Age-related decrease in the inductability of heat shock protein 72 in normal human skin

Oxidative stress protection by exogenous delivery of rhHsp70 chaperone to the retinal pigment epithelium (RPE), a possible therapeutic strategy against RPE degeneration

PURPOSE

To measure the cytoprotective effects of rhHsp70 against oxidative stress and study its cellular uptake, intracellular and intraocular distribution in the retinal pigment epithelium.

METHODS

Human retinal pigment epithelial cells (ARPE-19) were pre-treated with rhHsp70 for 24 h, 48 h, and 72 h before being exposed to 1.25 mM hydrogen peroxide. Non-treated cells served as control. We analysed interleukin 6 secretion, cell viability, and cytolysis. Uptake and intracellular distribution of fluorescently labelled rhHsp70 were investigated with flow cytometry and confocal microscopy, respectively. Ocular distribution of radioactively labelled rhHsp70 was followed ex vivo in porcine eyes by micro SPECT/CT.

RESULTS

After exposure to hydrogen peroxide, IL-6 secretion decreased by 35-39% when ARPE-19 cells were pre-treated with rhHsp70. Cell viability increased by 17-32%, and cell lysis, measured by the release of lactate dehydrogenase, decreased by 6-43%. ARPE-19 cells endocytosed rhHsp70 added to the culture medium and the protein was localized in late endosomes and lysosomes. Following intravitreal injection into isolated porcine eyes, we found 20% rhHsp70 in the RPE.

CONCLUSIONS

Recombinant hHsp70 protein offers protection against oxidative stress. RPE cells take up the exogenously delivered rhHsp70 and localize it in late endosomes and lysosomes. This work provides the basis for a therapeutic strategy to target aggregate-associated neurodegeneration in AMD.

The role of heat stress on the age related protein carbonylation

Since the proteins are involved in many physiological processes in the organisms, modifications of proteins have important outcomes. Protein modifications are classified in several ways and oxidative stress related ones take a wide place. Aging is characterized by the accumulation of oxidized proteins and decreased degradation of these proteins. On the other hand protein turnover is an important regulatory mechanism for the control of protein homeostasis. Heat shock proteins are a highly conserved family of proteins in the various cells and organisms whose expressions are highly inducible during stress conditions. These proteins participate in protein assembly, trafficking, degradation and therefore play important role in protein turnover. Although the entire functions of each heat shock protein are still not completely investigated, these proteins have been implicated in the processes of protection and repair of stress-induced protein damage. This study has focused on the heat stress related carbonylated proteins, as a marker of oxidative protein modification, in young and senescent fibroblasts. The results are discussed with reference to potential involvement of induced heat shock proteins. This article is part of a Special Issue entitled: Protein Modifications.

BIOLOGICAL SIGNIFICANCE

Age-related protein modifications, especially protein carbonylation take a wide place in the literature. In this direction, to highlight the role of heat shock proteins in the oxidative modifications may bring a new aspect to the literature. On the other hand, identified carbonylated proteins in this study confirm the importance of folding process in the mitochondria which will be further analyzed in detail.

The age-related failure of adaptive responses to contractile activity in skeletal muscle is mimicked in young mice by deletion of Cu,Zn superoxide dismutase

In muscle, aging is associated with a failure of adaptive responses to contractile activity, and this is hypothesized to play an important role in age-related loss of muscle mass and function. Mice lacking the Cu,Zn superoxide dismutase (Cu,ZnSOD, SOD1) show an accelerated, age-related loss of muscle mass and function. This work determined whether adult mice lacking Cu,ZnSOD (Sod1^−/− mice) show a premature failure of adaptive responses to contractions in a similar manner to old wild-type (WT) mice. Adult Sod1^−/− mice (6–8 months of age) had a ∼ 30% reduction in gastrocnemius muscle mass compared with age-matched WT mice. This lower muscle mass was associated with an activation of DNA binding by NFκB and AP-1 at rest. Measurements of the activity of reactive oxygen species (ROS) in single fibres from the muscles of Sod1^−/− mice at rest indicated an elevation in activity compared with fibres from WT mice. Following 15 min of isometric contractions, muscle fibres from WT mice showed an increase in the intracellular ROS activities and activation of NFκB and AP-1, but no changes in either ROS activity or NFκB and AP-1 activation were seen in the muscles of Sod1^−/− mice following contractions. This pattern of changes mimics that seen in the muscles of old WT mice, suggesting that the attenuated responses to contractile activity seen in old mice result from chronic exposure to increased oxidant activity. Data support the use of the Sod1^−/− mouse model to evaluate potential mechanisms that contribute to the loss of muscle mass and function in the elderly.

The heat shock proteins in cellular aging: is zinc the missing link?

T-cell functions are critical for the efficiency of the adaptive immune response. It is now clear that aging is associated with changes in the T-cell response to antigenic stimulation, one of the many changes collectively resulting in immune senescence. Several hypotheses have been proposed to explain such changes. We believe that chronic stimulation of T-cells enhances the appearance of apoptosis-resistant anergic dysfunctional cells; in humans in vivo these are predominantly specific for antigens of persistent viruses, especially CMV. Concomitantly, age-associated zinc deficiency is common and one hypothesis is that lack of zinc bioavailability contributes to impaired T-cell function. This could further compromise the integrity of T-cells under chronic antigenic stress, which can be modelled in long-term clonal cultures in vitro. Newly synthesized heat-shock proteins (HSPs) protect the cellular proteins from degradation under such conditions. In this short review we will briefly outline the role of heat-shock proteins and zinc deficiency in aging in order to finally discuss our own results in the context of a link between HSPs, aging and zinc.

Adaptive responses of mouse skeletal muscle to contractile activity: The effect of age

This study has characterised the time course of two major transcriptional adaptive responses to exercise (changes in antioxidant defence enzyme activity and heat shock protein (HSP) content) in muscles of adult and old male mice following isometric contractions and has examined the mechanisms involved in the age-related reduction in transcription factor activation. Muscles of B6XSJL mice were subjected to isometric contractions and analysed for antioxidant defence enzyme activities, heat shock protein content and transcription factor DNA binding activity. Data demonstrated a significant increase in superoxide dismutase (SOD) and catalase activity and HSP content of muscles of adult mice following contractile activity which was associated with increased activation of the transcription factors, nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and heat shock factor (HSF) following contractions. Significant increases in SOD and catalase activity and heat shock cognate (HSC70) content were seen in quiescent muscles of old mice. The increase in antioxidant defence enzyme activity following contractile activity seen in muscles of adult mice was not seen in muscles of old mice and this was associated with a failure to fully activate NF-kappaB and AP-1 following contractions. In contrast, although the production of HSPs was also reduced in muscles of old mice following contractile activity compared with muscles of adult mice following contractions, this was not due to a gross reduction in the DNA binding activity of HSF.

The heat shock proteins and plastic surgery

Heat shock proteins are diverse and essential components of cell physiology. Their expression is elevated in the cell undergoing stress, where they protect the cell from death by necrosis or apoptosis and accelerate recovery. Significant advances have been made in studies relevant to plastic surgery regarding these proteins and their manipulation. This review introduces the heat shock proteins and appraises these studies in skin, ultraviolet light exposure, neoplasia, wound healing, ageing, burns, and reconstructive surgery.

The ubiquitin-proteasome system at the crossroads of stress-response and ageing pathways: a handle for skin care?

The regulation of gene expression at the transcriptional level has been considered for long as the main mechanism of cellular adaptive responses. Since the turn of the century, however, it is becoming clear that higher organisms developed a complex, sensitive and maybe equally important network of regulatory pathways, relying largely on protein interactions, post-translational modifications and proteolysis. Here we review the involvement of the ubiquitin-proteasome pathway of protein degradation at different levels of cellular life in relation with ageing, and with a special focus on skin. It comes out that the ubiquitin system plays a major role in signal transduction associated with stress and ageing, in skin in particular through the control of retinoid and NF-kappaB pathways. The understanding of specific proteolytic targeting by E3 ubiquitin-ligases paves the way for a new generation of active molecules that may control particular steps of normal and pathological ageing.

The use of mature zebrafish (Danio rerio) as a model for human aging and disease

Zebrafish (Danio rerio) have been extensively utilized for understanding mechanisms of development. These studies have led to a wealth of resources including genetic tools, informational databases, and husbandry methods. In spite of all these resources, zebrafish have been underutilized for exploring pathophysiology of disease and the aging process. Zebrafish offer several advantages over mammalian models for these studies, including the ability to perform saturation mutagenesis and the capability to contain thousands of animals in a small space. In this review, we will discuss the use of mature zebrafish as an animal model and provide specific examples to support this novel use of zebrafish. Examples include demonstrating that clinical pathology can be performed in mature zebrafish and that age-associated changes in heat shock response can be observed in zebrafish. These highlights demonstrate the utility of zebrafish as a model for disease and aging.

Heat shock proteins can protect aged human and rodent cells from different stressful stimuli

Heat shock proteins (hsps) are induced by stressful stimuli and have been shown to protect cells and organs from such stresses both in vitro and in vivo. Because of this, mildly stressful stimuli, sufficient to induce hsp over-expression can protect against a subsequent more severe stress. In cells from aged individuals, however, no hsp induction is observed upon exposure to stress and no protective effect of a mild stress is observed. Here, we show that bypassing the block to hsp induction by artificially over-expressing hsps, can produce a protective effect against a variety of damaging stimuli in cells from aged rats or aged humans, indicating that hsps can have a protective effect in aged cells, provided successful over-expression can be achieved. Hence, hsps over-expression could be of therapeutic benefit in aged individuals if procedures to over-express the hsps can be developed either by devising non-stressful procedures to induce endogenous hsp over-expression or by developing vectors able to efficiently deliver exogenous hsps.

Subcorneal colocalization of the small heat shock protein, hsp27, with keratins and proteins of the cornified cell envelope

BACKGROUND

hsp27 is a member of the small heat shock protein family. Its expression in epidermal keratinocytes in situ and in tissue culture correlates with differentiation. Experimental evidence points to the fact that hsp27 is a molecular chaperone and is involved in the regulation of cell growth and differentiation.

OBJECTIVES

To investigate whether epidermal hsp27 through its chaperone function plays a role in the assembly of keratin filaments and the cornified cell envelope.

METHODS

We performed double staining immunofluorescence and immunogold microscopy on normal human skin (n = 15). We analysed the colocalization of hsp27 with actin, keratins and proteins of the cornified cell envelope (loricrin, filaggrin, transglutaminase 1).

RESULTS

Actin staining did not reveal detectable colocalization with hsp27. For keratins, transglutaminase, loricrin and filaggrin colocalization was found in more than 60% of the samples. Colocalization was confined to a narrow subcorneal layer with varying patterns of expression. Electron microscopy revealed that loricrin and filaggrin colocalize with hsp27 indirectly through binding to intermediate filaments.

CONCLUSIONS

These results provide morphological evidence that in normal human skin hsp27 might act as a chaperone of cornification. Investigations of the molecular hsp27 interactions with the proteins of the cornified cell envelope are necessary to gain further insight into terminal keratinocyte differentiation and disorders of keratinization.

Heat shock proteins in the photobiology of human skin

All organisms respond to sudden environmental changes with the increased transcription of genes belonging to the family of heat shock proteins (hsps). Hsp-inducing stress factors include elevated temperatures, alcohol, heavy metals, oxidants, and agents leading to protein denaturation. The induction of heat shock proteins is followed by a transient state of increased resistance to further stress and the heat shock response is generally thought to represent an evolutionary conserved adaptive mechanism to cope with hostile environmental conditions. Since the skin as a barrier organ has to cope with the potentially harmful consequences of exposure to ultraviolet radiation (UV), it appears reasonable to question whether hsps constitute a natural defence mechanism against UV. Hsps have been detected in resting as well as in stressed epidermal and dermal cells and overexpression of hsps is associated with increased resistance to UV-induced cell death. Furthermore, UV itself is able to induce the expression of specific hsps. Thus, hsps might provide an adaptive cellular response to increasing UV and enhancing the expression of hsps might turn out as a new way to deal with the immediate and long-term consequences of UV exposure. Prerequisite for the utilization of this concept is the development of non-toxic heat shock inducers and their evaluation for clinical efficacy and safety.

Increase in basal level of Hsp70, consisting chiefly of constitutively expressed Hsp70 (Hsc70) in aged rat brain

Alteration of proteins in the function and higher structure has been observed in aged organisms. Stress proteins, which have a role to protect proteins from denaturation, may respond to the protein denaturation with aging. We found that the basal level of Hsp70, consisting chiefly of constitutively expressed Hsp70 (Hsc70), in 24-month-old Wistar rats was significantly higher in some parts of the brain than that in 6-month-old rats. On the other hand, the basal level of Hsp70 was significantly lower in 24-month-old rats after restricted feeding, which is known to suppress aging, than those fed the diet ad libitum. In the pons, medulla, striatum, and thalamus of 24-month-old rat brain, the level of Hsp70 increased and the denaturation of the cytosol proteins was suppressed. These results suggest that the expression of Hsp70, mostly Hsc70, increases with aging and may have a role to suppress protein denaturation.

HSP70 induction may explain the long-lasting resistance to heat of Drosophila melanogaster having lived in hypergravity

In this study, we showed that in flies kept for 2 weeks at 1 (terrestrial gravity), 3 or 5 x g (hypergravity, HG) before transfer to 1 x g, resistance to heat remained higher in HG flies for several weeks after the transfer. The measurement of heat shock protein 70 (hsp70) indicated no induction of the protein in HG, but the study revealed that flies living in HG expressed more hsp70 only after being submitted to severe stress. The higher induction of hsp70 may explain the higher thermotolerance of these HG-treated young flies. Finally, an unknown protein was observed only in females. This protein may belong to a class of higher molecular weight hsp (hsp110), which have not previously been observed in Drosophila.

Age-related attenuation in the expression of the major heat shock proteins in human peripheral lymphocytes

A defining characteristic of human ageing is the reduced ability to maintain homeostasis in the face of adverse environmental stresses. This progressive impairment may be a major cause for the increased incidence of infections, and general morbidity and mortality in the elderly. Heat shock proteins (hsps) or stress proteins, induced in response to hyperthermia and to various other physical, chemical and biological stressors, are often also expressed constitutively at a lower level and perform many essential functions in the cell. Here we investigate age-related changes in the heat induced expression of a comprehensive range of hsps at the translational level using primary human peripheral lymphocytes in short term culture. Our study reveals age-related attenuation in the response of the well characterised up-regulated molecular chaperone system hsp 70, the steroid-receptor binding hsp 90 and the chaperonin hsp 60. A diminution with age is also demonstrated in the heat induced response of hsps 105, 56, 47, 40, 27, and 16. Differentially down-regulated proteins at 100, 38, and 18 kDa were also noted.

Heat shock transcription factor-1 regulates heat shock protein-72 expression in human keratinocytes exposed to ultraviolet B light

In response to ultraviolet radiation (UVR), skin keratinocytes increase expression of heat shock proteins that can protect cells from stress-induced damage. This heat shock response is known to be transcriptionally regulated in eukaryotic cells exposed to certain forms of environmental stress. In the skin, absorption of ultraviolet B light occurs primarily in the epidermis, and therefore, using primary cultures of normal human epidermal keratinocytes, we have examined whether transcriptional activation of the hsp72 gene occurs following UVB irradiation. Cultured keratinocytes were exposed to UVB (290-320 nm, 300 J per m2) and then incubated at 37 degrees C for various intervals before harvesting. Immediately following UV exposure, the heat shock transcription factor 1 (HSF1) dissociated from HSP72-HSF1 complexes, underwent trimerization and phosphorylation, and demonstrated DNA binding activity to the heat shock element in the promoter region of the hsp72 gene. UVB also increased hsp72 mRNA, with peak levels observed 1-3 h post-UVR. HSP72 protein was constitutively expressed in keratinocytes, and its expression was increased by UVB, with maximum levels at 6 h post-UVR. The stress response may be extremely important in the protection of human skin from UVB radiation, and modulation of heat shock protein expression and/or function offers a potential therapeutic target in the prevention of photoaging and skin cancer.