Pleural macrophages are the dominant cell population in the thoracic cavity with an inflammatory cytokine profile similar to peritoneal macrophages

Elevated branched-chain α-keto acids exacerbate macrophage oxidative stress and chronic inflammatory damage in type 2 diabetes mellitus

AIMS

Chronic inflammation is a primary reason for type 2 diabetes mellitus (T2DM) and its complications, while disordered branched-chain amino acids (BCAA) metabolism is found in T2DM, but the link between BCAA catabolic defects and inflammation in T2DM remains elusive and needs to be investigated.

METHODS

The changes in BCAA catabolism, inflammation, organ damage, redox status, and mitochondrial function in db/db mice with treatments of BCAA-overload or BCAA catabolism activator were analyzed in vivo. The changes in BCAA catabolic metabolism, as well as the direct effects of BCAAs/branched-chain alpha-keto acids (BCKAs) on cytokine release and redox status were also analyzed in primary macrophages in vitro.

RESULTS

Inactivation of branched-chain ɑ-ketoacid dehydrogenase (BCKDH) complex was found in multiple organs (liver, muscle and kidney) of db/db mice. Long-term high BCAA supplementation further increased BCKA levels, inflammation, tissue fibrosis (liver and kidney), and macrophage hyper-activation in db/db mice, while enhancing BCAA catabolism with pharmacological activator reduced these adverse effects in db/db mice. In vitro, the BCAA catabolism was unchanged in primary macrophages of db/db mice, and elevated BCKAs but not BCAAs promoted the cytokine production in primary macrophages. Moreover, BCKA stimulation was associated with increased mitochondrial oxidative stress and redox imbalance in macrophages and diabetic organs.

CONCLUSION

Impaired BCAA catabolism is strongly associated with chronic inflammation and tissue damage in T2DM, and this effect is at least partly due to the BCKAs-induced macrophage oxidative stress. This study highlights that targeting BCAA catabolism is a potential strategy to attenuate T2DM and its complications.

Innate Lymphoid Cells Play a Pathogenic Role in Pericarditis

We find that cardiac group 2 innate lymphoid cells (ILC2s) are essential for the development of IL-33-induced eosinophilic pericarditis. We show a pathogenic role for ILC2s in cardiac inflammation, in which ILC2s activated by IL-33 drive the development of eosinophilic pericarditis in collaboration with cardiac fibroblasts. ILCs, not T and B cells, are required for the development of pericarditis. ILC2s transferred to the heart of Rag2^-/-Il2rg^-/- mice restore their susceptibility to eosinophil infiltration. Moreover, ILC2s direct cardiac fibroblasts to produce eotaxin-1. We also find that eosinophils reside in the mediastinal cavity and that eosinophils transferred to the mediastinal cavity of eosinophil-deficient ΔdblGATA1 mice following IL-33 treatment migrate to the heart. Thus, the serous cavities may serve as a reservoir of cardiac-infiltrating eosinophils. In humans, patients with pericarditis show higher amounts of ILCs in pericardial fluid than do healthy controls and patients with other cardiac diseases. We demonstrate that ILCs play a critical role in pericarditis.

Phenotypic Switch of Human Peritoneal Macrophages during Childhood

INTRODUCTION

 Human peritoneal macrophages are resident in the abdominal cavity where they support the specific microenvironmental regulation. We have previously observed a phenotypic switch of murine macrophages during infancy that was associated with a functional development. To investigate the age related changes in human peritoneal macrophages, we analyzed peritoneal macrophages of children undergoing laparoscopic procedures.

MATERIALS AND METHODS

 Immunologically healthy children who received minimally invasive surgery in our department were included in this study. In all cases, the written consent was obtained. At the beginning of laparoscopy, physiologic NaCl-solution was instilled and manually removed through the umbilical trocar to gain macrophages. Lavage cells were processed for flow cytometry analysis. CD14+ myeloid cells were monitored for specific lineage marker expression.

RESULTS

 A total of 21 donors (age: 7 days-18 years) were included and divided into three groups. In all age groups, 97% of myeloid cells expressed CD11b. 70% of these expressed CD14. Three subsets of CD14 cells were detected on the basis of CD14/CD16 expression (CD14 + CD16dim, CD14 + CD16inter, and CD14 + CD16high). In neonates, >80% belonged to the CD14 + CD16high subset, reducing to 30% in adolescents. In none of the cases, the M2 markers CD23 and CD25 were expressed.

CONCLUSION

 This is the first study showing that lineage marker expression of peritoneal macrophages in neonates differs from that in adults. The knowledge about neonatal tissue resident macrophages might help to understand their complex interaction and to use specific macrophage properties for therapeutic approaches.

Stimulatory effect of desipramine on lung metastases of adenocarcinoma MADB 106 in stress highly-sensitive and stress non-reactive rats

The effect of antidepressant drugs on tumor progress is very poorly recognized. The aim of the present study was to examine the effect of individual reactivity to stress and 24-day desipramine (DES) administration on the metastatic colonization of adenocarcinoma MADB 106 cells in the lungs of Wistar rats. Wistar rats were subjected to stress procedure according to the chronic mild stress (CMS) model of depression for two weeks and stress highly-sensitive (SHS) and stress non-reactive (SNR) rats were selected. SHS rats were more prone to cancer metastasis than SNR ones and chronic DES treatment further increased the number of lung metastases by 59% and 50% in comparison to vehicle-treated appropriate control rats. The increase in lung metastases was connected with DES-induced skew macrophage activity towards M2 functional phenotype in SHS and SNR rats. Moreover, during 24h after DES injection in healthy rats, the decreased number of TCD8⁺ and B cells in SHS and SNR rats as well as NK cell cytotoxic activity in SNR rats could be attributed to the lowered capacity to defend against cancer metastasis observed in chronic DES treated and tumor injected rats.

Trace metal release after minimally-invasive repair of pectus excavatum

Background

Several studies have shown a high incidence of metal allergy after minimally-invasive repair of pectus excavatum (MIRPE). We postulated that MIRPE is associated with a significant release of trace metal ions, possibly causing the allergic symptoms.

Methods

We evaluated the concentration with chromium, cobalt and nickel in blood, urine and tissue in patients prior to MIRPE and in patients who underwent an explantation of the stainless-steel bar(s) after three years.

Results

Our study group consisted of 20 patients (mean age 19 years) who had bar explantation and our control group included 20 patients (mean age 16 years) prior to MIRPE. At the time of bar removal we detected significantly elevated concentrations of chromium and nickel in the tissue compared to patients prior to the procedure (p<0,001). We also found a significant increase in the levels of chromium in urine and nickel in blood in patients three years post MIRPE (p<0,001). Four patients temporarily developed symptoms of metal allergy, all had elevated metal values in blood and urine at explantation.

Conclusions

Minimally-invasive repair of pectus excavatum can lead to a significant trace metal exposure.

A Reservoir of Mature Cavity Macrophages that Can Rapidly Invade Visceral Organs to Affect Tissue Repair

A key feature of inflammation is the timely recruitment of leukocytes, including monocytes, from blood into tissues, the latter maturing into macrophages over a period of 2-3 days. Using multi-channel spinning disk microscopy, we identified a rapid pathway of macrophage recruitment into an injured organ via a non-vascular route requiring no maturation from monocytes. In response to a sterile injury in liver, a reservoir of fully mature F4/80(hi)GATA6(+) peritoneal cavity macrophages rapidly invaded into afflicted tissue via direct recruitment across the mesothelium. The invasion was dependent on CD44 and DAMP molecule ATP and resulted in rapid replication and switching of macrophage toward an alternatively activated phenotype. These macrophages dismantled the nuclei of necrotic cells releasing DNA and forming a cover across the injury site. Rapid invasion of mature macrophages from body cavity with capacity for induction of reparative phenotype may impact altered tissues ranging from trauma to infections to cancer. VIDEO ABSTRACT.