The stimuli for neuronal cell death in neurodegenerative disorders are multi-factorial and may include genetic predisposition, environmental factors, cellular stressors such as oxidative stress and free radical production, bioenergy failure, glutamate-induced excitotoxicity, neuroinflammation, disruption of Ca2+-regulating systems, mitochondrial dysfunction and misfolded protein accumulation. Cellular stress disrupts functioning of the endoplasmic reticulum (ER), a critical organelle for protein quality control, leading to induction of the unfolded protein response (UPR). ER stress may contribute to neurodegeneration in a range of neurodegenerative disorders. This review summarizes the molecular events occurring during ER stress and the unfolded protein response and it specifically evaluates the evidence suggesting the ER stress response plays a role in neurodegenerative disorders.

Thermotolerance, the acquired resistance of cells to stress, is a well-established phenomenon. Studies of the key mediators of this response, the heat shock proteins (HSPs), have led to the discovery of the important roles played by these proteins in the regulation of apoptotic cell death. Apoptosis is critical for normal tissue homeostasis and is involved in diverse processes including development and immune clearance. Apoptosis is tightly regulated by both proapoptotic and antiapoptotic factors, and dysregulation of apoptosis plays a significant role in the pathophysiology of many diseases. In the recent years, HSPs have been identified as key determinants of cell survival, which can modulate apoptosis by directly interacting with components of the apoptotic machinery. Therefore, manipulation of the HSPs could represent a viable strategy for the treatment of diseases. Here, we review the current knowledge with regard to the mechanisms of HSP-mediated regulation of apoptosis.

Many experimentally induced or disease-related cellular dysfunctions stress the endoplasmic reticulum, commonly resulting in an accumulation of unfolded proteins in the ER lumen which is sensed by three ER-resident transmembrane proteins, PERK, ATF6, and IRE1. Their activation by such ER stress affects the unfolded protein response, which consists of a shutoff of protein translation and at the same time the switching-on of specific transcription factors that control genes which function to reduce the burden of unfolded proteins to the ER. Here, we describe two sets of methods for monitoring the occurrence of ER stress and UPR signaling in human cells by analyzing markers of activation of all three ER stress sensor proteins. The first set of methods is based on the qualitative and quantitative analysis of UPR-induced transcripts by qPCR. The second set of methods consists of Western blot-based analysis of UPR-induced proteins or protein modifications. Their combined analysis allows assessment of activation of all three ER stress-activated signaling pathways that in combination are characteristic for the UPR.

BIM, a pro-apoptotic BH3-only protein, is a key regulator of the intrinsic (or mitochondrial) apoptosis pathway. Here, we show that BIM induction by endoplasmic reticulum (ER) stress is suppressed in rat PC12 cells overexpressing heat shock protein B1 (HSPB1 or HSP27) and that this is due to enhanced proteasomal degradation of BIM. HSPB1 and BIM form a complex that immunoprecipitates with p-ERK1/2. We found that HSPB1-mediated proteasomal degradation of BIM is dependent on MEK-ERK signaling. Other studies have shown that several missense mutations in HSPB1 cause the peripheral neuropathy, Charcot-Marie-Tooth (CMT) disease, which is associated with nerve degeneration. Here we show that cells overexpressing CMT-related HSPB1 mutants exhibited increased susceptibility to ER stress-induced cell death and high levels of BIM. These findings identify a novel function for HSPB1 as a negative regulator of BIM protein stability leading to protection against ER stress-induced apoptosis, a function that is absent in CMT-associated HSPB1 mutants.

The chick chorioallantoic membrane (CAM) assay model of angiogenesis has been highlighted as a relatively quick, low cost and effective model for the study of pro-angiogenic and anti-angiogenic factors. The chick CAM is a highly vascularised extraembryonic membrane which functions for gas exchange, nutrient exchange and waste removal for the growing chick embryo. It is beneficial as it can function as a treatment screening tool, which bridges the gap between cell based in vitro studies and in vivo animal experimentation. In this review, we explore the benefits and drawbacks of the CAM assay to study microcirculation, by the investigation of each distinct stage of the CAM assay procedure, including cultivation techniques, treatment applications and methods of determining an angiogenic response using this assay. We detail the angiogenic effect of treatments, including drugs, metabolites, genes and cells used in conjunction with the CAM assay, while also highlighting the testing of genetically modified cells. We also present a detailed exploration of the advantages and limitations of different CAM analysis techniques, including visual assessment, histological and molecular analysis along with vascular casting methods and live blood flow observations.