Saved by the Matrix: UPR Independent Survival under ER Stress

Chondroitin Sulfate from Halaelurus burgeri Skin Inhibits Hepatic Endoplasmic Reticulum Stress and Inflammation, and Regulates Gut Microbiota

SCOPE

Previous study has demonstrated the chemical structure of chondroitin sulfate (CHS) from Halaelurus burgeri skin and its effects on insulin resistance. However, the precise impact of this phenomenon on endoplasmic reticulum (ER) stress and inflammation, which contribute to insulin resistance, remains unclear. This study is to investigate the impact of CHS on ER stress, inflammatory response and signaling, and gut microbiota in high-fat diet (HFD)-fed mice.

METHODS AND RESULTS

HFD-fed C57BL/6J mice receive dietary gavage intervention of CHS for 18 weeks. Blood, liver tissue, and feces are harvested for further investigation. Results show that CHS inhibits ER stress, accompanied by lowered blood glucose, nitric oxide (NO), reactive oxygen (ROS), and free fatty acids (FFA) levels, and increases hepatic glycogen accumulation. Moreover, hepatic inflammation is improved by CHS treatment via inactivation of Toll-like receptor 4 (TLR4) signaling and its downstream c-jun N-terminal kinase (JNK) and nuclear factor kappa B (NFκB) pathways. Additionally, CHS regulates gut microbiota, particularly the decline in the Firmicutes to Bacteroidetes ratio. CHS also lowers fecal lipopolysaccharide and elevates several fecal short chain fatty acids.

CONCLUSION

These findings suggest that CHS from H. burgeri skin may be an alternative functional food supplement for anti-ER stress, anti-inflammtion, and regulation of gut microbiota.

NTRK1-mediated protection against manganese-induced neurotoxicity and cell apoptosis via IGF2 in SH-SY5Y cells

BACKGROUND

Excessive manganese (Mn) exposure has been linked to neurotoxicity, cognitive impairments. Neurotrophic Receptor Kinase 1 (NTRK1) encodes Tropomyosin kinase A (TrkA), a neurotrophic receptor, as a mediator of neuron differentiation and survival. Insulin-like growth factor 2 (IGF2), a pivotal member of the insulin gene family, plays a crucial role in brain development and neuroprotection. Despite this knowledge, the precise mechanisms through which NTRK1 and IGF2 influence cell responses to Mn-induced neuronal damage remain elusive.

METHODS

Cell apoptosis was assessed using CCK8, TUNEL staining, and Western blot analysis of cleaved Caspase-3. Lentiviral vectors facilitated NTRK1 overexpression, while small interfering RNAs (siRNAs) facilitated IGF2 knockdown. Real-time Quantitative PCR (qPCR) determined gene expression levels, while Western blotting measured protein expression.

RESULTS

The study reveals that NTRK1 inhibits MnCl2-induced apoptosis in SH-SY5Y cells. NTRK1 overexpression significantly upregulated IGF2 expression, and subsequent siRNA-IGF2 experiments confirmed IGF2's pivotal role in NTRK1-mediated neuroprotection. Notably, the study identifies that NTRK1 regulates the expression of IGF2 in the neuroprotective mechanism with the involvement of ER stress pathways.

DISCUSSION

The study reveals NTRK1's neuroprotective role via IGF2 against Mn-induced neurotoxicity and ER stress modulation in SH-SY5Y cells. These findings offer insights into potential therapies for neurodegenerative disorders related to Mn exposure and NTRK1 dysfunction, driving future research in this domain.

Novel insight into cGAS-STING pathway in ischemic stroke: from pre- to post-disease

Ischemic stroke, a primary cause of disability and the second leading cause of mortality, has emerged as an urgent public health issue. Growing evidence suggests that the Cyclic GMP-AMP synthase (cGAS)- Stimulator of interferon genes (STING) pathway, a component of innate immunity, is closely associated with microglia activation, neuroinflammation, and regulated cell death in ischemic stroke. However, the mechanisms underlying this pathway remain inadequately understood. This article comprehensively reviews the existing literature on the cGAS-STING pathway and its multifaceted relationship with ischemic stroke. Initially, it examines how various risk factors and pre-disease mechanisms such as metabolic dysfunction and senescence (e.g., hypertension, hyperglycemia, hyperlipidemia) affect the cGAS-STING pathway in relation to ischemic stroke. Subsequently, we explore in depth the potential pathophysiological relationship between this pathway and oxidative stress, endoplasmic reticulum stress, neuroinflammation as well as regulated cell death including ferroptosis and PANoptosis following cerebral ischemia injury. Finally, it suggests that intervention targeting the cGAS-STING pathway may serve as promising therapeutic strategies for addressing neuroinflammation associated with ischemic stroke. Taken together, this review concludes that targeting the microglia cGAS-STING pathway may shed light on the exploration of new therapeutic strategies against ischemic stroke.

cFLIPL Alleviates Myocardial Ischemia-Reperfusion Injury by Inhibiting Endoplasmic Reticulum Stress

PURPOSE

Endoplasmic reticulum stress (ERS) plays a crucial role in myocardial ischemia-reperfusion injury (MIRI). Cellular FLICE-inhibitory protein (cFLIP) is an essential regulator of apoptosis and plays a major role in regulating ERS. The present study aimed to investigate the effects of long isoform cFLIP (cFLIP_L) on endogenous apoptosis and the mechanism of ERS in MIRI.

METHODS

The cFLIP_L recombinant adenovirus vector was used to infect H9c2 cells and Sprague-Dawley (SD) rats. After infection for 72 h, ischemia was induced for 30 min, and reperfusion was then performed for 2 h to establish the MIRI model in SD rats. H9c2 cells were hypoxic for 4 h and then reoxygenated for 12 h to simulate ischemia/reperfusion (I/R) injury. Model parameters were evaluated by assessing cardiomyocyte viability, cell death (apoptosis), and ERS-related protein expression. In addition, tunicamycin (TM), an ERS agonist, was also added to the medium for pretreatment. Coimmunoprecipitation (Co-IP) of cFLIP_L and p38 MAPK protein was performed.

RESULTS

cFLIP_L expression was decreased in I/R injury and hypoxia/reoxygenation (H/R) injury, and cFLIP_L overexpression reduced myocardial infarction in vivo and increased the viability of H9c2 cells in vitro. I/R and H/R upregulated the protein expression of GRP78, IRE-1, and PERK to induce ERS and apoptosis. Interestingly, overexpression of cFLIP_L significantly inhibited ERS and subsequent apoptosis, which was reversed by an agonist of ERS. Moreover, Co-IP showed that cFLIP_L attenuated ERS and was associated with inhibiting the activation of p38 protein.

CONCLUSION

The expression of cFLIP_L is significantly downregulated in MIRI, and it is accompanied by excessive ERS and apoptosis. Upregulated cFLIP_L suppresses ERS to reduce myocardial apoptosis, which is associated with inhibiting the activity of p38 MAPK. Therefore, cFLIP_L may be a potential intervention target for MIRI.

Endoplasmic Reticulum Stress: An Emerging Therapeutic Target for Intervertebral Disc Degeneration

Low back pain (LBP) is a global health issue. Intervertebral disc degeneration (IDD) is a major cause of LBP. Although the explicit mechanisms underpinning IDD are unclear, endoplasmic reticulum (ER) stress caused by aberrant unfolded or misfolded proteins may be involved. The accumulation of unfolded/misfolded proteins may result in reduced protein synthesis and promote aberrant protein degradation to recover ER function, a response termed the unfolded protein response. A growing body of literature has demonstrated the potential relationships between ER stress and the pathogenesis of IDD, indicating some promising therapeutic targets. In this review, we summarize the current knowledge regarding the impact of ER stress on the process of IDD, as well as some potential therapeutic strategies for alleviating disc degeneration by targeting different pathways to inhibit ER stress. This review will facilitate understanding the pathogenesis and progress of IDD and highlights potential therapeutic targets for treating this condition.

Roles and Therapeutic Implications of Endoplasmic Reticulum Stress and Oxidative Stress in Cardiovascular Diseases

In different pathological states that cause endoplasmic reticulum (ER) calcium depletion, altered glycosylation, nutrient deprivation, oxidative stress, DNA damage or energy perturbation/fluctuations, the protein folding process is disrupted and the ER becomes stressed. Studies in the past decade have demonstrated that ER stress is closely associated with pathogenesis of obesity, insulin resistance and type 2 diabetes. Excess nutrients and inflammatory cytokines associated with metabolic diseases can trigger or worsen ER stress. ER stress plays a critical role in the induction of endothelial dysfunction and atherosclerosis. Signaling pathways including AMP-activated protein kinase and peroxisome proliferator-activated receptor have been identified to regulate ER stress, whilst ER stress contributes to the imbalanced production between nitric oxide (NO) and reactive oxygen species (ROS) causing oxidative stress. Several drugs or herbs have been proved to protect against cardiovascular diseases (CVD) through inhibition of ER stress and oxidative stress. The present article reviews the involvement of ER stress and oxidative stress in cardiovascular dysfunction and the potential therapeutic implications.