Neutrophils and the calcium-binding protein MRP-14 mediate carrageenan-induced antinociception in mice

Neurobiological mechanisms of botulinum neurotoxin-induced analgesia for neuropathic pain

Botulinum neurotoxins (BoNTs) are a family of neurotoxins produced by Clostridia and other bacteria that induce botulism. BoNTs are internalized into nerve terminals at the site of injection and cleave soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins to inhibit the vesicular release of neurotransmitters. BoNTs have been approved for multiple therapeutic applications, including the treatment of migraines. They have also shown efficacies for treating neuropathic pain, such as diabetic neuropathy, and postherpetic and trigeminal neuralgia. However, the mechanisms underlying BoNT-induced analgesia are not well understood. Peripherally administered BoNT is taken up by the nerve terminals and reduces the release of glutamate, calcitonin gene-related peptide, and substance P, which decreases neurogenic inflammation in the periphery. BoNT is retrogradely transported to sensory ganglia and central terminals in a microtubule-dependent manner. BoNTs decrease the expression of pronociceptive genes (ion channels or cytokines) from sensory ganglia and the release of neurotransmitters and neuropeptides from primary afferent central terminals, which likely leads to decreased central sensitization in the dorsal horn of the spinal cord or trigeminal nucleus. BoNT-induced analgesia is abolished after capsaicin-induced denervation of transient receptor potential vanilloid 1 (TRPV1)-expressing afferents or the knockout of substance P or the neurokinin-1 receptor. Although peripheral administration of BoNT leads to changes in the central nervous system (e.g., decreased phosphorylation of glutamate receptors in second-order neurons, reduced activation of microglia, contralateral localization, and cortical reorganization), whether such changes are secondary to changes in primary afferents or directly mediated by trans-synaptic, transcytotic, or the hematogenous transport of BoNT is controversial. To enhance their therapeutic potential, BoNTs engineered for specific targeting of nociceptive pathways have been developed to treat chronic pain. Further mechanistic studies on BoNT-induced analgesia can enhance the application of native or engineered BoNTs for neuropathic pain treatment with improved safety and efficacy.

Attenuation of COX-2 enzyme by modulating H2O2-mediated NF-κB signaling pathway by monoamine oxidase inhibitor (MAOI): a further study on the reprofiling of MAOI in acute inflammation

OBJECTIVE

This study aims to investigate the anti-inflammatory mechanism of monoamine oxidase inhibitor (MAOI) in carrageenan (CARR) induced inflammation models to reprofile their use. We also aimed to explore the role of monoamine oxidase (MAO)-mediated H₂O₂-NF-κB-COX-2 pathway in acute inflammation.

METHODS

In vitro anti-inflammatory activity and hydrogen peroxide (H₂O₂) scavenging activity were performed according to the established procedure. Inflammation was induced using CARR in BALB/c mice at the foot paw and peritoneal cavity. Hourly measurement of paw swelling was performed. The level of nitric oxide (NO), myeloperoxidase (MPO), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE₂) and nuclear factor κB (NF-κB) was determined using enzyme-linked immunosorbent assay (ELISA). Peritoneal fluid was collected to investigate total count, differential count of leukocytes, and capillary permeability.

RESULTS

In vitro anti-inflammatory evaluations revealed the potential role of MAOI to inhibit heat-induced protein denaturation and human red cell membrane destabilization. H₂O₂ inhibition activity of MAOI also proved their powerful role as an H₂O₂ scavenger. Treatment with MAOI in CARR-induced mice significantly reduced paw edema, leukocyte extravasation, and total and differential leukocyte count. The result of ELISA showed MAOI effectively reduce the level of COX-2, PGE₂ and NF-κB in inflamed tissue.

CONCLUSIONS

In short, this study demonstrates that inhibition of H₂O₂ by MAOI alleviates CARR-induced paw edema possibly by inhibiting the H₂O₂-mediated NF-κB-COX-2 pathway. The present investigation identifies MAOI might reprofile for the treatment of acute inflammation also, the MAO enzyme may use as a novel therapeutic target to design and develop new class of anti-inflammatory agents.

Sida tuberculata: In vitro cytotoxicity and in vivo anti-inflammatory effect

ETHNOPHARMACOLOGICAL RELEVANCE

Sida tuberculata R. E. Fries (Malvaceae) is a pioneer species considered a weed in farm fields in Southern Brazil. Widely distributed in South Brazil, S. tuberculata is popularly used to treat inflammatory conditions.

AIMS OF THE STUDY

The current study aimed to assess the in vitro cytotoxic and in vivo anti-inflammatory properties of S. tuberculata.

MATERIALS AND METHODS

Initially, extracts obtained from leaves (STLE) and roots (STRE) were submitted to cytotoxicity tests using human leukocytes (non-malignant cell line) and HepG2 and MCF-7 (tumor cell lines). In sequence, anti-inflammatory properties were investigated against carrageenan-induced peritonitis model.

RESULTS

In vitro analyses displayed a significant decrease in human leukocytes viability without genotoxic damage. IC₅₀ results from tumor cells presented significant decrease in cell viability, slightly more pronounced for STRE. In addition, STLE significantly inhibited the inflammatory and oxidative parameters (TBARS, NPSH, SOD, MPO activity, cell influx, and cytokines release).

CONCLUSION

Our findings indicate S. tuberculata extracts have cytotoxic potential more pronounced on tumor cell lines, as well as leaves extract shows a significant reduction in acute inflammation process, as already reported for Sida genus and specifically for this species.

Anti-Inflammatory Effects of BoNT/A Against Complete Freund's Adjuvant-Induced Arthritis Pain in Rats: Transcriptome Analysis

Arthritis is the most common cause to lead to chronic pain. Botulinum toxin type A (BoNT/A) has been widely used to treat chronic pain. In our previous study, we confirmed the anti-inflammatory and antinociceptive effects of BoNT/A in the Complete Freund’s Adjuvant (CFA)-induced arthritis model, but the underlying anti-inflammatory mechanism was not fully elucidated. The purpose of this study was to investigate the anti-inflammatory effects and mechanisms of BoNT/A on arthritis using transcriptomic analysis. The BoNT/A was injected into the rat ankle joint on day 21 after CFA injection. The von Frey and hot plate tests were applied to assess the pain-related behaviors at different time points. Five days after BoNT/A treatment, gene expression profiling in dorsal root ganglion (DRG) was performed using RNA sequencing (RNA-seq). The differentially expressed genes (DEGs) were analyzed by various tools. The mechanical allodynia and thermal hyperalgesia were significantly reversed after BoNT/A injection. RNA-seq revealed 97 DEGs between the CFA group and Sham group; these DEGs were enriched inflammatory response, IL-17 signaling pathway, etc. There are 71 DEGs between the CFA+BoNT/A group and the CFA group; these DEGs related to response to peptide, PI3K-Akt signaling pathway, ECM–receptor interactions, etc. Three key genes were significantly decreased after CFA-induced arthritis pain, while BoNT/A increased the expression of these genes. The identification of S100A9, S100A8, and MMP8 genes can provide new therapeutic targets for arthritis pain and affect the signaling pathway to play an anti-inflammatory role after the treatment of BoNT/A.

Emerging roles of neutrophil-borne S100A8/A9 in cardiovascular inflammation

Elevated neutrophil count is associated with higher risk of major adverse cardiac events including myocardial infarction and early development of heart failure. Neutrophils contribute to cardiac damage through a number of mechanisms, including attraction of other immune cells and release of inflammatory mediators. Recently, a number of independent studies have reported a causal role for neutrophil-derived alarmins (i.e. S100A8/A9) in inducing inflammation and cardiac injury following myocardial infarction (MI). Furthermore, a positive correlation between serum S100A8/A9 levels and major adverse cardiac events (MACE) in MI patients was also observed implying that targeting neutrophils or their inflammatory cargo could be beneficial in reducing heart failure. However, contradictory to this idea, neutrophils and neutrophil-derived S100A8/A9 also seem to play a vital role in the resolution of inflammation. Thus, a better understanding of how neutrophils balance these seemingly contrasting functions would allow us to develop effective therapies that preserve the inflammation-resolving function while restricting the damage caused by inflammation. In this review, we specifically discuss the mechanisms behind neutrophil-derived S100A8/A9 in promoting inflammation and resolution in the context of MI. We also provide a perspective on how neutrophils could be potentially targeted to ameliorate cardiac inflammation and the ensuing damage.

The value of calprotectin in synovial fluid for the diagnosis of chronic prosthetic joint infection

Aims

This study aimed to evaluate calprotectin in synovial fluid for diagnosing chronic prosthetic joint infection (PJI) .

Methods

A total of 63 patients who were suspected of PJI were enrolled. The synovial fluid calprotectin was tested by an enzyme-linked immunosorbent assay (ELISA). Laboratory test data, such as ESR, CRP, synovial fluid white blood cells (SF-WBCs), and synovial fluid polymorphonuclear cells (SF-PMNs), were documented. Chi-squared tests were used to compare the sensitivity and specificity of calprotectin and laboratory tests. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve was calculated to determine diagnostic efficacy.

Results

The median calprotectin level was 776 μg/ml (interquartile range (IQR) 536.5 to 1132) in the PJI group and 54.5 μg/ml (IQR, 38.75 to 78.25) in the aseptic failure (AF) group (p < 0.05). Using a threshold of 173 ug/ml, the sensitivity was 95.2%, with a 97.6% specificity, and the AUC was 0.993. The sensitivity of calprotectin of the antibiotic-treated PJI group was 100% versus 90.9% of the non-antibiotic-treated PJI group. Although 47.6% (ten cases) of the patients in the PJI group received antibiotics before aspiration, the diagnostic efficacy of calprotectin was not affected. The sensitivity and specificity of ESR, CRP, SF-WBCs, and SF-PMNs ranged from 76.2% to 90.5% and 64.3% to 85.7%, respectively.

Conclusion

Calprotectin in synovial fluid has great diagnostic efficacy for PJI diagnosisand outperformed ESR, CRP, SF-WBCs, and SF-PMNs.

Cite this article: Bone Joint Res 2020;9(8):450–457.

Parietal Block Using Bupivacaine in the Rat: An Anatomical, Behavioral and Histological Study

Purpose

Animal models of regional anaesthesia are useful for studying the effects of blocks and improve their efficacy. The aim of our experiments was to validate a multi-site paravertebral block in the rat.

Material and methods

Dissection and indigo carmine dye injection were performed in five rats (3 rats were dissected and 2 were dye injected). In other groups (n=7rats/group), after inflammation inductive carrageenan injection in the abdominal wall, bupivacaine or saline was injected laterally to the spinal column at the T5, T10, L1, L4 and S1 level. The efficacy of the block on mechanical nociception was measured using von Frey hairs. In addition, we measured c-Fos immunoreactive nuclei in the cord.

Results

The multi-site injection showed a perinervous distribution of the injected solution without intra-thoracic, intra-abdominal or epidural diffusion. Bilateral block with a relatively small volume of bupivacaine (0.5 mL) significantly increased the threshold to mechanical pain as compared to control (p=0.007) and significantly decreased the number of c-Fos immunoreactive nuclei in the posterior horn of the spinal cord (p<0.0001).

Conclusion

This study shows that a parietal abdominal wall block is easy to perform in the rat. This block allows investigators to explore the mechanisms of action of abdominal parietal wall blocks.

Mouse Models and Tools for the in vivo Study of Neutrophils

Neutrophils are the most abundant leukocytes in human blood and critical actors of the immune system. Many neutrophil functions and facets of their activity in vivo were revealed by studying genetically modified mice or by tracking fluorescent neutrophils in animals using imaging approaches. Assessing the roles of neutrophils can be challenging, especially when exact molecular pathways are questioned or disease states are interrogated that alter normal neutrophil homeostasis. This review discusses the main in vivo models for the study of neutrophils, their advantages and limitations. The side-by-side comparison underlines the necessity to carefully choose the right model(s) to answer a given scientific question, and exhibit caveats that need to be taken into account when designing experimental procedures. Collectively, this review suggests that at least two models should be employed to legitimately conclude on neutrophil functions.

S100 family proteins in inflammation and beyond

The S100 family proteins possess a variety of intracellular and extracellular functions. They interact with multiple receptors and signal transducers to regulate pathways that govern inflammation, cell differentiation, proliferation, energy metabolism, apoptosis, calcium homeostasis, cell cytoskeleton and microbial resistance. S100 proteins are also emerging as novel diagnostic markers for identifying and monitoring various diseases. Strategies aimed at targeting S100-mediated signaling pathways hold a great potential in developing novel therapeutics for multiple diseases. In this chapter, we aim to summarize the current knowledge about the role of S100 family proteins in health and disease with a major focus on their role in inflammatory conditions.

Assessment of Phenolic Compounds and Anti-Inflammatory Activity of Ethyl Acetate Phase of Anacardium occidentale L. Bark

The bark of A. occidentale L. is rich in tannins. Studies have described various biological activities of the plant, including antimicrobial, antioxidant, antiulcerogenic and antiinflammatory actions. The objective of this study was to assess the activity of the ethyl acetate phase (EtOAc) of A. occidentale on acute inflammation and to identify and quantify its phenolic compounds by HPLC. The method was validated and shown to be linear, precise and accurate for catechin, epicatechin, epigallocatechin and gallic acid. Swiss albino mice (Mus musculus) were treated with saline, Carrageenan (2.5%), Indomethacin (10 mg/kg), Bradykinin (6 nmol) and Prostaglandine E2 (5 µg) at different concentrations of EtOAc - A. occidentale (12.5; 25; 50; and 100 mg/kg/weight p.o.) for the paw edema test. Challenge was performed with carrageenan (500 µg/mL i.p.) for the doses 50 and 100 mg/kg of EtOAc. Levels of cytokines IL-1, TNF-α, IL-6 and IL-10 were also measured. All EtOAc - A. occidentale concentrations reduced the edema. At 50 and 100 mg/kg, an anti-inflammatory response of the EtOAc was observed. Carrageenan stimulus produced a neutrophil count of 28.6% while 50 and 100 mg/kg of the phase reduced this to 14.5% and 9.1%, respectively. The EtOAc extract reduced levels of IL-1 and TNF-α. These results suggest that the EtOAc plays a modulatory role in the inflammatory response. The chromatographic method can be used for the analysis of the phenolic compounds of the EtOAc phase.

Evaluation of the anti-inflammatory action of curcumin analog (DM1): Effect on iNOS and COX-2 gene expression and autophagy pathways

This work describes the anti-inflammatory effect of the curcumin-analog compound, sodium 4-[5-(4-hydroxy-3-methoxyphenyl)-3-oxo-penta-1,4-dienyl]-2-methoxy-phenolate (DM1), and shows that DM1 modulates iNOS and COX-2 gene expression in cultured RAW 264.7 cells and induces autophagy on human melanoma cell line A375.

Molecular and cellular mechanisms that initiate pain and itch

Somatosensory neurons mediate our sense of touch. They are critically involved in transducing pain and itch sensations under physiological and pathological conditions, along with other skin-resident cells. Tissue damage and inflammation can produce a localized or systemic sensitization of our senses of pain and itch, which can facilitate our detection of threats in the environment. Although acute pain and itch protect us from further damage, persistent pain and itch are debilitating. Recent exciting discoveries have significantly advanced our knowledge of the roles of membrane-bound G protein-coupled receptors and ion channels in the encoding of information leading to pain and itch sensations. This review focuses on molecular and cellular events that are important in early stages of the biological processing that culminates in our senses of pain and itch.

Inhibition of macrophage functions by the C-terminus of murine S100A9 is dependent on B-1 cells

The protein S100A9 plays a key role in the control of inflammatory response. The C-terminus of the murine S100A9 protein (mS100A9p) downregulates the spreading and phagocytic activity of adherent peritoneal cells. Murine peritoneal cells are constituted by macrophages and B-1 cells, and the latter exert an inhibitory effect on macrophage functions by secreting interleukin- (IL-) 10. Here, we investigated the influence of B-1 cells on the inhibitory effect evoked by mS100A9p on macrophages. mS100A9p did not alter spreading and phagocytosis either by peritoneal macrophages obtained from mice deprived of B-1 cells or by bone marrow-derived macrophages (BMDMϕ). Nevertheless, when BMDMϕ were cocultivated by direct or indirect contact with B-1 cells treated with mS100A9p, the phagocytosis by BMDMϕ was decreased, showing that the effect of mS100A9p on macrophages was modulated by B-1 cells and/or their secretory compounds. Furthermore, the inhibitory action of mS100A9p on phagocytosis by adherent peritoneal cells was abolished in cells obtained from IL-10 knockout mice. Taken together, the results show that mS100A9p has no direct inhibitory effect on macrophages; however, mS100A9p modulates B-1 cells, which in turn downregulates macrophages, at least in part, via IL-10. These data contribute to the characterization of S100A9 functions involving B-1 cells in the regulation of the inflammatory process.

Anti-inflammatory effect of triterpene 3β, 6β, 16β-trihydroxylup-20(29)-ene obtained from Combretum leprosum Mart & Eich in mice

ETHNOPHARMACOLOGICAL RELEVANCE

The 3β, 6β, 16β-trihydroxylup-20(29)-ene (TTHL) is a pentacyclic triterpene obtained from a medicinal plant named Combretum leprosum. In folk medicine, this plant is used to treat several diseases associated with inflammation and pain. We previously demonstrated that TTHL presents a significant antinociceptive effect, suggesting the involvement of the glutamatergic system.

AIM OF THE STUDY

This study was designed to investigate the effect of TTHL on nociception and vascular permeability induced by acetic acid. We also evaluated the effect of TTHL on carrageenan-induced peritonitis and the levels of cytokines (interleukin 1-β [IL-1β], tumor necrosis factor α [TNF-α] and interleukin 10 [IL-10]) on peritoneal fluid.

MATERIALS AND METHODS

TTHL was administered orally by intra-gastric gavage (i.g.) 60 min prior to experimentation. Abdominal contractions and vascular permeability were induced by an intraperitoneal (i.p.) injection of acetic acid (0.6%). We also investigated whether TTHL decreases carrageenan-induced peritonitis (750 μg/cavity) by measuring leukocyte migration and vascular permeability. In addition, we evaluated the effects of TTHL on TNF-α, IL-1β and IL-10 release induced by carrageenan on peritoneal fluid. The levels of these cytokines were measured by ELISA.

RESULTS

TTHL (0.01-10 mg/kg) administered by intra-gastric (i.g.) gavage inhibited (69±3%) acetic acid-induced abdominal constrictions, with an ID₅₀ of 0.15 (0.03-0.8) mg/kg. TTHL (10mg/kg) also reduced the leukocyte infiltration induced by acetic acid, with an inhibition of 59±9 but had no effect on abdominal vascular permeability. In addition, indomethacin (10 mg/kg, i.p.) reduced the nociceptive behavior (92±1%), total leukocyte migration (29±3%) and capillary permeability (71±3%) induced by acetic acid. While the glucocorticoid dexamethasone (2 mg/kg, s.c.) reduced partially but significantly the nociception (31±1%), besides to promote a marked reduction on total leukocyte migration (60±2%) to the peritoneal cavity caused by acetic acid. In a model of peritonitis induced by carrageenan, TTHL also reduced total leukocyte migration, mainly neutrophils (inhibition of 84±3% and 85±2% at 30 mg/kg and 100 mg/kg, respectively). Likewise, dexamethasone (0.5 mg/kg, i.p.) resulted in an inhibition of 93±3%. Nevertheless, carrageenan-induced abdominal vascular permeability was reduced by dexamethasone but was not altered by TTHL. Furthermore, dexamethasone and TTHL significantly reduced the TNF-α and IL-1β levels in peritoneal fluid, whereas the IL-10 levels were unchanged.

CONCLUSIONS

Altogether, our data confirm the antinociceptive effect of TTHL and demonstrate its effect in inflammatory animal models, providing novel data about this compound, which could be useful as an anti-inflammatory drug.

Delayed increase of S100A9 messenger RNA predicts hospital-acquired infection after septic shock

OBJECTIVE

Septic shock remains a serious disease with high mortality and increased risk of hospital-acquired infection. The prediction of outcome is of the utmost importance for selecting patients for therapeutic strategies aiming to modify the immune response. The aim of this study was to assess the capability of S100A9 messenger RNA in whole blood from patients with septic shock to predict survival and the occurrence of hospital-acquired infection.

DESIGN

Cohort study.

SETTING

Two intensive care units in a university hospital.

SUBJECTS

The study included patients with septic shock (n = 166) and healthy volunteers (n = 44).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For the patients with septic shock patients, overall mortality was 38% and the mean Simplified Acute Physiologic Scale II on shock onset was 52. Using quantitative reverse transcriptase-polymerase chain reactions, we found that median S100A9 messenger RNA was significantly lower in healthy volunteers than in patients with septic shock (p < .0001) between days 1 and 3 after onset of the septic shock and not significantly different between nonsurvivor and survivor patients (p = .1278). However, median S100A9 messenger RNA measured on days 7-10 was significantly higher in patients who were about to contract hospital-acquired infections compared with those who were not (p = .009). In the multivariate analysis, the S100A9 marker increased the probability of contracting hospital-acquired infections with an odds ratio of 1.12 per unit (p = .0054).

CONCLUSIONS

S100A9 messenger RNA is increased in septic shock and its delayed overexpression is associated with the occurrence of secondary hospital-acquired infection. This biomarker may be of major interest in identifying patients with increased risk of hospital-acquired infection who could benefit from targeted therapy aimed at restoring their immune functions.

The down regulation of neutrophil oxidative metabolism by S100A8 and S100A9: implication of the protease-activated receptor-2

S100A8 and S100A9 regulate polymorphonuclear neutrophils (PMNs) recruitment and represent 40% of PMN cytosolic protein weight. We have shown that S100A8/S100A9 inhibit PMN oxidative metabolism. The present study was designed to elucidate the mechanisms of this anti-oxidative effect. We hypothesized that the protease activated receptor-2 (PAR-2) played a role in the down-regulation of PMN oxidative metabolism by S100A8/S100A9. Freshly isolated PMNs were tested for their ability to oxidize dichlorofluorescin-diacetate. Functional inhibition of PAR-2 with ENMD-1068, the pepducin P2pal-21 or an antibody directed at PAR-2 cleavage/activation site, resulted in a significant inhibition of S100A8 and S100A9 anti-oxidative effect. Conversely, the controlled activation of PAR-2 potentiated S100 anti-oxidative effect. Taken together, the data indicate that the anti-oxidative effect of S100A8/A9 is initiated by PAR-2 activation. S100A8/S100A9 may therefore dampen inflammation without interfering with its initial strength. This finding opens translational possibilities to limit deleterious PMN activation with a dual PAR-2/S100 strategy.

Involvement of Interleukin-10 in the Anti-Inflammatory Effect of Sanyinjiao (SP6) Acupuncture in a Mouse Model of Peritonitis

In this study, we determined the anti-inflammatory effect of manual acupuncture at the Sanyinjiao or Spleen 6 (SP6) point on carrageenan-induced peritonitis in mice and investigated mechanisms that may underlie this effect. In the first set of experiments, male Swiss mice were allocated into five groups: the control (sterile saline), dexamethasone (DEXA), invasive sham-acupuncture (non-acupoint), SP6 acupuncture and carrageenan-treated groups. Ten minutes after needle retention or 30 min after DEXA treatment, mice received an intraperitoneal injection of carrageenan (750 μg/mouse). After 4 h, total leukocyte and differential cell counts (neutrophils and mononuclear), myeloperoxidase (MPO) activity, vascular permeability and cytokine levels were evaluated. In another set of experiments, adrenalectomized (ADX) mice were used to study the involvement of the adrenal gland on the therapeutic effects of acupuncture. Mice were allocated into two groups: the ADX and sham-operated animals (Sham ADX) that were subdivided into four subgroups each: the control (sterile saline), DEXA, SP6 acupuncture and carrageenan-treated groups. The SP6 and DEXA treatments inhibited the inflammatory cell infiltration, vascular permeability and MPO activity in carrageenan-injected mice. In addition, the SP6 treatment also increased interleukin (IL)-10 levels. In contrast, when the animals were adrenalectomized, the SP6 treatment failed to reduce total leukocyte and the plasma extravasation. In conclusion, this study clearly demonstrates the anti-inflammatory effect of SP6 acupuncture in a model of carrageenan-induced peritonitis. Our results demonstrated that SP6 acupuncture depends of the adrenal glands and increased IL-10 levels to produce its anti-inflammatory action.

Inflammation-associated S100 proteins: new mechanisms that regulate function

This review focuses on new aspects of extracellular roles of the calgranulins. S100A8, S100A9 and S100A12 are constitutively expressed in neutrophils and induced in several cell types. The S100A8 and S100A9 genes are regulated by pro- and anti-inflammatory mediators and their functions may depend on cell type, mediators within a particular inflammatory milieu, receptors involved in their recognition and their post-translational modification. The S100A8 gene induction in macrophages is dependent on IL-10 and potentiated by immunosuppressive agents. S100A8 and S100A9 are oxidized by peroxide, hypochlorite and nitric oxide (NO). HOCl generates intra-chain sulfinamide bonds; stronger oxidation promotes cross-linked forms that are seen in human atheroma. S100A8 is >200-fold more sensitive to oxidative cross-linking than low-density lipoprotein and may reduce oxidative damage. S100A8 and S100A9 can be S-nitrosylated. S100A8-SNO suppresses mast cell activation and inflammation in the microcirculation and may act as an NO transporter to regulate vessel tone in inflammatory lesions. S100A12 activates mast cells and is a monocyte and mast cell chemoattractant; a G-protein-coupled mechanism may be involved. Structure-function studies are discussed in relation to conservation and divergence of functions in S100A8. S100A12 induces cytokines in mast cells, but not monocytes/macrophages. It forms complexes with Zn(2+) and, by chelating Zn(2+), S100A12 significantly inhibits MMPs. Zn(2+) in S100A12 complexes co-localize with MMP-9 in foam cells in atheroma. In summary, S100A12 has pro-inflammatory properties that are likely to be stable in an oxidative environment, because it lacks Cys and Met residues. Conversely, S100A8 and S100A9 oxidation and S-nitrosylation may have important protective mechanisms in inflammation.

Involvement of proteinase-activated receptors 1 and 2 in spreading and phagocytosis by murine adherent peritoneal cells: modulation by the C-terminal of S100A9 protein

Proteinase-activated receptors (PAR) are widely recognized for their modulatory properties in inflammatory and immune responses; however, their direct role on phagocyte effector functions remains unknown. S100A9, a protein secreted during inflammatory responses, deactivates activated peritoneal macrophages, and its C-terminal portion inhibits spreading and phagocytosis of adherent peritoneal cells. Herein, the effect of PAR1 and PAR2 agonists was investigated on spreading and phagocytosis by adherent peritoneal cells, as well as the ability of murine C-terminal of S100A9 peptide (mS100A9p) to modulate this effect. Adherent peritoneal cells obtained from mouse abdominal cavity were incubated with PAR1 and PAR2 agonists and spreading and phagocytosis of Candida albicans particles were evaluated. PAR1 agonists increased both the spreading and the phagocytic activity, but PAR2 agonists only increased the spreading index. mS100A9p reverted both the increased spreading and phagocytosis induced by PAR1 agonists, but no interference in the increased spreading induced by PAR2 agonists was noticed. The shorter homologue peptide to the C-terminal of mS100A9p, corresponding to the H(92)-E(97) region, also reverted the increased spreading and phagocytosis induced by PAR1 agonists. These findings show that proteinase-activated receptors have an important role for spreading and phagocytosis of adherent peritoneal cells, and that the peptide corresponding to the C-terminal of S100A9 protein is a remarkable candidate for use as a novel compound to modulate PAR1 function.

Macrophage suppression following phagocytosis of apoptotic neutrophils is mediated by the S100A9 calcium-binding protein

The clearance of apoptotic cells by phagocytes is a fundamental process during tissue remodeling and resolution of inflammation. In turn, the phagocytosis of apoptotic cells generates signals that suppress pro-inflammatory activation of macrophages. These events occur during the resolution phase of inflammation and therefore the malfunctioning of this process may lead to inflammation-related tissue damage. Here, we demonstrate that the calcium-binding protein S100A9, normally abundant in the cytoplasm of neutrophils and also released by apoptotic neutrophils, is involved in the suppression of macrophages after the uptake of apoptotic neutrophils. Both, spontaneous and induced production of inflammatory species (nitric oxide, hydrogen peroxide and TNF-alpha) as well as the phagocytic activity were inhibited when macrophages were in presence of apoptotic neutrophils, conditioned medium from neutrophil cultures or a peptide corresponding to the C-terminal region of S100A9 protein. On the other hand, macrophages kept in the conditioned medium of neutrophils that was previously depleted of S100A9 were shown to resume the activated status. Finally, we demonstrate that the calcium-binding property of S100A9 might play a role in the suppression process, since the stimulation of intracellular calcium release with ionomycin significantly reversed the effects of the uptake of apoptotic neutrophils in macrophages. In conclusion, we propose that S100A9 is a novel component of the regulatory mechanisms of inflammation, acting side-by-side with other suppressor factors generated upon ingestion of apoptotic cells.

Antinociceptive effect of the C-terminus of murine S100A9 protein on experimental neuropathic pain

The synthetic peptide identical to the C-terminus of murine S100A9 protein (mS100A9p) has antinociceptive effect on different acute inflammatory pain models. In this study, the effect of mS100A9p was investigated on neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve in rats. Hyperalgesia, allodynia, and spontaneous pain were assessed to evaluate nociception. These three signs were detected as early as 2 days after sciatic nerve constriction and lasted for over 14 days after CCI. Rats were treated with different doses of mS100A9p by intraplantar, oral, or intrathecal routes on day 14 after CCI, and nociception was evaluated 1h later. These three routes of administration blocked hyperalgesia, allodynia and spontaneous pain. The duration of the effect of mS100A9p depends on the route used and phenomenon analyzed. Moreover, intraplantar injection of mS100A9p in the contralateral paw inhibited the hyperalgesia on day 14 days after CCI. The results obtained herein demonstrate the antinociceptive effect of the C-terminus of murine S100A9 protein on experimental neuropathic pain, suggesting a potential therapeutic use for it in persistent pain syndromes, assuming that tolerance does not develop to mS100A9p.

Neutrophilic cell-free exudate induces antinociception mediate by the protein S100A9

Calcium-binding protein S100A9 (MRP-14) induces antinociceptive effect in an experimental model of painful sensibility and participates of antinociception observed during neutrophilic peritonitis induced by glycogen or carrageenan in mice. In this study, the direct antinociceptive role of the protein S100A9 in neutrophilic cell-free exudates obtained of mice injected with glycogen was investigated. Mice were intraperitoneally injected with a glycogen solution, and after 4, 8, 24, and 48 hours, either the pattern of cell migration of the peritoneal exudate or the nociceptive response of animals was evaluated. The glycogen-induced neutrophilic peritonitis evoked antinociception 4 and 8 hours after inoculation of the irritant. Peritoneal cell-free exudates, collected in different times after the irritant injection, were transferred to naive animals which were submitted to the nociceptive test. The transference of exudates also induced antinociceptive effect, and neutralization of S100A9 activity by anti-S100A9 monoclonal antibody totally reverted this response. This effect was not observed when experiments were made 24 or 48 hours after glycogen injection. These results clearly indicate that S100A9 is secreted during glycogen-induced neutrophilic peritonitis, and that this protein is responsible by antinociception observed in the initial phase of inflammatory reaction. Thus, these data reinforce the hypothesis that the calcium-binding protein S100A9 participates of the endogenous control of inflammatory pain.

Effect of the C-terminus of murine S100A9 protein on experimental nociception

Calcium-binding protein S100A9 induces antinociception in mice evaluated by the writhing test. Similarly, a peptide identical to the C-terminus of murine S100A9 (mS100A9p) inhibits the hyperalgesia induced by jararhagin, a metalloprotease. Thus, we investigated the effect of mS100A9p on different models used to evaluate nociception. mS100A9p induced a dose-dependent inhibitory effect on the writhing test, and on mechanical hyperalgesia induced by carrageenan. mS100A9p inhibited thermal hyperalgesia induced by carrageenan. mS100A9p did not modify the nociceptive response in hot plate or tail-flick tests. These data demonstrate that the C-terminus of S100A9 protein interferes with control mechanisms of inflammatory pain.

The C-terminus of murine S100A9 protein inhibits hyperalgesia induced by the agonist peptide of protease-activated receptor 2 (PAR2)

BACKGROUND AND PURPOSE

S100A9 protein induces anti-nociception in rodents, in different experimental models of inflammatory pain. Herein, we investigated the effects of a fragment of the C-terminus of S100A9 (mS100A9p), on the hyperalgesia induced by serine proteases, through the activation of protease-activated receptor-2 (PAR2).

EXPERIMENTAL APPROACH

Mechanical and thermal hyperalgesia induced by PAR2 agonists (SLIGRL-NH2 and trypsin) was measured in rats submitted to the paw pressure or plantar tests, and Egr-1 expression was determined by immunohistochemistry in rat spinal cord dorsal horn. Calcium flux in human embryonic kidney cells (HEK), which naturally express PAR2, in Kirsten virus-transformed kidney cells, transfected (KNRK-PAR2) or not (KNRK) with PAR2, and in mouse dorsal root ganglia neurons (DRG) was measured by fluorimetric methods.

KEY RESULTS

mS100A9p inhibited mechanical hyperalgesia induced by trypsin, without modifying its enzymatic activity. Mechanical and thermal hyperalgesia induced by SLIGRL-NH2 were inhibited by mS100A9p. SLIGRL-NH2 enhanced Egr-1 expression, a marker of nociceptor activation, and this effect was inhibited by concomitant treatment with mS100A9p. mS100A9p inhibited calcium mobilization in DRG neurons in response to the PAR2 agonists trypsin and SLIGRL-NH2, but also in response to capsaicin and bradykinin, suggesting a direct effect of mS100A9 on sensory neurons. No effect on the calcium flux induced by trypsin or SLIGRL in HEK cells or KNRK-PAR2 cells was observed.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that mS100A9p interferes with mechanisms involved in nociception and hyperalgesia and modulates, possibly directly on sensory neurons, the PAR2-induced nociceptive signal.

The C-terminus of murine S100A9 inhibits hyperalgesia and edema induced by jararhagin

The effect of a synthetic peptide (H92-G110) identical to the C-terminus of murine S100A9 (mS100A9p) was investigated on hyperalgesia and edema induced by either jararhagin or papain in the rat paw. mS100A9p not only reverted hyperalgesia and edema induced by jararhagin, but also the highest concentration induced antinociception. Hemorrhage induced by jararhagin and its hydrolytic activity were inhibited by mS100A9p. These data suggest that mS100A9p might block jararhagin-induced hyperalgesia and edema by inhibiting jararhagin catalytic activity, since papain-induced hyperalgesia and edema were not inhibited by mS100A9p.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).