Induction Of Polymicrobial Sepsis Research Articles

Colony stimulating factor-1 producing endothelial cells and mesenchymal stromal cells maintain monocytes within a perivascular bone marrow niche

Macrophage colony stimulating factor-1 (CSF-1) plays a critical role in maintaining myeloid lineage cells. However, congenital global deficiency of CSF-1 (Csf1op/op) causes severe musculoskeletal defects that may indirectly affect hematopoiesis. Indeed, we show here that osteolineage-derived Csf1 prevented developmental abnormalities but had no effect on monopoiesis in adulthood. However, ubiquitous deletion of Csf1 conditionally in adulthood decreased monocyte survival, differentiation, and migration, independent of its effects on bone development. Bone histology revealed that monocytes reside near sinusoidal endothelial cells (ECs) and leptin receptor (Lepr)-expressing perivascular mesenchymal stromal cells (MSCs). Targeted deletion of Csf1 from sinusoidal ECs selectively reduced Ly6C- monocytes, whereas combined depletion of Csf1 from ECs and MSCs further decreased Ly6Chi cells. Moreover, EC-derived CSF-1 facilitated recovery of Ly6C- monocytes and protected mice from weight loss following induction of polymicrobial sepsis. Thus, monocytes are supported by distinct cellular sources of CSF-1 within a perivascular BM niche.

Suppression of Skeletal Muscle Interleukin‐6 Alters Circulatory Cytokine and Leukocyte Trafficking in Septic Female Mice

Interleukin‐6 (IL‐6) is one of the major cytokines released by skeletal muscle in response to blood pathogens. Nevertheless, the contribution of IL‐6 secreted by skeletal muscle (skmIL‐6) to innate immunity is not well understood. We utilized a floxed IL‐6 knockout mouse crossed with a skeletal muscle inducible CRE mouse to evaluate the contribution of skeletal muscle IL‐6 secretion to the circulatory cytokine profile and leukocyte trafficking in septic mice. Sepsis was induced using intraperitoneal injection of a standardized dose of cecal slurry (CS) collected from donor mice.METHODSTwenty‐four animals were studied at 6 and 12 hours after CS injection and plasma cytokines were measured using multiplex array. Cell differential counts were performed on blood, peritoneal lavage (PL), spleen and bone marrow. Mice in which the recombination of CRE was induced with raloxifene (skmIL‐6−/−) were compared to sham strain‐match controls (skmIL‐6+/+).RESULTSAt the 6‐hour time‐point after CS injection, the skmIL‐6−/− mice demonstrated significant reductions in INF‐d (skmIL‐6+/+ = 21 ± 8 vs. skmIL‐6−/− 7 ± 4, P < 0.01), IL‐5 (skmIL‐6+/+ = 232 ± 43 vs. skmIL‐6−/− 139 ± 52, P < 0.02), IL‐9 (skmIL‐6+/+ = 128 ± 82 vs. skmIL‐6−/− 22 ± 31, P < 0.02), IL‐10 (skmIL‐6+/+ = 10846 ± 4080 vs. skmIL‐6−/− 3350 ± 1456, P < 0.05), MIP‐1a (skmIL‐6+/+ = 1054 ± 398 vs. skmIL‐6−/− 477 ± 570, P < 0.05), MIP‐1b (skmIL‐6+/+ = 2576 ± 613 vs. skmIL‐6−/− 1432 ± 808, P < 0.05), and TNFa (skmIL‐6+/+ = 77 ± 40 vs. skmIL‐6−/− 29 ± 10, P < 0.01). At 12 hours, the only observed effect was a reduction in RANTES (skmIL‐6+/+ = 61 ± 7 vs. skmIL‐6−/− 37 ± 7, P < 0.05). In PL, 6 hours after cecal slurry injection, total leukocyte counts were unaffected. However, the %neutrophils was elevated from 21% in controls to 37% (P<0.0002) in skmIL‐6−/−. Lymphocytes dropped from 15 to 5% (P<0.002) and basophils dropped from 3.8 to 2% (P<0.01). At 12 hrs post cecal slurry injection, total leukocytes remained unchanged between skmIL‐6−/− and controls, but in PL neutrophils remained elevated (59% vs 45%, P=0.05), %lymphocytes were unchanged, but %monocytes increased from 9 to 13%, (P = 0.02); %eosinophils and %basophils were reduced (P < 0.03 and <0.02, respectively). There were no statistically significant differences between groups in the cell differential counts in blood, bone marrow or spleen. There were also no differences cell differentials in any tissue between raloxifene‐treated and untreated CRE mice.CONCLUSIONSInhibition of IL‐6 production by skeletal muscles suppressed circulatory cytokines and chemokines required to provide immunity against polymicrobial sepsis. Importantly, regulation of inflammatory cells and the timing of their recruitment to the primary site of infection (i.e. the peritoneum in the cecal slurry model) was dependent on skeletal muscle IL‐6. Most of the observed changes occurred 6 hours after induction of polymicrobial sepsis which is consistent with skeletal muscle IL‐6 being required for the early innate immune response in this model. These effects appear to be independent of the influence of raloxifene, the estrogen receptor activator, or CRE.Support or Funding InformationSupported by NIGMS1R01GM118895‐01.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

CLOCK modulates survival and acute lung injury in mice with polymicrobial sepsis

Polymicrobial sepsis is a potentially fatal condition and a significant burden on health care systems. Acute lung injury is the most common complication of sepsis and results in high mortality. However, there has been no recent significant progress in the treatment of sepsis or acute lung injury induced by sepsis. Here we show that mice deficient in the circadian protein CLOCK had better survival than wild-type mice after induction of polymicrobial sepsis by cecal ligation and puncture. Inflammatory cytokine production was attenuated and bacterial clearance was improved in CLOCK-deficient mice. Moreover, acute lung injury after induction of sepsis was significantly decreased in CLOCK-deficient mice. Genome-wide profiling analysis showed that inhibin signaling was reduced in CLOCK-deficient mice. These data establish the importance of circadian CLOCK–inhibin signaling in sepsis, which may have potential therapeutic implications.

Lipid-Rich Enteral Nutrition Improves the Defense Against an Opportunistic Infection During Polymicrobial Sepsis

The development of an immunosuppressive state during the protracted course of sepsis is associated with opportunistic infections and is considered to correlate with the extent of the proinflammatory response during early sepsis. Short-term intervention with enteral lipid-rich nutrition was shown to attenuate the acute inflammatory response. This study investigates the effects of lipid-rich nutrition on the immunosuppression induced by polymicrobial sepsis. Female BALB/c mice were either fasted or fed liquid lipid-rich nutrition or isocaloric control nutrition before and shortly after induction of polymicrobial sepsis through cecal ligation and puncture (CLP) or sham operation. After 4 days, mice were intranasally infected with Pseudomonas aeruginosa. Twenty-four hours after P. aeruginosa infection, fasted and control nutrition-fed CLP mice displayed a significantly higher bacterial load in the lungs than did corresponding sham-operated mice (P < 0.001 and P < 0.05, respectively). Fasted CLP mice expressed reduced pulmonary levels of proinflammatory cytokines interleukin 12 (IL-12) and interferon γ (IFN-γ) in comparison to sham mice (both P < 0.05). Lipid-rich nutrition prevented the increase in bacteria, promoted the IL-12 and IFN-γ production (IL-12 and IFN-γ [P < 0.05] vs. fasted and IFN-γ [P < 0.05] vs. control nutrition), and prevented the expression of the immunosuppressive cytokine IL-10 (P < 0.05 vs. control nutrition) in lungs of CLP mice. The preserved immune defense during late sepsis in lipid-rich fed mice was preceded by attenuation of the early inflammatory response (IL-6 [P = 0.05] and IL-10 [P < 0.01] vs. fasted CLP mice) at 6 h after CLP. In conclusion, short-term treatment with lipid-rich enteral nutrition improves the pulmonary antimicrobial defense during polymicrobial sepsis.

Polymyxin B-Conjugated α2-Macroglobulin as an Adjunctive Therapy to Sepsis: Modes of Action and Impact on Lethality

A drug targeting both the inflammatory initiators (lipopolysaccharide; LPS) and mediators [tumor necrosis factor-alpha (TNF-alpha)] should have advantage over a "single-factor targeting strategy" in sepsis prevention trials. We have prepared conjugates of polymyxin B (PMB) and the cytokine binding protein alpha2-macroglobulin (A2M). The conjugate binds TNF-alpha as well as LPS as studied by electrophoresis and phase partitioning. Compared with free PMB, the conjugate is nontoxic to cells and does not affect the viability of human monocytes. The A2M-PMB conjugate binds to the A2M receptor (CD91/low-density lipoprotein receptor-related protein 1) with affinity similar to that of the nonmodified protein. Fluorescein isothiocyanate-labeled LPS in the presence of A2M-PMB is rapidly transported into fibroblasts for degradation via receptor-mediated endocytosis. In vitro, A2M-PMB demonstrated inhibition of LPS-induced secretion of TNF-alpha from isolated monocytes as well as in the whole blood assay. The efficacy of the drug was tested in mice after induction of acute inflammation (LPS model) and after induction of a polymicrobial sepsis by cecal ligation and puncture (CLP) model. Treatment of mice with A2M-PMB up to 250 microg/g body weight was not toxic to the animal. When the drug was administered 30 min before or 30 min after the LPS challenge, a survival rate of 90 and 70%, respectively, was obtained compared with the placebo control group (5%). A2M-PMB also protected mice after induction of polymicrobial sepsis when administered 30 min before CLP. These results support our hypothesis that A2M-PMB acts as a polyvalent drug to target different host mediators as well as sepsis inducer at the same time.