Among the heat shock proteins (HSP), HSP27, HSP70 and HSP90 are the most studied stress-inducible HSPs, and are induced in response to a wide variety of physiological and environmental insults, thus ...allowing cells to survive to lethal conditions based on their powerful cytoprotective functions. Different functions of HSPs have been described to explain their cytoprotective functions, including their most basic role as molecular chaperones, that is to regulate protein folding, transport, translocation and assembly, especially helping in the refolding of misfolded proteins, as well as their anti-apoptotic properties. In cancer cells, the expression and/or activity of the three HSPs is abnormally high, and is associated with increased tumorigenicity, metastatic potential of cancer cells and resistance to chemotherapy. Associating with key apoptotic factors, they are powerful anti-apoptotic proteins, having the capacity to block the cell death process at different levels. Altogether, the properties suggest that HSP27, HSP70 and HSP90 are appropriate targets for modulating cell death pathways. In this review, we summarize the role of HSP90, HSP70 and HSP27 in apoptosis and the emerging strategies that have been developed for cancer therapy based on the inhibition of the three HSPs.
At dawn of a scorching summer day, land plants must anticipate upcoming extreme midday temperatures by timely establishing molecular defences that can keep heat‐labile membranes and proteins ...functional. A gradual morning pre‐exposure to increasing sub‐damaging temperatures induces heat‐shock proteins (HSPs) that are central to the onset of plant acquired thermotolerance (AT). To gain knowledge on the mechanisms of AT in the model land plant Physcomitrium patens, we used label‐free LC–MS/MS proteomics to quantify the accumulated and depleted proteins before and following a mild heat‐priming treatment. High protein crowding is thought to promote protein aggregation, whereas molecular chaperones prevent and actively revert aggregation. Yet, we found that heat priming (HP) did not accumulate HSP chaperones in chloroplasts, although protein crowding was six times higher than in the cytosol. In contrast, several HSP20s strongly accumulated in the cytosol, yet contributing merely 4% of the net mass increase of heat‐accumulated proteins. This is in poor concordance with their presumed role at preventing the aggregation of heat‐labile proteins. The data suggests that under mild HP unlikely to affect protein stability. Accumulating HSP20s leading to AT, regulate the activity of rare and specific signalling proteins, thereby preventing cell death under noxious heat stress.
Quantitative proteomics showed that a mild heat pre‐treatment leading to acquired thermotolerance in moss strongly induces the accumulation of cytosolic HSP20s, albeit in low amounts compared to other HSPs. The cytosol was found to be the least crowded cellular compartment, suggesting that in addition to their general anti‐aggregation function, cytosolic HSP20s carry specific signalling functions to regulate noxious heat‐induced apoptosis.
In this forward-looking perspective, the current technologies for low-temperature waste heat recovery are first analyzed from two aspects: (i) the local waste heat recovery technology and (ii) global ...optimization of energy flow network. Based on the analysis, barriers for the further promotion of waste heat recovery are outlined, and they include the lack of global optimization methodology, distributed waste heat recovery system with high costs, and mismatches between waste heat source and demand. To address these issues, perspectives on three aspects are provided. First, advanced graphical analysis and optimization methodology integrating the heat exchange and energy conversion can promote the user-friendly optimization. Second, concentrated waste heat recovery and supply can save the investment, installation area and operation costs, thereby making the waste heat recovery cost-effective. Third, thermal storage, thermal transportation and high temperature heat pump can better couple the waste heat source and user demand from time-scale, spatial scale and energy grade, respectively. Visions for the future are combined with technical details to provide comprehensive perspectives for the next-step waste heat recovery.
•Technologies for low-temperature waste heat recovery are analyzed.•Optimizing method for combined heat exchange and conversion network is discussed.•Concentrated waste heat recovery and supply is a cost-saving option.•Technologies for the waste heat source and user demand coupling are discussed.
Combined heat and power (CHP) plants are operating under more fluctuating working conditions due to the increasingly inconsistent demands for heat and power and integration of renewable energy. This ...paper proposes to use an electric heat pump (EHP) to decouple heat and power and save energy by recovering waste heat from the cooling water. The thermodynamic model of the CHP unit under dynamic working conditions is established, and the dynamic EHP model based on an efficiency factor is proposed. The heat-power decoupling and energy-saving potential with different heat and power outputs and the heat pump DH ratio (χHP) are analyzed for a CHP unit as a case study. Absorption heat pump (AHP) and EHP-based waste heat recovery systems are also compared. The results indicate that the heat-power decoupling potential is bigger when χHP and the heat demand are increasing. The energy-saving effect is clearer by increasing the coefficient of performance (COP), χHP, or both. AHP and EHP can help the system obtain a certain level of heat-power decoupling and energy-saving effects, but these effects of the AHP-based system are smaller than that of EHP, especially under the working conditions of high heat demand and low power demand.
•A heat-power decoupling method with waste heat recovery using large HP is proposed.•Thermodynamic model for CHP unit in dynamic working conditions is developed.•Integration of HP-based waste heat recovery system can bring energy-saving benefits.•Heat-power decoupling and energy saving with EHP is better than that with AHP.•The energy saving effect is improved by increasing COP or heating ratio of HP.
The heat shock response is a universal transcriptional response to proteotoxic stress orchestrated by heat shock transcription factor Hsf1 in all eukaryotic cells. Despite over 40 years of intense ...research, the mechanism of Hsf1 activity regulation remains poorly understood at the molecular level. In metazoa, Hsf1 trimerizes upon heat shock through a leucine‐zipper domain and binds to DNA. How Hsf1 is dislodged from DNA and monomerized remained enigmatic. Here, using purified proteins, we demonstrate that unmodified trimeric Hsf1 is dissociated from DNA in vitro by Hsc70 and DnaJB1. Hsc70 binds to multiple sites in Hsf1 with different affinities. Hsf1 trimers are monomerized by successive cycles of entropic pulling, unzipping the triple leucine‐zipper. Starting this unzipping at several protomers of the Hsf1 trimer results in faster monomerization. This process directly monitors the concentration of Hsc70 and DnaJB1. During heat shock adaptation, Hsc70 first binds to a high‐affinity site in the transactivation domain, leading to partial attenuation of the response, and subsequently, at higher concentrations, Hsc70 removes Hsf1 from DNA to restore the resting state.
Synopsis
Heat shock transcription factor 1 (Hsf1) is a central regulator of the heat shock response (HSR) in eukaryotic cells. This study demonstrates that the Hsp70 system attenuates the metazoa HSR and restores the resting state, by monomerizing trimeric Hsf1 and thus dissociating it from DNA.
Hsp70 chaperones together with J‐domain co‐chaperones dissociate Hsf1 from DNA in vitro.
Hsf1 is bound by Hsp70s at distinct sites with different affinities, allowing Hsf1 to closely monitor cellular Hsp70 levels.
Starting at the binding site adjacent to the trimerization domain, Hsp70s monomerize Hsf1 trimers by successive cycles of entropic pulling.
Mutation or deletion of the identified binding sites potentiate Hsf1 activity in cell culture models.
Hsp70 and J‐domain chaperones attenuate the heat shock response in metazoa by monomerizing heat shock transcription factor 1 (Hsf1) and thus removing it from DNA.
Various molecular and cellular processes are involved in renal fibrosis, such as oxidative stress, inflammation, endothelial cell injury, and apoptosis. Heat shock proteins (HSPs) are implicated in ...the progression of chronic kidney disease (CKD). Our aim was to evaluate changes in urine and serum HSP levels over time and their relationships with the clinical parameters of CKD in children. In total, 117 children with CKD and 56 healthy children were examined. The CKD group was followed up prospectively for 24 months. Serum and urine HSP27, HSP40, HSP47, HSP60, HSP70, HSP72, and HSP90 levels and serum anti-HSP60 and anti-HSP70 levels were measured by ELISA at baseline, 12 months, and 24 months. The urine levels of all HSPs and the serum levels of HSP40, HSP47, HSP60, HSP70, anti-HSP60, and anti-HSP70 were higher at baseline in the CKD group than in the control group. Over the months, serum HSP47 and HSP60 levels steadily decreased, whereas HSP90 and anti-HSP60 levels steadily increased. Urine HSP levels were elevated in children with CKD; however, with the exception of HSP90, they decreased over time. In conclusion, our study demonstrates that CKD progression is a complicated process that involves HSPs, but they do not predict CKD progression. The protective role of HSPs against CKD may weaken over time, and HSP90 may have a detrimental effect on the disease course.
The First Law of Thermodynamics states that energy can neither be created nor destroyed. Heat exchangers are devices built for efficient heat transfer from one fluid to another. They are widely used ...in engineering processes and include examples such as intercoolers, preheaters, boilers and condensers in power plants. Heat exchangers are becoming more and more important to manufacturers striving to control energy costs.Process Heat Transfer Rules of Thumb investigates the design and implementation of industrial heat exchangers. It provides the background needed to understand and master the commercial software packages used by professional engineers for design and analysis of heat exchangers. This book focuses on the types of heat exchangers most widely used by industry, namely shell-and-tube exchangers (including condensers, reboilers and vaporizers), air-cooled heat exchangers and double-pipe (hairpin) exchangers. It provides a substantial introduction to the design of heat exchanger networks using pinch technology, the most efficient strategy used to achieve optimal recovery of heat in industrial processes.
. Utilizes leading commercial software important to professional engineers designing heat exchangers.. Illustrates design procedures using complete step-by-step worked examples. . Provides details on how to develop an initial configuration for a heat exchanger and how to systematically modify it to obtain a final design. . Abundant example problems solved manually and with the integration of computer software.
Heat-shock transcription factor 1 (HSF1) orchestrates the fast and vast cellular response to heat shock through increased expression of heat-shock proteins. However, how HSF1 rapidly and reversibly ...regulates transcriptional reprogramming remains poorly defined. Here by combining super-resolution imaging, in vitro reconstitution and high-throughput sequencing, we reveal that HSF1 forms small nuclear condensates via liquid-liquid phase separation at heat-shock-protein gene loci and enriches multiple transcription apparatuses through co-phase separation to promote the transcription of target genes. Furthermore, the phase-separation capability of HSF1 is fine-tuned through phosphorylation at specific sites within the regulatory domain. Last, we discovered that HSP70 disperses HSF1 condensates to attenuate transcription following the cessation of heat shock and further prevents the gel-like phase transition of HSF1 under extended heat-shock stress. Our work reveals an inducible and reversible phase-separation feedback mechanism for dynamic regulation of HSF1 activity to drive the transcriptional response and maintain protein homeostasis during acute stress.
Hot weather and heat extremes: health risks Ebi, Kristie L; Capon, Anthony; Berry, Peter ...
The Lancet (British edition),
08/2021, Volume:
398, Issue:
10301
Journal Article
Peer reviewed
Open access
Hot ambient conditions and associated heat stress can increase mortality and morbidity, as well as increase adverse pregnancy outcomes and negatively affect mental health. High heat stress can also ...reduce physical work capacity and motor-cognitive performances, with consequences for productivity, and increase the risk of occupational health problems. Almost half of the global population and more than 1 billion workers are exposed to high heat episodes and about a third of all exposed workers have negative health effects. However, excess deaths and many heat-related health risks are preventable, with appropriate heat action plans involving behavioural strategies and biophysical solutions. Extreme heat events are becoming permanent features of summer seasons worldwide, causing many excess deaths. Heat-related morbidity and mortality are projected to increase further as climate change progresses, with greater risk associated with higher degrees of global warming. Particularly in tropical regions, increased warming might mean that physiological limits related to heat tolerance (survival) will be reached regularly and more often in coming decades. Climate change is interacting with other trends, such as population growth and ageing, urbanisation, and socioeconomic development, that can either exacerbate or ameliorate heat-related hazards. Urban temperatures are further enhanced by anthropogenic heat from vehicular transport and heat waste from buildings. Although there is some evidence of adaptation to increasing temperatures in high-income countries, projections of a hotter future suggest that without investment in research and risk management actions, heat-related morbidity and mortality are likely to increase.
There is an ongoing debate as to whether the UHI intensity (UHII) is enhanced or dampened under heat waves (HWs). Using a comprehensive dataset including continuous surface energy flux data for three ...summers (2016–18) and automated weather station data for six summers (2013–18) in Shanghai, China, we find synergies between UHIs and HWs when either a coastal or an inland suburban site is used as the reference site. We further find that during HWs, the increase of net radiation at the urban site is larger than that at the suburban site. More importantly, the latent heat flux is slightly reduced at the urban site but is slightly increased at the suburban site, while the increase of the sensible heat flux is larger at the urban site. This change of surface energy partitioning, together with the increased anthropogenic heat flux during HWs, exacerbates the UHII. The change of surface energy partitioning is consistent with the observed decrease of relative humidity ratio between urban and suburban areas. The UHII is stronger when the regional wind speed is reduced and under sea breeze, both of which are found to be associated with HWs in our study region. This study suggests that there are multiple factors controlling the interactions between UHIs and HWs, which may explain why synergies between UHIs and HWs are only found in certain metropolitan regions and/or under certain HW events.
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