Geranylgeranylacetone-induced heat shock protein70 expression reduces retinal ischemia-reperfusion injury through PI3K/AKT/mTOR signaling

Roles of HSP70 in autophagic protection of cardiomyocytes induced by heat acclimation: A review

In conditions of extreme high temperature, the heart is susceptible to injury induced by heat stress, which can manifest as myocardial ischemia and hypoxia, cardiomyocyte apoptosis, oxidative damage, and inflammatory responses. The normal function of cardiomyocytes is contingent upon the maintenance of protein homeostasis, and dysregulation of protein homeostasis is the underlying cause of myocardial structural damage. Autophagy and Heat Shock Protein 70 (Hsp70) play pivotal roles in regulating cellular protein quality and mitigating stress injury. Heat acclimation has been shown to induce Hsp70 expression and provide cardiomyocyte protection. However, the mechanism by which Hsp70 mediates cardiomyocyte autophagy to exert protective effects has not been fully elucidated. The objective of this review is to synthesize the existing literature on the effects of Hsp70 on autophagy during heat exposure, to explore the potential mechanisms by which Hsp70 regulates myocardial autophagy and the molecular pathways it involves, and to provide a theoretical basis for future therapeutic strategies for cardiac diseases.

Clusterin activates the heat shock response via the PI3K/Akt pathway to protect cardiomyocytes from high-temperature-induced apoptosis

High temperature (HT) is a common symptom of infectious myocarditis. This study investigates the effects of HT on the heat shock response (HSR) and apoptosis in cardiomyocytes, with the aim of providing insights into potential treatment strategies for myocarditis. Rat cardiomyocytes (H9c2 cells) were exposed to 42°C for 1 h, followed by a return to 37°C to simulate high fever conditions. The cells were divided into seven groups: control, oe-NC, oe-CLU, HT, HT + oe-NC, HT + oe-CLU, and HT + oe-CLU + LY294002 (PI3K inhibitor). Protein levels of HSP70, HSP90, Bax, Bcl2, CLU, p-PI3K, and p-Akt were measured by Western blot, while mRNA expression of HSP70, HSP90, Bax, Bcl2, and CLU was assessed via reverse transcription quantitative polymerase chain reaction. Cell proliferation (cell counting kit-8 assay), apoptosis (flow cytometry), and reactive oxygen species (ROS) levels (MitoSOX assay) were also evaluated. HT exposure led to decreased cell proliferation, increased apoptosis, and elevated ROS levels (p < 0.001), while also inducing expression of HSP70 and HSP90 (p < 0.0001). Overexpression of Clusterin (CLU) enhanced HSP70 and HSP90 levels, reduced apoptosis, improved cell proliferation, and decreased ROS under HT conditions (p < 0.0001). The PI3K inhibitor reversed these protective effects, confirming the involvement of the PI3K/Akt pathway (p < 0.05). CLU activates the PI3K/Akt pathway, thereby enhancing the HSR and protecting cardiomyocytes. These findings suggest that CLU could be a potential therapeutic target for myocarditis treatment.

The Role of Heat Shock Protein 70 (HSP70) in the Pathogenesis of Ocular Diseases-Current Literature Review

Heat shock proteins (HSPs) have been attracting the attention of researchers for many years. HSPs are a family of ubiquitous, well-characterised proteins that are generally regarded as protective multifunctional molecules that are expressed in response to different types of cell stress. Their activity in many organs has been reported, including the heart, brain, and retina. By acting as chaperone proteins, HSPs help to refold denatured proteins. Moreover, HSPs elicit inhibitory activity in apoptotic pathways and inflammation. Heat shock proteins were originally classified into several subfamilies, including the HSP70 family. The aim of this paper is to systematise information from the available literature about the presence of HSP70 in the human eye and its role in the pathogenesis of ocular diseases. HSP70 has been identified in the cornea, lens, and retina of a normal eye. The increased expression and synthesis of HSP70 induced by cell stress has also been demonstrated in eyes with pathologies such as glaucoma, eye cancers, cataracts, scarring of the cornea, ocular toxpoplasmosis, PEX, AMD, RPE, and diabetic retinopathy. Most of the studies cited in this paper confirm the protective role of HSP70. However, little is known about these molecules in the human eye and their role in the pathogenesis of eye diseases. Therefore, understanding the role of HSP70 in the pathophysiology of injuries to the cornea, lens, and retina is essential for the development of new therapies aimed at limiting and/or reversing the processes that cause damage to the eye.

Geranylgeranylacetone mitigates sepsis-associated intestinal injury through CHIP-dependent anti-inflammation and anti-oxidative effect

Geranylgeranylacetone (GGA), an isoprenoid compound widely utilized as an antiulcer agent in Asia, confers protection against ischemia, anoxia, and oxidative stress by rapidly enhancing the expression of HSP70. Nevertheless, the impact of GGA on sepsis-associated intestinal injury remains unexplored. Thus, this study is crafted to elucidate the protective efficacy and underlying mechanisms of GGA against septic intestinal damage. Our findings revealed that GGA significantly extended the survival duration of septic mice, and mitigated lipopolysaccharide (LPS)-induced alterations in intestinal permeability and tissue damage. Furthermore, GGA effectively suppressed LPS-induced cytokine release, attenuated levels of reactive oxygen species (ROS) and malondialdehyde, and bolstered antioxidant-related parameters within the intestinal tissue of LPS-stimulated mice. Mechanistically, GGA significantly increased HSP70 expression and promoted E3 ubiquitin ligase CHIP to play the role in ubiquitination and degradation of karyopherin-α2 (KPNA2), resulting in inhibition of nuclear translocation of NF-κB and reduced NOX1, NOX2 and NOX4 expression. The inhibitory action of GGA on cytokine release and ROS generation was abolished by CHIP knockdown in IEC-6 cells treated with LPS. Simultaneously, the downregulation of CHIP reversed the suppressive role of GGA in the LPS-induced NF-κB activation and the expression of NOX1, NOX2 and NOX4 in IEC-6 cells. The effects of GGA on mitigating intestinal damage, inflammation and oxidative stress caused by LPS were eliminated in CHIP knockout mice. Our results demonstrate that the protective effect of GGA against LPS-caused intestinal injury of mice is dependent on CHIP activation, which promotes KPNA2 degradation and restrains translocation of NF-κB into nucleus, leading to suppressing LPS-induced inflammatory response and oxidative stress.

Traditional Chinese medicine and its active substances reduce vascular injury in diabetes via regulating autophagic activity

Due to its high prevalence, poor prognosis, and heavy burden on healthcare costs, diabetic vascular complications have become a significant public health issue. Currently, the molecular and pathophysiological mechanisms underlying diabetes-induced vascular complications remain incompletely understood. Autophagy, a highly conserved process of lysosomal degradation, maintains intracellular homeostasis and energy balance via removing protein aggregates, damaged organelles, and exogenous pathogens. Increasing evidence suggests that dysregulated autophagy may contribute to vascular abnormalities in various types of blood vessels, including both microvessels and large vessels, under diabetic conditions. Traditional Chinese medicine (TCM) possesses the characteristics of "multiple components, multiple targets and multiple pathways," and its safety has been demonstrated, particularly with minimal toxicity in liver and kidney. Thus, TCM has gained increasing attention from researchers. Moreover, recent studies have indicated that Chinese herbal medicine and its active compounds can improve vascular damage in diabetes by regulating autophagy. Based on this background, this review summarizes the classification, occurrence process, and related molecular mechanisms of autophagy, with a focus on discussing the role of autophagy in diabetic vascular damage and the protective effects of TCM and its active compounds through the regulation of autophagy in diabetes. Moreover, we systematically elucidate the autophagic mechanisms by which TCM formulations, individual herbal extracts, and active compounds regulate diabetic vascular damage, thereby providing new candidate drugs for clinical treatment of vascular complications in diabetes. Therefore, further exploration of TCM and its active compounds with autophagy-regulating effects holds significant research value for achieving targeted therapeutic approaches for diabetic vascular complications.

Tanshinone IIA protects mouse testes from heat stress injury by inhibiting apoptosis and TGFβ1/Smad2/Smad3 signaling pathway

Heat stress can cause testicular damage and affect male fertility. Tanshinone IIA (TSA) is a monomer substance derived from plants, with antioxidant and anti-apoptotic effects. Whether it can repair testicular damage caused by heat stress is unclear. This study aims to construct a mouse testicular heat stress injury model and intervene with TSA. Various methods such as histopathology, high-throughput sequencing, bioinformatics analysis, and molecular biology were used to investigate whether TSA can alleviate heat stress-induced testicular injury and its mechanism. Results showed that heat stress significantly reduced the diameter of the mouse seminiferous tubules, increased cell apoptosis in the testicular tissue, and significantly decreased testosterone levels. After TSA intervention, testicular morphology and cell apoptosis improved significantly, and testosterone secretion function was restored. High-throughput transcriptome sequencing found that key differentially expressed genes between the HS group and the control and TSA groups clustered in the apoptosis and TGFβ signaling pathways. Using western blot technology, we found that the HS group upregulated TGFβ1/Smad2/Smad3 pathway protein expression, causing cell apoptosis, testicular tissue organic lesions, and affecting testicular secretion function. Through TSA intervention, we found that it can inhibit TGFβ1/Smad2/Smad3 pathway protein expression, thereby restoring testicular damage caused by heat stress. This study confirms that TSA can effectively restore testicular damage caused by heat stress in mice, possibly by inhibiting the TGFβ1/Smad2/Smad3 pathway to suppress apoptosis.

Geranylgeranylacetone Ameliorates Skin Inflammation by Regulating and Inducing Thioredoxin via the Thioredoxin Redox System

Geranylgeranylacetone (GGA) exerts cytoprotective activity against various toxic stressors via the thioredoxin (TRX) redox system; however, its effect on skin inflammation and molecular mechanism on inducing the TRX of GGA is still unknown. We investigated the effects of GGA in a murine irritant contact dermatitis (ICD) model induced by croton oil. Both a topical application and oral administration of GGA induced TRX production and Nrf2 activation. GGA ameliorated ear swelling, neutrophil infiltration, and inhibited the expression of TNF-α, IL-1β, GM-CSF, and 8-OHdG. GGA's cytoprotective effect was stronger orally than topically in mice. In vitro studies also showed that GGA suppressed the expression of NLRP3, TNF-α, IL-1β, and GM-CSF and scavenged ROS in PAM212 cells after phorbol myristate acetate stimulation. Moreover, GGA induced endogenous TRX production and Nrf2 nuclear translocation in PAM212 cells (dependent on the presence of ROS) and activated the PI3K-Akt signaling pathway. GGA significantly downregulated thioredoxin-interacting protein (TXNIP) levels in PAM212 cells treated with or without Nrf2 siRNA. After knocking down Nrf2 in PAM212 cells, the effect of GGA on TRX induction was significantly inhibited. This suggests that GGA suppress ICD by inducing endogenous TRX, which may be regulated by PI3K/Akt/Nrf2 mediation of the TRX redox system.

Oxidative Stress: A Suitable Therapeutic Target for Optic Nerve Diseases?

Optic nerve disorders encompass a wide spectrum of conditions characterized by the loss of retinal ganglion cells (RGCs) and subsequent degeneration of the optic nerve. The etiology of these disorders can vary significantly, but emerging research highlights the crucial role of oxidative stress, an imbalance in the redox status characterized by an excess of reactive oxygen species (ROS), in driving cell death through apoptosis, autophagy, and inflammation. This review provides an overview of ROS-related processes underlying four extensively studied optic nerve diseases: glaucoma, Leber's hereditary optic neuropathy (LHON), anterior ischemic optic neuropathy (AION), and optic neuritis (ON). Furthermore, we present preclinical findings on antioxidants, with the objective of evaluating the potential therapeutic benefits of targeting oxidative stress in the treatment of optic neuropathies.