S100A9: The Unusual Suspect Connecting Viral Infection and Inflammation.

The study of S100A9 in viral infections has seen increased interest since the COVID-19 pandemic. S100A8/A9 levels were found to be correlated with the severity of COVID-19 disease, cytokine storm, and changes in myeloid cell subsets. These data led to the hypothesis that S100A8/A9 proteins might play an active role in COVID-19 pathogenesis. This review explores the structures and functions of S100A8/9 and the current knowledge on the involvement of S100A8/A9 and its constituents in viral infections. The potential roles of S100A9 in SARS-CoV-2 infections are also discussed.

The impact of the herbicide glyphosate and its metabolites AMPA and MPA on the metabolism and functions of human blood neutrophils and their sex-dependent effects on reactive oxygen species and CXCL8/IL-8 production.

Significant levels of glyphosate, the world's most widely used herbicide, and its primary metabolites, AMPA and MPA, are detected in various human organs and body fluids, including blood. Several studies have associated the presence of glyphosate in humans with health problems, and effects on immune cells and their functions have been reported. However, the impact of this molecule and its metabolites on neutrophils, the most abundant leukocytes in the human bloodstream, is still poorly documented. We isolated neutrophils from human donor blood and investigated the effects of exposure to glyphosate, AMPA, and MPA on viability, energy metabolism, and essential antimicrobial functions in vitro. We observed that neutrophil viability was unaffected at the blood-relevant average concentrations of the general population and exposed workers, as well as at higher intoxication concentrations. Neutrophil energy metabolism was also not altered following exposure to the chemicals. However, while phagocytosis was unaffected, reactive oxygen species generation and CXCL8/IL-8 production were altered by exposure to the molecules. Alterations in function following exposure to glyphosate and metabolites differed according to the sex of the donors, which could be linked to glyphosate's known role as an endocrine disruptor. While ROS generation was increased in both sexes, male neutrophils exposed to glyphosate had increased intracellular production of CXCL8/IL-8, with no effect on female neutrophils. Conversely, exposure to the metabolites AMPA and MPA decreased extracellular production of this chemokine only in female neutrophils, with MPA also increasing intracellular production in male cells exposed to the chemoattractant N-formyl-methionine-leucyl-phenylalanine. Our study highlights the effects of glyphosate and its metabolites on the antimicrobial functions of neutrophils, which could be associated with health problems as future studies provide a better understanding of the risks associated with glyphosate use. Advances in knowledge will enable better and potentially stricter regulations to protect the public.

Deletion of S100a8 and S100a9 Enhances Skin Hyperplasia and Promotes the Th17 Response in Imiquimod-Induced Psoriasis.

High concentrations of the damage-associated molecular patterns S100A8 and S100A9 are found in skin and serum from patients suffering from psoriasis, an IL-17-related disease. Notably, although the expression of these proteins correlates with psoriatic disease severity, the exact function of S100A8 and S100A9 in psoriasis pathogenesis remains unclear. In this study, we investigated the role of S100A8 and S100A9 in psoriasis-associated skin hyperplasia and immune responses using S100a8-/- and S100a9-/- mice in an imiquimod-induced model of psoriasis. We found that S100a8-/- and S100a9-/- psoriatic mice exhibit worsened clinical symptoms relative to wild-type mice and increased expression of S100A9 and S100A8 proteins in keratinocytes, respectively. In addition, the loss of S100A8 enhances proliferation of keratinocytes and disrupts keratinocyte differentiation. We further detected elevated production of IL-17A and -F from CD4+ T cells in the absence of S100A8 and S100A9, as well as increased infiltration of neutrophils in the skin. In addition, treatment with anti-IL-17A and -F was found to reduce psoriasis symptoms and skin hyperplasia in S100a8-/- and S100a9-/- mice. These data suggest that S100A8 and S100A9 regulate psoriasis by inhibiting production of IL-17A and -F, thereby, to our knowledge, providing new insights into their biological functions.

Effectiveness of a multi-faceted intervention to deprescribe proton pump inhibitors in primary care: protocol for a population-based, pragmatic, cluster-randomized controlled trial.

BACKGROUND: Inappropriately using proton pump inhibitors (PPI) is associated with severe adverse drug reactions and may have major consequences on healthcare costs. Deprescribing (the process by which a healthcare professional supervises the withdrawal of an inappropriate medication, to manage polypharmacy and improve outcomes) should be considered when an inappropriate PPI prescription is identified. Deprescribing interventions directed solely to prescribers have limited efficacy and are rarely targeted to patients. The aim of this trial is to assess the efficacy of a multi-faceted intervention with patients and general practitioners (GPs) to deprescribe PPI. METHODS: We will conduct a pragmatic, cluster-randomized, population-based, controlled trial in two regions of Western France. GPs with practices with over 100 patients, and their adult patient to whom over 300 defined daily doses (DDD) of PPIs have been dispensed in the year before baseline will be included. A total of 1300 GPs and 33,000 patients will be cluster-randomized by GPs practices. Three arms will be compared: i) a multi-faceted intervention associating a) a patient education brochure about PPI deprescribing sent directly to patients (the brochure was designed using a mixed-methods study), and b) a personalized letter with the Bruyere's PPI deprescribing algorithm sent to their respective GPs, or ii) a single intervention where only the GPs received the letter and algorithm, or iii) no intervention. The primary outcome will be PPI deprescribing, defined as the proportion of patients achieving at least a 50% decrease in the amount of PPI dispensed to them (DDD/year) at 12 months compared to baseline. Secondary outcomes will include incremental cost-utility ratio (using EQ-5D-5L scale and National Health Insurance's database), acid rebound (using the Gastroesophageal Reflux Disease Impact Scale), and the patients' attitudes towards deprescribing (using the French rPATD). DISCUSSION: Based on previous trials, we anticipate more than 10% "successful PPI deprescribing" in the multi-faceted intervention compared to the single intervention on GPs and the control arm. The study has been funded through a national grant and will be launched in autumn 2020, for early results by the end of 2022. TRIAL REGISTRATION: Clinicaltrials.gov NCT04255823 ; first registered on February 5, 2020.

Editor's Choice - A Cost Effectiveness Analysis of Outpatient versus Inpatient Hospitalisation for Lower Extremity Arterial Disease Endovascular Revascularisation in France: A Randomised Controlled Trial.

OBJECTIVE: The AMBUVASC trial evaluated the cost effectiveness of outpatient vs. inpatient hospitalisation for endovascular repair of lower extremity arterial disease (LEAD). METHODS: AMBUVASC was a national multicentre, prospective, randomised controlled trial conducted in nine public and two private French centres. The primary endpoint was the incremental cost effectiveness ratio (ICER), defined by cost per quality adjusted life year (QALY). Analysis was conducted from a societal perspective, excluding indirect costs, and considering a one month time horizon. RESULTS: From 16 February 2016 to 29 May 2017, 160 patients were randomised (80 per group). A modified intention to treat analysis was performed with 153 patients (outpatient hospitalisation: n = 76; inpatient hospitalisation: n = 77). The patients mainly presented intermittent claudication (outpatient arm: 97%; inpatient arm: 92%). Rates of peri-operative complications were 20% (15 events) and 18% (14 events) for the outpatient and inpatient arms respectively (p = .81). Overall costs (difference: €187.83; 95% confidence interval [CI] -275.68-651.34) and QALYs (difference: 0.00277; 95% CI -0.00237 - 0.00791) were higher for outpatients due to more re-admissions than the inpatient arm. The mean ICER was €67 741 per QALY gained for the base case analysis with missing data imputed using multiple imputation by predictive mean matching. The outpatient procedure was not cost effective for a willingness to pay of €50 000 per QALY and the probability of being cost effective was only 59% for a €100 000/QALY threshold. CONCLUSION: Outpatient hospitalisation is not cost effective compared with inpatient hospitalisation for endovascular repair of patients with claudication at a €50 000/QALY threshold.

Patient-centered simulations to assess the usefulness of the 70-gene signature for adjuvant chemotherapy administration in early-stage breast cancer.

PURPOSE: From the MINDACT trial, Cardoso et al. did not demonstrate a significant efficacy for adjuvant chemotherapy (CT) for women with early-stage breast cancer presenting high clinical and low genomic risks. Our objective was to assess the usefulness of the 70-gene signature in this population by using an alternative endpoint: the number of Quality-Adjusted Life-Years (QALYs), i.e., a synthetic measure of quantity and quality of life. METHODS: Based on the results of the MINDACT trial, we simulated a randomized clinical trial consisting of 1497 women with early-stage breast cancer presenting high clinical and low genomic risks. The individual preferences for the different health states and corresponding decrements were obtained from the literature. RESULTS: The gain in terms of 5-year disease-free survival was 2.8% (95% CI from - 0.1 to 5.7%, from 90.4% for women without CT to 93.3% for women with CT). In contrast, due to the associated side effects, CT significantly reduced the number of QALYs by 62 days (95% CI from 55 to 70 days, from 4.13 years for women without CT to 3.96 years for women with CT). CONCLUSION: Our results support the conclusions published by Cardoso et al. by providing additional evidence that the 70-gene signature can be used to avoid overtreatment by CT for women with high clinical risk but low genomic risk.

S100A9 induces differentiation of acute myeloid leukemia cells through TLR4.

S100A8 and S100A9 are calcium-binding proteins predominantly expressed by neutrophils and monocytes and play key roles in both normal and pathological inflammation. Recently, both proteins were found to promote tumor progression through the establishment of premetastatic niches and inhibit antitumor immune responses. Although S100A8 and S100A9 have been studied in solid cancers, their functions in hematological malignancies remain poorly understood. However, S100A8 and S100A9 are highly expressed in acute myeloid leukemia (AML), and S100A8 expression has been linked to poor prognosis in AML. We identified a small subpopulation of cells expressing S100A8 and S100A9 in AML mouse models and primary human AML samples. In vitro and in vivo analyses revealed that S100A9 induces AML cell differentiation, whereas S100A8 prevents differentiation induced by S100A9 activity and maintains AML immature phenotype. Treatment with recombinant S100A9 proteins increased AML cell maturation, induced growth arrest, and prolonged survival in an AML mouse model. Interestingly, anti-S100A8 antibody treatment had effects similar to those of S100A9 therapy in vivo, suggesting that high ratios of S100A9 over S100A8 are required to induce differentiation. Our in vitro studies on the mechanisms/pathways involved in leukemic cell differentiation revealed that binding of S100A9 to Toll-like receptor 4 (TLR4) promotes activation of p38 mitogen-activated protein kinase, extracellular signal-regulated kinases 1 and 2, and Jun N-terminal kinase signaling pathways, leading to myelomonocytic and monocytic AML cell differentiation. These findings indicate that S100A8 and S100A9 are regulators of myeloid differentiation in leukemia and have therapeutic potential in myelomonocytic and monocytic AMLs.

Meta-analysis of predictive models to assess the clinical validity and utility for patient-centered medical decision making: application to the CAncer of the Prostate Risk Assessment (CAPRA).

BACKGROUND: The Cancer of the Prostate Risk Assessment (CAPRA) score was designed and validated several times to predict the biochemical recurrence-free survival after a radical prostatectomy. Our objectives were, first, to study the clinical validity of the CAPRA score, and, second, to assess its clinical utility for stratified medicine from an original patient-centered approach. METHODS: We proposed a meta-analysis based on a literature search using MEDLINE. Observed and predicted biochemical-recurrence-free survivals were compared to assess the calibration of the CAPRA score. Discriminative capacities were evaluated by estimating the summary time-dependent ROC curve. The clinical utility of the CAPRA score was evaluated according to the following stratified decisions: active monitoring for low-risk patients, prostatectomy for intermediate-risk patients, or radio-hormonal therapy for high risk patients. For this purpose, we assessed CAPRA's clinical utility in terms of its ability to maximize time-dependent utility functions (i.e. Quality-Adjusted Life-Years - QALYs). RESULTS: We identified 683 manuscripts and finally retained 9 studies. We reported good discriminative capacities with an area under the SROCt curve at 0.73 [95%CI from 0.67 to 0.79], while graphical calibration seemed acceptable. Nevertheless, we also described that the CAPRA score was unable to discriminate between the three medical alternatives, i.e. it did not allow an increase in the number of life years in perfect health (QALYs) of patients with prostate cancer. CONCLUSIONS: We confirmed the prognostic capacities of the CAPRA score. In contrast, we were not able to demonstrate its clinical usefulness for stratified medicine from a patient-centered perspective. Our results also highlighted the confusion between clinical validity and utility. This distinction should be better considered in order to develop predictive tools useful in practice.

A mini-review of quality of life as an outcome in prostate cancer trials: patient-centered approaches are needed to propose appropriate treatments on behalf of patients.

BACKGROUND: Patients with prostate cancer (PC) may be ready to make trade-offs between their quantity and their quality of life. For instance, elderly patients may prefer the absence of treatment if it is associated with a low-risk of disease progression, compared to treatments aiming at preventing disease progression but with a substantial deterioration of their Health-Related Quality of Life (HRQoL). Therefore, it seems relevant to compare the treatments by considering both survival and HRQoL. In this mini-review, the aim was to question whether the potential trade-offs between survival and HRQoL are considered in high impact factor journals. METHODS: The study was conducted from the PubMed database for recent papers published between May 01, 2013, and May 01, 2015. We also restricted our search to nine medical journals with 2013 impact factor > 15. RESULTS: Among the 30 selected studies, only six collected individual HRQoL as a secondary endpoint by using the Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire. In four studies, the time to HRQoL change was analyzed, but its definitions varied. In two studies, the mean changes in HRQoL between the baseline and the 12- or 16-week follow-up were analyzed. None of the six studies reported in a single endpoint both the quantity and the quality of life. CONCLUSIONS: Our mini-review, which only focused on recent publications in journals with high-impact, suggests moving PC clinical research towards patient-centered outcomes-based studies. This may help physicians to propose the most appropriate treatment on behalf of patients. We recommend the use of indicators such as Quality-Adjusted Life-Years (QALYs) as principal endpoint in future clinical trials.

Cooperation between IL-7 Receptor and Integrin α2ß1 (CD49b) Drives Th17-Mediated Bone Loss.

Th17 cells are critical effectors in inflammation and tissue damage such as bone erosion, but the mechanisms regulating their activation in this process are not fully understood. In this study, we considered the cooperation between cytokine receptors and integrin pathways in Th17-osteoclast function. We found that human Th17 cells coexpress IL-7R and the collagen-binding integrin α2ß1 (CD49b), and IL-7 increases their adhesion to collagen via α2ß1 integrin. In addition, coengagement of the two receptors in human Th17 cells cooperatively enhanced their IL-17 production and their osteoclastogenic function. The functional cooperation between IL-7R and α2ß1 integrin involves activation of the JAK/PI3K/AKT (protein kinase B) and MAPK/ERK pathways. We also showed that IL-7-induced bone loss in vivo is associated with Th17 cell expansion. Moreover, blockade of α2ß1 integrin with a neutralizing mAb inhibited IL-7-induced bone loss and osteoclast numbers by reducing Th17 cell numbers in the bone marrow and reducing the production of IL-17 and the receptor activator of NF-κB ligand. Thus, the cooperation between IL-7R and α2ß1 integrin can represent an important pathogenic pathway in Th17-osteoclast function associated with inflammatory diseases.

Regulation of TLR3 Activation by S100A9.

Recognition of viral dsRNA by endosomal TLR3 activates innate immune response during virus infection. Trafficking of TLR3 to the endolysosomal compartment arising from fusion of late endosome (LE) with lysosome is required for recognition and detection of pathogen associated molecular patterns, which results in activation of the TLR3-dependent signaling cascade. Existing knowledge about the mechanism(s) and cellular factor(s) governing TLR3 trafficking is limited. In the current study, we identified intracellular S100A9 protein as a critical regulator of TLR3 trafficking. S100A9 was required for maturation of TLR3 containing early endosome (EE) into LE, the compartment that fuses with lysosome to form the endolysosomal compartment. A drastic reduction in cytokine production was observed in S100A9-knockout (KO) primary macrophages following RNA virus infection and treatment of cells with polyinosinic-polycytidylic acid (polyIC; a dsRNA mimetic that acts as a TLR3 agonist). Mechanistic studies revealed colocalization and interaction of S100A9 with TLR3 following polyIC treatment. S100A9-TLR3 interaction was critical for maturation of TLR3 containing EE into LE because TLR3 could not be detected in the LE of polyIC-treated S100A9-KO macrophages. Subsequently, TLR3 failed to colocalize with its agonist (i.e., biotin-labeled polyIC) in S100A9-deficient macrophages. The in vivo physiological role of S100A9 was evident from loss of cytokine production in polyIC-treated S100A9-KO mice. Thus, we identified intracellular S100A9 as a regulator of TLR3 signaling and demonstrated that S100A9 functions during pre-TLR3 activation stages by facilitating maturation of TLR3 containing EE into LE.

DAMP molecule S100A9 acts as a molecular pattern to enhance inflammation during influenza A virus infection: role of DDX21-TRIF-TLR4-MyD88 pathway.

Pathogen-associated molecular patterns (PAMPs) trigger host immune response by activating pattern recognition receptors like toll-like receptors (TLRs). However, the mechanism whereby several pathogens, including viruses, activate TLRs via a non-PAMP mechanism is unclear. Endogenous "inflammatory mediators" called damage-associated molecular patterns (DAMPs) have been implicated in regulating immune response and inflammation. However, the role of DAMPs in inflammation/immunity during virus infection has not been studied. We have identified a DAMP molecule, S100A9 (also known as Calgranulin B or MRP-14), as an endogenous non-PAMP activator of TLR signaling during influenza A virus (IAV) infection. S100A9 was released from undamaged IAV-infected cells and extracellular S100A9 acted as a critical host-derived molecular pattern to regulate inflammatory response outcome and disease during infection by exaggerating pro-inflammatory response, cell-death and virus pathogenesis. Genetic studies showed that the DDX21-TRIF signaling pathway is required for S100A9 gene expression/production during infection. Furthermore, the inflammatory activity of extracellular S100A9 was mediated by activation of the TLR4-MyD88 pathway. Our studies have thus, underscored the role of a DAMP molecule (i.e. extracellular S100A9) in regulating virus-associated inflammation and uncovered a previously unknown function of the DDX21-TRIF-S100A9-TLR4-MyD88 signaling network in regulating inflammation during infection.

Prospective, multicenter, controlled study of quality of life, psychological adjustment process and medical outcomes of patients receiving a preemptive kidney transplant compared to a similar population of recipients after a dialysis period of less than three years--The PreKit-QoL study protocol.

BACKGROUND: Treatment of end stage renal disease has an impact on patients' physical and psychological health, including quality of life (QoL). Nowadays, it is known that reducing the dialysis period has many advantages regarding QoL and medical outcomes. Although preemptive transplantation is the preferred strategy to prevent patients undergoing dialysis, its psychological impact is unknown. Moreover, transplantation can be experienced in a completely different manner among patients who were on dialysis and those who still had a functioning kidney at the time of surgery. Longitudinal data are often collected to allow analyzing the evolution of patients' QoL over time using questionnaires. Such data are often difficult to interpret due to the patients' changing standards, values, or conceptualization of what the questionnaire is intended to measure (e.g. QoL). This phenomenon is referred to as response shift and is often linked to the way the patients might adapt or cope with their disease experience. Whether response shift is experienced in a different way among patients who were on dialysis and those who still had a functioning kidney at time of surgery is unknown and will be studied in the PreKit-QoL study (trial registration number: NCT02154815). Understanding the psychological impact of pre-emptive transplantation is an important issue since it can be associated with long-term patient and graft survival. METHODS/DESIGN: Adult patients with a pre-emptive transplantation (n = 130) will be prospectively included along with a control group of patients with a pre-transplant dialysis period < 36 months (n = 260). Only first and single kidney transplantation will be considered. Endpoints include: comparison of change between groups in QoL, anxiety and depressive disorders, perceived stress, taking into account response shift. These criteria will be evaluated every 6 months prior to surgery, at hospital discharge, at three and six months, one and two years after transplantation. DISCUSSION: The PreKit-QoL study assesses and compares the evolution of QoL and other psychological criteria in preemptive and dialyzed patients taking patients' adaptation into account through response shift analyses. Our study might help to conceive specific, adapted educational programs and psychological support to prevent a possible premature loss of the kidney as a consequence of non-compliance in patients that may be insufficiently prepared for transplantation. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02154815 , registered on May 28, 2014.

α2ß1 integrin regulates Th17 cell activity and its neutralization decreases the severity of collagen-induced arthritis.

Th17 cells play a critical role in the pathogenesis of rheumatoid arthritis (RA), but the mechanisms by which these cells regulate the development of RA are not fully understood. We have recently shown that α2ß1 integrin, the receptor of type I collagen, is the major collagen-binding integrin expressed by human Th17 cells. In this study, we examined the role of α2ß1 integrin in Th17-mediated destructive arthritis in the murine model of collagen-induced arthritis (CIA). We found that α2ß1 integrin is expressed on synovial Th17 cells from CIA mice and its neutralization with a specific mAb significantly reduced inflammation and cartilage degradation, and protected the mice from bone erosion. Blockade of α2ß1 integrin led to a decrease in the number of Th17 cells in the joints and to a reduction of IL-17 levels in CIA mice. This was associated with an inhibition of receptor activator of NF-κB ligand levels and osteoclast numbers, and reduction of bone loss. We further show that α2ß1 integrin is expressed on synovial Th17 cells from RA patients, and that its ligation with collagen costimulated the production of IL-17 by polarized human Th17 cells by enhancing the expression of retinoic acid receptor-related orphan receptor C through ERK and PI3K/AKT. Our findings provide the first evidence, to our knowledge, that α2ß1 integrin is an important pathway in Th17 cell activation in the pathogenesis of CIA, suggesting that its blockade can be beneficial for the treatment of RA and other Th17-associated autoimmune diseases.

A personalized follow-up of kidney transplant recipients using video conferencing based on a 1-year scoring system predictive of long term graft failure (TELEGRAFT study): protocol for a randomized controlled trial.

BACKGROUND: Numerous well-established clinical parameters are taken into consideration for the follow-up adaptation of kidney transplant recipients, but there are important disparities between countries, centres and clinicians. Therefore, novel scoring systems have been developed, for instance the Kidney Transplant Failure Score (KTFS) which aims to stratify patients according to their risk of return to dialysis. We hypothesize that the efficiency of the follow-up after one year post-transplantation can be improved by adapting it to the risk of graft failure defined by the KTFS estimation. METHODS/DESIGN: We propose a phase IV, open label, randomized, multicentric and prospective study. The study is registered with the Clinical Trials Registry NCT01615900. 250 patients will be allocated to one of two arms: the eHealth program versus the standard of care at hospital. In the standard group, patients classified at low-risk (KTFS ≤ 4.17) will be scheduled 4 visits at hospital per year, whilst high-risk patients will visit hospital 6 times. In the eHealth group, patients classified at low-risk will be interviewed 3 times by video conferencing and once at hospital, whilst 6 visits at hospital and 6 video conferencing will be scheduled for high-risk patients. DISCUSSION: The current study allows to scientifically evaluate the etiologic impact of a novel eHealth program. This is important to clarify the possible contribution of telemedicine in the improvement of medical follow-up. The proposed design based on 4 different sub-groups can be interesting to evaluate other personalized medicine programs.

Metabolic regulation of neutrophil functions in homeostasis and diseases.

Neutrophils are the most abundant leukocytes in humans and play a role in the innate immune response by being the first cells attracted to the site of infection. While early studies presented neutrophils as almost exclusively glycolytic cells, recent advances show that these cells use several metabolic pathways other than glycolysis, such as the pentose phosphate pathway, oxidative phosphorylation, fatty acid oxidation, and glutaminolysis, which they modulate to perform their functions. Metabolism shifts from fatty acid oxidation-mediated mitochondrial respiration in immature neutrophils to glycolysis in mature neutrophils. Tissue environments largely influence neutrophil metabolism according to nutrient sources, inflammatory mediators, and oxygen availability. Inhibition of metabolic pathways in neutrophils results in impairment of certain effector functions, such as NETosis, chemotaxis, degranulation, and reactive oxygen species generation. Alteration of these neutrophil functions is implicated in certain human diseases, such as antiphospholipid syndrome, coronavirus disease 2019, and bronchiectasis. Metabolic regulators such as AMPK, HIF-1α, mTOR, and Arf6 are linked to neutrophil metabolism and function and could potentially be targeted for the treatment of diseases associated with neutrophil dysfunction. This review details the effects of alterations in neutrophil metabolism on the effector functions of these cells.

Damage-associated molecular pattern S100A9 increases bactericidal activity of human neutrophils by enhancing phagocytosis.

The damage-associated molecular-pattern S100A9 is found at inflammatory sites in infections and various autoimmune diseases. It is released at very high concentrations in the extracellular milieu by activated neutrophils and monocytes in response to various agents. This proinflammatory protein is found in infected mucosae and tissue abscesses where it acts notably as a potent neutrophil activator. In this study, we examined the role of S100A9 in the control of infections. S100A9 was found to increase human neutrophil bactericidal activity toward Escherichia coli. Although S100A9 induced the accumulation of reactive oxygen species over time through the activation of NADPH oxidase, its antimicrobial activity was mediated mainly by enhancing the efficiency of neutrophil phagocytosis. Interestingly, S100A9 did not act by increasing cell surface expression of CD16, CD32, or CD64 in neutrophils, indicating that its biological effect in FcR-mediated phagocytosis is independent of upregulation of FcγR levels. However, S100A9-induced phagocytic activity required the phosphorylation of Erk1/2, Akt, and Syk. Taken together, our results demonstrate that S100A9 stimulates neutrophil microbicidal activity by promoting phagocytosis.

Immune Cells Release MicroRNA-155 Enriched Extracellular Vesicles That Promote HIV-1 Infection.

The hallmark of HIV-1 infection is the rapid dysregulation of immune functions. Recent investigations for biomarkers of such dysregulation in people living with HIV (PLWH) reveal a strong correlation between viral rebound and immune activation with an increased abundance of extracellular vesicles (EVs) enriched with microRNA-155. We propose that the activation of peripheral blood mononuclear cells (PBMCs) leads to an increased miR-155 expression and production of miR-155-rich extracellular vesicles (miR-155-rich EVs), which can exacerbate HIV-1 infection by promoting viral replication. PBMCs were incubated with either HIV-1 (NL4.3Balenv), a TLR-7/8 agonist, or TNF. EVs were harvested from the cell culture supernatant by differential centrifugation, and RT-qPCR quantified miR-155 in cells and derived EVs. The effect of miR-155-rich EVs on replication of HIV-1 in incubated PBMCs was then measured by viral RNA and DNA quantification. HIV-1, TLR7/8 agonist, and TNF each induced the release of miR-155-rich EVs by PBMCs. These miR-155-rich EVs increased viral replication in PBMCs infected in vitro. Infection with HIV-1 and inflammation promote the production of miR-155-rich EVs, enhancing viral replication. Such autocrine loops, therefore, could influence the course of HIV-1 infection by promoting viral replication.

Acute inflammatory response via neutrophil activation protects against the development of chronic pain.

The transition from acute to chronic pain is critically important but not well understood. Here, we investigated the pathophysiological mechanisms underlying the transition from acute to chronic low back pain (LBP) and performed transcriptome-wide analysis in peripheral immune cells of 98 participants with acute LBP, followed for 3 months. Transcriptomic changes were compared between patients whose LBP was resolved at 3 months with those whose LBP persisted. We found thousands of dynamic transcriptional changes over 3 months in LBP participants with resolved pain but none in those with persistent pain. Transient neutrophil-driven up-regulation of inflammatory responses was protective against the transition to chronic pain. In mouse pain assays, early treatment with a steroid or nonsteroidal anti-inflammatory drug (NSAID) also led to prolonged pain despite being analgesic in the short term; such a prolongation was not observed with other analgesics. Depletion of neutrophils delayed resolution of pain in mice, whereas peripheral injection of neutrophils themselves, or S100A8/A9 proteins normally released by neutrophils, prevented the development of long-lasting pain induced by an anti-inflammatory drug. Analysis of pain trajectories of human subjects reporting acute back pain in the UK Biobank identified elevated risk of pain persistence for subjects taking NSAIDs. Thus, despite analgesic efficacy at early time points, the management of acute inflammation may be counterproductive for long-term outcomes of LBP sufferers.