the alterations in cognitive behavioral functions by regulating the HSP90-HSF1 pathway.

Disrupted HSF1 regulation in normal and exceptional brain aging

Brain aging is a major risk factor for cognitive diseases such as Alzheimer's disease (AD) and vascular dementia. The rate of aging and age-related pathology are modulated by stress responses and repair pathways that gradually decline with age. However, recent reports indicate that exceptional longevity sustains and may even enhance the stress response. Whether normal and exceptional aging result in either attenuated or enhanced stress responses across all organs is unknown. This question arises from our understanding that biological age differs from chronological age and evidence that the rate of aging varies between organs. Thus, stress responses may differ between organs and depend upon regenerative capacity and ability to manage damaged proteins and proteotoxicity. To answer these questions, we assessed age-dependent changes in brain stress responses with normally aged wild type and long-lived Dwarf mice. Results from this study show that normal aging unfavorably impacts activation of the brain heat shock (HS) axis with key changes noted in the transcription factor, HSF1, and its regulation. Exceptional aging appears to preserve and strengthen many elements of HSF1 activation in the brain. These results support the possibility that reconstitution of aging brain stress responses requires a multi-factorial approach that addresses HSF1 protein levels, its DNA binding, and regulatory elements such as phosphorylation and protein interactions.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Relationship between heat shock proteins and cellular resistance to drugs and ageing

BACKGROUND AND AIMS

Ageing is a multifactorial degenerative process which causes a decrease in the cellular capacity for repair and adaptation to external stressors. In this way, it is important to maintain the proper balance of the proteome. Heat shock proteins (HSP) will intervene in this balance, which are responsible for the correct assembly, folding and translocation of other proteins when cells are subjected to stressors. This type of protein is overexpressed in human tumor cells, while its deficit, both in function and quantity, contributes to ageing processes. The present work aims to analyze the response of cells from studies carried out in normal and tumor cells that are subjected to stressors.

METHODS AND RESULTS

A PubMed search was performed using the keywords "cell ageing, cell longevity, resistance, HSP, heat shock proteins, thermal shock proteins". This search generated 212 articles. Subsequently, a series of inclusion and exclusion criteria were applied to select the articles of interest to be evaluated. Normal cells subjected to external stressors at low doses increase the number of HSP, causing them to become more resistant. In addition, tumor cells expressing high levels of HSP show greater resistance to treatment and increased cell replication. HSP intervene in the cellular resistance of both normal and tumor cells.

CONCLUSIONS

In the case of normal cells, the increase in HSP levels makes them respond effectively to an external stressor, increasing their resistance and not causing cell death. In the case of tumor cells, there is an increase in resistance to treatment.

Heat Shock Factor 1 Directly Regulates Postsynaptic Scaffolding PSD-95 in Aging and Huntington's Disease and Influences Striatal Synaptic Density

PSD-95 (Dlg4) is an ionotropic glutamate receptor scaffolding protein essential in synapse stability and neurotransmission. PSD-95 levels are reduced during aging and in neurodegenerative diseases like Huntington's disease (HD), and it is believed to contribute to synaptic dysfunction and behavioral deficits. However, the mechanism responsible for PSD-95 dysregulation under these conditions is unknown. The Heat Shock transcription Factor 1 (HSF1), canonically known for its role in protein homeostasis, is also depleted in both aging and HD. Synaptic protein levels, including PSD-95, are influenced by alterations in HSF1 levels and activity, but the direct regulatory relationship between PSD-95 and HSF1 has yet to be determined. Here, we showed that HSF1 chronic or acute reduction in cell lines and mice decreased PSD-95 expression. Furthermore, Hsf1(+/-) mice had reduced PSD-95 synaptic puncta that paralleled a loss in thalamo-striatal excitatory synapses, an important circuit disrupted early in HD. We demonstrated that HSF1 binds to regulatory elements present in the PSD-95 gene and directly regulates PSD-95 expression. HSF1 DNA-binding on the PSD-95 gene was disrupted in an age-dependent manner in WT mice and worsened in HD cells and mice, leading to reduced PSD-95 levels. These results demonstrate a direct role of HSF1 in synaptic gene regulation that has important implications in synapse maintenance in basal and pathological conditions.

Role of heat shock proteins in aging and chronic inflammatory diseases

Advanced age is associated with a decline in response to stress. This contributes to the establishment of chronic inflammation, one of the hallmarks of aging and age-related disease. Heat shock proteins (HSP) are determinants of life span, and their progressive malfunction leads to age-related pathology. To discuss the function of HSP on age-related chronic inflammation and illness. An updated review of literature and discussion of relevant work on the topic of HSP in normal aging and chronic inflammatory pathology was performed. HSP contribute to inflamm-aging. They also play a key role in age-associated pathology linked to chronic inflammation such as autoimmune disorders, neurological disease, cardiovascular disorder, and cancer. HSP may be targeted for control of their effects related to age and chronic inflammation. Research on HSP functions in age-linked chronic inflammatory disorders provides an opportunity to improve health span and delay age-related chronic disorders.

Recent advances in understanding the role of proteostasis

Maintenance of a functional proteome is achieved through the mechanism of proteostasis that involves precise coordination between molecular machineries assisting a protein from its conception to demise. Although each organelle within a cell has its own set of proteostasis machinery, inter-organellar communication and cell non-autonomous signaling bring forth the multidimensional nature of the proteostasis network. Exposure to extrinsic and intrinsic stressors can challenge the proteostasis network, leading to the accumulation of aberrant proteins or a decline in the proteostasis components, as seen during aging and in several diseases. Here, we summarize recent advances in understanding the role of proteostasis and its regulation in aging and disease, including monogenetic and infectious diseases. We highlight some of the emerging as well as unresolved questions in proteostasis that need to be addressed to overcome pathologies associated with damaged proteins and to promote healthy aging.

Augmentation of the heat shock axis during exceptional longevity in Ames dwarf mice

How the heat shock axis, repair pathways, and proteostasis impact the rate of aging is not fully understood. Recent reports indicate that normal aging leads to a 50% change in several regulatory elements of the heat shock axis. Most notably is the age-dependent enhancement of inhibitory signals associated with accumulated heat shock proteins and hyper-acetylation associated with marked attenuation of heat shock factor 1 (HSF1)–DNA binding activity. Because exceptional longevity is associated with increased resistance to stress, this study evaluated regulatory check points of the heat shock axis in liver extracts from 12 months and 24 months long-lived Ames dwarf mice and compared these findings with aging wild-type mice. This analysis showed that 12M dwarf and wild-type mice have comparable stress responses, whereas old dwarf mice, unlike old wild-type mice, preserve and enhance activating elements of the heat shock axis. Old dwarf mice thwart negative regulation of the heat shock axis typically observed in usual aging such as noted in HSF1 phosphorylation at Ser307 residue, acetylation within its DNA binding domain, and reduction in proteins that attenuate HSF1–DNA binding. Unlike usual aging, dwarf HSF1 protein and mRNA levels increase with age and further enhance by stress. Together these observations suggest that exceptional longevity is associated with compensatory and enhanced HSF1 regulation as an adaptation to age-dependent forces that otherwise downregulate the heat shock axis.

A molecular perspective on age-dependent changes to the heat shock axis

Aging is a complex process associated with progressive damage that leads to cellular dysfunction often accompanied by frailty and age-related diseases. Coping with all types of physiologic stress declines with age. While representing a primordial, cross-species response in poikilo- and homeotherms, the age-dependent perturbation of the stress response is more complex than previously thought. This short review examines how age influences the stress axis at multiple levels that involve both activating and attenuating pathways.