1 4673 148 NEW INSIGHTS INTO THE PATHOGENESIS AND TREATMENT OF IRRITABLE BOWEL SYNDROME. IRRITABLE BOWEL SYNDROME (IBS) IS ONE OF THE MOST COMMON FUNCTIONAL GASTROINTESTINAL DISORDERS (FGID), CHARACTERIZED BY ABDOMINAL PAIN AND A CHANGE IN STOOL FORM THAT CANNOT BE EXPLAINED BY STRUCTURAL ABNORMALITIES. ITS PREVALENCE RANGES FROM 9 TO 23% OF THE WORLDWIDE POPULATION. THE PATHOPHYSIOLOGY OF IBS IS DIVERSE AND NOT WELL UNDERSTOOD. BIOPSYCHOSOCIAL CONCEPT ASSUMES THAT THE DISEASE IS A PRODUCT OF PSYCHOSOCIAL FACTORS AND ALTERED AT MULTIPLE LEVELS OF GUT PHYSIOLOGY INTERACTIONS. SOME AETIOLOGICAL FACTORS HAVE BEEN IDENTIFIED, YET. ONE OF THE MOST IMPORTANT IS THE DISRUPTION OF BRAIN-GUT MUTUAL COMMUNICATION THAT LEADS TO VISCERAL HYPERSENSITIVITY. ALSO GENETIC AND EPIGENETIC FACTORS ARE INVOLVED. CHRONIC STRESS MAY PREDISPOSE TO IBS AS WELL AS EXACERBATE ITS SYMPTOMS. BOTH QUANTITATIVE AND QUALITATIVE DISORDERS OF THE GUT MICROBIOTA ARE OBSERVED. THERE IS ALSO A RELATIONSHIP BETWEEN THE IBS SYMPTOMS AND THE INTAKE OF A SPECIFIC TYPE OF FOOD PRODUCTS. IN THE DIARRHOEA TYPE OF IBS THE ROLE OF PREVIOUS GASTROINTESTINAL INFECTION IS DEMONSTRATED. RECENT STUDIES HAVE SUGGESTED THAT VISCERAL HYPERSENSITIVITY IN PATIENTS WITH IBS MAY BE SECONDARY TO THE ACTIVATION OF THE IMMUNE CELLS AND LOW-GRADE INFLAMMATION. CLINICAL SYMPTOMS OF IBS INCLUDE ABDOMINAL PAIN AND CHANGE IN BOWEL HABITS AS WELL AS SOMATIC AND PSYCHIATRIC COMORBIDITIES. IBS IS DIAGNOSED ON THE BASIS OF ROME DIAGNOSTIC CRITERIA. RECENTLY, THEIR NEWEST VERSION (ROME IV) HAS BEEN PRESENTED. THE AIM OF THIS REVIEW IS TO SUMMARIZE THE PAST DECADE PROGRESS IN IBS DIAGNOSIS, MAIN PATHOPHYSIOLOGICAL ASPECTS AND THERAPEUTIC MANAGEMENT STRATEGY. 2017 2 2167 48 EPIGENETIC MECHANISMS IN IRRITABLE BOWEL SYNDROME. IRRITABLE BOWEL SYNDROME (IBS) IS A BRAIN-GUT AXIS DISORDER CHARACTERIZED BY ABDOMINAL PAIN AND ALTERED BOWEL HABITS. IBS IS A MULTIFACTORIAL, STRESS-SENSITIVE DISORDER WITH EVIDENCE FOR FAMILIAL CLUSTERING ATTRIBUTED TO GENETIC OR SHARED ENVIRONMENTAL FACTORS. HOWEVER, THERE ARE WEAK GENETIC ASSOCIATIONS REPORTED WITH IBS AND A LACK OF EVIDENCE TO SUGGEST THAT MAJOR GENETIC FACTOR(S) CONTRIBUTE TO IBS PATHOPHYSIOLOGY. STUDIES ON ANIMAL MODELS OF STRESS, INCLUDING EARLY LIFE STRESS, SUGGEST A ROLE FOR ENVIRONMENTAL FACTORS, SPECIFICALLY, STRESS ASSOCIATED WITH DYSREGULATION OF CORTICOTROPIN RELEASING FACTOR AND HYPOTHALAMUS-PITUITARY-ADRENAL (HPA) AXIS PATHWAYS IN THE PATHOPHYSIOLOGY OF IBS. RECENT EVIDENCE SUGGESTS THAT EPIGENETIC MECHANISMS, WHICH CONSTITUTE MOLECULAR CHANGES NOT DRIVEN BY A CHANGE IN GENE SEQUENCE, CAN MEDIATE ENVIRONMENTAL EFFECTS ON CENTRAL AND PERIPHERAL FUNCTION. EPIGENETIC ALTERATIONS INCLUDING DNA METHYLATION CHANGES, HISTONE MODIFICATIONS, AND DIFFERENTIAL EXPRESSION OF NON-CODING RNAS (MICRORNA [MIRNA] AND LONG NON-CODING RNA) HAVE BEEN ASSOCIATED WITH SEVERAL DISEASES. THE OBJECTIVE OF THIS REVIEW IS TO ELUCIDATE THE MOLECULAR FACTORS IN THE PATHOPHYSIOLOGY OF IBS WITH AN EMPHASIS ON EPIGENETIC MECHANISMS. EMERGING EVIDENCE FOR EPIGENETIC CHANGES IN IBS INCLUDES CHANGES IN DNA METHYLATION IN ANIMAL MODELS OF IBS AND PATIENTS WITH IBS, AND VARIOUS MIRNAS THAT HAVE BEEN ASSOCIATED WITH IBS AND ENDOPHENOTYPES, SUCH AS INCREASED VISCERAL SENSITIVITY AND INTESTINAL PERMEABILITY. DNA METHYLATION, IN PARTICULAR, IS AN EMERGING FIELD IN THE REALM OF COMPLEX DISEASES AND A PROMISING MECHANISM WHICH CAN PROVIDE IMPORTANT INSIGHTS INTO IBS PATHOGENESIS AND IDENTIFY POTENTIAL TARGETS FOR TREATMENT. 2020 3 4428 39 MOLECULAR BASIS OF THE IRRITABLE BOWEL SYNDROME. IRRITABLE BOWEL SYNDROME (IBS) IS A FUNCTIONAL DISORDER CHARACTERIZED BY ABDOMINAL PAIN, DISCOMFORT AND BLOATING. THE PATHOPHYSIOLOGY OF IBS IS POORLY UNDERSTOOD, BUT THE PRESENCE OF PSYCHOSOCIAL BASIS IS NOW KNOWN. THERE IS AN INCREASING NUMBER OF PUBLICATIONS SUPPORTING THE ROLE OF GENETICS IN IBS. MOST OF THE VARIATIONS ARE FOUND IN GENES ASSOCIATED WITH THE BRAIN-GUT AXIS, REVEALING THE STRONG CORRELATION OF BRAIN-GUT AXIS AND IBS. MIRNAS, WHICH PLAY CRITICAL ROLES IN PHYSIOLOGICAL PROCESSES, ARE NOT WELL STUDIED IN IBS. HOWEVER, SO FAR THERE IS FOUND AN INVOLVEMENT OF ALTERATIONS IN MIRNA EXPRESSION OR SEQUENCE, IN IBS SYMPTOMS. IBS PHENOTYPE IS AFFECTED BY EPIGENETIC ALTERATION AND ENVIRONMENT. CHANGES IN DNA AND HISTONE METHYLATION ARE OBSERVED IN PATIENTS WHO SUFFERED CHILDHOOD TRAUMA OR ABUSE, RESULTING IN ALTERED GENE EXPRESSION, SUCH AS THE GLUCOCORTICOID RECEPTOR GENE. FINALLY, DIET IS ANOTHER FACTOR ASSOCIATED WITH IBS, WHICH MAY CONTRIBUTE TO SYMPTOM ONSET. CERTAIN FOODS MAY AFFECT ON BACTERIAL METABOLISM AND EPIGENETIC MODIFICATIONS, PREDISPOSING TO IBS. 2014 4 4518 41 MULTI-OMICS FOR BIOMARKER APPROACHES IN THE DIAGNOSTIC EVALUATION AND MANAGEMENT OF ABDOMINAL PAIN AND IRRITABLE BOWEL SYNDROME: WHAT LIES AHEAD. RELIABLE BIOMARKERS FOR COMMON DISORDERS OF GUT-BRAIN INTERACTION CHARACTERIZED BY ABDOMINAL PAIN, INCLUDING IRRITABLE BOWEL SYNDROME (IBS), ARE CRITICALLY NEEDED TO ENHANCE CARE AND DEVELOP INDIVIDUALIZED THERAPIES. THE DYNAMIC AND HETEROGENEOUS NATURE OF THE PATHOPHYSIOLOGICAL MECHANISMS THAT UNDERLIE VISCERAL HYPERSENSITIVITY HAVE CHALLENGED SUCCESSFUL BIOMARKER DEVELOPMENT. CONSEQUENTLY, EFFECTIVE THERAPIES FOR PAIN IN IBS ARE LACKING. HOWEVER, RECENT ADVANCES IN MODERN OMICS TECHNOLOGIES OFFER NEW OPPORTUNITIES TO ACQUIRE DEEP BIOLOGICAL INSIGHTS INTO MECHANISMS OF PAIN AND NOCICEPTION. NEWER METHODS FOR LARGE-SCALE DATA INTEGRATION OF COMPLEMENTARY OMICS APPROACHES HAVE FURTHER EXPANDED OUR ABILITY TO BUILD A HOLISTIC UNDERSTANDING OF COMPLEX BIOLOGICAL NETWORKS AND THEIR CO-CONTRIBUTIONS TO ABDOMINAL PAIN. HERE, WE REVIEW THE MECHANISMS OF VISCERAL HYPERSENSITIVITY, FOCUSING ON IBS. WE DISCUSS CANDIDATE BIOMARKERS FOR PAIN IN IBS IDENTIFIED THROUGH SINGLE OMICS STUDIES AND SUMMARIZE EMERGING MULTI-OMICS APPROACHES FOR DEVELOPING NOVEL BIOMARKERS THAT MAY TRANSFORM CLINICAL CARE FOR PATIENTS WITH IBS AND ABDOMINAL PAIN. 2023 5 5835 45 STRESS-INDUCED VISCERAL PAIN: TOWARD ANIMAL MODELS OF IRRITABLE-BOWEL SYNDROME AND ASSOCIATED COMORBIDITIES. VISCERAL PAIN IS A GLOBAL TERM USED TO DESCRIBE PAIN ORIGINATING FROM THE INTERNAL ORGANS, WHICH IS DISTINCT FROM SOMATIC PAIN. IT IS A HALLMARK OF FUNCTIONAL GASTROINTESTINAL DISORDERS SUCH AS IRRITABLE-BOWEL SYNDROME (IBS). CURRENTLY, THE TREATMENT STRATEGIES TARGETING VISCERAL PAIN ARE UNSATISFACTORY, WITH DEVELOPMENT OF NOVEL THERAPEUTICS HINDERED BY A LACK OF DETAILED KNOWLEDGE OF THE UNDERLYING MECHANISMS. STRESS HAS LONG BEEN IMPLICATED IN THE PATHOPHYSIOLOGY OF VISCERAL PAIN IN BOTH PRECLINICAL AND CLINICAL STUDIES. HERE, WE DISCUSS THE COMPLEX ETIOLOGY OF VISCERAL PAIN REVIEWING OUR CURRENT UNDERSTANDING IN THE CONTEXT OF THE ROLE OF STRESS, GENDER, GUT MICROBIOTA ALTERATIONS, AND IMMUNE FUNCTIONING. FURTHERMORE, WE REVIEW THE ROLE OF GLUTAMATE, GABA, AND EPIGENETIC MECHANISMS AS POSSIBLE THERAPEUTIC STRATEGIES FOR THE TREATMENT OF VISCERAL PAIN FOR WHICH THERE IS AN UNMET MEDICAL NEED. MOREOVER, WE DISCUSS THE MOST WIDELY DESCRIBED RODENT MODELS USED TO MODEL VISCERAL PAIN IN THE PRECLINICAL SETTING. THE THEORY BEHIND, AND APPLICATION OF, ANIMAL MODELS IS KEY FOR BOTH THE UNDERSTANDING OF UNDERLYING MECHANISMS AND DESIGN OF FUTURE THERAPEUTIC INTERVENTIONS. TAKEN TOGETHER, IT IS APPARENT THAT STRESS-INDUCED VISCERAL PAIN AND ITS PSYCHIATRIC COMORBIDITIES, AS TYPIFIED BY IBS, HAS A MULTIFACETED ETIOLOGY. MOREOVER, TREATMENT STRATEGIES STILL LAG FAR BEHIND WHEN COMPARED TO OTHER PAIN MODALITIES. THE DEVELOPMENT OF NOVEL, EFFECTIVE, AND SPECIFIC THERAPEUTICS FOR THE TREATMENT OF VISCERAL PAIN HAS NEVER BEEN MORE PERTINENT. 2015 6 105 50 A REVIEW OF MICROBIOTA AND IRRITABLE BOWEL SYNDROME: FUTURE IN THERAPIES. IRRITABLE BOWEL SYNDROME (IBS), ONE OF THE MOST FREQUENT DIGESTIVE DISORDERS, IS CHARACTERIZED BY CHRONIC AND RECURRENT ABDOMINAL PAIN AND ALTERED BOWEL HABIT. THE ORIGIN SEEMS TO BE MULTIFACTORIAL AND IS STILL NOT WELL DEFINED FOR THE DIFFERENT SUBTYPES. GENETIC, EPIGENETIC AND SEX-RELATED MODIFICATIONS OF THE FUNCTIONING OF THE NERVOUS AND IMMUNE-ENDOCRINE SUPERSYSTEMS AND REGULATION OF BRAIN-GUT PHYSIOLOGY AND BILE ACID PRODUCTION AND ABSORPTION ARE CERTAINLY INVOLVED. ACQUIRED PREDISPOSITION MAY ACT IN CONJUNCTION WITH INFECTIOUS, TOXIC, DIETARY AND LIFE EVENT-RELATED FACTORS TO ENHANCE EPITHELIAL PERMEABILITY AND ELICIT MUCOSAL MICROINFLAMMATION, IMMUNE ACTIVATION AND DYSBIOSIS. NOTABLY, STRONG EVIDENCE SUPPORTS THE ROLE OF BACTERIAL, VIRAL AND PARASITIC INFECTIONS IN TRIGGERING IBS, AND TARGETING MICROBIOTA SEEMS PROMISING IN VIEW OF THE POSITIVE RESPONSE TO MICROBIOTA-RELATED THERAPIES IN SOME PATIENTS. HOWEVER, THE LACK OF HIGHLY PREDICTIVE DIAGNOSTIC BIOMARKERS AND THE COMPLEXITY AND HETEROGENEITY OF IBS PATIENTS MAKE MANAGEMENT DIFFICULT AND UNSATISFACTORY IN MANY CASES, REDUCING PATIENT HEALTH-RELATED QUALITY OF LIFE AND INCREASING THE SANITARY BURDEN. THIS ARTICLE REVIEWS SPECIFIC ALTERATIONS AND INTERVENTIONS TARGETING THE GUT MICROBIOTA IN IBS, INCLUDING PREBIOTICS, PROBIOTICS, SYNBIOTICS, NON-ABSORBABLE ANTIBIOTICS, DIETS, FECAL TRANSPLANTATION AND OTHER POTENTIAL FUTURE APPROACHES USEFUL FOR THE DIAGNOSIS, PREVENTION AND TREATMENT OF IBS. 2018 7 6254 46 THE MICROBIOME AND IRRITABLE BOWEL SYNDROME - A REVIEW ON THE PATHOPHYSIOLOGY, CURRENT RESEARCH AND FUTURE THERAPY. IRRITABLE BOWEL SYNDROME (IBS) IS A FUNCTIONAL DISORDER WHICH AFFECTS A LARGE PROPORTION OF THE POPULATION GLOBALLY. THE PRECISE ETIOLOGY OF IBS IS STILL UNKNOWN, ALTHOUGH CONSENSUS UNDERSTANDING PROPOSES IBS TO BE OF MULTIFACTORIAL ORIGIN WITH YET UNDEFINED SUBTYPES. GENETIC AND EPIGENETIC FACTORS, STRESS-RELATED NERVOUS AND ENDOCRINE SYSTEMS, IMMUNE DYSREGULATION AND THE BRAIN-GUT AXIS SEEM TO BE CONTRIBUTING FACTORS THAT PREDISPOSE INDIVIDUALS TO IBS. IN ADDITION TO FOOD HYPERSENSITIVITY, TOXINS AND ADVERSE LIFE EVENTS, CHRONIC INFECTIONS AND DYSBIOTIC GUT MICROBIOTA HAVE BEEN SUGGESTED TO TRIGGER IBS SYMPTOMS IN TANDEM WITH THE PREDISPOSING FACTORS. THIS REVIEW WILL SUMMARIZE THE PATHOPHYSIOLOGY OF IBS AND THE ROLE OF GUT MICROBIOTA IN RELATION TO IBS. CURRENT METHODOLOGIES FOR MICROBIOME STUDIES IN IBS SUCH AS GENOME SEQUENCING, METAGENOMICS, CULTUROMICS AND ANIMAL MODELS WILL BE DISCUSSED. THE MYRIAD OF THERAPY OPTIONS SUCH AS IMMUNOGLOBULINS (IMMUNE-BASED THERAPY), PROBIOTICS AND PREBIOTICS, DIETARY MODIFICATIONS INCLUDING FODMAP RESTRICTION DIET AND GLUTEN-FREE DIET, AS WELL AS FECAL TRANSPLANTATION WILL BE REVIEWED. FINALLY THIS REVIEW WILL HIGHLIGHT FUTURE DIRECTIONS IN IBS THERAPY RESEARCH, INCLUDING IDENTIFICATION OF NEW MOLECULAR TARGETS, APPLICATION OF 3-D GUT MODEL, GUT-ON-A-CHIP AND PERSONALIZED THERAPY. 2019 8 6375 53 THE ROLE OF NEURO-IMMUNE INTERACTION IN CHRONIC PAIN CONDITIONS; FUNCTIONAL SOMATIC SYNDROME, NEUROGENIC INFLAMMATION, AND PERIPHERAL NEUROPATHY. FUNCTIONAL SOMATIC SYNDROMES ARE INCREASINGLY DIAGNOSED IN CHRONICALLY ILL PATIENTS PRESENTING WITH AN ARRAY OF SYMPTOMS NOT ATTRIBUTED TO PHYSICAL AILMENTS. CONDITIONS SUCH AS CHRONIC FATIGUE SYNDROME, FIBROMYALGIA SYNDROME, OR IRRITABLE BOWEL SYNDROME ARE COMMON DISORDERS THAT BELONG IN THIS BROAD CATEGORY. SUCH SYNDROMES ARE CHARACTERISED BY THE PRESENCE OF ONE OR MULTIPLE CHRONIC SYMPTOMS INCLUDING WIDESPREAD MUSCULOSKELETAL PAIN, FATIGUE, SLEEP DISORDERS, AND ABDOMINAL PAIN, AMONGST OTHER ISSUES. SYMPTOMS ARE BELIEVED TO RELATE TO A COMPLEX INTERACTION OF BIOLOGICAL AND PSYCHOSOCIAL FACTORS, WHERE A DEFINITE AETIOLOGY HAS NOT BEEN ESTABLISHED. THEORIES SUGGEST CAUSATIVE PATHWAYS BETWEEN THE IMMUNE AND NERVOUS SYSTEMS OF AFFECTED INDIVIDUALS WITH SEVERAL RISK FACTORS IDENTIFIED IN PATIENTS PRESENTING WITH ONE OR MORE FUNCTIONAL SYNDROMES. RISK FACTORS INCLUDING STRESS AND CHILDHOOD TRAUMA ARE NOW RECOGNISED AS IMPORTANT CONTRIBUTORS TO CHRONIC PAIN CONDITIONS. EMOTIONAL, PHYSICAL, AND SEXUAL ABUSE DURING CHILDHOOD IS CONSIDERED A SEVERE STRESSOR HAVING A HIGH PREVALENCE IN FUNCTIONAL SOMATIC SYNDROME SUFFERS. SUCH TRAUMA PERMANENTLY ALTERS THE BIOLOGICAL STRESS RESPONSE OF THE SUFFERS LEADING TO NEUROEXCITATORY AND OTHER NERVE ISSUES ASSOCIATED WITH CHRONIC PAIN IN ADULTS. TRAUMATIC AND CHRONIC STRESS RESULTS IN EPIGENETIC CHANGES IN STRESS RESPONSE GENES, WHICH ULTIMATELY LEADS TO DYSREGULATION OF THE HYPOTHALAMIC-PITUITARY AXIS, THE AUTONOMIC NERVOUS SYSTEM, AND THE IMMUNE SYSTEM MANIFESTING IN A BROAD ARRAY OF SYMPTOMS. IMPORTANTLY, THESE SYSTEMS ARE KNOWN TO BE DYSREGULATED IN PATIENTS SUFFERING FROM FUNCTIONAL SOMATIC SYNDROME. FUNCTIONAL SOMATIC SYNDROMES ARE ALSO HIGHLY PREVALENT CO-MORBIDITIES OF PSYCHIATRIC CONDITIONS, MOOD DISORDERS, AND ANXIETY. CONSEQUENTLY, THIS REVIEW AIMS TO PROVIDE INSIGHT INTO THE ROLE OF THE NERVOUS SYSTEM AND IMMUNE SYSTEM IN CHRONIC PAIN DISORDERS ASSOCIATED WITH THE MUSCULOSKELETAL SYSTEM, AND CENTRAL AND PERIPHERAL NERVOUS SYSTEMS. 2022 9 5869 40 SUSCEPTIBILITY TO STRESS-INDUCED VISCERAL SENSITIVITY: A BAD LEGACY FOR NEXT GENERATIONS. DESPITE HIGH PREVALENCE, THE PRECISE IRRITABLE BOWEL SYNDROME (IBS) PATHOPHYSIOLOGY REMAINS POORLY UNDERSTOOD LIKELY DUE TO THE HETEROGENEITY OF IBS POPULATIONS AND THE MULTIFACTORIAL ETIOLOGY OF THIS DISORDER. AMONG RISK FACTORS, GENETIC PREDISPOSITION AND EARLY LIFE TRAUMA HAVE BEEN REPORTED. IN THIS CONTEXT, THE DEBATE ON GENETIC OR ENVIRONMENTAL INFLUENCES IN THE IBS PATHOGENESIS IS STILL OPEN. THE STUDY BY VAN DER WIJNGAARD ET AL., REPORTING FOR THE FIRST TIME THAT SUSCEPTIBILITY TO STRESS-INDUCED VISCERAL HYPERSENSITIVITY IN MATERNALLY SEPARATED RATS CAN BE TRANSFERRED TO THE NEXT GENERATION WITHOUT ANY FURTHER EXPOSURE OF F2 INDIVIDUALS TO MATERNAL SEPARATION, SUPPORTS THE IMPORTANCE OF ENVIRONMENTAL INFLUENCE IN THE IBS PHENOTYPE. EPIGENETIC MECHANISMS SUCH AS HYPERMETHYLATION IN THE PROMOTER REGION OF THE GLUCOCORTICOID RECEPTOR GENE MEDIATING THE LONG-TERM AND TRANSGENERATIONAL BEHAVIORAL EFFECTS OF MATERNAL CARE ON THE DEVELOPMENT HAVE BEEN SHOWN IN SOME BUT NOT IN ALL STUDIES. VAN DER WIJNGAARD ET AL. INCRIMINATED MATERNAL CARE IN THE TRANSMITTED SUSCEPTIBILITY TO STRESS-INDUCED VISCERAL HYPERSENSITIVITY, BUT NOT CHANGES IN GLUCOCORTICOID RECEPTOR PROTEIN EXPRESSION IN THE BRAIN. THIS FINDING OPENS A BROAD FIELD OF FUTURE DIRECTIONS AIMED AT EVALUATING THE MECHANISMS INVOLVED IN THE TRANSMISSION ACROSS GENERATIONS OF THE DIGESTIVE FEATURES OF IBS, INCLUDING, FOR EXAMPLE, ON THE ROLE OF GUT MICROBIOTA CHANGES IN VERTICAL TRANSMISSION OR EPIGENETIC MODIFICATIONS OF INTESTINAL MAST CELLS AND THE JUNCTIONAL REGION OF INTESTINAL EPITHELIAL CELLS IN VERTICAL TRANSFER. 2013 10 6260 33 THE MOLECULAR NEUROBIOLOGY OF CHRONIC PAIN-INDUCED DEPRESSION. THE INCREASING NUMBER OF INDIVIDUALS WITH COMORBIDITIES POSES AN URGENT NEED TO IMPROVE THE MANAGEMENT OF PATIENTS WITH MULTIPLE CO-EXISTING DISEASES. AMONG THESE COMORBIDITIES, CHRONIC PAIN AND MOOD DISORDERS, TWO LONG-LASTING DISABLING CONDITIONS THAT SIGNIFICANTLY REDUCE THE QUALITY OF LIFE, COULD BE CITED FIRST. THE RECENT DEVELOPMENT OF ANIMAL MODELS ACCELERATED THE STUDIES FOCUSING ON THE UNDERLYING MECHANISMS OF THE CHRONIC PAIN AND DEPRESSION/ANXIETY COMORBIDITY. THIS REVIEW PROVIDES AN OVERVIEW OF CLINICAL AND PRE-CLINICAL STUDIES PERFORMED OVER THE PAST TWO DECADES ADDRESSING THE MOLECULAR ASPECTS OF THE COMORBID RELATIONSHIP OF CHRONIC PAIN AND DEPRESSION. WE THUS FOCUSED ON THE STUDIES THAT INVESTIGATED THE MOLECULAR CHARACTERISTICS OF THE COMORBID RELATIONSHIP BETWEEN CHRONIC PAIN AND MOOD DISORDERS, ESPECIALLY MAJOR DEPRESSIVE DISORDERS, FROM THE GENETIC AND EPIGENETIC POINT OF VIEW TO KEY NEUROMODULATORS WHICH HAVE BEEN SHOWN TO PLAY AN IMPORTANT ROLE IN THIS COMORBIDITY. 2019 11 1329 44 DEPRESSION ASSOCIATED WITH DIABETES: FROM PATHOPHYSIOLOGY TO TREATMENT. DIABETES IS A CHRONIC AND PROGRESSIVE SYNDROME COMMONLY ASSOCIATED WITH SEVERAL NEUROPSYCHIATRIC COMORBITIES, OF WHICH DEPRESSION IS THE MOST STUDIED. THE PREVALENCE OF DEPRESSION IS ABOUT TWO OR THREE TIMES HIGHER IN DIABETIC PATIENTS COMPARED TO THE GENERAL POPULATION. IT IS BELIEVED THAT THE DIABETES - DEPRESSION RELATION MAY BE BIDIRECTIONAL, I.E., THE DEPRESSION CAN LEAD TO DIABETES AND CONVERSELY DIABETES COULD FACILITATE THE EMERGENCE OF DEPRESSION. DEPRESSION IS ONE OF THE MOST NEGLECTED SYMPTOMS IN DIABETIC PATIENTS AND IS DIRECTLY LINKED WITH LOWERING OF QUALITY OF LIFE. THE TREATMENT OF DEPRESSION IN THESE PATIENTS IS STILL QUITE INEFFECTIVE AND IN MANY CASES TREATMENTREFRACTORY. FURTHERMORE, SOME OF THE FIRST CHOICE DRUGS USED TO TREAT THE DEPRESSION AFFECT THE BLOOD GLUCOSE CONTROL, AGGRAVATING THE HYPERGLYCEMIC STATE. THESE ISSUES UNDERSCORE THE URGENCY IN STUDIES SEARCHING FOR NEW PHARMACOLOGICAL TARGETS FOR THE TREATMENT OF DEPRESSION ASSOCIATED WITH DIABETES. FOR THIS, A BETTER UNDERSTANDING OF THE PATHOPHYSIOLOGY THAT RELATES THIS COMORBIDITY BECOMES CRITICAL. IN THIS RESPECT, THIS REVIEW WILL FOCUS ON SOME HYPOTHESES THAT HAVE BEEN PROPOSED TO EXPLAIN THE MECHANISMS UNDERLYING DEPRESSION ASSOCIATED WITH DIABETES, HIGHLIGHTING THE TREATMENT OPTIONS CURRENTLY AVAILABLE AND THEIR LIMITATIONS. AMONG THESE HYPOTHESES, WE WILL POINT OUT THE HYPERGLYCEMIA AS A PRIMARY METABOLIC CAUSE OF THE DEPRESSION DEVELOPMENT, THE INVOLVEMENT OF THE DYSREGULATION OF HYPOTHALAMIC PITUITARY-ADRENAL (HPA) AXIS AND OF NEUROTRANSMITTER SYSTEMS, SPECIALLY MONOAMINERGIC SYSTEM. BESIDES, THE ROLE OF OXIDATIVE STRESS, NEUROINFLAMMATION AND CELL DEATH, ESPECIALLY IN HIPPOCAMPUS AND PREFRONTAL CORTEX, BRAIN AREAS IMPORTANT FOR THE MEDIATION AND MODULATION OF EMOTIONAL BEHAVIOR WILL ALSO BE DISCUSSED. FINALLY, WE WILL BRING UP THE INFLUENCE OF THE EPIGENETIC REGULATION WITH RESPECT TO NEUROPSYCHIATRIC DISORDERS. 2016 12 2816 46 FIBROMYALGIA: PATHOGENESIS, MECHANISMS, DIAGNOSIS AND TREATMENT OPTIONS UPDATE. FIBROMYALGIA IS A SYNDROME CHARACTERIZED BY CHRONIC AND WIDESPREAD MUSCULOSKELETAL PAIN, OFTEN ACCOMPANIED BY OTHER SYMPTOMS, SUCH AS FATIGUE, INTESTINAL DISORDERS AND ALTERATIONS IN SLEEP AND MOOD. IT IS ESTIMATED THAT TWO TO EIGHT PERCENT OF THE WORLD POPULATION IS AFFECTED BY FIBROMYALGIA. FROM A MEDICAL POINT OF VIEW, THIS PATHOLOGY STILL PRESENTS INEXPLICABLE ASPECTS. IT IS KNOWN THAT FIBROMYALGIA IS CAUSED BY A CENTRAL SENSITIZATION PHENOMENON CHARACTERIZED BY THE DYSFUNCTION OF NEURO-CIRCUITS, WHICH INVOLVES THE PERCEPTION, TRANSMISSION AND PROCESSING OF AFFERENT NOCICEPTIVE STIMULI, WITH THE PREVALENT MANIFESTATION OF PAIN AT THE LEVEL OF THE LOCOMOTOR SYSTEM. IN RECENT YEARS, THE PATHOGENESIS OF FIBROMYALGIA HAS ALSO BEEN LINKED TO OTHER FACTORS, SUCH AS INFLAMMATORY, IMMUNE, ENDOCRINE, GENETIC AND PSYCHOSOCIAL FACTORS. A RHEUMATOLOGIST TYPICALLY MAKES A DIAGNOSIS OF FIBROMYALGIA WHEN THE PATIENT DESCRIBES A HISTORY OF PAIN SPREADING IN ALL QUADRANTS OF THE BODY FOR AT LEAST THREE MONTHS AND WHEN PAIN IS CAUSED BY DIGITAL PRESSURE IN AT LEAST 11 OUT OF 18 ALLOGENIC POINTS, CALLED TENDER POINTS. FIBROMYALGIA DOES NOT INVOLVE ORGANIC DAMAGE, AND SEVERAL DIAGNOSTIC APPROACHES HAVE BEEN DEVELOPED IN RECENT YEARS, INCLUDING THE ANALYSIS OF GENETIC, EPIGENETIC AND SEROLOGICAL BIOMARKERS. SYMPTOMS OFTEN BEGIN AFTER PHYSICAL OR EMOTIONAL TRAUMA, BUT IN MANY CASES, THERE APPEARS TO BE NO OBVIOUS TRIGGER. WOMEN ARE MORE PRONE TO DEVELOPING THE DISEASE THAN MEN. UNFORTUNATELY, THE CONVENTIONAL MEDICAL THERAPIES THAT TARGET THIS PATHOLOGY PRODUCE LIMITED BENEFITS. THEY REMAIN LARGELY PHARMACOLOGICAL IN NATURE AND TEND TO TREAT THE SYMPTOMATIC ASPECTS OF VARIOUS DISORDERS REPORTED BY THE PATIENT. THE STATISTICS, HOWEVER, HIGHLIGHT THE FACT THAT 90% OF PEOPLE WITH FIBROMYALGIA ALSO TURN TO COMPLEMENTARY MEDICINE TO MANAGE THEIR SYMPTOMS. 2021 13 1314 39 DELINEATING CONDITIONS AND SUBTYPES IN CHRONIC PAIN USING NEUROIMAGING. DIFFERENTIATING SUBTYPES OF CHRONIC PAIN STILL REMAINS A CHALLENGE-BOTH FROM A SUBJECTIVE AND OBJECTIVE POINT OF VIEW. PERSONALIZED MEDICINE IS THE CURRENT GOAL OF MODERN MEDICAL CARE AND IS LIMITED BY THE SUBJECTIVE NATURE OF PATIENT SELF-REPORTING OF SYMPTOMS AND BEHAVIORAL EVALUATION. PHYSIOLOGY-FOCUSED TECHNIQUES SUCH AS GENOME AND EPIGENETIC ANALYSES INFORM THE DELINEATION OF PAIN GROUPS; HOWEVER, EXCEPT UNDER RARE CIRCUMSTANCES, THEY HAVE DILUTED EFFECTS THAT AGAIN, SHARE A COMMON RELIANCE ON BEHAVIORAL EVALUATION. THE APPLICATION OF STRUCTURAL NEUROIMAGING TOWARDS DISTINGUISHING PAIN SUBTYPES IS A GROWING FIELD AND MAY INFORM PAIN-GROUP CLASSIFICATION THROUGH THE ANALYSIS OF BRAIN REGIONS SHOWING HYPERTROPHIC AND ATROPHIC CHANGES IN THE PRESENCE OF PAIN. ANALYTICAL TECHNIQUES SUCH AS MACHINE-LEARNING CLASSIFIERS HAVE THE CAPACITY TO PROCESS LARGE VOLUMES OF DATA AND DELINEATE DIAGNOSTICALLY RELEVANT INFORMATION FROM NEUROIMAGING ANALYSIS. THE ISSUE OF DEFINING A "BRAIN TYPE" IS AN EMERGING FIELD AIMED AT INTERPRETING OBSERVED BRAIN CHANGES AND DELINEATING THEIR CLINICAL IDENTITY/SIGNIFICANCE. IN THIS REVIEW, 2 CHRONIC PAIN CONDITIONS (MIGRAINE AND IRRITABLE BOWEL SYNDROME) WITH SIMILAR CLINICAL PHENOTYPES ARE COMPARED IN TERMS OF THEIR STRUCTURAL NEUROIMAGING FINDINGS. INDEPENDENT INVESTIGATIONS ARE COMPARED WITH FINDINGS FROM APPLICATION OF MACHINE-LEARNING ALGORITHMS. FINDINGS ARE DISCUSSED IN TERMS OF DIFFERENTIATING PATIENT SUBGROUPS USING NEUROIMAGING DATA IN PATIENTS WITH CHRONIC PAIN AND HOW THEY MAY BE APPLIED TOWARDS DEFINING A PERSONALIZED PAIN SIGNATURE THAT HELPS SEGREGATE PATIENT SUBGROUPS (EG, MIGRAINE WITH AND WITHOUT AURA, WITH OR WITHOUT NAUSEA; IRRITABLE BOWEL SYNDROME VS OTHER FUNCTIONAL GASTROINTESTINAL DISORDERS). 2019 14 2252 33 EPIGENETIC MODULATION OF VISCERAL NOCICEPTION. EPIGENETICS IS A PROCESS THAT ALTERS GENE ACTIVITY OR PHENOTYPE WITHOUT ANY CHANGES IN THE UNDERLYING DNA SEQUENCE OR GENOTYPE. THESE BIOLOGICAL CHANGES MAY HAVE DELETERIOUS EFFECTS AND CAN LEAD TO VARIOUS HUMAN DISEASES. ONGOING RESEARCH IS CONTINUING TO ILLUMINATE THE ROLE OF EPIGENETICS IN A VARIETY OF PATHOPHYSIOLOGIC PROCESSES. SEVERAL CATEGORIES OF EPIGENETIC MECHANISMS HAVE BEEN STUDIED INCLUDING CHROMATIN REMODELING, DNA METHYLATION, HISTONE MODIFICATION, AND NON-CODING RNA MECHANISMS. THESE EPIGENETIC CHANGES CAN HAVE A LONG-TERM EFFECT ON GENE EXPRESSION WITHOUT ANY UNDERLYING CHANGES IN THE DNA SEQUENCES. THE UNDERLYING PATHOPHYSIOLOGY OF DISORDERS OF BRAIN-GUT INTERACTION AND STRESS-INDUCED VISCERAL PAIN ARE NOT FULLY UNDERSTOOD AND THE ROLE OF EPIGENETIC MECHANISMS IN THESE DISORDERS ARE STARTING TO BE BETTER UNDERSTOOD. CURRENT WORK IS UNDERWAY TO DETERMINE HOW EPIGENETICS PLAYS A ROLE IN THE NEUROBIOLOGY OF PATIENTS WITH CHRONIC VISCERAL PAIN AND HEIGHTENED VISCERAL NOCICEPTION. MORE RECENTLY, BOTH ANIMAL MODELS AND HUMAN STUDIES HAVE SHOWN HOW EPIGENETIC REGULATION MODULATES STRESS-INDUCED VISCERAL PAIN. WHILE MUCH MORE WORK IS NEEDED TO FULLY DELINEATE THE MECHANISTIC ROLE OF EPIGENETICS IN THE NEUROBIOLOGY OF CHRONIC VISCERAL NOCICEPTION, THE CURRENT STUDY BY LOUWIES ET AL., IN NEUROGASTROENTEROLOGY AND MOTILITY PROVIDES ADDITIONAL EVIDENCE SUPPORTING THE INVOLVEMENT OF EPIGENETIC ALTERATIONS IN THE CENTRAL NUCLEUS OF THE AMYGDALA IN STRESS-INDUCED VISCERAL HYPERSENSITIVITY IN RODENTS. 2022 15 4144 38 MECHANISMS OF STRESS-INDUCED VISCERAL PAIN. EVIDENCE SUGGESTS THAT LONG-TERM STRESS FACILITATES VISCERAL PAIN THROUGH SENSITIZATION OF PAIN PATHWAYS AND PROMOTES CHRONIC VISCERAL PAIN DISORDERS SUCH AS THE IRRITABLE BOWEL SYNDROME (IBS). THIS REVIEW WILL DESCRIBE THE IMPORTANCE OF STRESS IN EXACERBATING IBS-INDUCED ABDOMINAL PAIN. ADDITIONALLY, WE WILL BRIEFLY REVIEW OUR UNDERSTANDING OF THE ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS BY BOTH CHRONIC ADULT STRESS AND FOLLOWING EARLY LIFE STRESS IN THE PATHOGENESIS OF IBS. THE REVIEW WILL FOCUS ON THE GLUCOCORTICOID RECEPTOR AND CORTICOTROPIN-RELEASING HORMONE-MEDIATED MECHANISMS IN THE AMYGDALA INVOLVED IN STRESS-INDUCED VISCERAL HYPERSENSITIVITY. ONE POTENTIAL MECHANISM UNDERLYING PERSISTENT EFFECTS OF STRESS ON VISCERAL SENSITIVITY COULD BE EPIGENETIC MODULATION OF GENE EXPRESSION. WHILE THERE ARE RELATIVELY FEW STUDIES EXAMINING EPIGENETICALLY MEDIATED MECHANISMS INVOLVED IN STRESS-INDUCED VISCERAL NOCICEPTION, ALTERATIONS IN DNA METHYLATION AND HISTONE ACETYLATION PATTERNS WITHIN THE BRAIN, HAVE BEEN LINKED TO ALTERATIONS IN NOCICEPTIVE SIGNALING VIA INCREASED EXPRESSION OF PRO-NOCICEPTIVE NEUROTRANSMITTERS. THIS REVIEW WILL DISCUSS THE LATEST STUDIES INVESTIGATING THE LONG-TERM EFFECTS OF STRESS ON VISCERAL SENSITIVITY. ADDITIONALLY, WE WILL CRITICALLY REVIEW THE IMPORTANCE OF EXPERIMENTAL MODELS OF ADULT STRESS AND EARLY LIFE STRESS IN ENHANCING OUR UNDERSTANDING OF THE BASIC MOLECULAR MECHANISMS OF NOCICEPTIVE PROCESSING. 2018 16 2963 34 GENETIC AND EPIGENETIC MECHANISMS LINKING PAIN AND PSYCHIATRIC DISORDERS. THE NEUROPHYSIOLOGICAL LINK BETWEEN NEUROPATHIC PAIN AND DEPRESSION REMAINS UNKNOWN DESPITE EVIDENT HIGH COMORBIDITY OF THESE TWO DISORDERS. HOWEVER, THERE IS CONVINCING EVIDENCE THAT GENOTYPE PLAYS A ROLE IN BOTH PAIN AND DEPRESSION. USING VARIOUS TYPES OF GENETIC ANALYSIS - POPULATION GENETICS, CYTOGENETICS AND MOLECULAR TECHNOLOGIES - SPECIFIC GENES HAVE BEEN IMPLICATED IN MEDIATING ALMOST ALL ASPECTS OF NOCICEPTION AND MOOD DISORDERS. THE CURRENT REVIEW ATTEMPTS TO IDENTIFY SPECIFIC GENES AND EPIGENETIC MECHANISMS COMMON TO BOTH DISORDERS. IT IS CONCLUDED THAT EXTERNAL AND INTERNAL FACTORS (INFLAMMATION, STRESS, GENDER, ETC.) THAT CONTRIBUTE TO THE PATHOLOGIES MAY DO SO THROUGH EPIGENETIC MECHANISMS THAT MAY AFFECT EXPRESSION OF THESE PARTICULAR GENES. THE POSSIBLE INVOLVEMENT OF EPIGENETIC REGULATION IN PAIN AND PSYCHIATRIC DISORDERS SUGGESTS THAT TREATMENTS TARGETING EPIGENETIC MECHANISMS THAT MEDIATE ADVERSE LIFE EVENTS SHOULD BE CONSIDERED. 2015 17 6252 36 THE MICROBIOME AND CANCER: IMPLICATIONS FOR ONCOLOGY NURSING SCIENCE. BACKGROUND: APPROXIMATELY 1.6 MILLION AMERICANS WERE DIAGNOSED WITH CANCER IN 2014. TO COMBAT THEIR DISEASE, MANY INDIVIDUALS RECEIVED EITHER CURATIVE OR PALLIATIVE TREATMENTS THAT PRODUCED UNDESIRED SYMPTOMS. THESE SYMPTOMS, WHICH OFTEN CAUSE SIGNIFICANT DISTRESS FOR INDIVIDUALS COPING WITH CANCER, MAY SHARE BIOLOGIC UNDERPINNINGS SUCH AS EPIGENETIC CHANGES AND IMMUNE DYSREGULATION. ALTERATIONS IN THE NORMAL FLORA OF THE GUT MAY ALSO INFLUENCE CANCER SYMPTOMS. OBJECTIVE: THE AIM OF THIS REVIEW IS TO DESCRIBE THE EMERGING ROLE FOR THE GUT MICROBIOME IN CANCER RESEARCH, ESPECIALLY THE POTENTIAL RELATIONSHIP BETWEEN THE GUT MICROBIOME AND CANCER SYMPTOMS. METHODS: EXTANT LITERATURE WAS REVIEWED AND SYNTHESIZED. RESULTS: THE MAJORITY OF STUDIES LINKING THE GUT MICROBIOTA AND CANCER ARE ANIMAL MODELS AND FOCUS ON THE RELATIONSHIP BETWEEN DYSBIOSIS AND COLORECTAL CANCER. EMERGING EVIDENCE SUPPORTS THAT THE "GUT-BRAIN" CONNECTION IS A PLAUSIBLE MECHANISM FOR "PSYCHONEUROLOGICAL" CANCER SYMPTOMS SUCH AS DEPRESSION, PAIN, AND FATIGUE. CONCLUSIONS: THERE IS COMPELLING EVIDENCE THAT THE GUT MICROBIOTA AFFECTS CANCER VIA SEVERAL MECHANISMS, INCLUDING MICROBIAL DIVERSITY AND NUMBER, METABOLISM, AND/OR IMMUNE INITIATION. HOWEVER, MORE RESEARCH IS NECESSARY TO ELUCIDATE THESE MECHANISMS, PARTICULARLY AMONG A VARIETY OF CANCERS AND CANCER-RELATED SYMPTOMS. IMPLICATIONS FOR PRACTICE: A BETTER UNDERSTANDING OF THE ROLE OF THE GUT MICROBIOTA IN CANCER SYMPTOMS MAY LEAD TO THE DEVELOPMENT OF TARGETED INDIVIDUALIZED INTERVENTIONS AFFECTING THE GUT MICROBIOTA THAT PREVENT OR AMELIORATE DYSBIOSIS, THEREBY REDUCING SYMPTOMS. THESE INTERVENTIONS MAY EMPHASIZE SELF-CARE MANAGEMENT STRATEGIES ESSENTIAL FOR WELLNESS, SUCH AS DIET, NUTRITION, AND STRESS REDUCTION. 2016 18 6392 32 THE ROLE OF THE GUT MICROBIOTA IN SCHIZOPHRENIA: CURRENT AND FUTURE PERSPECTIVES. OBJECTIVES: SCHIZOPHRENIA IS A POORLY UNDERSTOOD CHRONIC DISEASE. ITS PATHOPHYSIOLOGY IS COMPLEX, DYNAMIC, AND LINKED TO EPIGENETIC MECHANISMS AND MICROBIOTA INVOLVEMENT. NOWADAYS, CORRELATING SCHIZOPHRENIA WITH THE ENVIRONMENT MAKES SENSE OWING TO ITS MULTIDIMENSIONAL IMPLICATIONS: TEMPORAL AND SPATIAL VARIABILITY. MICROBIOTA INVOLVEMENT AND EPIGENETIC MECHANISMS ARE FACTORS THAT ARE CURRENTLY BEING CONSIDERED TO BETTER UNDERSTAND ANOTHER DIMENSION OF SCHIZOPHRENIA. METHODS: THIS REVIEW SUMMARISES AND DISCUSSES CURRENTLY AVAILABLE INFORMATION, FOCUSSING ON THE MICROBIOTA, EPIGENETIC MECHANISMS, TECHNOLOGICAL APPROACHES AIMED AT PERFORMING EXHAUSTIVE ANALYSES OF THE MICROBIOTA, AND PSYCHOTHERAPIES, TO ESTABLISH FUTURE PERSPECTIVES. RESULTS: THE CONNECTION BETWEEN THE MICROBIOTA, EPIGENETIC MECHANISMS AND TECHNOLOGICAL DEVELOPMENTS ALLOWS FOR FORMULATING NEW APPROACHES OBJECTIVELY ORIENTED TOWARDS THE DEVELOPMENT OF ALTERNATIVE PSYCHOTHERAPIES THAT MAY HELP TREAT SCHIZOPHRENIA. CONCLUSIONS: IN THIS REVIEW, THE GUT MICROBIOTA AND EPIGENETIC MECHANISMS WERE CONSIDERED AS KEY REGULATORS, REVEALING A POTENTIAL NEW AETIOLOGY OF SCHIZOPHRENIA. LIKEWISE, CONTINUOUS TECHNOLOGICAL ADVANCES (E.G. CULTUROMICS), AIMED AT THE MICROBIOTA-GUT-BRAIN AXIS GENERATE NEW EVIDENCE ON THIS CONCEPT. 2018 19 3016 38 GENETICS AND EPIGENETICS OF IBD. INFLAMMATORY BOWEL DISEASES (IBD) ARE CHRONIC INTERMITTENT INFLAMMATORY DISORDERS OF THE GASTROINTESTINAL TRACT OF UNKNOWN ETIOLOGY BUT A CLEAR GENETIC PREDISPOSITION. PROMPTED BY THE FIRST INVESTIGATIONS ON IBD FAMILIES AND TWINS, THE GENETIC AND EPIGENETIC STUDIES HAVE PRODUCED AN UNPRECEDENTED AMOUNT OF INFORMATION IN COMPARISON WITH OTHER IMMUNE-MEDIATED OR COMPLEX DISEASES. NEW INFLAMMATORY PATHWAYS AND POSSIBLE MECHANISMS OF ACTION HAVE BEEN DISCLOSED, POTENTIALLY LEADING TO NEW-TARGETED THERAPY. HOWEVER, THE IDENTIFICATION OF GENETIC MARKERS DUE TO THE GREAT DISEASE HETEROGENEITY AND THE OVERWHELMING CONTRIBUTION OF ENVIRONMENTAL RISK FACTORS HAS NOT MODIFIED YET THE DISEASE MANAGEMENT. THE POSSIBILITY FOR THE FUTURE OF A BETTER PREDICTION OF DISEASE COURSE, RESPONSE TO THERAPY AND THERAPY-RELATED ADVERSE EVENTS MAY ALLOW A MORE EFFICIENT AND PERSONALIZED STRATEGY. THIS REVIEW WILL FOCUS ON MORE RECENT DISCOVERIES THAT MAY POTENTIALLY BE OF RELEVANCE IN DAILY CLINICAL PRACTICE. 2020 20 6026 34 THE BIOLOGY OF STRESS INTOLERANCE IN PATIENTS WITH CHRONIC PAIN-STATE OF THE ART AND FUTURE DIRECTIONS. STRESS HAS BEEN CONSISTENTLY LINKED TO NEGATIVE IMPACTS ON PHYSICAL AND MENTAL HEALTH. MORE SPECIFICALLY, PATIENTS WITH CHRONIC PAIN EXPERIENCE STRESS INTOLERANCE, WHICH IS AN EXACERBATION OR OCCURRENCE OF SYMPTOMS IN RESPONSE TO ANY TYPE OF STRESS. THE PATHOPHYSIOLOGICAL MECHANISMS UNDERLYING THIS PHENOMENON REMAIN UNSOLVED. IN THIS STATE-OF-THE-ART PAPER, WE SUMMARISED THE ROLE OF THE AUTONOMIC NERVOUS SYSTEM (ANS) AND HYPOTHALAMUS-PITUITARY-ADRENAL (HPA) AXIS, THE TWO MAJOR STRESS RESPONSE SYSTEMS IN STRESS INTOLERANCE. WE PROVIDED INSIGHTS INTO SUCH MECHANISMS BASED ON EVIDENCE FROM CLINICAL STUDIES IN BOTH PATIENTS WITH CHRONIC PAIN, SHOWING DYSREGULATED STRESS SYSTEMS, AND HEALTHY CONTROLS SUPPORTED BY PRECLINICAL STUDIES, HIGHLIGHTING THE LINK BETWEEN THESE SYSTEMS AND SYMPTOMS OF STRESS INTOLERANCE. FURTHERMORE, WE EXPLORED THE POSSIBLE REGULATING ROLE FOR (EPI)GENETIC MECHANISMS INFLUENCING THE ANS AND HPA AXIS. THE LINK BETWEEN STRESS AND CHRONIC PAIN HAS BECOME AN IMPORTANT AREA OF RESEARCH AS IT HAS THE POTENTIAL TO INFORM THE DEVELOPMENT OF INTERVENTIONS TO IMPROVE THE QUALITY OF LIFE FOR INDIVIDUALS LIVING WITH CHRONIC PAIN. AS STRESS HAS BECOME A PREVALENT CONCERN IN MODERN SOCIETY, UNDERSTANDING THE CONNECTION BETWEEN STRESS, HPA AXIS, ANS, AND CHRONIC HEALTH CONDITIONS SUCH AS CHRONIC PAIN IS CRUCIAL TO IMPROVE PUBLIC HEALTH AND WELL-BEING. 2023