Définition
Heat shock proteins (HSPs) are a family of molecular chaperones that protect cells from stress. HSP70 is the most studied — it prevents protein misfolding, supports autophagy, and buffers cells against heat, oxidative stress, and ischemia. Heat exposure (sauna) is the most direct way to upregulate HSPs.
Heat shock proteins were discovered through their dramatic induction by heat stress — hence the name — but their functions extend to general protein homeostasis. HSP70 binds nascent and misfolded proteins, preventing aggregation and assisting refolding or targeted degradation through the ubiquitin-proteasome system or autophagy. This role in proteostasis is why HSP70 function is central to aging biology: loss of proteostasis is one of the hallmarks of aging.
HSP70 is upregulated by multiple stressors through HSF1 (heat shock factor 1), the master transcription factor for the heat shock response. HSF1 is normally held inactive by binding to existing HSP70. When cells encounter stress that generates misfolded proteins, HSP70 is recruited to these substrates, liberating HSF1 to trimerize, enter the nucleus, and activate expression of more HSPs.
The sauna literature in longevity is built largely on heat shock protein biology. The Finnish cohort studies (Laukkanen et al., JAMA Internal Medicine) showed that frequent sauna use (4–7 sessions per week at 80–90°C for 20 minutes) associated with 40% lower all-cause mortality and substantial reductions in cardiovascular events. The putative mechanisms include HSP upregulation, improved endothelial function, blood pressure reduction, and cardiovascular conditioning similar to moderate exercise.
HSP70 also interacts with mitochondrial quality control, immune function, and metabolic health. For women, sauna has been associated with reduced hot flash severity in perimenopause and support for cardiovascular aging — one of the most evidence-backed lifestyle additions in the 40s and 50s.
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