Evaluating endoplasmic reticulum stress and unfolded protein response through the lens of ecology and evolution

PANoptosis: a new insight for oral diseases

PANoptosis, a burgeoning area of research, is a unique type of programmed cell death typified by pyroptosis, apoptosis, and necroptosis, yet it defies singular classification by any one mode of death. The assembly and activation of PANoptosomes are pivotal processes in PANoptosis, with several PANoptosomes already identified. Linkages between PANoptosis and the pathophysiology of various systemic illnesses are established, with increasing recognition of its association with oral ailments. This paper aims to deepen understanding by conducting a comprehensive analysis of the molecular pathways driving PANoptosis and exploring its potential implications in oral diseases.

Potential role of endoplasmic reticulum stress in doxorubicin-induced cardiotoxicity-an update

As a chemotherapy agent, doxorubicin is used to combat cancer. However, cardiotoxicity has limited its use. The existing strategies fail to eliminate doxorubicin-induced cardiotoxicity, and an in-depth exploration of its pathogenesis is in urgent need to address the issue. Endoplasmic reticulum stress (ERS) occurs when Endoplasmic Reticulum (ER) dysfunction results in the accumulation of unfolded or misfolded proteins. Adaptive ERS helps regulate protein synthesis to maintain cellular homeostasis, while prolonged ERS stimulation may induce cell apoptosis, leading to dysfunction and damage to tissue and organs. Numerous studies on doxorubicin-induced cardiotoxicity strongly link excessive activation of the ERS to mechanisms including oxidative stress, calcium imbalance, autophagy, ubiquitination, and apoptosis. The researchers also found several clinical drugs, chemical compounds, phytochemicals, and miRNAs inhibited doxorubicin-induced cardiotoxicity by targeting ERS. The present review aims to outline the interactions between ERS and other mechanisms in doxorubicin-induced cardiotoxicity and summarize ERS's role in this type of cardiotoxicity. Additionally, the review enumerates several clinical drugs, phytochemicals, chemical compounds, and miRNAs targeting ERS for considering therapeutic regimens that address doxorubicin-induced cardiotoxicity.

Developmental endothelial locus 1: the present and future of an endogenous factor in vessels

Developmental Endothelial Locus-1 (DEL-1), also known as EGF-like repeat and discoidin I-like domain-3 (EDIL3), is increasingly recognized for its multifaceted roles in immunoregulation and vascular biology. DEL-1 is a protein that is mainly produced by endothelial cells. It interacts with various integrins to regulate the behavior of immune cells, such as preventing unnecessary recruitment and inflammation. DEL-1 also helps in resolving inflammation by promoting efferocytosis, which is the process of clearing apoptotic cells. Its potential as a therapeutic target in immune-mediated blood disorders, cardiovascular diseases, and cancer metastasis has been spotlighted due to its wide-ranging implications in vascular integrity and pathology. However, there are still unanswered questions about DEL-1's precise functions and mechanisms. This review provides a comprehensive examination of DEL-1's activity across different vascular contexts and explores its potential clinical applications. It underscores the need for further research to resolve existing controversies and establish the therapeutic viability of DEL-1 modulation.

Primary Cell Culture as a Model System for Evolutionary Molecular Physiology

Primary cell culture is a powerful model system to address fundamental questions about organismal physiology at the cellular level, especially for species that are difficult, or impossible, to study under natural or semi-natural conditions. Due to their ease of use, primary fibroblast cultures are the dominant model system, but studies using both somatic and germ cells are also common. Using these models, genome evolution and phylogenetic relationships, the molecular and biochemical basis of differential longevities among species, and the physiological consequences of life history evolution have been studied in depth. With the advent of new technologies such as gene editing and the generation of induced pluripotent stem cells (iPSC), the field of molecular evolutionary physiology will continue to expand using both descriptive and experimental approaches.

Protein folding, cellular stress and cancer

Proteins are acknowledged as the phenotypical manifestation of the genotype, because protein-coding genes carry the information for the strings of amino acids that constitute the proteins. It is widely accepted that protein function depends on the corresponding "native" structure or folding achieved within the cell, and that native protein folding corresponds to the lowest free energy minimum for a given protein. However, protein folding within the cell is a non-deterministic dissipative process that from the same input may produce different outcomes, thus conformational heterogeneity of folded proteins is the rule and not the exception. Local changes in the intracellular environment promote variation in protein folding. Hence protein folding requires "supervision" by a host of chaperones and co-chaperones that help their client proteins to achieve the folding that is most stable according to the local environment. Such environmental influence on protein folding is continuously transduced with the help of the cellular stress responses (CSRs) and this may lead to changes in the rules of engagement between proteins, so that the corresponding protein interactome could be modified by the environment leading to an alternative cellular phenotype. This allows for a phenotypic plasticity useful for adapting to sudden and/or transient environmental changes at the cellular level. Starting from this perspective, hereunder we develop the argument that the presence of sustained cellular stress coupled to efficient CSRs may lead to the selection of an aberrant phenotype as the resulting adaptation of the cellular proteome (and the corresponding interactome) to such stressful conditions, and this can be a common epigenetic pathway to cancer.

Expression patterns of heat-shock genes during stopover and the trade-off between refueling and stress response in a passerine migrant

Migrating birds are often exposed to variable environments and face a multitude of stress exposures along their long-distance flights. During stopover refueling, migratory birds must balance the need to accumulate energy reserves to continue their migration with the need to respond to environmental and physiological stressors. We examined the gene expression patterns of different Heat Shock Proteins (HSPs) in migrating birds during stopover at different body condition states (lean vs. fat), to provide some first insights on the role of HSPs in bird migration and explore the concept of a trade-off between refueling and stress response. Our results showed upregulation of HSP expression at release that could be associated with muscle growth and increased cholesterol and lipid synthesis needed for birds to fuel their upcoming migration. On the other hand, during capture, upregulation of HSP5 could be attributed to physiological recovery from the non-stop endurance flight when crossing the Sahara Desert-Mediterranean Sea ecological barrier. All birds significantly increased their fuel loads up to 48% of lean body mass and we provide evidence for muscle rebuilding during stopover as flight muscle mass increased by 10%, highlighting the fact that stopover sites can play a major role in the physiological recovery of migrants.

Autophagy protects against Cd-induced cell damage in primary chicken hepatocytes via mitigation of oxidative stress and endoplasmic reticulum stress

Cadmium (Cd) is widespread globally in the environment as a toxic metal. Although it is well known to induce hepatotoxicity in the cells, defense mechanisms against the detrimental effects of Cd are still unknown. We examined the role of autophagy (a cellular defense mechanism) on Cd-induced cytotoxicity in bird hepatocytes. Primary chicken hepatocytes were cultured with different concentrations (0, 1, 2.5, 5, and 10 μM) of cadmium chloride (CdCl₂) for 12 h. We assessed the effects of CdCl₂ on the cell viability, antioxidant status, reactive oxygen species (ROS) generation, autophagy response and endoplasmic reticulum (ER) stress. Further, it is also evaluated that insight into underling molecular mechanisms involved in the study. In this study, CdCl₂-induce hepatotoxicity was caused by drastically increased ROS generation as well as a reduction level of antioxidant enzymes. It was also demonstrated that marked activation of ER stress markers (GRP78, IRE1, PERK, ATF4, ATF6 and XBP-1 s) was observed. Simultaneously, increased activation of autophagy in low-dose CdCl₂ (1 μM) exposed group was observed, but high-dose CdCl₂ (10 μM) inhibited autophagy and significantly promoted apoptosis, as indicated by the expression of the autophagy related genes for P62, Beclin-1, ATG3, ATG5, ATG9, and the detection of autophagic vacuoles. Pretreatment with autophagy agonist Rapamycin (RAP) has successfully reduced ROS production, attenuated ER stress and enhanced hepatocytes viability, while the autophagy inhibitor 3-Methyladenine (3-MA) had the opposite effect. Hence, these findings stipulate that Cd could inhibit viability of hepatocytes in a dose-dependent manner. Autophagy relieves hepatotoxicity of Cd via reducing ROS generation and regulating ER stress. We identified autophagy as a novel protective mechanism involved in Cd-mediated chicken hepatotoxicity.

Atherosclerosis and Inflammation: Insights from the Theory of General Pathological Processes

Recent advances have greatly improved our understanding of the molecular mechanisms behind atherosclerosis pathogenesis. However, there is still a need to systematize this data from a general pathology perspective, particularly with regard to atherogenesis patterns in the context of both canonical and non-classical inflammation types. In this review, we analyze various typical phenomena and outcomes of cellular pro-inflammatory stress in atherosclerosis, as well as the role of endothelial dysfunction in local and systemic manifestations of low-grade inflammation. We also present the features of immune mechanisms in the development of productive inflammation in stable and unstable plaques, along with their similarities and differences compared to canonical inflammation. There are numerous factors that act as inducers of the inflammatory process in atherosclerosis, including vascular endothelium aging, metabolic dysfunctions, autoimmune, and in some cases, infectious damage factors. Life-critical complications of atherosclerosis, such as cardiogenic shock and severe strokes, are associated with the development of acute systemic hyperinflammation. Additionally, critical atherosclerotic ischemia of the lower extremities induces paracoagulation and the development of chronic systemic inflammation. Conversely, sepsis, other critical conditions, and severe systemic chronic diseases contribute to atherogenesis. In summary, atherosclerosis can be characterized as an independent form of inflammation, sharing similarities but also having fundamental differences from low-grade inflammation and various variants of canonical inflammation (classic vasculitis).

Persistent Lipid Accumulation Leads to Persistent Exacerbation of Endoplasmic Reticulum Stress and Inflammation in Progressive NASH via the IRE1α/TRAF2 Complex

Non-alcoholic steatohepatitis (NASH) is a metabolic disorder that often leads to other severe liver diseases, yet treatment options are limited. Endoplasmic reticulum (ER) stress is an important pathogenetic mechanism of NASH and plays a key role in tandem steatosis as well as liver inflammation. This study aims to develop a progressive NASH model through sustained lipid accumulation and to elucidate its molecular mechanism through IRE1α/TRAF2 complex. Male SD rats were fed a high-fat diet (HFD) for 4, 8, and 12 weeks to induce progressive NASH. MRNA sequencing and PPI analysis were used to screen core genes. Transmission electron microscopy, immunofluorescence staining, ELISA, qRT-PCR, and Western blotting were used at each time point to compare differences between each index of progressive NASH at 4, 8, and 12 weeks. Sustained lipid accumulation led to structural disruption of the ER, a reduction in ER number, and an increase of lipid droplet aggregation in hepatocytes. Persistent lipid accumulation led to a persistent increase in mRNA and protein expression of the IRE1α/TRAF2 complex, IKK/IκB/NF-κB signaling pathway and ASK1/JNK1 signaling pathway, and TNF-α, IL-1β, and IL-6 also continued to increase. Persistent lipid accumulation led to a persistent exacerbation of ER stress and inflammation in progressive NASH via the IRE1α/TRAF2 complex.

PPAR-γ signaling in nonalcoholic fatty liver disease: Pathogenesis and therapeutic targets

Non-alcoholic fatty liver disease (NAFLD), currently the leading cause of global chronic liver disease, has emerged as a major public health problem, more efficient therapeutics of which are thus urgently needed. Peroxisome proliferator-activated receptor γ (PPAR-γ), ligand-activated transcription factors of the nuclear hormone receptor superfamily, is considered a crucial metabolic regulator of hepatic lipid metabolism and inflammation. The role of PPAR-γ in the pathogenesis of NAFLD is gradually being recognized. Here, we outline the involvement of PPAR-γ in the pathogenesis of NAFLD through adipogenesis, insulin resistance, inflammation, oxidative stress, endoplasmic reticulum stress, and fibrosis. In addition, the evidence for PPAR-γ- targeted therapy for NAFLD are summarized. Altogether, PPAR-γ is a promising therapeutic target for NAFLD, and the development of drugs that can balance the beneficial and undesirable effects of PPAR-γ will bring new light to NAFLD patients.

Modulation of the endoplasmic reticulum stress and unfolded protein response mitigates the behavioral effects of early-life stress

BACKGROUND

Early-life stress (ELS) affects brain development and increases the risk of mental disorders associated with the dysfunction of the medial prefrontal cortex (mPFC). The mechanisms of ELS action are not well understood. Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) are cellular processes involved in brain maturation through the regulation of pro-survival or proapoptotic processes. We hypothesized that ER stress and the UPR in the mPFC are involved in the neurobiology of ELS.

METHODS

We performed a maternal separation (MS) procedure from postnatal days 1 to 14 in rats. Before each MS, pups were injected with an inhibitor of ER stress, salubrinal or a vehicle. The mRNA and protein expression of UPR and apoptotic markers were evaluated in the mPFC using RT-qPCR and Western blot methods, respectively. We also estimated the numbers of neurons and glial cells using stereological methods. Additionally, we assessed behavioral phenotypes related to fear, anhedonia and response to psychostimulants.

RESULTS

MS slightly enhanced the activation of the UPR in juveniles and modulated the expression of apoptotic markers in juveniles and preadolescents but not in adults. Additionally, MS did not affect the numbers of neurons and glial cells at any age. Both salubrinal and vehicle blunted the expression of UPR markers in juvenile and preadolescent MS rats, often in a treatment-specific manner. Moreover, salubrinal and vehicle generally alleviated the behavioral effects of MS in preadolescent and adult rats.

CONCLUSIONS

Modulation of ER stress and UPR processes may potentially underlie susceptibility or resilience to ELS.

Baicalein facilitates gastric cancer cell apoptosis by triggering endoplasmic reticulum stress via repression of the PI3K/AKT pathway

OBJECTIVE

Gastric cancer (GC) remains a prevailing threat to life. Baicalein exhibits anti-cancer properties. This study estimated the mechanism of baicalein in GC cell apoptosis by mediating endoplasmic reticulum stress (ERS) through the PI3K/AKT pathway.

METHODS

After treatment with different concentrations of baicalein, GC cell (HGC-27 and AGS) viability was detected by MTT assay. AGS cells more sensitive to baicalein treatment were selected as study subjects. The IC50 of baicalein on AGS cells was determined. Colony formation, cell cycle, and apoptosis were detected using crystal violet staining and flow cytometry. Levels of ERS-related and BTG3/PI3K/AKT pathway-related proteins were determined by Western blot. Intracellular Ca²⁺ level was measured using Fluo-3 AM fluorescence working solution. GC mouse models were established by subcutaneously injecting AGS cells into the right rib and were intragastrically administrated with baicalein. Tumor volume and weight were recorded. Expression of Ki67 in tumor tissues and positive expression of apoptotic cells were detected by immunohistochemistry and TUNEL staining.

RESULTS

Baicalein inhibited cell proliferation and induced G0/G1 arrest and apoptosis by regulating the cell cycle, and triggered ERS in GC cells. Baicalein impeded the PI3K/AKT pathway by activating BTG3, thereby triggering ERS and inducing apoptosis. BTG3 inhibition reversed baicalein-induced apoptosis and ERS. Baicalein regulated GC cells in a concentration-dependent manner. Moreover, in xenograft mice, baicalein prevented tumor growth, decreased Ki67-positive cells, activated BTG3, and inhibited the PI3K/AKT pathway, thus activating ERS and increasing apoptotic cells.

CONCLUSION

Baicalein facilitates GC cell apoptosis by triggering ERS via repression of the PI3K/AKT pathway.

Endoplasmic reticulum stress-mediated cell death in liver injury

The endoplasmic reticulum is an important intracellular organelle that plays an important role in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) and unfolded protein response (UPR) are induced when the body is exposed to adverse external stimuli. It has been established that ERS can induce different cell death modes, including autophagy, apoptosis, ferroptosis, and pyroptosis, through three major transmembrane receptors on the ER membrane, including inositol requirement enzyme 1α, protein kinase-like endoplasmic reticulum kinase and activating transcription factor 6. These different modes of cell death play an important role in the occurrence and development of various diseases, such as neurodegenerative diseases, inflammation, metabolic diseases, and liver injury. As the largest metabolic organ, the liver is rich in enzymes, carries out different functions such as metabolism and secretion, and is the body's main site of protein synthesis. Accordingly, a well-developed endoplasmic reticulum system is present in hepatocytes to help the liver perform its physiological functions. Current evidence suggests that ERS is closely related to different stages of liver injury, and the death of hepatocytes caused by ERS may be key in liver injury. In addition, an increasing body of evidence suggests that modulating ERS has great potential for treating the liver injury. This article provided a comprehensive overview of the relationship between ERS and four types of cell death. Moreover, we discussed the mechanism of ERS and UPR in different liver injuries and their potential therapeutic strategies.

Relocation to avoid costs: A hypothesis on red carotenoid-based signals based on recent CYP2J19 gene expression data

In many vertebrates, the enzymatic oxidation of dietary yellow carotenoids generates red keto-carotenoids giving color to ornaments. The oxidase CYP2J19 is here a key effector. Its purported intracellular location suggests a shared biochemical pathway between trait expression and cell functioning. This might guarantee the reliability of red colorations as individual quality signals independent of production costs. We hypothesize that the ornament type (feathers vs. bare parts) and production costs (probably CYP2J19 activity compromising vital functions) could have promoted tissue-specific gene relocation. We review current avian tissue-specific CYP2J19 expression data. Among the ten red-billed species showing CYP2J19 bill expression, only one showed strong hepatic expression. Moreover, a phylogenetically-controlled analysis of 25 red-colored species shows that those producing red bare parts are less likely to have strong hepatic CYP2J19 expression than species with only red plumages. Thus, both production costs and shared pathways might have contributed to the evolution of red signals.

Traditional Chinese medicine prescription Shenling BaiZhu powder to treat ulcerative colitis: Clinical evidence and potential mechanisms

Ulcerative colitis (UC), characterized by syndromes including abdominal pain, bloody stool, diarrhea, weight loss, and repeated relapse, is a non-specific inflammatory intestinal disease. In recent years, with the changing dietary habits in China, the incidence of UC has shown an upward trend. UC belongs to the category of recorded as "diarrhea," "chronic dysentery," and "hematochezia" in traditional Chinese medicine (TCM), and Shenling BaiZhu powder (SLBZP) is one of the most effective and commonly used prescriptions. In this review, we aim to systematically summarize the clinical application and pharmacological mechanism of SLBZP in the treatment of UC to provide a theoretical basis for its clinical use and experimental evaluation of SLBZP. Our results showed that both SLBZP and SLBZP in combination with chemical drugs, have a significant therapeutic effect against UC with few adverse reactions. Furthermore, combined therapy was better than western medicine. Further, pathophysiological studies indicated that SLBZP has anti-inflammatory, immunomodulatory, antioxidant effects, regulation relative cell signal transduction and regulation of gut microbiota. Although evidence suggests superior therapeutic efficacy of SLBZP for treating UC and the relative mechanism has been studied extensively, various shortcomings limit the existing research on the topic. There is a lack of UC animal models, especially UC with TCM syndromes, with no uniform standard and certain differences between the animal model and clinical syndrome. The dosage, dosage form, and therapeutic time of SLBZP are inconsistent and lack pharmacological verification, and clinical trial data are not detailed or sufficiently rigorous. In addition, SLSZP is composed of multiple Chinese drugs that contain massive numbers of ingredients and which or several components contribute to therapeutic effects. How they work synergistically together remains unknown. Therefore, on the one hand, large sample prospective cohort studies to clarify the clinical efficacy and safety of SLBZP in the treatment of UC are needed. In contrast, researchers should strengthen the study of the molecular biological mechanism of active ingredients and its synergistic actions, clarifying the mechanism of SLBZP in treating UC by multi-component, multi-target, and multi-pathway.

Proteostasis and resilience: on the interphase between individual's and intracellular stress

A long proportion of the population is resilient to the negative consequences of stress. Glucocorticoids resulting from endocrine responses to stress are essential adaptive mediators, but also drive alterations to brain function, negatively impacting neuronal connectivity, synaptic plasticity, and memory-related processes. Recent evidence has indicated that organelle function and cellular stress responses are relevant determinant of vulnerability and resistance to environmental stress. At the molecular level, a fundamental mechanism of cellular stress adaptation is the maintenance of proteostasis, which also have key roles in sustaining basal neuronal function. Here, we discuss recent evidence suggesting that proteostasis unbalance at the level of the endoplasmic reticulum, the main site for protein folding in the cell, represents a possible mechanistic link between individuals and cellular stress.

Endoplasmic reticulum stress in airway hyperresponsiveness

Airway hyperresponsiveness(AHR) is a major clinical phenomenon in lung diseases (asthma, COPD and pulmonary fibrosis) and not only a high-risk factor for perioperative airway spasm leading to hypoxaemia, haemodynamic instability and even "silent lung", but also a potential risk for increased mortality from underlying diseases (e.g. asthma, COPD). Airway reactivity is closely linked to airway inflammation, remodelling and increased mucus secretion, and endoplasmic reticulum stress is an important mechanism for the development of these pathologies. This review, therefore, focuses on the effects of endoplasmic reticulum stress on the immune cells involved in airway hyperreactivity (epithelial cells, dendritic cells, eosinophils and neutrophils) in inflammation and mucus & sputum secretion; and on the differentiation and remodelling of airway smooth muscle cells and epithelial cells. The aim is to clarify the mechanisms associated with endoplasmic reticulum stress in airway hyperresponsiveness and to find new ideas and methods for the prevention of airway hyperresponsiveness in the perioperative period.

Recent progress in small-molecule fluorescent probes for endoplasmic reticulum imaging in biological systems

Endoplasmic reticulum (ER) is an indispensable organelle in eukaryotic cells involved in protein synthesis and processing, as well as calcium storage and release. Therefore, maintaining the quality of ER is of great importance for cellular homeostasis. Aberrant fluctuations of bioactive species in the ER will result in homeostasis disequilibrium and further cause ER stress, which has evolved to contribute to the pathogenesis of various diseases. Therefore, the real-time monitoring of various bioactive species in the ER is of high priority to ascertain the mysterious roles of ER, which will contribute to unveiling the corresponding mechanism of organism disturbances. Recently, fluorescence imaging has emerged as a robust technique for the direct visualization of molecular events due to its outstanding sensitivity, high temporal-spatial resolution and noninvasive nature. In this review, we comprehensively summarize the recent progress in design strategies, bioimaging applications, potential directions and challenges of ER-targetable small-molecular fluorescent probes.

Xbp1 and Brachyury establish an evolutionarily conserved subcircuit of the notochord gene regulatory network

Gene regulatory networks coordinate the formation of organs and structures that compose the evolving body plans of different organisms. We are using a simple chordate model, the Ciona embryo, to investigate the essential gene regulatory network that orchestrates morphogenesis of the notochord, a structure necessary for the proper development of all chordate embryos. Although numerous transcription factors expressed in the notochord have been identified in different chordates, several of them remain to be positioned within a regulatory framework. Here, we focus on Xbp1, a transcription factor expressed during notochord formation in Ciona and other chordates. Through the identification of Xbp1-downstream notochord genes in Ciona, we found evidence of the early co-option of genes involved in the unfolded protein response to the notochord developmental program. We report the regulatory interplay between Xbp1 and Brachyury, and by extending these results to Xenopus, we show that Brachyury and Xbp1 form a cross-regulatory subcircuit of the notochord gene regulatory network that has been consolidated during chordate evolution.

Emerging role of UFMylation in secretory cells involved in the endocrine system by maintaining ER proteostasis

Ubiquitin-fold modifier 1 (UFM1) is a ubiquitin-like molecule (UBL) discovered almost two decades ago, but our knowledge about the cellular and molecular mechanisms of this novel protein post-translational modification is still very fragmentary. In this review, we first summarize the core enzymes and factors involved in the UFMylation cascade, which, similar to ubiquitin, is consecutively catalyzed by UFM1-activating enzyme 5 (UBA5), UFM1-conjugating enzyme 1 (UFC1) and UFM1-specific ligase 1 (UFL1). Inspired by the substantial implications of UFM1 machinery in the secretory pathway, we next concentrate on the puzzling role of UFMylation in maintaining ER protein homeostasis, intending to illustrate the underlying mechanisms and future perspectives. At last, given a robust ER network is a hallmark of healthy endocrine secretory cells, we emphasize the function of UFM1 modification in physiology and pathology in the context of endocrine glands pancreas and female ovaries, aiming to provide precise insight into other internal glands of the endocrine system.

Is cancer a disease set up by cellular stress responses?

For several decades, the somatic mutation theory (SMT) has been the dominant paradigm on cancer research, leading to the textbook notion that cancer is fundamentally a genetic disease. However, recent discoveries indicate that mutations, including "oncogenic" ones, are widespread in normal somatic cells, suggesting that mutations may be necessary but not sufficient for cancer to develop. Indeed, a fundamental but as yet unanswered question is whether or not the first step in oncogenesis corresponds to a mutational event. On the other hand, for some time, it has been acknowledged the important role in cancer progression of molecular processes that participate in buffering cellular stress. However, their role is considered secondary or complementary to that of putative oncogenic mutations. Here we present and discuss evidence that cancer may have its origin in epigenetic processes associated with cellular adaptation to stressful conditions, and so it could be a direct consequence of stress-buffering mechanisms that allow cells with aberrant phenotypes (not necessarily associated with genetic mutations) to survive and propagate within the organism. We put forward the hypothesis that there would be an inverse correlation between the activation threshold of the cellular stress responses (CSRs) and the risk of cancer, so that species or individuals with low-threshold CSRs will display a higher incidence or risk of cancer.

Growth Hormone Releasing Hormone in Endothelial Barrier Function

Growth hormone releasing hormone (GHRH) is the integral regulator of the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis. It exerts mitogenic effects in a plethora of progressive cancers. Recent evidence suggests the emerging role of that 44-amino acid (aa) neuropeptide in lung endothelial barrier function (EBF), which will be discussed herein.

Unfolded Protein Response: A Regulator of the Endothelial Barrier

Recent evidence suggest that the endothelial barrier function is enhanced by the mild activation of the unfolded protein response (UPR), which aims to suppress abnormal increases of endoplasmic reticulum stress. Heat shock protein 90 inhibitors and growth hormone releasing hormone antagonists exert the capacity to activate this multifaceted cellular mechanism (UPR). Thus, investigations on the signalling network involved in those events, may deliver exciting opportunities in diseases related to endothelial barrier dysfunction. The diverse spectrum of those pathologies include sepsis and Acute Respiratory Distress Syndrome (ARDS).