Therapeutic blockade of the interleukin-6 receptor (IL-6R) allows sIL-6R generation by proteolytic cleavage

Tocilizumab-Induced Unexpected Increase of Several Inflammatory Cytokines in Critically Ill COVID-19 Patients: The Anti-Inflammatory Side of IL-6

Early evidence during the coronavirus disease 2019 (COVID-19) pandemic indicated high levels of interleukin (IL)-6 in patients with severe COVID-19. This led to the off-label use of tocilizumab (TCZ) during the first wave of the pandemic. While the monoclonal antibody blocks IL-6 pathway, its effect on other inflammatory cytokines remains poorly described. To better understand the effect of TCZ on the biological inflammatory profile, we monitored a large panel of inflammatory cytokines in critically ill COVID-19 patients receiving off-label TCZ. Twenty-three patients with polymerase chain reaction-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were included in the study, among which 15 patients received TCZ and 8 patients did not. Serum samples were collected for 8 days, before and following TCZ administration or hospital admission for the control group. Serum profile of 12 cytokines (IL-1β, -2, -4, -6, -8, -10, -12, -13, -17, -18, tumor necrosis factor α (TNF-α), interferon-gamma (IFN-γ), and sIL-6R were assessed in these two groups. Although the increased IL-6 concentrations after TCZ infusion were expected, we observed an unexpected increase in IL-1β, -2, -4, -10, -12p70, -18, and sIL-6R levels in the treated patients with maximal values reaching 2 to 4 days after TCZ. In contrast, no change in cytokine levels was observed in the control group. Our results suggested that some inflammatory pathways escape IL-6R blockade and even appeared amplified. This finding highlights an old observation of the anti-inflammatory effects of IL-6 as already suggested over 20 years ago. Clinical Trial Registration number: NCT04346017.

High levels of interleukin-6 are associated with final infarct size and adverse clinical events in patients with STEMI

Objective

Inflammation has emerged as a new treatment target in patients with coronary artery disease and inflammation seems to play an important role in ischaemia/reperfusion injury that follows ST-elevation myocardial infarction (STEMI). We aimed to explore the role of acute and sustained interleukin 6 (IL-6) signalling, including soluble IL-6 receptor (IL-6R), with regard to infarct size, adverse remodelling and future cardiovascular events in patients with STEMI.

Methods

We included 269 patients with first-time STEMI, symptom duration <6 hours and treated with percutaneous coronary intervention. Blood sampling and cardiac MRI were performed in the acute phase and after 4 months. Clinical events and all-cause mortality were registered during 12-month and 70-month follow-up, respectively.

Results

IL-6 levels above median at all sampling points were significantly associated with increased infarct size and reduced left ventricular ejection fraction (LVEF). IL-6 levels in the highest quartile were at all sampling points associated with an increased risk of having an adverse clinical event during the first 12 months and with long-term all-cause mortality. IL-6R was not associated with infarct size, LVEF, myocardial salvage or long-term all-cause mortality.

Conclusion

Acute and sustained elevation of IL-6 measured 4 months after STEMI were associated with larger infarct size, reduced LVEF and adverse clinical events including all-cause mortality. The results add important information to the sustained role of inflammation in patients with STEMI and IL-6 as a potential target for long-term intervention.

Trial registration number

NCT00922675.

IL-6/STAT3 Is a Promising Therapeutic Target for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common malignant tumor of which the occurrence and development, the tumorigenicity of HCC is involving in multistep and multifactor interactions. Interleukin-6 (IL-6), a multifunctional inflammatory cytokine, has increased expression in HCC patients and is closely related to the occurrence of HCC and prognosis. IL-6 plays a role by binding to the IL-6 receptor (IL-6R) and then triggering the Janus kinase (JAK) associated with the receptor, stimulating phosphorylation and activating signal transducer and activator of transcription 3 (STAT3) to initiate downstream signals, participating in the processes of anti-apoptosis, angiogenesis, proliferation, invasion, metastasis, and drug resistance of cancer cells. IL-6/STAT3 signal axes elicit an immunosuppressive in tumor microenvironment, it is important to therapy HCC by blocking the IL-6/STAT3 signaling pathway. Recent, some inhibitors of IL-6/STAT3 have been development, such as S31-201 or IL-6 neutralizing monoclonal antibody (IL-6 mAb), Madindoline A (Inhibits the dimerization of IL-6/IL-6R/gpl30 trimeric complexes), C188-9 and Curcumin (Inhibits STAT3 phosphorylation), etc. for treatment of cancers. Overall, consideration of the IL-6/STAT3 signaling pathway, and its role in the carcinogenesis and progression of HCC will contribute to the development of potential drugs for targeting treatment of liver cancer.

Multifactorial expression of IL-6 with update on COVID-19 and the therapeutic strategies of its blockade (Review)

Interleukin 6 (IL-6), a cytokine produced by various cells of the human body (macrophages, lymphocytes, astrocytes, ischemic myocytes, endothelial cells) has both pro-inflammatory and anti-inflammatory properties, being a key component in regulating various physiologic and pathological processes. The structure of this molecule and the receptor system it possesses are important due to the different activities that IL-6 can exert; through trans-signaling pro-inflammatory activities are mediated, while through classic signaling, IL-6 is responsible for anti-inflammatory and regenerative activities. IL-6 signaling is involved in coronary artery disease and the global COVID-19 pandemic. This proatherogenic cytokine reaches elevated serum levels in the cytokine storm generated by SARS-CoV-2, and is also associated with smoking or obesity-classic cardiovascular risk factors which promote inflammatory states. IL-6 levels are proportionally correlated with dyslipidemia, hypertension and glucose dysregulation, and they are associated with poor outcomes in patients with unstable angina or acute myocardial infarction. IL-6 targeting for treatment development (not only) in cardiovascular disease and COVID-19 is still a matter of ongoing research, although tocilizumab has proven to be effective in reducing the proatherogenic effects of IL-6 and is suggested to improve COVID-19 patient survival.

Progress in Understanding the IL-6/STAT3 Pathway in Colorectal Cancer

As a pleiotropic cytokine, interleukin-6 (IL-6) not only regulates the cellular immune response, but it also promotes tumor development by activating multiple carcinogenic pathways. IL-6 expression is significantly elevated in colorectal cancer (CRC) and is closely related to CRC development and patient prognosis. In CRC, IL-6 activates signal transducers and activators of transduction-3 (STAT3) to promote tumor initiation and tumor growth. IL-6/STAT3 signalling has a profound effect on tumor-infiltrating immune cells in the tumor immune microenvironment in CRC. Additionally, IL-6/STAT3 pathway activates downstream target genes to protect tumor cells from apoptosis; drive tumor cell proliferation, cell cycle progression, invasion and metastasis; promote tumor angiogenesis; and stimulate drug resistance. Therefore, a thorough understanding of the many effects of the IL-6/STAT3 pathway in CRC is needed, which the present review examines.

Patients with obstructive sleep apnea have suppressed levels of soluble cytokine receptors involved in neurodegenerative disease, but normal levels with airways therapy

Purpose

Obstructive sleep apnea (OSA) results in systemic intermittent hypoxia. By one model, hypoxic stress signaling in OSA patients alters the levels of inflammatory soluble cytokines TNF and IL6, damages the blood brain barrier, and activates microglial targeting of neuronal cell death to increase the risk of neurodegenerative disorders and other diseases. However, it is not yet clear if OSA significantly alters the levels of the soluble isoforms of TNF receptors TNFR1 and TNFR2 and IL6 receptor (IL6R) and co-receptor gp130, which have the potential to modulate TNF and IL6 signaling.

Methods

Picogram per milliliter levels of the soluble isoforms of these four cytokine receptors were estimated in OSA patients, in OSA patients receiving airways therapy, and in healthy control subjects. Triplicate samples were examined using Bio-Plex fluorescent bead microfluidic technology. The statistical significance of cytokine data was estimated using the nonparametric Wilcoxon rank-sum test. The clustering of these high-dimensional data was visualized using t-distributed stochastic neighbor embedding (t-SNE).

Results

OSA patients had significant twofold to sevenfold reductions in the soluble serum isoforms of all four cytokine receptors, gp130, IL6R, TNFR1, and TNFR2, as compared with control individuals (p = 1.8 × 10⁻¹³ to 4 × 10⁻⁸). Relative to untreated OSA patients, airways therapy of OSA patients had significantly higher levels of gp130 (p = 2.8 × 10⁻¹³), IL6R (p = 1.1 × 10⁻⁹), TNFR1 (p = 2.5 × 10⁻¹⁰), and TNFR2 (p = 5.7 × 10⁻⁹), levels indistinguishable from controls (p = 0.29 to 0.95). The data for most airway-treated patients clustered with healthy controls, but the data for a few airway-treated patients clustered with apneic patients.

Conclusions

Patients with OSA have aberrantly low levels of four soluble cytokine receptors associated with neurodegenerative disease, gp130, IL6R, TNFR1, and TNFR2. Most OSA patients receiving airways therapy have receptor levels indistinguishable from healthy controls, suggesting a chronic intermittent hypoxia may be one of the factors contributing to low receptor levels in untreated OSA patients.

Electronic supplementary material

The online version of this article (10.1007/s11325-020-02205-y) contains supplementary material, which is available to authorized users.

Macrolets: Outsized Extracellular Vesicles Released from Lipopolysaccharide-Stimulated Macrophages that Trap and Kill Escherichia coli

Macrophages release a variety of extracellular vesicles (EVs). Here we describe a previously unreported class of EVs that are released from macrophages in response to Escherichia coli endotoxin, lipopolysaccharide (LPS), that we have named "macrolets" since they are extruded as large "droplets" released from macrophages. Morphologically, macrolets are anuclear, bounded by a single lipid membrane and structurally dependent on an actin cytoskeleton. Macrolets are enriched in tetraspanins and separable on this basis from their parent macrophages. Macrolets are distinguished from classic exosomes by their larger size (10–30 μm), discoid shape, and the presence of organelles. Macrolets are rich in both interleukin 6 (IL-6) and interleukin 6 receptor (IL-6R),and are capable of trapping and killing E. coli in association with production of reactive oxygen species. Our observations offer insights into the mechanisms by which macrophage activities may be amplified in sites of infection, inflammation, and healing.

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Macrolets, outsized extracellular vesicles, release from LPS-stimulated macrophages

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Macrolets are rich in tetraspanin proteins such as CD81, CD63, and CD9

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Macrolets capture and internalize E. coli bacteria within acidic compartments

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Macrolets kill E. coli by a mechanism associated with production of ROS and superoxide