BACKGROUND:RYGB is an effective treatment option for metabolic dysfunction-associated steatotic liver disease (MASLD). The optimal configuration for the biliopancreatic limb (BPL) remains uncertain. OBJECTIVES:To assess whether BPL length in Roux-en-Y gastric bypass (RYGB) affects improvement in MASLD. SETTING:University Hospital Center. METHODS:We conducted a retrospective cohort study of adults who underwent RYGB between 2019 and 2024. Patients were dichotomized a priori by BPL length: ≈70 cm (short) versus ≥100 cm (long). Outcomes were evaluated at baseline, 3 months (3M), 1 year (1Y), and 2 years (2Y) postoperatively. Primary outcomes were MASLD-related noninvasive tests (NITs) including the Nonalcoholic Fatty Liver Disease (NAFLD) Fibrosis Score (NFS) and Noninvasive Nonalcoholic Steatohepatitis Detection Score (NI-NASH DS). RESULTS:Compared with short BPL, long BPL was associated with lower NI-NASH DS at 3M (-1.19; 95% confidence interval [CI], -1.93 to -.48; q < .01) and 1Y (-.77; 95% CI, -1.37 to -.15; q < .05) and lower NFS at 1Y (-.39; 95% CI, -.70 to -.09; q < .05) and 2Y (-.53; 95% CI, -.96 to -.10; q < .05). Glycated hemoglobin was lower at 1Y (-.10; 95% CI, -.20 to .00; q < .05) and 2Y (-.20; 95% CI, -.30 to -.00; q < .05), while total weight loss was similar. Total cholesterol and low-density lipoprotein cholesterol were lower at 1Y and 2Y. Nutritional markers were largely comparable. CONCLUSIONS:A longer BPL (≥100 cm) was associated with greater improvements in MASLD-related NIT trajectories at 1Y and 2Y after RYGB, with better glycemic control and similar weight loss, without evidence of nutritional deficiency.

Background Optimal timing of cholecystectomy after acute biliary pancreatitis (abP) remains debated. While early surgery is recommended for mild abP, guidance for more severe disease is less well defined, and outcome heterogeneity suggests clinically relevant modifiers. Aims To assess the impact of surgical timing, disease severity, and sex on outcomes after cholecystectomy following abP. Methods This single-center retrospective cohort study included 205 patients undergoing cholecystectomy after abP. Outcomes were compared between early one-stage (during index admission) and interval two-stage cholecystectomy, stratified by abP severity and sex. Results Overall morbidity did not differ between one-stage and two-stage cholecystectomy. However, one-stage surgery was associated with higher postoperative inflammatory response, need for intensive care, and longer hospitalization. In mild abP, males underwent more complex cholecystectomies, with longer operative time, increased blood loss, higher conversion rates, and more frequent intensive care. In moderate/severe abP, outcomes were largely comparable between sexes, except for prolonged intensive care need and a trend toward longer hospitalization in women after one-stage cholecystectomy. Conclusion Post-cholecystectomy outcomes after abP depend on the interaction between disease severity, surgical timing, and sex. While early cholecystectomy appears safe in mild abP, sex-specific vulnerabilities and resource utilization should be considered supporting tailored timing strategies.

Colorectal liver metastases (CRLM) occur in up to 50

Purpose Optimal management of retroperitoneal soft tissue sarcoma (RPS) often requires extensive tumor resections, frequently involving gastrointestinal organs. The impact of these procedures on the nutritional status and hemoglobin (Hb) levels of RPS patients remain unexplored. In this study, we aimed to evaluate preoperative nutritional status as well as the prevalence of anemia in RPS patients, and to investigate longitudinal changes throughout the disease course in order to identify potential strategies for prehabilitation. Materials and methods Patients undergoing resection of primary and recurrent RPS at Heidelberg University Hospital were retrospectively analyzed. Changes in nutritional parameters and Hb levels throughout the disease course were analyzed using hierarchical linear regression models. Multivariable Cox regression analyses were performed to identify independent predictors of overall survival. Subgroup analyses were conducted for primary tumors, first, second and third recurrences. Results Amongst 370 patients analyzed, comprising 219 with primary disease, we observed neither a significant prevalence of preoperative malnutrition nor notable changes in BMI or serum albumin levels throughout the disease course. Preoperative anemia affected up to 40% of RPS patients, and Hb levels significantly decreased over the course of the disease ( p = 0.022), particularly in correlation with the number of tumor resections performed ( p = 0.010). Low preoperative Hb levels were associated with increased 30-day mortality and they were identified as an independent prognostic factor for shorter overall survival in primary RPS as well as in second and third recurrences. Conclusion Anemia screening should be performed preoperatively and during regular follow-ups to enable early-on therapy, thus potentially improving patient outcomes in RPS.

Pancreatic cancer (PC) is one of the most aggressive malignancies, characterized by an increasing incidence and unfavorable prognosis. Despite recent advances, surgical resection combined with chemotherapy remains the only potentially curative therapeutic option. Therefore, it is of paramount importance to identify novel therapeutic targets and develop effective treatment strategies. Pancreatic ductal adenocarcinoma (PDAC), the most prevalent form of PC, originates from exocrine cells and is subjected to both intrinsic and extrinsic cellular stresses, including oncogene activation, loss of tumor suppressors, a hypoxic and immunosuppressive tumor microenvironment (TME), and chemotherapy, causing an accumulation of misfolded proteins within the endoplasmic reticulum (ER). The loss of ER proteostasis activates the unfolded protein response (UPR), an intracellular sensing-signaling network that enables cancer cells to alleviate ER stress and restore cellular proteostasis. The key UPR sensor Inositol-Requiring Enzyme 1 (IRE1) is an ER membrane protein that activates the transcription factor X-Box Protein 1 Spliced (XBP1s) through its cytoplasmic kinase-RNase module, promoting protein folding, secretion capacity, and proteasomal degradation of misfolded proteins. Additionally, it regulates IRE1-dependent decay (RIDD) of various mRNA and functions through scaffold interactions. In this review, we synthesize current evidence on the cell-autonomous and cell-non-autonomous roles of IRE1 in tumor initiation, progression, metastasis, and drug resistance in PDAC and outline key research directions to investigate IRE1 as a potential therapeutic target.

The last two decades of research on carbon dioxide have demonstrated that CO2 is far more than a waste product of aerobic metabolism leading to acidosis and that it elicits biological responses directly via non-pH-dependent molecular interactions. New specialized methodologies have mapped CO2 incorporation into specific regions of CO2-sensitive proteins and linked these events to altered cellular function. CO2 affects a host of biological responses related to respiratory disease, including control of respiration, protein maturation, alveolar fluid homeostasis, wound repair, innate immunity, host defense, and airway contractility. Elevated CO2 (hypercapnia) appears to be primarily deleterious in pulmonary diseases, leading to a heightened interest in strategies to reduce excess CO2 in patients with hypercapnic respiratory failure. Here, we summarize recently generated knowledge on molecular CO2 sensing and signaling and the potential translational relevance of these processes in the context of respiratory disease. We need to grow this field further by encouraging experts in basic and translational science to contribute to more fully elucidating CO2 sensing, signaling, and downstream effects. Understanding the biology and clinical consequences of perturbations in CO2 homeostasis should no longer be considered secondary to studying oxygen sensing and signaling in respiratory medicine.

BACKGROUND:Sarcopenia and age are risk factors for poor outcomes in acute pancreatitis (aP). However, the role of sarcopenia independent of patients' age remains unclear, and assessment methods vary. AIMS:This study assessed sarcopenia, using the Hounsfield unit average calculation (HUAC) for the psoas muscle, and its impact on aP outcomes, independent of other risk factors. METHODS:208 aP patients who received early computed tomography (CT) were classified as sarcopenic or non-sarcopenic based on HUAC. Propensity score matching (PSM) reduced heterogeneity. Clinical outcomes and independent predictors of intensive care unit (ICU) admission were determined by multivariable logistic regression. RESULTS:After PSM, sarcopenic patients (n = 53) had longer hospital (24.9 ± 20.6d vs. 18.2 ± 27.3d; p = 0.0006) and ICU stays (9.5 ± 16.5d vs. 6.2 ± 25.8d; p = 0.0077) than non-sarcopenic patients (n = 53). ICU admission was more frequent (58.5 % vs. 37.7 %; p = 0.0325), and aP-associated morbidity such as pleural effusion occurred more often (p = 0.0019). Independent predictors of ICU admission included pleural effusion or ascites (p = 0.0116) and impaired coagulation (p = 0.0365). CONCLUSION:Sarcopenia identified via HUAC in early aP is associated with a worse clinical outcome. Pleural effusion or ascites and changes in blood coagulation independently predict ICU admission in sarcopenic aP patients. Early nutritional and physical therapy should be considered to prevent and treat sarcopenia in aP patients.

IntroductionRenin-angiotensin-aldosterone system inhibitors (RAAS-I) have been shown to prolong overall survival in patients with liver metastasized colorectal cancer in combination with antiangiogenic treatment. The effects of RAAS-I combined with neoadjuvant chemotherapy on colorectal cancer liver metastasis remain unexplored. We aimed to study the response of patients undergoing liver resection to RAAS-I in combination with neoadjuvant therapy to elucidate their potential benefits.MethodsBetween February 2005 and May 2012, 62 patients fulfilled the inclusion criteria for distant metastasis (cM1) and comparable computed tomography or magnetic resonance tomography scans in the Picture Archiving Communication System of our center before and after neoadjuvant chemotherapy. Follow-up data and clinicopathological characteristics were collected from a prospective database and retrospectively investigated. The chemotherapeutic response to liver metastasis was evaluated according to the Response Evaluation Criteria in Solid Tumors criteria 1.1.ResultsComparing the average reduction of measured lesions, a significant response to chemotherapy was detected in the patients receiving RAAS-I (n = 24) compared to those who did not (n = 38) (P = 0.031). Interestingly, the effect was more distinctive when the size reduction was compared between high responses with more than 50% size reduction of all measured lesions (P = 0.011). In the subgroup analysis of patients receiving bevacizumab treatment, high responses to chemotherapy were observed only in the RAAS-I cohort (28.6% versus 0%, P = 0.022).ConclusionsFor neoadjuvantly treated patients, concomitant antihypertensive treatment with RAAS-I showed a higher total size reduction of liver metastasis as a sign of treatment response, especially in combination with antiangiogenic treatment with bevacizumab.

Study objective: Higher levels of carbon dioxide (CO2) increase the invasive abilities of colon cancer cells in vitro. Studies assessing target values for end-tidal CO2 concentrations (EtCO2) to improve surgical outcome after colorectal cancer surgery are lacking. Therefore, we evaluated whether intraoperative EtCO2 was associated with differences in recurrence-free survival after elective colorectal cancer (CRC) surgery. Design: Single center, retrospective analysis. Setting: Anesthesia records, surgical databases and hospital information system of a tertiary university hospital. Patients: We analyzed 528 patients undergoing elective resection of colorectal cancer at Heidelberg University Hospital between 2009 and 2018. Interventions: None. Measurements: Intraoperative mean EtCO2 values were calculated. The study cohort was equally stratified into low-and high-EtCO2 groups. The primary endpoint measure was recurrence-free survival until last known followup. Groups were compared using Kaplan-Meier analysis. Cox-regression analysis was used to control for covariates. Sepsis, reoperations, surgical site infections and cardiovascular events during hospital stay, and overall survival were secondary outcomes. Main results: Mean EtCO2 was 33.8 mmHg +/- 1.2 in the low- EtCO2 group vs. 37.3 mmHg +/- 1.6 in the high-EtCO2 group. Median follow-up was 3.8 (Q1-Q3, 2.5-5.1) years. Recurrence-free survival was higher in the low-EtCO2 group (log-rank-test: p = .024). After correction for confounding factors, lower EtCO2 was associated with increased recurrence-free survival (HR = 1.138, 95%-CI:1.015-1.276, p = .027); the hazard for the primary outcome decreased by 12.1% per 1 mmHg decrease in mean EtCO2. 1-year and 5-year survival was also higher in the low-EtCO2 group. We did not find differences in the other secondary endpoints. Conclusions: Lower intraoperative EtCO2 target values in CRC surgery might benefit oncological outcome and should be evaluated in confirmative studies.

Liver fibrosis is characterized by excessive deposition of extracellular matrix due to chronic inflammation of the liver. Hepatic stellate cells (HSCs) become activated and produce increased amounts of extracellular matrix. Loss of HIF-prolyl-hydroxylase 1 (PHD1) attenuates HSC activation and fibrotic tissue remodeling in a murine model of biliary liver fibrosis. Herein, the protective effect of PHD1 deficiency (PHD1-/-) in an additional (toxic) model of liver fibrosis was validated and the effect of dimethyloxalylglycine (DMOG), a pan-HIF-prolyl-hydroxylase inhibitor, on the development of liver fibrosis, was evaluated. Liver fibrosis was induced utilizing carbon tetrachloride in wild-type (WT) and PHD1-/- mice treated with either vehicle or DMOG. To assess fibrosis development, expression of profibrotic genes in the livers was analyzed by Sirius red staining. When compared with WT mice, PHD1-/- mice developed less-severe liver fibrosis. DMOG treatment did not prevent this liver fibrosis. PHD1-/- mice had fewer α-SMA+ cells and less macrophage infiltration compared with WT mice. Expression of profibrogenic and proinflammatory genes was reduced in livers from carbon tetrachloride-exposed PHD1-/- mice. In vitro analyses of PHD1-deficient human HSCs revealed attenuated mRNA levels of profibrotic genes, as well as impaired migration and invasion. Although PHD1 deficiency attenuated activation of HSCs, pharmacologic PHD inhibition did not ameliorate fibrosis development. These data indicate that selective PHD1 inhibitors could prove effective in preventing and treating liver fibrosis.

Roux-en-Y gastric bypass (RYGB) in patients with body mass index (BMI) ≥ 50 kg/m 2 is a challenging procedure and BMI ≥ 50 kg/m 2 has been identified as independent risk factor for postoperative complications and increased morbidity in previous studies. The objective of the present study was to assess whether a BMI ≥ 50 kg/m 2 and various established risk factors maintain their significance in patients undergoing fully robotic RYGB (rRYGB). A single-center analysis of prospectively collected data of 113 consecutive patients undergoing standardized rRYGB with robotic stapling technique and hand-sewn gastrojejunostomy using the daVinci Xi system. Surgical outcomes were analyzed considering a number of individual perioperative risk factors including BMI ≥ 50 kg/m 2 . The mean BMI of the total cohort was 50.6 ± 5.5 kg/m 2 and 63.7% of patients had a BMI ≥ 50 kg/m 2 . There were no major surgical and perioperative complications in patients with BMI ≥ 50 kg/m 2 as well as in those with BMI < 50 kg/m 2 after rRYGB. We identified female sex and surgeon experience but neither body weight, BMI, metabolic disorders, ASA nor EOSS scores as independent factors for shorter operation times (OT) in multivariate analyses. Complication rates and length of hospital stay (LOS) did not significantly differ between patients with potential risk factors and those without. rRYGB is a safe procedure in both, patients with BMI ≥ 50 kg/m 2 and with BMI < 50 kg/m 2 . Higher body weight and BMI did affect neither OT nor LOS. A fully robotic approach for RYGB might help to overcome “traditional” risk factors identified in conventional laparoscopic bariatric surgery. However, larger and prospective studies are necessary to confirm these results.

The modulation of macrophage phenotype from a pro-inflammatory to an anti-inflammatory state holds therapeutic potential in the treatment of inflammatory disease. We have previously shown that arginase-2 (Arg2), a mitochondrial enzyme, is a key regulator of the macrophage anti-inflammatory response. Here, we investigate the therapeutic potential of Arg2 enhancement via target site blockers (TSBs) in human macrophages. TSBs are locked nucleic acid antisense oligonucleotides that were specifically designed to protect specific microRNA recognition elements (MREs) in human ARG2 3' UTR mRNA. TSBs targeting miR-155 (TSB-155) and miR-3202 (TSB-3202) MREs increased ARG2 expression in human monocyte-derived macrophages. This resulted in decreased gene expression and cytokine production of TNF-α and CCL2 and, for TSB-3202, in an increase in the anti-inflammatory macrophage marker, CD206. Proteomic analysis demonstrated that a network of pro-inflammatory responsive proteins was modulated by TSBs. In silico bioinformatic analysis predicted that TSB-3202 suppressed upstream pro-inflammatory regulators including STAT-1 while enhancing anti-inflammatory associated proteins. Proteomic data were validated by confirming increased levels of sequestosome-1 and decreased levels of phosphorylated STAT-1 and STAT-1 upon TSB treatment. In conclusion, upregulation of Arg2 by TSBs inhibits pro-inflammatory signaling and is a promising novel therapeutic strategy to modulate inflammatory signaling in human macrophages.

CO 2 is produced during aerobic respiration. Normally, levels of CO 2 in the blood are tightly regulated but pCO 2 can rise (hypercapnia, pCO 2  > 45 mmHg) in patients with lung diseases, for example, chronic obstructive pulmonary disease (COPD). Hypercapnia is a risk factor in COPD but may be of benefit in the context of destructive inflammation. The effects of CO 2 per se, on transcription, independent of pH change are poorly understood and warrant further investigation. Here we elucidate the influence of hypercapnia on monocytes and macrophages through integration of state-of-the-art RNA-sequencing, metabolic and metabolomic approaches. THP-1 monocytes and interleukin 4–polarized primary murine macrophages were exposed to 5% CO 2 versus 10% CO 2 for up to 24 h in pH-buffered conditions. In hypercapnia, we identified around 370 differentially expressed genes (DEGs) under basal and about 1889 DEGs under lipopolysaccharide-stimulated conditions in monocytes. Transcripts relating to both mitochondrial and nuclear-encoded gene expression were enhanced in hypercapnia in basal and lipopolysaccharide-stimulated cells. Mitochondrial DNA content was not enhanced, but acylcarnitine species and genes associated with fatty acid metabolism were increased in hypercapnia. Primary macrophages exposed to hypercapnia also increased activation of genes associated with fatty acid metabolism and reduced activation of genes associated with glycolysis. Thus, hypercapnia elicits metabolic shifts in lipid metabolism in monocytes and macrophages under pH-buffered conditions. These data indicate that CO 2 is an important modulator of monocyte transcription that can influence immunometabolic signaling in immune cells in hypercapnia. These immunometabolic insights may be of benefit in the treatment of patients experiencing hypercapnia.

Background: Increased levels of CO 2 reduce macrophage function during inflammatory processes and wound healing. However, little is known how macrophages sense CO 2 and adapt upon high levels of CO 2 during differentiation and activation. We, therefore, elucidated the effects of CO 2 on gene and protein expression during basic inflammatory processes, such as monocyte differentiation and macrophage activation. Methods: Monocyte differentiation was induced by phorbol 12-myristate 13-acetate (PMA). Primary macrophages (BMDMs) were polarized using different cytokines to induce proinflammatory (M1) macrophages (lipopolysaccharides) or immunomodulatory (M2) macrophages (interleukin-4). Cells were simultaneously subjected to different levels of CO 2 . Morphological changes, mRNA and protein expression of markers for cell differentiation and macrophage polarization were determined. Cell culture medium was buffered and intracellular pH (pHi) was monitored to determine pH-dependent effects of CO 2 . Direct effects of CO 2 on PKC protein function were analyzed. Results: High levels of CO 2 attenuated PMA-induced cell differentiation of human monocytes. In BMDMs, CO 2 significantly reduced transcript levels of M1-marker. Mechanistically, CO 2 mitigated PMA-stimulated PKC activity and function. Experiments with buffered medium revealed that changes in pH were responsible for most, but not all, of the CO 2 -mediated effects on monocyte differentiation and macrophage polarization. Pharmacological and genetic inhibition of carbonic anhydrases (CA) uncoupled the CO 2 -elicited intracellular pH-response, thereby preventing CO 2 -sensitivity during monocyte differentiation, activation, and migration, which could be reversed by CRISPR-mediated upregulation of CA2. Conclusion: Carbon dioxide is highly immunomodulatory and might thus affect wound healing properties in vivo. In M1 (but not M2) macrophages, CO 2 is sensed by CA2-driven changes in pHi. MJS received funding from the German Research Foundation (DFG; STR 1570/1-1) and the Braun Foundation (Braun®; BBST-D-18-00018). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Rifampicin and rifabutin can activate the pregnane X receptor (PXR, NR1I2 ), thereby inducing pharmacokinetically important genes/proteins and reducing exposure to co-administered drugs. Because induction effects vary considerably between these antibiotics, differences could be due to unequal rifamycin-induced activation or tissue expression of the three major NR1I2 splice variants, PXR.1 (NM_003889), PXR.2 (NM_022002), and PXR.3 (NM_033013). Consequently, PXR activation (PXR reporter gene assays) and mRNA expression levels of total NR1I2 , PXR.1, PXR.2, and PXR.3 were investigated by polymerase chain reaction in colon and liver samples from eleven surgical patients, in LS180 cells, and primary human hepatocytes. Compared to the colon, total NR1I2 mRNA expression was higher in the liver. Both tissues showed similar expression levels of PXR.1 and PXR.3, respectively. PXR.2 was not quantifiable in the colon samples. Rifampicin and rifabutin similarly enhanced PXR.1 and PXR.2 activity when transfected into LS180 cells, while PXR.3 could not be activated. In LS180 cells, rifampicin (10 μM) reduced total NR1I2 and PXR.3 expression 2-fold after 24 h, while rifabutin (10 μM) increased total NR1I2 , PXR.1, PXR.2, and PXR.3 mRNA by approx. 50% after 96-h exposure. In primary human hepatocytes, rifampicin (10 μM) suppressed total NR1I2 , PXR.1, and PXR.3 after 48-h exposure, and rifabutin (10 μM) had no significant impact on total NR1I2 or any of the splice variants studied. In conclusion, both antibiotics activated the studied PXR splice variants similarly but modified their expression differently. While rifampicin can suppress mRNA of PXR forms, rifabutin rather increases their expression levels.

Colitis-associated colorectal cancer (CAC) is a severe complication of inflammatory bowel disease (IBD). HIF-prolyl hydroxylases (PHD1, PHD2, and PHD3) control cellular adaption to hypoxia and are considered promising therapeutic targets in IBD. However, their relevance in the pathogenesis of CAC remains elusive. We induced CAC in Phd1-/-, Phd2+/-, Phd3-/-, and WT mice with azoxymethane (AOM) and dextran sodium sulfate (DSS). Phd1-/- mice were protected against chronic colitis and displayed diminished CAC growth compared to WT mice. In Phd3 -/- mice, colitis activity and CAC growth remained unaltered. In Phd2+/- mice, colitis activity was unaffected, but CAC growth was aggravated. Mechanistically, Phd2 deficiency (i) increased the number of tumor-associated macrophages (TAMs) in AOM/DSS-induced tumors, (ii) promoted the expression of EGFR ligand epiregulin ( Ereg) in macrophages, and (iii) augmented signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling which at least in part contributed to aggravated tumor cell proliferation in colitis-associated tumors. Consistently, Phd2 deficiency in hematopoietic ( Vav:Cre-Phd2f/f) but not in intestinal epithelial cells ( Villin:Cre-Phd2f/f) increased CAC growth. In conclusion, the three different PHD isoenzymes have distinct and non-redundant, either promoting (PHD1), diminishing (PHD2), or neutral effects (PHD3) on CAC growth. KBK received funding from the German Cancer Aid. MJS. received funding from the German Research Foundation (DFG; STR 1570/1-1) and the Braun Foundation (Braun®; BBST-D-18-00018). MSch received funding from the German Federal Ministry of Education and Research (BMBF; 031L0084). JMH received funding from the Heidelberg Stiftung Chirurgie. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

CO2 is produced during aerobic respiration. Normally, levels of CO2 in the blood are tightly regulated but pCO(2) can rise (hypercapnia, pCO(2) > 45 mmHg) in patients with lung diseases, for example, chronic obstructive pulmonary disease (COPD). Hypercapnia is a risk factor in COPD but may be of benefit in the context of destructive inflammation. The effects of CO2 per se, on transcription, independent of pH change are poorly understood and warrant further investigation. Here we elucidate the influence of hypercapnia on monocytes and macrophages through integration of state-of-the-art RNA-sequencing, metabolic and metabolomic approaches. THP-1 monocytes and interleukin 4-polarized primary murine macrophages were exposed to 5% CO2 versus 10% CO2 for up to 24 h in pH-buffered conditions. In hypercapnia, we identified around 370 differentially expressed genes (DEGs) under basal and about 1889 DEGs under lipopolysaccharide-stimulated conditions in monocytes. Transcripts relating to both mitochondrial and nuclear-encoded gene expression were enhanced in hypercapnia in basal and lipopolysaccharide-stimulated cells. Mitochondrial DNA content was not enhanced, but acylcarnitine species and genes associated with fatty acid metabolism were increased in hypercapnia. Primary macrophages exposed to hypercapnia also increased activation of genes associated with fatty acid metabolism and reduced activation of genes associated with glycolysis. Thus, hypercapnia elicits metabolic shifts in lipid metabolism in monocytes and macrophages under pH-buffered conditions. These data indicate that CO2 is an important modulator of monocyte transcription that can influence immunometabolic signaling in immune cells in hypercapnia. These immunometabolic insights may be of benefit in the treatment of patients experiencing hypercapnia.

CO2, the primary gaseous product of respiration, is a major physiologic gas, the biology of which is poorly understood. Elevated CO2 is a feature of the microenvironment in multiple inflammatory diseases that suppresses immune cell activity. However, little is known about the CO2-sensing mechanisms and downstream pathways involved. We found that elevated CO2 correlates with reduced monocyte and macrophage migration in patients undergoing gastrointestinal surgery and that elevated CO2 reduces migration in vitro. Mechanistically, CO2 reduces autocrine inflammatory gene expression, thereby inhibiting macrophage activation in a manner dependent on decreased intracellular pH. Pharmacologic or genetic inhibition of carbonic anhydrases (CAs) uncouples a CO2-elicited intracellular pH response and attenuates CO2 sensitivity in immune cells. Conversely, CRISPR-driven upregulation of the isoenzyme CA2 confers CO2 sensitivity in nonimmune cells. Of interest, we found that patients with chronic lung diseases associated with elevated systemic CO2 (hypercapnia) display a greater risk of developing anastomotic leakage following gastrointestinal surgery, indicating impaired wound healing. Furthermore, low intraoperative pH levels in these patients correlate with reduced intestinal macrophage infiltration. In conclusion, CO2 is an immunomodulatory gas sensed by immune cells through a CA2-coupled change in intracellular pH.

BACKGROUND:Peritoneal adhesion formation is common after abdominal surgery and results in severe complications. Tissue hypoxia is one of the main drivers of peritoneal adhesions. Thus, we determined the clinical role of hypoxia-inducible factor (HIF)-1 signaling in peritoneal adhesions and investigated whether the biguanide antidiabetic drug metformin shows HIF-inhibitory effects and could be repurposed to prevent adhesion formation.STUDY DESIGN:As part of the ReLap study (DRKS00013001), adhesive tissue from patients undergoing relaparotomy was harvested and graded using the adhesion grade score. HIF-1 signaling activity within tissue biopsies was determined and correlated with adhesion severity. The effect of metformin on HIF-1 activity was analyzed by quantification of HIF target gene expression and HIF-1 protein stabilization in human mesothelial cells and murine fibroblast under normoxia and hypoxia. Mice were treated with vehicle or metformin 3 days before and until 7 days after induction of peritoneal adhesions; alternatively, metformin treatment was discontinued 48 hours before induction of peritoneal adhesions.RESULTS:HIF-1 signaling activity correlated with adhesion severity in patient biopsies. Metformin significantly mitigated HIF-1 activity in vitro and in vivo. Oral treatment with metformin markedly prevented adhesion formation in mice even when the treatment was discontinued 48 hours before surgery. Although metformin treatment did not alter macrophage polarization, metformin reduced proinflammatory leucocyte infiltration and attenuated hypoxia-induced profibrogenic expression patterns and myofibroblast activation.CONCLUSIONS:Metformin mitigates adhesion formation by inhibiting HIF-1-dependent (myo)fibroblast activation, conferring an antiadhesive microenvironment after abdominal surgery. Repurposing the clinically approved drug metformin might be useful to prevent or treat postoperative adhesions.