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White AR. The firestorm within: A narrative review of extreme heat and wildfire smoke effects on brain health. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 922:171239. [PMID: 38417511 DOI: 10.1016/j.scitotenv.2024.171239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 02/21/2024] [Accepted: 02/22/2024] [Indexed: 03/01/2024]
Abstract
Climate change is generating increased heatwaves and wildfires across much of the world. With these escalating environmental changes comes greater impacts on human health leading to increased numbers of people suffering from heat- and wildfire smoke-associated respiratory and cardiovascular impairment. One area of health impact of climate change that has received far less attention is the effects of extreme heat and wildfire smoke exposure on human brain health. As elevated temperatures, and wildfire-associated smoke, are increasingly experienced simultaneously over summer periods, understanding this combined impact is critical to management of human health especially in the elderly, and people with dementia, and other neurological disorders. Both extreme heat and wildfire smoke air pollution (especially particulate matter, PM) induce neuroinflammatory and cerebrovascular effects, oxidative stress, and cognitive impairment, however the combined effect of these impacts are not well understood. In this narrative review, a comprehensive examination of extreme heat and wildfire smoke impact on human brain health is presented, with a focus on how these factors contribute to cognitive impairment, and dementia, one of the leading health issues today. Also discussed is the potential impact of combined heat and wildfire smoke on brain health, and where future efforts should be applied to help advance knowledge in this rapidly growing and critical field of health research.
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Affiliation(s)
- Anthony R White
- Mental Health and Neuroscience Program, QIMR Berghofer Medical Research Institute, Herston, Queensland 4006, Australia; A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Neulaniementie 2, 70211 Kuopio, Finland; School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia; School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, QLD, Australia.
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Effect of thermal preconditioning on Hsp70 expression in the medulla oblongata and on hemodynamics during passive hyperthermia. Brain Res 2019; 1723:146404. [PMID: 31454515 DOI: 10.1016/j.brainres.2019.146404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/21/2019] [Accepted: 08/23/2019] [Indexed: 11/24/2022]
Abstract
A short-term episode of elevated core body temperature that induces Hsp70 expression (thermal preconditioning) may protect against heatstroke during subsequent hyperthermia. The protective effects of thermal preconditioning may involve several cellular and immunological mechanisms and improvements in baroreflex sensitivity. To substantiate the hypothesis that the protective effect of thermal preconditioning also occurs in conditions with intact thermoregulation, we examined the evolution of spontaneous cardiovagal baroreflex sensitivity and the protective effect of Hsp70 expression after thermal preconditioning in nonanesthetized Wistar-Kyoto rats with implanted telemetric transmitters. In the baroreflex centers of the medulla oblongata, thermal preconditioning induced Hsp70 in perineuronal and perivascular oligodendrocytes, microglia, and endothelial cells but not in neurons. The maximal Hsp70 expression was detected 4 h after preconditioning, but a significant number of Hsp70-positive cells was still present 72 h after preconditioning. Increased c-Fos expression in the neurons of baroreflex centers was detectable only 4 h after preconditioning. The mean values of cardiovagal baroreflex sensitivity did not show significant differences during the 72-hour follow-up period after thermal preconditioning. Similarly, cardiovascular variability measures of the autonomic nervous system activity were also not significantly affected by thermal preconditioning. During passive hyperthermia, thermal preconditioning had no statistically significant effect on thermoregulation and the onset of arterial pressure decline. Our data suggest that thermal preconditioning induces a glial type of Hsp70 expression in the baroreflex centers of the medulla oblongata. However, this response was not associated with cardiovagal baroreflex sensitization and protection against hemodynamic instability during passive hyperthermia.
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Gualtieri F, Nowakowska M, von Rüden EL, Seiffert I, Potschka H. Epileptogenesis-Associated Alterations of Heat Shock Protein 70 in a Rat Post-Status Epilepticus Model. Neuroscience 2019; 415:44-58. [DOI: 10.1016/j.neuroscience.2019.06.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 06/18/2019] [Accepted: 06/25/2019] [Indexed: 02/02/2023]
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Abstract
The most common neurodegenerative diseases are Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease, frontotemporal lobar degeneration, and the motor neuron diseases, with AD affecting approximately 6% of people aged 65 years and older, and PD affecting approximately 1% of people aged over 60 years. Specific proteins are associated with these neurodegenerative diseases, as determined by both immunohistochemical studies on post-mortem tissue and genetic screening, where protein misfolding and aggregation are key hallmarks. Many of these proteins are shown to misfold and aggregate into soluble non-native oligomers and large insoluble protein deposits (fibrils and plaques), both of which may exert a toxic gain of function. Proteotoxicity has been examined intensively in cell culture and in in vivo models, and clinical trials of methods to attenuate proteotoxicity are relatively new. Therapies to enhance cellular protein quality control mechanisms such as upregulation of chaperones and clearance/degradation pathways, as well as immunotherapies against toxic protein conformations, are being actively pursued. In this article, we summarize the common pathophysiology of neurodegenerative disease, and review therapies in early-phase clinical trials that target the proteotoxic component of several neurodegenerative diseases.
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Affiliation(s)
- Luke McAlary
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada.
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, V6T 2B5, Canada.
| | - Steven S Plotkin
- Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1, Canada.
- Genome Sciences and Technology Program, University of British Columbia, Vancouver, BC, V6T 1Z2, Canada.
| | - Neil R Cashman
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, V6T 2B5, Canada.
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San Gil R, Ooi L, Yerbury JJ, Ecroyd H. The heat shock response in neurons and astroglia and its role in neurodegenerative diseases. Mol Neurodegener 2017; 12:65. [PMID: 28923065 PMCID: PMC5604514 DOI: 10.1186/s13024-017-0208-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 09/01/2017] [Indexed: 12/13/2022] Open
Abstract
Protein inclusions are a predominant molecular pathology found in numerous neurodegenerative diseases, including amyotrophic lateral sclerosis and Huntington's disease. Protein inclusions form in discrete areas of the brain characteristic to the type of neurodegenerative disease, and coincide with the death of neurons in that region (e.g. spinal cord motor neurons in amyotrophic lateral sclerosis). This suggests that the process of protein misfolding leading to inclusion formation is neurotoxic, and that cell-autonomous and non-cell autonomous mechanisms that maintain protein homeostasis (proteostasis) can, at times, be insufficient to prevent protein inclusion formation in the central nervous system. The heat shock response is a pro-survival pathway induced under conditions of cellular stress that acts to maintain proteostasis through the up-regulation of heat shock proteins, a superfamily of molecular chaperones, other co-chaperones and mitotic regulators. The kinetics and magnitude of the heat shock response varies in a stress- and cell-type dependent manner. It remains to be determined if and/or how the heat shock response is activated in the different cell-types that comprise the central nervous system (e.g. neurons and astroglia) in response to protein misfolding events that precede cellular dysfunctions in neurodegenerative diseases. This is particularly relevant considering emerging evidence demonstrating the non-cell autonomous nature of amyotrophic lateral sclerosis and Huntington's disease (and other neurodegenerative diseases) and the destructive role of astroglia in disease progression. This review highlights the complexity of heat shock response activation and addresses whether neurons and glia sense and respond to protein misfolding and aggregation associated with neurodegenerative diseases, in particular Huntington's disease and amyotrophic lateral sclerosis, by inducing a pro-survival heat shock response.
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Affiliation(s)
- Rebecca San Gil
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, 2522 Australia
| | - Lezanne Ooi
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, 2522 Australia
| | - Justin J. Yerbury
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, 2522 Australia
| | - Heath Ecroyd
- Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Northfields Ave, Wollongong, 2522 Australia
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Xu G, Fromholt S, Ayers JI, Brown H, Siemienski Z, Crosby KW, Mayer CA, Janus C, Borchelt DR. Substantially elevating the levels of αB-crystallin in spinal motor neurons of mutant SOD1 mice does not significantly delay paralysis or attenuate mutant protein aggregation. J Neurochem 2015; 133:452-64. [PMID: 25557022 DOI: 10.1111/jnc.13022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 12/10/2014] [Accepted: 12/16/2014] [Indexed: 12/14/2022]
Abstract
There has been great interest in enhancing endogenous protein maintenance pathways such as the heat-shock chaperone response, as it is postulated that enhancing clearance of misfolded proteins could have beneficial disease modifying effects in amyotrophic lateral sclerosis and other neurodegenerative disorders. In cultured cell models of mutant SOD1 aggregation, co-expression of αB-crystallin (αB-crys) has been shown to inhibit the formation of detergent-insoluble forms of mutant protein. Here, we describe the generation of a new line of transgenic mice that express αB-crys at > 6-fold the normal level in spinal cord, with robust increases in immunoreactivity throughout the spinal cord grey matter and, specifically, in spinal motor neurons. Surprisingly, spinal cords of mice expressing αB-crys alone contained 20% more motor neurons per section than littermate controls. Raising αB-crys by these levels in mice transgenic for either G93A or L126Z mutant SOD1 had no effect on the age at which paralysis developed. In the G93A mice, which showed the most robust degree of motor neuron loss, the number of these cells declined by the same proportion as in mice expressing the mutant SOD1 alone. In paralyzed bigenic mice, the levels of detergent-insoluble, misfolded, mutant SOD1 were similar to those of mice expressing mutant SOD1 alone. These findings indicate that raising the levels of αB-crys in spinal motor neurons by 6-fold does not produce the therapeutic effects predicted by cell culture models of mutant SOD1 aggregation. Enhancing the protein chaperone function may present a therapeutic approach to amyotrophic lateral sclerosis caused by mutations in SOD1, and other neurodegenerative disorders characterized by cytosolic protein aggregation. Previous studies in cell models suggested that the chaperone known as αB-crystallin (αB-crys) can prevent mutant SOD1 aggregation. We report that transgenic expression of αB-crys at > 6-fold the normal level in spinal cords of mice expressing mutant SOD1 produces no therapeutic benefit.
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Affiliation(s)
- Guilian Xu
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKnight Brain Institute, University of Florida, Gainesville, Florida, USA
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Webb KC, Eby JM, Hariharan V, Hernandez C, Luiten RM, Le Poole IC. Enhanced bleaching treatment: opportunities for immune-assisted melanocyte suicide in vitiligo. Exp Dermatol 2014; 23:529-33. [PMID: 24840876 DOI: 10.1111/exd.12449] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2014] [Indexed: 01/13/2023]
Abstract
Depigmentation in vitiligo occurs by progressive loss of melanocytes from the basal layer of the skin, and can be psychologically devastating to patients. T cell-mediated autoimmunity explains the progressive nature of this disease. Rather than being confronted with periods of rapid depigmentation and bouts of repigmentation, patients with long-standing, treatment-resistant vitiligo can undergo depigmentation treatment. The objective is to remove residual pigmentation to achieve a cosmetically acceptable result--that of skin with a uniform appearance. In the United States, only the use of mono-benzyl ether of hydroquinone (MBEH) is approved for this purpose. However, satisfactory results can take time to appear, and there is a risk of repigmentation. MBEH induces necrotic melanocyte death followed by a cytotoxic T-cell response to remaining, distant melanocytes. As cytotoxic T-cell responses are instrumental to depigmentation, we propose that combining MBEH with immune adjuvant therapies will accelerate immune-mediated melanocyte destruction to achieve faster, more definitive depigmentation than with MBEH alone. As Toll-like Receptor (TLR) agonists--imiquimod, CpG, and Heat Shock Protein 70 (HSP 70)--all support powerful Th1 responses, we propose that using MBEH in combination with these agents can achieve superior depigmentation results for vitiligo patients.
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Affiliation(s)
- Kirsten C Webb
- Department of Dermatology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA
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May LA, Kramarenko II, Brandon CS, Voelkel-Johnson C, Roy S, Truong K, Francis SP, Monzack EL, Lee FS, Cunningham LL. Inner ear supporting cells protect hair cells by secreting HSP70. J Clin Invest 2013; 123:3577-87. [PMID: 23863716 DOI: 10.1172/jci68480] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 05/03/2013] [Indexed: 02/02/2023] Open
Abstract
Mechanosensory hair cells are the receptor cells of hearing and balance. Hair cells are sensitive to death from exposure to therapeutic drugs with ototoxic side effects, including aminoglycoside antibiotics and cisplatin. We recently showed that the induction of heat shock protein 70 (HSP70) inhibits ototoxic drug-induced hair cell death. Here, we examined the mechanisms underlying the protective effect of HSP70. In response to heat shock, HSP70 was induced in glia-like supporting cells but not in hair cells. Adenovirus-mediated infection of supporting cells with Hsp70 inhibited hair cell death. Coculture with heat-shocked utricles protected nonheat-shocked utricles against hair cell death. When heat-shocked utricles from Hsp70-/- mice were used in cocultures, protection was abolished in both the heat-shocked utricles and the nonheat-shocked utricles. HSP70 was detected by ELISA in the media surrounding heat-shocked utricles, and depletion of HSP70 from the media abolished the protective effect of heat shock, suggesting that HSP70 is secreted by supporting cells. Together our data indicate that supporting cells mediate the protective effect of HSP70 against hair cell death, and they suggest a major role for supporting cells in determining the fate of hair cells exposed to stress.
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Affiliation(s)
- Lindsey A May
- National Institute on Deafness and Other Communication Disorders, NIH, Rockville, Maryland 20850, USA
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Farmer KL, Li C, Dobrowsky RT. Diabetic peripheral neuropathy: should a chaperone accompany our therapeutic approach? Pharmacol Rev 2012; 64:880-900. [PMID: 22885705 DOI: 10.1124/pr.111.005314] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Diabetic peripheral neuropathy (DPN) is a common complication of diabetes that is associated with axonal atrophy, demyelination, blunted regenerative potential, and loss of peripheral nerve fibers. The development and progression of DPN is due in large part to hyperglycemia but is also affected by insulin deficiency and dyslipidemia. Although numerous biochemical mechanisms contribute to DPN, increased oxidative/nitrosative stress and mitochondrial dysfunction seem intimately associated with nerve dysfunction and diminished regenerative capacity. Despite advances in understanding the etiology of DPN, few approved therapies exist for the pharmacological management of painful or insensate DPN. Therefore, identifying novel therapeutic strategies remains paramount. Because DPN does not develop with either temporal or biochemical uniformity, its therapeutic management may benefit from a multifaceted approach that inhibits pathogenic mechanisms, manages inflammation, and increases cytoprotective responses. Finally, exercise has long been recognized as a part of the therapeutic management of diabetes, and exercise can delay and/or prevent the development of painful DPN. This review presents an overview of existing therapies that target both causal and symptomatic features of DPN and discusses the role of up-regulating cytoprotective pathways via modulating molecular chaperones. Overall, it may be unrealistic to expect that a single pharmacologic entity will suffice to ameliorate the multiple symptoms of human DPN. Thus, combinatorial therapies that target causal mechanisms and enhance endogenous reparative capacity may enhance nerve function and improve regeneration in DPN if they converge to decrease oxidative stress, improve mitochondrial bioenergetics, and increase response to trophic factors.
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Affiliation(s)
- Kevin L Farmer
- Department of Pharmacology and Toxicology, The University of Kansas, Lawrence, KS 66045, USA
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Zhang Z, Zhang ZY, Wu Y, Schluesener HJ. Immunolocalization of Toll-like receptors 2 and 4 as well as their endogenous ligand, heat shock protein 70, in rat traumatic brain injury. Neuroimmunomodulation 2012; 19:10-9. [PMID: 22067617 DOI: 10.1159/000326771] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 02/23/2011] [Indexed: 01/01/2023] Open
Abstract
OBJECTIVE Toll-like receptors (TLRs) are essential to the innate immune system for recognizing not only microbial pathogens but also endogenous ligands from injured cells, suggesting that TLRs are a sensitive detection system to tissue injury and play roles in initiating tissue degeneration/regeneration. In this study, the effects of traumatic brain injury (TBI) on lesional expression of TLR2, TLR4, their most common adaptor molecule myeloid differentiation factor 88 (MyD88) and their endogenous ligand, heat shock protein 70 (HSP70), were investigated. METHODS Rat TBI was induced using an open-skull weight-drop model. TLR2, TLR4, MyD88 and HSP70 expression was studied by immunohistochemistry. RESULTS TLR2, TLR4, HSP70 and MyD88 were mainly found in lesioned regions and subcortical white matter. While infiltration of TLR2+ cells became significant on day 2, significant accumulation of TLR4+, MyD88+ and HSP70+ cells was already seen on day 1, and the numbers of immunopositive cells increased continuously until day 4. Furthermore, double staining together with morphological classification showed that major cellular sources for TLR2, TLR4 and MyD88 were macrophages/microglia in lesioned areas and astrocytes in subcortical white matter. But for HSP70, the major cellular sources were neurons in perilesion and macrophages/microglia in lesion areas and astrocytes in subcortical white matter. DISCUSSION In summary, our data reveal distinct patterns of localization of TLR+ resident and infiltrating cells in TBI rat brain. Infiltrating activated monocytic cells are the major source of TLR+ cells. These findings warrant further investigation of the roles of TLRs in controlling immune and degenerative/regenerative processes after TBI.
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Affiliation(s)
- Zhiren Zhang
- Institute of Immunology, Third Military University of PLA, Chongqing, PR China.
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