Heat shock protein expression in brain: a protective role spanning intrinsic thermal resistance and defense against neurotropic viruses

Insights Into the Role of Mortalin in Alzheimer’s Disease, Parkinson’s Disease, and HIV-1-Associated Neurocognitive Disorders

Mortalin is a chaperone protein that regulates physiological functions of cells. Its multifactorial role allows cells to survive pathological conditions. Pharmacological, chemical, and siRNA-mediated downregulation of mortalin increases oxidative stress, mitochondrial dysfunction leading to unregulated inflammation. In addition to its well-characterized function in controlling oxidative stress, mitochondrial health, and maintaining physiological balance, recent evidence from human brain autopsies and cell culture–based studies suggests a critical role of mortalin in attenuating the damage seen in several neurodegenerative diseases. Overexpression of mortalin provides an important line of defense against accumulated proteins, inflammation, and neuronal loss, a key characteristic feature observed in neurodegeneration. Neurodegenerative diseases are a group of progressive disorders, sharing pathological features in Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and HIV-associated neurocognitive disorder. Aggregation of insoluble amyloid beta-proteins and neurofibrillary tangles in Alzheimer’s disease are among the leading cause of neuropathology in the brain. Parkinson’s disease is characterized by the degeneration of dopamine neurons in substantia nigra pars compacta. A substantial synaptic loss leading to cognitive decline is the hallmark of HIV-associated neurocognitive disorder (HAND). Brain autopsies and cell culture studies showed reduced expression of mortalin in Alzheimer’s, Parkinson’s, and HAND cases and deciphered the important role of mortalin in brain cells. Here, we discuss mortalin and its regulation and describe how neurotoxic conditions alter the expression of mortalin and modulate its functions. In addition, we also review the neuroprotective role of mortalin under neuropathological conditions. This knowledge showcases the importance of mortalin in diverse brain functions and offers new opportunities for the development of therapeutic targets that can modulate the expression of mortalin using chemical compounds.

Feasibility study of a novel rectal cooling system for hypothermic radical prostatectomy in a swine model

Thermal damage and inflammatory responses of the sphincter and neurovascular bundles (NVBs) are responsible for post-prostatectomy incontinence and erectile dysfunction. Intraoperative hypothermia in the pelvic cavity may reduce the occurrence of these complications. We evaluated the feasibility of a novel rectal cooling system using an animal model. A novel rectal cooling system consisting of a cooling console and a multi-lumen rectal balloon was developed. We conducted animal tests on male pigs to evaluate the efficacy and safety of the system. The primary endpoint was to maintain the temperature of the NVBs at 25℃ (±5℃) during and after the electrocauterization of the bladder neck for 10 seconds. The safety endpoint was device-related complications or significant changes in the core body temperature of the pigs. The NVB temperature was below 30℃ within 3 minutes of activation of the rectal balloon. The temperature of the proximal NVB was consistently maintained below 25℃ in all cases. The temperature 1 cm from the bladder neck did not rise above 38°C and dropped to the initial level within 1 minute after electrocauterization. During cooling, the minimum temperature at the apex of the prostate was reduced to 10.1℃. There were no device-related complications or significant changes in core body temperature throughout the experiment. Animal tests suggest the feasibility and safety of this novel rectal cooling system. A first-in-human trial to assess the safety and efficacy of this system during radical prostatectomy is warranted.

Functional genomics study of acute heat stress response in the small yellow follicles of layer-type chickens

This study investigated global gene and protein expression in the small yellow follicle (SYF; 6-8 mm in diameter) tissues of chickens in response to acute heat stress. Twelve 30-week-old layer-type hens were divided into four groups: control hens were maintained at 25 °C while treatment hens were subjected to acute heat stress at 36 °C for 4 h without recovery, with 2-h recovery, and with 6-h recovery. SYFs were collected at each time point for mRNA and protein analyses. A total of 176 genes and 93 distinct proteins with differential expressions were identified, mainly associated with the molecular functions of catalytic activity and binding. The upregulated expression of heat shock proteins and peroxiredoxin family after acute heat stress is suggestive of responsive machineries to protect cells from apoptosis and oxidative insults. In conclusion, both the transcripts and proteins associated with apoptosis, stress response, and antioxidative defense were upregulated in the SYFs of layer-type hens to alleviate the detrimental effects by acute heat stress. However, the genomic regulations of specific cell type in response to acute heat stress of SYFs require further investigation.

Short-Term Heat Shock Affects Host-Virus Interaction in Mice Infected with Highly Pathogenic Avian Influenza Virus H5N1

Highly pathogenic avian influenza virus (HPAIV) H5N1 is a highly contagious virus that can cause acute respiratory infections and high human fatality ratio due to excessive inflammatory response. Short-term heat shock, as a stressful condition, could induce the expression of heat shock proteins that function as molecular chaperones to protect cells against multiple stresses. However, the protective effect of short-term heat shock in influenza infection is far from being understood. In this study, mice were treated at 39°C for 4 h before being infected with HPAIV H5N1. Interestingly, short-term heat shock significantly increased the levels of HSP70 and pro-inflammatory cytokines IL-6, TNF-α, IFN-β, and IFN-γ in the lung tissues of mice. Following HPAIV H5N1 infection, short-term heat shock alleviated immunopathology and viral replication in lung tissue and repressed the weight loss and increased the survival rate of H5N1-infected mice. Our data reported that short-term heat shock provided beneficial anti-HPAIV H5N1 properties in mice model, which offers an alternative strategy for non-drug prevention for influenza infection.

Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival

Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl-geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies.

Heat shock response and homeostatic plasticity

Heat shock response and homeostatic plasticity are mechanisms that afford functional stability to cells in the face of stress. Each mechanism has been investigated independently, but the link between the two has not been extensively explored. We explore this link. The heat shock response enables cells to adapt to stresses such as high temperature, metabolic stress and reduced oxygen levels. This mechanism results from the production of heat shock proteins (HSPs) which maintain normal cellular functions by counteracting the misfolding of cellular proteins. Homeostatic plasticity enables neurons and their target cells to maintain their activity levels around their respective set points in the face of stress or disturbances. This mechanism results from the recruitment of adaptations at synaptic inputs, or at voltage-gated ion channels. In this perspective, we argue that heat shock triggers homeostatic plasticity through the production of HSPs. We also suggest that homeostatic plasticity is a form of neuroprotection.

Does paracetamol help or hinder healing in bacterial infections?

Community nursing teams, alongside other primary care services and nurses in working in community hospitals, are caring for people who are older, sicker and require more complex care. The nurse's ability to use evidence to make informed judgements is vitally important to patient care. Nurses often give paracetamol that is prescribed on an 'as required' basis to patients with bacterial infections who are pyrexial. This practice is supported by guidelines from the National Institute of Health and Care Excellence and the British National Formulary. This article reviews the evidence and suggests that the administration of paracetamol in people with pyrexia should be reconsidered and given on an individualised basis rather than as a routine.

Reduction in heat shock protein 90 correlates to neuronal vulnerability in the rat piriform cortex following status epilepticus

In the present study, we addressed the question of whether the distinct patterns of heat shock protein (HSP) 70 and HSP90 expressions in the brain region represents the regional specific responses to status epilepsticus (SE) in an effort to better understand the role of HSPs in epileptogenic insult. HSP70 immunoreactivity was increased in CA3 pyramidal cells as well as dentate granule cells at 12h-1week after SE. HSP70 immunoreactivity was transiently increased in neurons within the piriform cortex (PC) following SE. Linear regression analysis showed no correlation between the intensity of NeuN and that of HSP70. In contrast to HSP70, HSP90 immunoreactivity was decreased in CA1-3 pyramidal cells at 4days-4weeks after SE. In addition, HSP90 immunoreactivity was decreased in PC neurons at 12h-4weeks after SE. linear regression analysis showed a direct proportional relationship between the intensity of NeuN and that of HSP90. Therefore, these findings suggest that HSP90 degradation may be closely related to neuronal vulnerability to SE insult.

A qualitative description of the peptide sharing between poliovirus and Homo sapiens

In a companion paper, we reported that pentapeptides from human poliovirus 1, Mahoney strain, occur repeatedly in human proteins for a total of more than 18,000 overlaps. In the present study, we describe the distribution of the polio pentapeptides throughout biochemical pathways and networks characterizing functions and tissues in the human host. The present study might be of help to better define the poliovirus-host relationships as well as for designing peptide modules with anti-polio activity.

p21-LacZ reporter mice reflect p53-dependent toxic insult

There is an urgent need to discover less toxic and more selective drugs to treat disease. The use of transgenic mice that report on toxic insult-induced transcription can provide a valuable tool in this regard. To exemplify this strategy, we have generated transgenic mice carrying a p21-LacZ transgene. Transgene activity reflected endogenous p21 gene activation in various tissues, displayed compound-specific spatial expression signatures in the brain and immune tissues and enabled p53-dependent and p53-independent responses to be identified. We discuss the application of these mice in delineating the molecular events in normal cellular growth and disease and for the evaluation of drug toxicity.