Evidence for anti-inflammatory effects of C5a on the innate IL-17A/IL-23 axis.

There is growing evidence that the complement activation product C5a positively or negatively regulates inflammatory functions. The studies presented here report that C5a exerts anti-inflammatory effects by altering production of the cytokines IL-17A and IL-23 during endotoxic shock in young adult male C57BL/6J mice and has similar effects on macrophages from the same mice. IL-17A and IL-23 both appeared in plasma during endotoxemia, and their neutralization improved survival. The relevant sources of IL-17A during endotoxemia were not CD4(+) cells, γδ T cells, or NK cells but CD11b(+)F4/80(+) macrophages. The addition in vitro of C5a to lipopolysaccharide-activated peritoneal macrophages dose dependently antagonized the production of IL-17A (IC(50), 50-100 nM C5a) and IL-23 (IC(50), 10 nM C5a). This suppression required the receptor C5aR, but was independent of the second C5a receptor, C5L2. Genetic absence of C5aR was associated with much higher levels of IL-17A and IL-23 during endotoxic shock. Mechanistically, C5a mediated its effects on the IL-17A/IL-23 axis in a 2-step process. C5a caused activation of the PI3K-Akt and MEK1/2-ERK1/2 pathways, resulting in induction of IL-10, which powerfully inhibited production of IL-17A and IL-23. These data identify previously unknown mechanisms by which the anaphylatoxin C5a limits acute inflammation and antagonizes the IL-17A/IL-23 axis.

Risk factors for severe COVID-19 among patients with systemic lupus erythematosus: a real-world analysis of a large representative US administrative claims database, 2020-2021.

OBJECTIVES: To identify risk factors for progression to severe COVID-19 and estimate the odds of severe COVID-19 associated with vaccination among patients with systemic lupus erythematosus (SLE). METHODS: This retrospective cohort study identified adults with SLE in the Merative™ MarketScan® Databases. Patients were continuously enrolled the year before 1 April 2020 (baseline) and had a COVID-19 diagnosis between 1 April 2020 and the earliest of death, enrolment end or 31 December 2021. Severe COVID-19 was defined as hospitalisation with a COVID-19 diagnosis. Demographics on 1 April 2020, baseline comorbidities, corticosteroid use ≤30 days before COVID-19 diagnosis and other SLE medication use ≤6 months before COVID-19 diagnosis were assessed. Vaccination was identified by claims for a COVID-19 vaccine or vaccine administration. Backward stepwise logistic regression estimated odds of progression to severe COVID-19 associated with patient characteristics and vaccination. RESULTS: Among 2890 patients with SLE with COVID-19, 500 (16.4%) had a COVID-19-related hospitalisation. Significant risk factors for progression to severe COVID-19 included rituximab (OR (95% CI) 2.92 (1.67 to 5.12)), renal failure (2.15 (95% CI 1.56 to 2.97)), Medicaid (vs Commercial; 2.01 (95% CI 1.58 to 2.57)), complicated hypertension (1.96 (95% CI 1.38 to 2.77)) and time of infection, among others. Vaccination had a significant protective effect (0.68(95% CI 0.54 to 0.87)) among all patients with SLE with COVID-19, but the effect was not significant among those with prior use of belimumab, rituximab or corticosteroids. CONCLUSIONS: Certain chronic comorbidities and SLE medications increase the odds of progression to severe COVID-19 among patients with SLE, but vaccination confers significant protection. Vaccine effectiveness may be attenuated by SLE treatments. Protective measures such as pre-exposure prophylaxis and booster vaccines should be encouraged among patients with SLE.

Complement dependency of cardiomyocyte release of mediators during sepsis.

We have recently shown that antibody-induced blockade of C5a, C5a receptors, or IL-17A greatly reduced the harmful outcomes of sepsis. In the current study, normal cardiomyocytes from young (300 g) male Sprague-Dawley rats responded in vitro to C5a (ED(50)=55 nM) with release of IL-6 and TNFα, peaking between 2 to 8 h. Neutralizing antibodies to mouse C5a or IL-17A (ED(50)=40 µg for each, based on improved survival) reduced spontaneous in vitro release of cardiosuppressive cytokines and chemokines in cardiomyocytes obtained from mice with polymicrobial sepsis. A non-neutralizing C5a antibody had no such effects. Cardiomyocytes from septic mice (C57Bl/6) showed increased mRNA for TNFR1, IL-6 (gp80), and C5aR at 6 h after sepsis. Cardiomyocytes from septic C5aR(-/-) or C5L2(-/-) mice did not show spontaneous in vitro release of cytokines and chemokines. These data suggest that cardiomyocytes from septic mice release suppressive cytokines in a C5a-, C5aR-, and IL-17A-dependent manner, followed by mediator reactivity with receptors on cardiomyocytes, resulting in defective contractility and relaxation. These data may be relevant to a strategy for the treatment of heart dysfunction developing during sepsis.

Renal injury in scleromyxoedema due to monoclonal gammopathy associated C3 glomerulonephritis.

Scleromyxoedema is a rare mucinosis that primarily affects the skin. It is associated with monoclonal gammopathy and has many extracutaneous manifestations, however, renal involvement is rare. We report the case of a woman with monoclonal gammopathy and scleromyxoedema presenting with progressive exertional dyspnoea and acute renal failure. Workup of her renal failure revealed monoclonal gammopathy associated C3 glomerulonephritis. She was treated with intravenous steroids and discharged with plans to pursue annual monoclonal gammopathy laboratory monitoring. Given the rarity of renal scleromyxoedema, careful investigation of extracutaneous manifestations and comorbidities is critical to discern the primary pathological process in patients with scleromyxoedema who develop renal insufficiency.

Complement Activation in Trauma Patients Alters Platelet Function.

Trauma remains the main cause of death for both civilians and those in uniform. Trauma-associated coagulopathy is a complex process involving inflammation, coagulation, and platelet dysfunction. It is unknown whether activation of complement, which occurs invariably in trauma patients, is involved in the expression of trauma-associated coagulopathy. We designed a prospective study in which we enrolled 40 trauma patients and 30 healthy donors upon arrival to the emergency department of BIDMC. Platelets from healthy individuals were incubated with sera from trauma patients and their responsiveness to a thrombin receptor-activating peptide was measured using aggregometry. Complement deposition on platelets from trauma patients was measured by flow cytometry. Normal platelets displayed hypoactivity after incubation with trauma sera even though exposure to trauma sera resulted in increased agonist-induced calcium flux. Depletion of complement from sera further blocked activation of hypoactive platelets. Conversely, complement activation increased aggregation of platelets. Platelets from trauma patients were found to have significantly higher amounts of C3a and C4d on their surface compared with platelets from controls. Depletion of complement (C4d, C3a) reversed the ability of trauma sera to augment agonist-induced calcium flux in donor platelets. Our data indicate that complement enhances platelet aggregation. Despite its complement content, trauma sera render platelets hypoactive and complement depletion further blocks activation of hypoactive platelets. The defect in platelet activation induced by trauma sera is distal to receptor activation since agonist-induced Ca2+ flux is elevated in the presence of trauma sera owing to complement deposition.