Endogenous Modulator Research Articles

Targeting the "Undruggable": Small-Molecule Inhibitors of Proliferating Cell Nuclear Antigen (PCNA) in the Spotlight in Cancer Therapy.

PCNA plays multiple roles in cancer development, including cell proliferation regulation, DNA repair, replication, and serving as a widely used biomarker and therapeutic target. Despite its significant role in oncology, PCNA has historically been considered "undruggable" due to the absence of known endogenous small molecule modulators and identifiable ligand binding sites. Unlike other protein-protein interfaces, PCNA lacks explicit binding grooves, featuring a relatively small and shallow surface pocket, which hinders the discovery of traditional small molecule targets. Recent breakthroughs have introduced promising PCNA-targeting candidates, with ATX-101 and AOH1996 entering phase I clinical trials for cancer therapy, garnering academic and industry interest. These achievements provide new evidence for PCNA as a drug target. This article provides insight and perspective on the application of small-molecule PCNA inhibitors in cancer treatment, covering PCNA function, its relationship with cancer, structural modification of small molecule inhibitors, and discovery strategies.

Conditioned pain modulation: controlling for the order of baseline and conditioning.

Conditioned pain modulation (CPM) is assumed to capture endogenous pain modulation. In standard CPM designs, the evaluation of a painful test stimulus (TS) (baseline) is followed by a second evaluation of the TS during/after application of a painful conditioning stimulus (CS) (treatment). However, these standard CPM within designs (baseline always preceding treatment) do not control for order effects, which might help to distinguish specific CPM inhibition from general habituation. To tackle this issue, we conducted 2 separate studies where we controlled for order effects to investigate whether CPM effects depend on the order of baseline and treatment. In both studies, a sample of 60 participants underwent 2 CPM test blocks: one standard order block (baseline before treatment) and one reversed order block (treatment before baseline), separated by a 20-minute break (randomized order across participants). Pain thresholds and pain ratings of phasic heat stimuli served as measures of TS. Cold water (study 1) and cuff pressure algometry (study 2) served as CS. We found significant CPM order effects in both studies and for both measures of TS (pain threshold and ratings). Only the standard CPM order (baseline before treatment) yielded robust pain inhibition effects, whereas the reversed order (treatment before baseline) led to no modulation or seeming pain facilitation. Because control for order effects is otherwise mandatory in within designs, it is surprising that it has been neglected in standard CPM protocols. Finding pain inhibition only in the standard CPM order suggests that CPM inhibition is at least partially confounded with habituation.

Endogenous pain modulation is not different in basketball or volleyball athletes with patellar tendinopathy compared to asymptomatic athletic controls

Endogenous pain modulation is not different in basketball or volleyball athletes with patellar tendinopathy compared to asymptomatic athletic controls

Effect of dwarfism and endogenous gibberellin modulation via growth regulators on heat stress tolerance in wheat

Effect of dwarfism and endogenous gibberellin modulation via growth regulators on heat stress tolerance in wheat

Fine-tuning gibberellin improves rice alkali-thermal tolerance and yield.

Soil alkalinization and global warming are predicted to pose major challenges to agriculture in the future, as they continue to accelerate, markedly reducing global arable land and crop yields1,2. Therefore, strategies for future agriculture are needed to further improve globally cultivated, relatively high-yielding Green Revolution varieties (GRVs) derived from the SEMIDWARF1 (SD1) gene3,4. Here we propose that precise regulation of the phytohormone gibberellin (GA) to optimal levels is the key to not only confer alkali-thermal tolerance to GRVs, but also to further enhance their yield. Endogenous modulation of ALKALI-THERMAL TOLERANCE 1/2(ATT1/2), quantitative trait loci encoding GA20-oxidases or exogenous application of GA minimized rice yield loss affected by sodic soils. Mechanistically, high GA concentrations induce reactive oxygen species over-accumulation, whereas low GA concentrations repress the expression ofstress-tolerance genes by means of DELLA-NGR5-mediated H3K27me3 methylation. We further showed that ATT1 induces large fluctuations in GA levels, whereas ATT2 is the ideal candidate for fine-tuning GA concentrations to appropriate levels to balance reactive oxygen species and H3K27me3 methylation to improve alkali-thermal tolerance and yield. Thus, ATT2 is expected to be a potential new post-Green Revolution gene that could be harnessed to develop and use marginal lands for sustainable agriculture in the future.

Effects of Repetitive Transcranial Magnetic Stimulation Applied over the Primary Motor Cortex on the Offset Analgesia Phenomenon

In this study, we investigate the effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) applied over the left upper limb primary motor cortex (M1) on the offset analgesia (OA) phenomenon, a measure of endogenous pain modulation. In particular, we aim to determine whether rTMS influences OA differently in the forearm region, corresponding to the stimulated cortical area, compared to the trigeminal region. Twenty-two healthy volunteers underwent three experimental sessions: a baseline session without stimulation, an active rTMS session, and a sham rTMS session. Quantitative sensory testing (QST) paradigms, including warm and cold detection thresholds, heat pain threshold corresponding to a visual analogue scale (VAS) score of approximately 50–60 out of 100 (Pain50–60), and constant and offset trials, were assessed in both the forearm and trigeminal regions. The results revealed that active rTMS significantly enhanced the OA phenomenon in the forearm during the late phase, while no significant effects were observed in the trigeminal region. These findings suggest that rTMS may modulate central pain mechanisms in a body region-specific manner, potentially linked to the somatotopic organization of M1. This study points to possible mechanisms of action of rTMS for pain relief, highlighting the importance of region-specific effects in chronic pain treatment. Further research is needed to investigate the underlying mechanisms and clinical applicability of rTMS in patients with chronic pain conditions, especially when OA is compromised.

6-Nitrodopamine is an endogenous mediator of rat seminal vesicles contractility.

6-Nitrodopamine (6-ND) released from rat vas deferens acts an endogenous modulator of vas deferens contractility. To investigate whether rat isolated seminal vesicles (RISV) releases 6-ND, the mechanisms involved in the release, and the modulatory role of 6-ND on tissue contractility. Rat seminal vesicles were removed and placed in Krebs-Henseleit's solution at 37°C for 30 min, and an aliquot was used to analyze the concentrations of 6-ND, dopamine, noradrenaline, and adrenaline by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The effect of mechanical removal of the epithelium and the effects of pre-incubation of RISV strips with Nω-nitro-L-arginine methyl ester (L-NAME; in combination or not with L-arginine), tetrodotoxin (TTX), GKT137831, and hydrogen peroxide (H2O2) on 6-ND release were evaluated. For functional studies, RISV strips were mounted in an organ bath and tied to an isometric force transducer. The expressions of tyrosine hydroxylase and endothelial nitric oxide synthase (eNOS, type III NOS) were investigated by immunohistochemistry and/or fluorescence in situ hybridization (FISH). 6-ND was the major released catecholamine from RISV strips compared with noradrenaline, adrenaline, and dopamine. Epithelium removal significantly reduced the release of 6-ND, noradrenaline and dopamine. In RISV strips obtained from animals chronically treated with L-NAME, the 6-ND release significantly reduced. Pre-incubation with L-NAME reduced 6-ND release, which was partly restored by co-incubation with L-arginine. Pre-incubation with TTX had no effect on the release of any catecholamine, whereas GKT137831 and H2O2 significantly increased 6-ND release. All catecholamines produced concentration-dependent RISV contractions, but 6-ND was approximately 30× less potent than the others. 6-ND (0.1 nM) significantly potentiated noradrenaline-, adrenaline-, and dopamine-induced contractions, with such potentiations inhibited by TTX. Immunohistochemistry and FISH assays in RISV tissues identified tyrosine hydroxylase in epithelial cells and eNOS expression in both epithelial and endothelial cells. This is the first demonstration that epithelial-derived 6-ND modulates rat seminal vesicle contractility.

The effects of socioeconomic position on endogenous pain modulation: A quasi-experimental approach.

Socioeconomic Position (SEP) is a multidimensional construct encompassing education, income, occupation, and neighborhood distress, influencing chronic pain severity, interference, and duration. However, its impact on placebo analgesia, where reduced pain perception occurs due to treatment belief, remains understudied. Using a quasi-experimental approach, we investigated SEP's influence on placebo analgesia in 401 participants with temporomandibular disorder (TMD) and 400 pain-free individuals. Using latent class analysis, we grouped participants into two SEP groups based on self-reported education, income, occupation, and neighborhood distress indices, including the area deprivation and distressed community indexes. Ancestry Informative Markers (AIMs) and self-reported race were included to account for genetic and demographic influences. Placebo analgesia was elicited using verbal suggestion and classical conditioning. Linear mixed models were employed to analyze SEP's impact, while multiple regression and ANCOVA assessed AIMs' and race's effects. Comparable placebo effects were observed between participants with TMD and pain-free individuals (F(1,4765.73) = 0.49, p = 0.48). A trend was noted in the main effect of SEP (F(1,4764.5) = 3.64, p = 0.056). Among TMD participants, those with distressed SEP exhibited lower placebo analgesia (F(1,4765.73) = 7.9, p = 0.005), while placebo response did not differ by SEP in pain-free participants (F(1,4765.73) = 0.27, p = 0.59). East Asian ancestry (β = 5.71, 95% CI [1.50, 9.92]) and self-reported Asian (mean = 24.20, sem = 1.52, p = 0.020) were associated with greater placebo analgesia. This study highlights the interplay of SEP, AIMs, and race in placebo analgesia and calls for tailored pain management interventions. PERSPECTIVE: SEP significantly contributes to pain disparities. This quasi-experimental study demonstrates analogous placebo analgesia between chronic pain and pain-free individuals but finds lower placebo analgesia only among individuals with chronic pain and distressed SEP. This highlights a link between chronic pain, SEP, and impaired placebo effects, suggesting new avenues for research.

Mechanisms underlying modulation of human GlyRα3 receptors by Zn2+ and pH.

Glycine receptors (GlyRs) regulate motor control and pain processing in the central nervous system through inhibitory synaptic signaling. The subtype GlyRα3 expressed in nociceptive sensory neurons of the spinal dorsal horn is a key regulator of physiological pain perception. Disruption of spinal glycinergic inhibition is associated with chronic inflammatory pain states, making GlyRα3 an attractive target for pain treatment. GlyRα3 activity is modulated by numerous endogenous and exogenous ligands that consequently affect pain sensitization. To understand the mechanism of two such endogenous modulators, Zn2+ and protons, we have used cryo-electron microscopy to determine structures of full-length human GlyRα3 in various functional states. Whereas acidic pH reduces peak glycine response, Zn2+ displays biphasic modulation in a concentration-dependent manner. Our findings reveal the effector sites and also capture intermediate conformations in the gating cycle. Combined with molecular dynamics simulations and electrophysiology, this work provides important insights into GlyRα3 activation and regulation.

Quantification of persulfidation on specific proteins: are we nearly there yet?

Hydrogen sulfide (H2S) played a pivotal role in the early evolution of life on Earth before the predominance of atmospheric oxygen. The legacy of a persistent role for H2S in life's processes recently emerged through its discovery in modern biochemistry as an endogenous cellular signalling modulator involved in numerous biological processes. One major mechanism through which H2S signals is protein cysteine persulfidation, an oxidative post-translational modification. In recent years, chemoproteomic technologies have been developed to allow the global scanning of protein persulfidation targets in mammalian cells and tissues, providing a powerful tool to elucidate the broader impact of altered H2S in organismal physiological health and human disease states. While hundreds of proteins were confirmed to be persulfidated by global persulfidome methodologies, the targeting of specific proteins of interest and the investigation of further mechanistic studies are still underdeveloped due to a lack of stringent specificity of the methods and the inherent instability of persulfides. This review provides an overview of the processes of endogenous H2S production, oxidation, and signalling and highlights the application and limitations of current persulfidation labelling approaches for investigation of this important evolutionarily conserved biological switch for protein function.

Tonic Cold Pain Temporal Summation and Translesional Cold Pressor Test-Induced Pronociception in Spinal Cord Injury: Association with Spontaneous and Below-Level Neuropathic Pain.

Background/Objectives: Although increased nociceptive excitability and deficient endogenous pain modulation are considered key features of pronociception and central sensitization, their contribution to neuropathic pain (NP) characteristics in SCI is unclear. The aim of this study was to characterize tonic cold perception and endogenous pain modulation in individuals with and without SCI-NP, considering the stage and severity of SCI and, secondarily, NP phenotype. Methods: Temporal summation of pain (TSP) and neuropathic features were assessed using the numerical rating scale (NRS) and Douleur Neuropathique 4 screening questionnaire (DN4) during the tonic cold pressor test (CPT, 12 °C 60 s) applied to the dominant hand and foot. CPT-induced pronociception was assessed as change in algometer pressure pain thresholds (PPTs) measured at the V2, C6, and L4 dermatomes. Results: A total of 72 individuals were recruited (age-sex-matched noninjured, n = 24; SCI-NP, n = 24; SCI-noNP, n = 24 [AIS A: n = 12, AIS B-D: n = 12; subacute SCI: n = 12, chronic SCI: n = 12]). TSP in response to the foot CPT was higher in subacute compared to chronic incomplete SCI-NP, while TSP to the hand CPT was significantly higher in chronic compared to the subacute complete SCI-NP group. Evoked pain intensity during the hand CPT correlated with duration of below-level SCI-NP. The hand CPT induced widespread pronociception (lower PPT), which correlated with 7-day non-evoked (spontaneous) pain intensity in individuals with incomplete SCI-NP. Individuals with below-level NP, but not at-level NP, showed higher TSP during the foot CPT and greater hand CPT-induced L4 dermatome pronociception. Conclusions: Collectively, measurements of above and below-level temporal summation of pain and translesional-induced pronociception in the SCI-NP group highlight the role of these mechanisms in widespread central sensitization, spontaneous pain intensity, and spinothalamic tract hyperexcitability, especially in individuals diagnosed with below-level NP.

Mechanism of NACHO-mediated assembly of pentameric ligand-gated ion channels.

Pentameric ligand-gated ion channels (pLGICs) are cell surface receptors of crucial importance for animal physiology1-4. This diverse protein family mediates the ionotropic signals triggered by major neurotransmitters and includes γ-aminobutyric acid receptors (GABAARs) and acetylcholine receptors (nAChRs). Receptor function is fine-tuned by a myriad of endogenous and pharmacological modulators3. A functional pLGIC is built from five homologous, sometimes identical, subunits, each containing a β-scaffold extracellular domain (ECD), a four-helix transmembrane domain (TMD) and intracellular loops of variable length. Although considerable progress has been made in understanding pLGICs in structural and functional terms, the molecular mechanisms that enable their assembly at the endoplasmic reticulum (ER)5 in a vast range of potential subunit configurations6 remain unknown. Here, we identified candidate pLGICs assembly factors selectively associated with an unassembled GABAAR subunit. Focusing on one of the candidates, we determined the cryo-EM structure of an assembly intermediate containing two α1 subunits of GABAAR each bound to an ER-resident membrane protein NACHO. The structure showed how NACHO shields the principal (+) transmembrane interface of α1 subunits containing an immature extracellular conformation. Crosslinking and structure-prediction revealed an adjacent surface on NACHO for β2 subunit interactions to guide stepwise oligimerisation. Mutations of either subunit-interacting surface on NACHO also impaired the formation of homopentameric α7 nAChRs, pointing to a generic framework for pLGIC assembly. Our work provides the foundation for understanding the regulatory principles underlying pLGIC structural diversity.

Can Offset Analgesia Magnitude Provide Additional Information About Endogenous Pain Modulation in People With Knee Osteoarthritis?: An Experimental Study.

To investigate the relationship between offset analgesia magnitude and the responsiveness to conditioned pain modulation (CPM), temporal summation of (second) pain (TSP), and clinical pain severity in people with knee osteoarthritis (KOA). Electrical stimuli were applied to 88 participants with KOA to measure offset analgesia at the volar forearm of the dominant hand, and CPM and TSP at the most symptomatic knee and ipsilateral volar wrist. Clinical pain severity was assessed using the pain subscale of the Knee injury and Osteoarthritis Outcome Score (KOOS PAIN ). Linear mixed-effects models evaluated pain modulatory effects across all tests, and Spearman partial correlations assessed associations between offset analgesia, CPM, TSP, and KOOS PAIN while accounting for covariates of interest. Participants unable to validly finish all psychophysical tests were excluded from effect and correlation analyses but were evaluated for predictors of nonvalid completion using bivariate Stochastic Search Variable Selection. Significant pain modulation was observed across all psychophysical tests ( P <0.05), and no meaningful predictors of nonvalid test completion were found. Offset analgesia magnitude did not significantly correlate with CPM, TSP, or KOOS PAIN ( P ≥0.05), with a maximum partial correlation coefficient of ρ =0.21. Offset analgesia was not associated with CPM, TSP, or KOOS PAIN in people with KOA. Despite the lack of case-control studies comparing offset analgesia between people with KOA and healthy controls, these findings suggest that offset analgesia may provide information about endogenous pain modulation beyond CPM and TSP, though its clinical translation remains uncertain.

NaHS protects brain, heart, and lungs as remote organs from renal ischemia/reperfusion-induced oxidative stress in male and female rats

Acute Kidney Injury (AKI) is frequently observed in hospitalized patients in intensive care units, often caused by renal ischemia-reperfusion injury (IRI). IRI disrupts the function of various ‘remote organs’ such as the lungs, pancreas, intestine, liver, heart, and brain through inflammation, oxidative stress, apoptosis, leukocyte infiltration, and increased urea and creatinine levels. Gender differences in renal IRI-induced injury are noted. H2S, an endogenous gaseous modulator, shows potential in vasodilation, bronchodilation, and hypotension and can regulate apoptosis, inflammation, angiogenesis, metabolism, and oxidative stress. This study aims to investigate the protective effects of NaHS on brain, heart, and lung injuries following renal IR and to assess the oxidative system status as a potential mechanism in male and female rats.Forty-eight Wistar rats were randomly divided into eight groups (n = 6): Control/Saline, Sham/Saline, IR/Saline, and IR/NaHS in both sexes. Forty-five minutes of bilateral renal ischemia followed by 24-hour reperfusion was induced in the IR groups. NaHS (100µM/Kg, IP) was administered 10 min before clamp release in treated groups. BUN, SCr, BUN/SCr, albuminuria, histopathology, and oxidative stress biomarkers of the brain, heart, and lung were assessed as remote organs. IR increased serum markers of renal function, albuminuria, malondialdehyde levels, and tissue injury scores while reducing nitrite levels and superoxide dismutase and glutathione peroxidase activities. NaHS treatment reversed the adverse effects of IR in remote organs in both sexes, although it showed limited improvement in renal function. Our findings demonstrate that NaHS has a beneficial effect on remote organ injury following renal IR by mitigating oxidative stress, with noted tissue-specific and gender-specific differences in response. These findings suggest NaHS as a potential therapeutic agent for mitigating multi-organ injury after renal IR, with effects varying by tissue and gender.

Neurogenic-derived 6-nitrodopamine is the most potent endogenous modulator of the mouse urinary bladder relaxation

6-Nitrodopamine (6-ND) modulates vas deferens, seminal vesicles, and corpus cavernosum contractility; however, its role on the lower urinary tract organs has not been evaluated. Investigations of isolated urinary bladders from wild-type (WT) mice revealed 6-ND release was comparable to that of dopamine and adrenaline, whereas noradrenaline was hardly detected, as assessed by liquid chromatography coupled to tandem mass spectrometry. In vitro, 6-ND induced concentration-dependent relaxations in carbachol pre-contracted bladders with high potency (pEC50: 8.04 ± 0.86), independently of eNOS/sGC activity. Co-incubation of 6-ND (1–10 μM) antagonizes the contractile effects of acetylcholine (p < 0.05). Experiments using nitric oxide synthase (NOS) knockout mice demonstrated that 6-ND release from isolated urinary bladder was significantly reduced by neuronal NOS (nNOS−/−) deletion and abolished by triple NOSs deletion (n/i/eNOS−/−), while no significant changes were observed in endothelial (eNOS−/−) or inducible (iNOS−/−) knockout mice. Incubation with tetrodotoxin resulted in a significant decrease in 6-ND release in bladders obtained from WT, but not in nNOS−/− mice. The bladders from nNOS−/− and n/i/eNOS−/− mice exhibited significantly higher contractile responses to electric field stimulation (EFS), compared to eNOS−/−, iNOS−/−, or WT bladders. The hyperreactivity observed in triple NOS knockouts was reversed by the incubation with bladder mucosal layer obtained from a donor WT mice, but not with the muscular layer. These findings clearly demonstrate 6-ND is the most potent endogenous relaxing agent of urinary bladder, and inhibition of its release is associated with bladder hyperreactivity.

The effects of neighborhood disadvantage and adverse childhood experiences on conditioned pain modulation in adults with chronic low back pain

Chronic low back pain (cLBP) remains a major health crisis worldwide. Current conceptualizations of cLBP utilize the biopsychosocial model, yet research on social factors remains limited. Adverse childhood experiences (ACEs) are a risk factor for a variety of chronic health problems, including cLBP. However, the extent to which socioeconomic context might influence associations between ACEs and cLBP remains unclear. Socioeconomic factors such as healthcare access and living conditions, which cluster at the neighborhood level, may affect how ACEs relate to cLBP in adulthood. This study examined (1) the relationship between ACEs and conditioned pain modulation (CPM), and (2) the moderating effect of area-level deprivation index (ADI) in a sample of community-dwelling adults with cLBP. 183 adults with cLBP (53% female, 62.8% non-Hispanic Black) reported on ACEs, ADI, sociodemographics, and completed experimental testing of conditioned pain modulation (CPM). Greater ACEs were associated with a less efficient CPM response for individuals residing in low neighborhood deprivation (p < 0.01). ACEs were not significantly associated with CPM for those residing in average (p = 0.31) or high deprivation (p = 0.15). Our findings suggest that a history of ACEs is associated with diminished ability to inhibit pain, especially among individuals living in less deprived neighborhoods. The association between ACEs and CPM was weakest for the portion of our sample residing in neighborhoods with the most deprivation. People from disadvantaged backgrounds may experience numerous psychosocial stressors that hinder CPM, making it difficult to assess the specific impact of ACEs on CPM. Trial registrationThis study utilized baseline data collected as part of a parent trial titled “Examining Racial and SocioEconomic Disparities in Chronic Low Back Pain” (ERASED - ClinicalTrials.gov ID: NCT03338192). PerspectiveThis study demonstrates that early life adversity is associated with abnormal endogenous pain modulation, particularly for participants who live in neighborhoods characterized by less deprivation.

Pain sensitization and pain-related psychological factors in patients with temporomandibular disorders: an observational cross-sectional study.

There is conflicting evidence on how central processing impairments affect patients with temporomandibular disorders (TMD). Moreover, there is sparse research on the assessment of endogenous pain modulation in this population through conditioned pain modulation (CPM) testing. The main objective of this observational study was to evaluate the possible differences between myofascial TDM patients and healthy pain-free controls on psychophysical variables suggestive of central processing impairments (including temporal summation (TSP), pressure pain threshold (PPT) and conditioned pain modulation (CPM)). This is a cross-sectional observational study including a sample of patients with TMD and pain-free controls recruited from private and university clinics in Spain. Outcome measures included local and distal PPTs, temporal summation, conditioned pain modulation and psychological factors of depression, anxiety, kinesiophobia, fear avoidance beliefs and pain catastrophizing. Fifty-nine patients with TMD of myofascial origin (32 years [IR: 25-43]) and 30 healthy, pain-free controls (29.5 years [IR: 25-41]) participated in the study and completed the evaluations. Patients with TMD showed significantly reduced CPM (p = 0.001; t = 3.31) and both local and distal PPTs (p < 0.05) when compared with controls, after adjusting for the influence of age and sex. TSP did not show any difference between the groups (p = 0.839; Z = 0.20). All psychological factors were higher in patients with TMD (p < 0.005), except for anxiety (p = 0.134). Patients with myofascial TMD included in this study exhibited signs of altered central processing, linked to impaired descending pain modulation, distal hyperalgesia and psychological factors like depression, kinesiophobia, fear avoidance beliefs and pain catastrophizing but not anxiety.

The negative chronotropic effects of (±)-propranolol and (±)-4-NO2-propranolol in the rat isolated right atrium are due to blockade of the 6-nitrodopamine receptor.

The positive chronotropic action induced by 6-nitrodopamine (6-ND) is selectively blocked by β1-adrenoceptor antagonists at concentrations that do not affect the positive chronotropic effect induced by dopamine, noradrenaline, and adrenaline. Here, the effects of ( ±)-propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranolol were investigated in the rat isolated right atrium. The atrium was mounted in glass chambers containing gassed (95%O2:5%CO2) and warmed (37°C) Krebs-Henseleit's solution, and the isometric tension registered (PowerLab system). ( ±)-Propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranolol caused concentration-dependent falls in the spontaneous atrial frequency (pIC50: 4.80 ± 0.10, 4.64 ± 0.10, and 4.95 ± 0.10, respectively). The calculated pA2 values for ( ±)-propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranol on noradrenaline-induced positive chronotropism were 8.44 ± 0.08, 6.41 ± 0.07, and 9.21 ± 0.29, respectively. The positive chronotropism induced by 6-ND (10pM) was blocked by ( ±)-propranolol (1µM) and ( ±)-4-NO2-propranolol (30nM), whereas ( ±)-7-NO2-propranolol (1µM) had no effect on 6-ND-induced responses. The pIC50 of ( ±)-propranolol, ( ±)-4-NO2-propranolol, and ( ±)-7-NO2-propranolol were significantly shifted to the right in L-NAME-treated atria. The discrepancy between pA2 values of ( ±)-propranolol and its respective pIC50 indicates that the falls in atrial rate induced by ( ±)-propranolol should not be attributed to b-adrenergic antagonism. The reduced chronotropism by ( ±)-propranolol was unaffected by the sodium channel inhibitors tetrodotoxin and lidocaine but that was abolished in atria pre-treated with ( ±)-4-NO2-propranolol. The finding that ( ±)-propranolol reduces spontaneous atrial rate only in concentrations that affect 6-ND-induced positive chronotropism confirms the role of this catecholamine as an endogenous modulator of heart chronotropism. ( ±)-4-NO2-Propranolol behaves as a selective antagonist of 6-ND in the rat isolated atrium.

Endogenous pain modulation after sleep restriction in migraine: a blinded crossover study

BackgroundPatients with migraine are vulnerable to insufficient sleep, but the impact of sleep restriction is largely unknown. In addition, the importance of sleep may be different in patients with migraine who mostly have attack onsets during sleep, so called sleep-related migraine, compared to patients with non-sleep-related migraine. In this study we investigate the effect of sleep restriction on endogenous pain modulation in patients with migraine and healthy controls. We also compared the effect of sleep restriction in sleep-related and in non-sleep-related migraine.MethodsMeasurements were conducted in 39 patients with migraine between attacks and 31 controls, once after habitual sleep and once after two consecutive nights of partial sleep restriction. There were 29 and 10 patients with non-sleep-related and sleep-related migraine respectively. Test stimulus was 2-min tonic noxious heat to the left volar forearm. Temporal summation was calculated as the regression coefficient for rated pain in the late part of this 2-min stimulation. Conditioning stimulus was right hand-immersion in 7 °C water. Conditioned pain modulation was defined as the difference in rated pain with and without the conditioning stimulus and was calculated for temporal summation and mean rated pain for the test stimulus. The effect of sleep restriction on temporal summation and conditioned pain modulation was compared in migraine subjects and controls using two-level models with recordings nested in subjects.ResultsConditioned pain modulation for temporal summation of heat pain tended to be reduced after sleep restriction in patients with migraine compared to controls (p = 0.060) and, in an exploratory analysis, was reduced more after sleep restriction in sleep-related than in non-sleep-related migraine (p = 0.017). No other differences between groups after sleep restriction were found for temporal summation or conditioned pain modulation.ConclusionPatients with migraine may have a subtly altered endogenous pain modulation system. Sleep restriction may have an increased pronociceptive effect on this system, suggesting a mechanism for vulnerability to insufficient sleep in migraine. This effect seems to be larger in sleep-related migraine than in non-sleep-related migraine.

Intelligent Supramolecular Modification for Implants: Endogenous Regulation of Bone Defect Repair in Osteoporosis.

Addressing osteoporosis-related bone defects, a supramolecular strategy is innovated for modifying carbon fiber reinforced polyether ether ketone (CF/PEEK) composites. By covalently attaching intelligent macromolecules via in situ RAFT polymerization, leveraging the unique pathological microenvironment in patients with iron-overloaded osteoporosis, intelligent supramolecular modified implant surface possesses multiple endogenous modulation capabilities. After implantation, surface brush-like macromolecules initially resist macrophage adhesion, thereby reducing the level of immune inflammation. Over time, the molecular chains undergo conformational changes due to Fe (III) mediated supramolecular self-assembly, transforming into mechanistic signals. These signals are then specifically transmitted to pre-osteoblast cell through the binding capacity of the KRSR short peptide at the molecular terminus, induced their osteogenic differentiation via the YAP/β-catenin signaling axis. Furthermore, osteoblasts secrete alkaline phosphatase (ALP), which significantly hydrolyzes phosphate ester bonds in surface macromolecular side groups, resulting in the release of alendronate (ALN). This process further improves the local osteoporotic microenvironment. This intelligent surface modification tailors bone repair to individual conditions, automatically realize multiple endogenous regulation once implanted, and truly realize spontaneous activation of a series of responses conducive to bone repair in vivo. It is evidenced by improved bone regeneration in iron-overloaded osteoporotic rabbits and supported by in vitro validations.