Macrophage-activating lipopeptide-2 exerts protective effects in a murine sepsis model

Pushing the envelope: Immune mechanism and application landscape of macrophage-activating lipopeptide-2

Mycoplasma fermentans can cause respiratory diseases, arthritis, genitourinary tract infections, and chronic fatigue syndrome and have been linked to the development of the human immunodeficiency virus. Because mycoplasma lacks a cell wall, its outer membrane lipoproteins are one of the main factors that induce inflammation in the organism and contribute to disease development. Macrophage-activating lipopeptide-2 (MALP-2) modulates the inflammatory response of monocytes/macrophages in a bidirectional fashion, indirectly enhances the cytotoxicity of NK cells, promotes oxidative bursts in neutrophils, upregulates surface markers on lymphocytes, enhances antigen presentation on dendritic cells and induces immune inflammatory responses in sebocytes and mesenchymal cells. MALP-2 is a promising vaccine adjuvant for this application. It also promotes vascular healing and regeneration, accelerates wound and bone healing, suppresses tumors and metastasis, and reduces lung infections and inflammation. MALP-2 has a simple structure, is easy to synthesize, and has promising prospects for clinical application. Therefore, this paper reviews the mechanisms of MALP-2 activation in immune cells, focusing on the application of MALP-2 in animals/humans to provide a basis for the study of pathogenesis in Mycoplasma fermentans and the translation of MALP-2 into clinical applications.

The Influence of Macrophage-Activating Lipopeptide-2 in Regard to Liver-Specific Changes Within a Murine Two-Hit Model

Trauma hemorrhage (TH) and subsequent sepsis are well known to frequently result in severe organ damage. Although macrophage-activating lipopeptide-2 (MALP-2) has been described to exert beneficial effects on organ damage, and further clinical course after both isolated trauma and sepsis, little is known about the impact of MALP-2 in a clinically realistic two-hit scenario of TH and subsequent sepsis. As the liver represents a key organ for the posttraumatic immune response and development of complications, the effects of MALP-2 on the posttraumatic hepatic immunologic response and tissue damage were investigated in a murine "two-hit" model. In C57BL/6 mice, blood pressure-controlled (35 ± 5 mm Hg) TH was induced. Cecal ligation and puncture (CLP) was performed 48 h after TH. Mice were divided into two control groups (control 1, TH and laparotomy without CLP; control 2, TH and CLP) and three experimental groups (TH + CLP) treated with MALP-2 at different timepoints (ETH, end of TH; ECLP, end of CLP; 6CLP, 6 h after CLP). The observation time lasted for 168 h after induction of TH. Kupffer cells (KC) were isolated and cultured, and MPO activity was analyzed. Cell culture supernatants were taken for cytokine analysis (TNF-α, IL-6, MCP-1, GM-CSF, IL-10). Histological analysis was performed using the Hepatic Injury Severity Scoring (HISS). Statistical evaluation was carried out using SPSS (version 24.0.0; IBM, Armonk, NY, USA). MPO activity of control 1 group was lowest compared with all the other groups (p < 0.01). MPO activity of control 2 group was significantly higher than that in all experimental groups (ETH (p < 0.01), ECLP (p < 0.01), and 6CLP (p = 0.03)). Within the experimental groups, MPO activity was significantly reduced in the ETH (p = 0.04) and the ECLP (p < 0.01) groups compared with the 6CLP group. Moreover, ETH was also associated with the most pronounced reduction of cytokine expression by KC (p < 0.05). HISS revealed the largest damage in the group control 2. TH and subsequent sepsis lead to a distinct immunologic reaction in the liver with an increase of cytokine expression of KC and pronounced infiltration of granulocytes with associated severe tissue damage. MALP application decreases the hepatic immune response and liver damage, with the most pronounced effects if applied at the end of TH.

The Influence of Macrophage-Activating Lipopeptide 2 (MALP-2) on Local and Systemic Inflammatory Response in a Murine Two-Hit Model of Hemorrhagic Shock and Subsequent Sepsis

Pulmonary complications after severe trauma and sepsis remain to be the main cause for adverse outcome. MALP-2 has been described to exert beneficial effects on organ damage and the further course after isolated trauma and sepsis. However, the impact of MALP-2 on a clinically realistic two-hit scenario of trauma and subsequent sepsis remains unknown. We, therefore, investigated if the systemic inflammatory response and pulmonary immune response and damage are beneficially modulated by MALP-2 in a murine two-hit model. Blood pressure-controlled trauma-hemorrhage (TH) and cecal ligation and puncture (CLP) were induced in C57/BL6 mice. Mice were divided into 2 control groups (control 1: TH without CLP; control 2: TH and CLP) and 3 experimental groups treated with MALP-2 at different time points (ETH, end of TH; ECLP, end of CLP; and 6CLP 6 h after CLP). Survival rates were assessed over the observation period of 168 h after the induction of TH. Concentrations of plasma inflammatory cytokines and chemokines (TNF-α, IL-6, MIP-1α, IFN-γ, and IL-10) were assessed, and bacterial clearance of the lungs was determined. Furthermore, pulmonary MPO activity assay to evaluate the infiltration of polymorphonuclear neutrophils (PMN) and histological evaluation were performed. Survival rates were evaluated. Compared with control group 1, the level of TNF-α in the ECLP group showed a significant increase (ECLP, 2.27 pg./ml ± 1.39 vs. control 1: 0.16 pg./ml ± 0.11, p = 0.021). In contrast, levels of IFN-γ were significantly reduced in groups ETH and 6CLP compared with control group 1 (control 1: 8.92 pg./ml ± 4.38 vs. ETH: 1.77 pg./ml ± 4.34, p = 0.026 resp. vs. 6CLP: 1.83 pg./ml ± 4.49, p = 0.014). While systemic concentrations of inflammatory mediators were not affected by MALP-2 treatment, the lung tissue presented with significant alterations. Reduced MPO activity was lowest in group ECLP (ECLP 11,196.77 ± 547.81 vs. ETH 12,773.94 ± 1011.76; p = 0.023 resp. vs. 6CLP 13,155.19 ± 423.99, p = 0.016) in experimental groups. Also, histological damage after MALP-2 application was lowest in ECLP animals (ECLP 0.50 ± 0.08 vs. ETH 0.71 ± 0.05, p = 0.034 resp. vs. 6CLP 0.64 ± 0.08, p = 0.021). Furthermore, MALP-2 treatment was associated with a trend towards improved survival in the ECLP group (ECLP 83.3% vs. ETH 66.7 and 6CLP 58.3%, p > 0.05). Based on our results, MALP-2 might have beneficial effects on the clinical course after hemorrhage and sepsis by reducing pulmonary damage and PMN infiltration. This might also affect survival. According to our data, MALP-2 should be given at the earliest possible time point after the onset of sepsis. However, the optimal dosage and confirmation of our results in larger cohorts need to be the focus of further research.

Attenuation of pulmonary ACE2 activity impairs inactivation of des-Arg9 bradykinin/BKB1R axis and facilitates LPS-induced neutrophil infiltration

Angiotensin-converting enzyme 2 (ACE2) is a terminal carboxypeptidase with important functions in the renin-angiotensin system and plays a critical role in inflammatory lung diseases. ACE2 cleaves single-terminal residues from several bioactive peptides such as angiotensin II. However, few of its substrates in the respiratory tract have been identified, and the mechanism underlying the role of ACE2 in inflammatory lung disease has not been fully characterized. In an effort to identify biological targets of ACE2 in the lung, we tested its effects on des-Arg⁹ bradykinin (DABK) in airway epithelial cells on the basis of the hypothesis that DABK is a biological substrate of ACE2 in the lung and ACE2 plays an important role in the pathogenesis of acute lung inflammation partly through modulating DABK/bradykinin receptor B1 (BKB1R) axis signaling. We found that loss of ACE2 function in mouse lung in the setting of endotoxin inhalation led to activation of the DABK/BKB1R axis, release of proinflammatory chemokines such as C-X-C motif chemokine 5 (CXCL5), macrophage inflammatory protein-2 (MIP2), C-X-C motif chemokine 1 (KC), and TNF-α from airway epithelia, increased neutrophil infiltration, and exaggerated lung inflammation and injury. These results indicate that a reduction in pulmonary ACE2 activity contributes to the pathogenesis of lung inflammation, in part because of an impaired ability to inhibit DABK/BKB1R axis-mediated signaling, resulting in more prompt onset of neutrophil infiltration and more severe inflammation in the lung. Our study identifies a biological substrate of ACE2 within the airways, as well as a potential new therapeutic target for inflammatory diseases.

Identification of potential biomarkers for post-traumatic complications released after trauma-hemorrhage from murine Kupffer cells and its investigation in lung and liver

CONTEXT

Early diagnosis of complications after severe trauma by specific biomarkers remains difficult.

OBJECTIVE

Identify potential new biomarkers for early diagnosis of post-traumatic complications.

MATERIAL AND METHODS

Mice underwent pressure-controlled hemorrhage or sham procedure. Four hours later, genome-wide expression of isolated Kupffer cells was compared with controls using Affymetrix-Genechip-Expression-Analysis and real-time-PCR.

RESULTS

Expression analysis and real-time-PCR revealed a significant increase of gene expression of Cxcl10, Il4ra, Csf2rb2, Lcn2, and Gbp5.

CONCLUSION

Cxcl10, Il4ra, Csf2rb2, Lcn2, and Gbp5 might represent new biomarkers for early diagnosis of post-traumatic complications, if they are linked to the development of post-traumatic complications.

MALP-2 pre-treatment modulates systemic inflammation in hemorrhagic shock

Background

TLR-2 is expressed on the surface of leucocytes, lung and liver tissue and initiates the activation of immune response after interaction with components of the bacterial cell wall. In this experiment we investigated whether immunostimulation with TLR-2 agonists under conditions of sterile inflammation (hemorrhagic shock (HS)) may affect the immune response and remote organ inflammation.

Methods

Male C57/BL6 mice were subjected to standardized pressure-controlled HS (MAP of 35 mmHg for 90 minutes). The TLR-2 agonist macrophage-activated lipopeptide-2 (MALP-2) was administered (i.p.) either 12 hours prior to the induction of HS (Group MALP PT) or after the hypotensive period (90 minutes) (Group MALP T). After six hours, plasma cytokine levels (IL-6, KC, IL-10, and MCP-1) and lung and liver MPO activity were assessed.

Results

Pre-treatment with MALP-2 resulted in a significant attenuation of the systemic pro-inflammatory (IL-6) response (MALP PT: 0.83±0.2 ng/ml vs. MALP T: 1.7±0.09 ng/ml) (p<0.05). In comparison to the liver MPO activity, lung MPO levels in in group MALP PT did not show differences to levels measured in MALP T mice (1.200±200 ng/mg vs. 1.800±200 ng/mg).

Conclusions

After initial inflammation, MALP-2 pre-treatment was associated with attenuated systemic immune response after sterile stimulus. The TLR-2 agonist appears to affect sterile inflammation pathways. The exact mechanisms should be studied further to better understand these affects.

Androstenediol exerts salutary effects on chemokine response after trauma-hemorrhage and sepsis in mice

OBJECTIVES

The pathogenesis of multiple organ dysfunction syndrome and sepsis after polytrauma is related to the posttraumatic immune response and the associated release of inflammatory mediators. There exists a gender dimorphism in the posttraumatic host response. Sex steroids are believed to beneficially modulate the posttraumatic immune response. The specific effect of androstenediol on chemokines after trauma is unknown. We investigated whether the application of androstenediol has an effect on plasma chemokine levels and the associated remote organ damage in a two-hit mouse-model of trauma-hemorrhage, cecal ligation, and cecal puncture.

MATERIALS AND METHODS

Traumatic hemorrhage was induced followed by androstenediol application and volume resuscitation. Thereafter, androstenediol was given once daily in combination with a vehicle (Intralipid). The control group was injected with a solution containing only the vehicle at the same time points as the treatment groups' androstenediol applications. Sepsis was induced by cecal ligation and cecal puncture 48 hours afterward. Four hours after cecal ligation and cecal puncture, plasma measurements of chemokines were performed. Pulmonary infiltration by polymorphonuclear lymphocytes was measured by immunhistochemical staining and myeloperoxidase measurements were taken.

RESULTS

Application of androstenediol led to significantly decreased monocyte chemoattractant protein-1, monocyte chemoattractant protein-3, macrophage inflammatory protein-1α, and macrophage inflammatory protein-1β levels compared with the control animals after trauma-hemorrhage, cecal ligation, and cecal puncture (P < 0.05). Pulmonary infiltration and myeloperoxidase activity were significantly decreased in androstenediol-treated animals (P < 0.05).

CONCLUSION

Androstenediol modulates the immune response after trauma-hemorrhage, cecal ligation, and cecal puncture by reducing systemic chemokine levels, which are known to direct immune cells into the tissue possibly leading to organ damage. Androstenediol represents a potential therapeutic agent after major trauma in high-risk patients.

Protective effects of finasteride on the pulmonary immune response in a combined model of trauma-hemorrhage and polymicrobial sepsis in mice

Literature supports findings about a gender specific outcome following multiple trauma. Male sex hormones such as dihydrotestosterone (DHT) exert deleterious effects on the posttraumatic immune response whereas increased estradiol concentrations are correlated with improved outcome. Pretreatment with the 5α-reductase inhibitor finasteride resulted in an improved outcome following trauma-hemorrhage (TH) in mice. The present study tested the hypothesis that finasteride exerts beneficial effects on the posttraumatic immune response also in a combined setting of TH and sepsis when administered during the resuscitation process.

MATERIAL AND METHODS

Male C57BL/6N-mice were subjected to TH (blood pressure, 35 mm Hg, 60 min) followed by finasteride application and fluid resuscitation. Thereafter, finasteride was administered every 12h. 24h after TH, sepsis was induced by cecal ligation and puncture (CLP) or sham operation was performed. Plasma cytokines (MIP-1α, MIP-1β, TNF-α, MCP-1, IL-6), productive capacity by alveolar macrophages (AM) and systemic estradiol levels were determined 4 h thereafter. The expression of pro-inflammatory mediators in lung tissue was evaluated by PCR. Pulmonary infiltration of PMN was determined by immunohistochemical staining.

RESULTS

Finasteride treatment resulted in a reduced posttraumatic cytokine secretion of AM as well as in a decreased concentration of MCP-1 and MIP-1β in lung tissue. Systemic estradiol levels were increased following finasteride treatment.

CONCLUSION

Finasteride mediates salutary effects on the pulmonary immune response using a therapeutical approach following TH-CLP in mice. Thus, finasteride might represent a relevant therapeutic substance following major trauma also in the clinical setting.