Sulfoxide-containing polymers conjugated prodrug micelles with enhanced anticancer activity and reduced intestinal toxicity.

Poly(ethylene glycol) (PEG) is widely utilized as a hydrophilic coating to extend the circulation time and improve the tumor accumulation of polymeric micelles. Nonetheless, PEGylated micelles often activate complement proteins, leading to accelerated blood clearance and negatively impacting drug efficacy and safety. Here, we have crafted amphiphilic block copolymers that merge hydrophilic sulfoxide-containing polymers (psulfoxides) with the hydrophobic drug 7-ethyl-10-hydroxylcamptothecin (SN38) into drug-conjugate micelles. Our findings show that the specific variant, PMSEA-PSN38 micelles, remarkably reduce protein fouling, prolong blood circulation, and improve intratumoral accumulation, culminating in significantly increased anti-cancer efficacy compared with PEG-PSN38 counterpart. Additionally, PMSEA-PSN38 micelles effectively inhibit complement activation, mitigate leukocyte uptake, and attenuate hyperactivation of inflammatory cells, diminishing their ability to stimulate tumor metastasis and cause inflammation. As a result, PMSEA-PSN38 micelles show exceptional promise in the realm of anti-metastasis and significantly abate SN38-induced intestinal toxicity. This study underscores the promising role of psulfoxides as viable PEG substitutes in the design of polymeric micelles for efficacious anti-cancer drug delivery.

Prevalence of anti-lymphocyte IgM autoantibodies driving complement activation in COVID-19 patients.

Introduction: COVID-19 patients can develop autoantibodies against a variety of secreted and membrane proteins, including some expressed on lymphocytes. However, it is unclear what proportion of patients might develop anti-lymphocyte antibodies (ALAb) and what functional relevance they might have. Methods: We evaluated the presence and lytic function of ALAb in the sera of a cohort of 85 COVID-19 patients (68 unvaccinated and 17 vaccinated) assigned to mild (N=63), or moderate/severe disease (N=22) groups. Thirty-seven patients were followed-up after recovery. We also analyzed in vivo complement deposition on COVID-19 patients' lymphocytes and examined its correlation with lymphocyte numbers during acute disease. Results: Compared with healthy donors (HD), patients had an increased prevalence of IgM ALAb, which was significantly higher in moderate/severe disease patients and persisted after recovery. Sera from IgM ALAb+ patients exhibited complement-dependent cytotoxicity (CDC) against HD lymphocytes. Complement protein C3b deposition on patients' CD4 T cells was inversely correlated with CD4 T cell numbers. This correlation was stronger in moderate/severe disease patients. Discussion: IgM ALAb and complement activation against lymphocytes may contribute to the acute lymphopenia observed in COVID-19 patients.

Exploring complement biomarkers in suspected axial spondyloarthritis.

OBJECTIVES: To investigate lectin pathway proteins (LPPs) as biomarkers for axial spondyloarthritis (axSpA) in a cross-sectional cohort with a suspicion of axSpA, comprising newly diagnosed axSpA and chronic low back pain (cLBP) individuals. METHODS: Serum samples from 515 participants within the OptiRef cohort, including 151 axSpA patients and 364 cLBP patients, were measured using immunoassays for LPPs (mannan-binding lectin (MBL), collectin liver-1 (CL-L1), M-ficolin, H-ficolin and L-ficolin, MBL-associated serine proteases (MASP)-1, -2 and -3, MBL-associated proteins (MAp19 and MAp44) and the complement activation product C3dg). RESULTS: Serum levels of L-ficolin, MASP-2 and C3dg were elevated in axSpA patients, whereas levels of MASP-3 and CL-L1 were decreased, and this remained significant for C3dg and MASP-3 after adjustment for C reactive protein (CRP). A univariate regression analysis showed serum levels of CL-L1, MASP-2, MASP-3 and C3dg to predict the diagnosis of axSpA, and MASP-3 and C3dg remained significant in a multivariate logistic regression analysis. Assessment of the diagnostic potential showed that a combination of human leukocyte antigen B27 (HLA-B27) and measurements of L-ficolin, MASP-3 and C3dg increased the diagnostic specificity for axSpA, however, with a concomitant loss of sensitivity. CONCLUSIONS: Serum levels of complement activation, that is, C3dg, and MASP-3 differed significantly between axSpA and cLBP patients after adjustment for CRP. Although combining HLA-B27 with measurements of L-ficolin, MASP-3 and C3dg increased the diagnostic specificity for axSpA, this seems unjustified due to the concomitant loss of sensitivity. However, both C3dg and MASP-3 were associated with axSpA diagnosis in multivariate logistic regression, suggesting an involvement of complement in the inflammatory processes and possibly pathogenesis in axSpA.

Interaction Studies of Hexameric and Pentameric IgMs with Serum-Derived C1q and Recombinant C1q Mimetics.

The interaction between IgM and C1q represents the first step of the classical pathway of the complement system in higher vertebrates. To identify the significance of particular IgM/C1q interactions, recombinant IgMs were used in both hexameric and pentameric configurations and with two different specificities, along with C1q derived from human serum (sC1q) and two recombinant single-chain variants of the trimeric globular region of C1q. Interaction and complement activation assays were performed using the ELISA format, and bio-layer interferometry measurements to study kinetic behavior. The differences between hexameric and pentameric IgM conformations were only slightly visible in the interaction assay, but significant in the complement activation assay. Hexameric IgM requires a lower concentration of sC1q to activate the complement compared to pentameric IgM, leading to an increased release of C4 compared to pentameric IgM. The recombinant C1q mimetics competed with sC1q in interaction assays and were able to inhibit complement activation. The bio-layer interferometry measurements revealed KD values in the nanomolar range for the IgM/C1q interaction, while the C1q mimetics exhibited rapid on and off binding rates with the IgMs. Our results make C1q mimetics valuable tools for developing recombinant C1q, specifically its variants, for further scientific studies and clinical applications.

Crepuscular rays - The bright side of complement after tissue injury.

Acute injuries trigger an intense activation of the body's defense mechanisms aiming to limit damage and initiate healing. Among the crucial components of the intravascular immune system, the complement system plays a significant role in traumatic injuries, albeit often negatively. It has been suggested that excessive activation of the complement system, transitioning from a localized and timed response to a systemic one, can lead to a loss of its host-protective characteristics. Complement activation products have been associated with the severity of injuries, which sometimes serve as predictors for the onset of organ dysfunctions. Animal studies utilizing complement-targeting agents have provided the basis for considering complement in the management of traumatic injuries in humans. However, numerous studies suggest that the spatial and temporal aspects of complement inhibition are crucial for its efficacy. Understanding the underlying mechanism of the injury is essential to determine where, when, and whether complement inhibition is warranted. Despite the detrimental effects of uncontrolled complement activation, its regulated activation may contribute to essential aspects of healing, such as waste removal and regeneration. This review focuses on the beneficial roles of complement activation in trauma, which are often overlooked or given less consideration but are of immense importance.

Engineered IgM and IgG cleaving enzymes for mitigating antibody neutralization and complement activation in AAV gene transfer.

Systemic dosing of adeno-associated viral (AAV) vectors poses potential risk of adverse side effects including complement activation triggered by anti-capsid immunity. Due to the multifactorial nature of toxicities observed in this setting, a wide spectrum of immune modulatory regimens are being investigated in the clinic. Here, we discover an IgM cleaving enzyme (IceM) that degrades human IgM, a key trigger in the anti-AAV immune cascade. We then engineer a fusion enzyme (IceMG) with dual proteolytic activity against human IgM and IgG. IceMG cleaves B cell surface antigen receptors and inactivates phospholipase gamma signaling in vitro. Importantly, IceMG is more effective at inhibiting complement activation compared with an IgG cleaving enzyme alone. Upon IV dosing, IceMG rapidly and reversibly clears circulating IgM and IgG in macaques. Antisera from these animals treated with IceMG shows decreased ability to neutralize AAV and activate complement. Consistently, pre-conditioning with IceMG restores AAV transduction in mice passively immunized with human antisera. Thus, IgM cleaving enzymes show promise in simultaneously addressing multiple aspects of anti-AAV immunity mediated by B cells, circulating antibodies and complement. These studies have implications for improving safety of AAV gene therapies and possibly broader applications including organ transplantation and autoimmune diseases.

Complement activation in wasp venom-induced acute kidney injury.

Previous studies have highlighted the significant role of complement activation in kidney injuries induced by rhabdomyolysis, intravascular hemolysis, sepsis, and ischemia-reperfusion. Nevertheless, the specific role and mechanism of complement activation in acute kidney injury (AKI) caused by wasp venom remain unclear. The aim of this study was to elucidate the specific complement pathway activated and investigate complement activation in AKI induced by wasp venom. In this study, a complement-depleted mouse model was used to investigate the role of complement in wasp venom-induced AKI. Mice were randomly categorized into control, cobra venom factor (CVF), AKI, and CVF + AKI groups. Compared to the AKI group, the CVF + AKI group showed improved pathological changes in kidneys and reduced blood urea nitrogen (BUN) levels. The expression levels of renal complement 3 (C3), complement 5 (C5), complement 1q (C1q), factor B (FB), mannose-binding lectin (MBL), and C5b-9 in AKI group were upregulated compared with the control group. Conversely, the renal tissue expression levels of C3, C5, C1q, FB, MBL, and C5b-9 were decreased in the CVF + AKI group compared to those in the AKI group. Complement activation occurs through all three pathways in AKI induced by wasp venom. Furthermore, complement depletion by CVF attenuates wasp venom-induced nephrotoxicity, suggesting that complement activation plays a primary role in the pathogenesis of wasp venom-induced AKI.

External quality assurance program for diagnostic complement laboratories: evaluation of the results of the past seven years.

Introduction: The complement external quality assurance (EQA) program was first organized in 2010 by a group of researchers working in diagnostic complement laboratories. Starting in 2016, INSTAND e.V., a German, non-profit interdisciplinary scientific medical society dedicated to providing expert EQA programs for medical laboratories, started organizing the EQAs for complement diagnostic laboratories together with the same group of experienced scientists and doctors who also work as EQA experts. The aim of the current work is to provide descriptive analysis of the past seven years' complement EQA results and evaluate timeline changes in proficiency testing. Methods: Each year, in March and October, blinded samples (normal, pathological) were sent to the participating diagnostic laboratories, where complement parameters were evaluated exactly as in daily routine samples. Since no reference method/target values exist for these parameters, and participants used different units for measurement, the reported results were compared to the stable mean (Algorithm A) of the participants using the same method/measurement units. A reported result was qualified as "passed" if it fell into the 30-50% evaluation/target range around the mean of reported results (depending on the given parameter). Results: While the number of participating laboratories has increased in the past years (from around 120 to 347), the number of complement laboratories providing multiple determinations remained mostly unchanged (around 30 worldwide). C3, C4, C1-inhibitor antigen and activity determinations provided the best proficiency results, with >90% passing quotas in the past years, independent of the applied method. Determination of the functional activity of the three activation pathways was good in general, but results showed large variance, especially with the pathological samples. Complement factor C1q and regulators FH and FI are determined by only a few laboratories, with variable outcomes (in general in the 85-90% pass range). Activation products sC5b-9 and Bb were determined in 30 and 10 laboratories, respectively, with typical passing quotas in the 70-90% range, without a clear tendency over the past years. Conclusion: With these accumulated data from the past seven years, it is now possible to assess sample-, method-, and evaluation related aspects to further improve proficiency testing and protocolize diagnostic complement determinations.

Phospholipid Type Regulates Protein Corona Composition and In Vivo Performance of Lipid Nanodiscs.

Over the years, there has been significant interest in PEGylated lipid-based nanocarriers within the drug delivery field. The inevitable interplay between the nanocarriers and plasma protein plays a pivotal role in their in vivo biological fate. Understanding the factors influencing lipid-based nanocarrier and protein corona interactions is of paramount importance in the design and clinical translation of these nanocarriers. Herein, discoid-shaped lipid nanodiscs (sNDs) composed of different phospholipids with varied lipid tails and head groups were fabricated. We investigated the impact of phospholipid components on the interaction between sNDs and serum proteins, particle stability, and biodistribution. The results showed that all of these lipid nanodiscs remained stable over a 15 day storage period, while their stability in the blood serum demonstrated significant differences. The sND composed of POPG exhibited the least stability due to its potent complement activation capability, resulting in rapid blood clearance. Furthermore, a negative correlation between the complement activation capability and serum stability was identified. Pharmacokinetic and biodistribution experiments indicated that phospholipid composition did not influence the capability of sNDs to evade the accelerated blood clearance phenomenon. Complement deposition on the sND was inversely associated with the area under the curve. Additionally, all lipid nanodiscs exhibited dominant adsorption of apolipoprotein. Remarkably, the POPC-based lipid nanodisc displayed a significantly higher deposition of apolipoprotein E, contributing to an obvious brain distribution, which provides a promising tool for brain-targeted drug delivery.

Regeneration in Mice of Injured Skin, Heart, and Spinal Cord by α-Gal Nanoparticles Recapitulates Regeneration in Amphibians.

The healing of skin wounds, myocardial, and spinal cord injuries in salamander, newt, and axolotl amphibians, and in mouse neonates, results in scar-free regeneration, whereas injuries in adult mice heal by fibrosis and scar formation. Although both types of healing are mediated by macrophages, regeneration in these amphibians and in mouse neonates also involves innate activation of the complement system. These differences suggest that localized complement activation in adult mouse injuries might induce regeneration instead of the default fibrosis and scar formation. Localized complement activation is feasible by antigen/antibody interaction between biodegradable nanoparticles presenting α-gal epitopes (α-gal nanoparticles) and the natural anti-Gal antibody which is abundant in humans. Administration of α-gal nanoparticles into injuries of anti-Gal-producing adult mice results in localized complement activation which induces rapid and extensive macrophage recruitment. These macrophages bind anti-Gal-coated α-gal nanoparticles and polarize into M2 pro-regenerative macrophages that orchestrate accelerated scar-free regeneration of skin wounds and regeneration of myocardium injured by myocardial infarction (MI). Furthermore, injection of α-gal nanoparticles into spinal cord injuries of anti-Gal-producing adult mice induces recruitment of M2 macrophages, that mediate extensive angiogenesis and axonal sprouting, which reconnects between proximal and distal severed axons. Thus, α-gal nanoparticle treatment in adult mice mimics physiologic regeneration in amphibians. These studies further suggest that α-gal nanoparticles may be of significance in the treatment of human injuries.

Pregnancy as a susceptible state for thrombotic microangiopathies.

Pregnancy and the postpartum period represent phases of heightened vulnerability to thrombotic microangiopathies (TMAs), as evidenced by distinct patterns of pregnancy-specific TMAs (e.g., preeclampsia, HELLP syndrome), as well as a higher incidence of nonspecific TMAs, such as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, during pregnancy. Significant strides have been taken in understanding the underlying mechanisms of these disorders in the past 40 years. This progress has involved the identification of pivotal factors contributing to TMAs, such as the complement system, ADAMTS13, and the soluble VEGF receptor Flt1. Regardless of the specific causal factor (which is not generally unique in relation to the usual multifactorial origin of TMAs), the endothelial cell stands as a central player in the pathophysiology of TMAs. Pregnancy has a major impact on the physiology of the endothelium. Besides to the development of placenta and its vascular consequences, pregnancy modifies the characteristics of the women's microvascular endothelium and tends to render it more prone to thrombosis. This review aims to delineate the distinct features of pregnancy-related TMAs and explore the contributing mechanisms that lead to this increased susceptibility, particularly influenced by the "gravid endothelium." Furthermore, we will discuss the potential contribution of histopathological studies in facilitating the etiological diagnosis of pregnancy-related TMAs.

Free PEG Suppresses Anaphylaxis to PEGylated Nanomedicine in Swine.

Covalent conjugation of poly(ethylene glycol) (PEG) is frequently employed to enhance the pharmacokinetics and biodistribution of various protein and nanoparticle therapeutics. Unfortunately, some PEGylated drugs can induce elevated levels of antibodies that can bind PEG, i.e., anti-PEG antibodies (APA), in some patients. APA in turn can reduce the efficacy and increase the risks of allergic reactions, including anaphylaxis. There is currently no intervention available in the clinic that specifically mitigates allergic reactions to PEGylated drugs without the use of broad immunosuppression. We previously showed that infusion of high molecular weight free PEG could safely and effectively suppress the induction of APA in mice and restore prolonged circulation of various PEGylated therapeutics. Here, we explored the effectiveness of free PEG as a prophylaxis against anaphylaxis induced by PEG-specific allergic reactions in swine. Injection of PEG-liposomes (PL) resulted in anaphylactoid shock (pseudoanaphylaxis) within 1-3 min in both naïve and PL-sensitized swine. In contrast, repeated injection of free PEG alone did not result in allergic reactions, and injection of free PEG effectively suppressed allergic reactions to PL, including in previously PL-sensitized swine. These results strongly support the further investigation of free PEG for reducing APA and allergic responses to PEGylated therapeutics.

A Prospective Study on Complement Activation Distinguishes Focal Segmental Glomerulosclerosis from Minimal Change Disease.

Introduction: Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) are related podocytopathies with distinct kidney outcomes. Surprisingly, elevated urinary activation fragments have been found in FSGS despite little complement deposition on immunofluorescence (IF) staining. Whether complement activation distinguishes FSGS from MCD, participating in the development of segmental lesions, remains unknown. Methods: We performed an observational study in patients with MCD and FSGS, and proteinuria ≥1 g/g of creatinine. We included both primary and secondary or unknown causes. We compared urinary fragments of terminal pathway activation, sC5b9, and C5a expressed as creatinine ratios, between MCD and FSGS. Results: Patients with FSGS (n = 41) had a serum albumin of 31±10 g/l and proteinuria of 5.1 (2.6-9.1) g/g at sampling, whereas those with MCD (n = 15) had a lower serum albumin (22 ± 9 g/l; P = 0.002), and a proteinuria of 3.8 (1.9-7.7) g/g (P = 0.40). Urinary sC5b9 and C5a were 8.7 (1.7-52.3) and 1.26 (0.45-1.84) µg/mmol of creatinine, respectively in patients with FSGS; compared to 0.8 (0.0-1.5) and 0.06 (0.01-0.15) µg/mmol of creatinine in MCD (P < 0.001), respectively. We found no association between urinary complement fragments and age, estimated glomerular filtration rate (eGFR), or chronic kidney lesions. When analyzing samples with proteinuria ≥ 3 g/g, the c-statistics for urinary sC5b9 and C5a were 0.96 and 1.00, respectively, in differentiating FSGS from MCD. Conclusion: We found no urinary complement activation fragments in MCD, in comparison to FSGS, despite similar levels of proteinuria. This suggests a role for complement activation in the pathogenesis of FSGS and provides an additional tool for distinguishing these 2 entities.

Unmasking the long-term effects: unravelling neuropsychiatric and neurological consequences of COVID-19.

The COVID-19 pandemic has not only burdened healthcare systems but has also led to a new emerging medical enigma that is post-COVID-19 syndrome or "long COVID." Characterized by persistent symptoms that extend beyond the acute phase of the illness, long COVID has rapidly become a public health concern with ambiguous neurological and neuropsychiatric dimensions. This narrative review aims at synthesizing available research to decode the long-term impacts of COVID-19 on neurological and mental health. Drawing from a multitude of studies, this review synthesizes evidence on various neuropsychiatric and neurological symptoms, including cognitive deficits, mood disorders, and more. The narrative delves into potential pathogenic mechanisms, hoping to fill existing research gaps and offering directions for future inquiry. The objective is not just academic; it has immediate real-world implications. Understanding these long-term effects is crucial for developing effective treatments and interventions, thereby better serving the millions of individuals living with these lingering symptoms. As healthcare systems continue to grapple with the fallout from the pandemic, this review provides much-needed context and insights into an area that demands urgent research and action.

Pharmacodynamics and Mechanism of Astragali Radix and Anemarrhenae Rhizoma in Treating Chronic Heart Failure by Inhibiting Complement Activation.

Astragali radix (AR) and anemarrhenae rhizoma (AAR) are used clinically in Chinese medicine for the treatment of chronic heart failure (CHF), but the exact therapeutic mechanism is unclear. In this study, a total of 60 male C57BL/6 mice were divided into 5 groups, namely sham, model, AR, AAR, and AR-AAR. In the sham group, the chest was opened without ligation. In the other groups, the chest was opened and the transverse aorta was ligated to construct the transverse aortic constriction model. After 8 weeks of feeding, mice were given medicines by gavage for 4 weeks. Left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) were detected by echocardiography. Heart weight index (HWI) and wheat germ agglutinin staining were used to evaluate cardiac hypertrophy. Hematoxylin-eosin staining was used to observe the pathological morphology of myocardial tissue. Masson staining was used to evaluate myocardial fibrosis. The content of serum brain natriuretic peptide (BNP) was detected by enzyme-linked immunosorbent assay kit. The content of serum immunoglobulin G (IgG) was detected by immunoturbidimetry. The mechanism of AR-AAR in the treatment of CHF was explored by proteomics. Western blot was used to detect the protein expressions of complement component 1s (C1s), complement component 9 (C9), and terminal complement complex 5b-9 (C5b-9). The results show that AR-AAR inhibits the expression of complement proteins C1s, C9, and C5b-9 by inhibiting the production of IgG antibodies from B cell activation, which further inhibits the complement activation, attenuates myocardial fibrosis, reduces HWI and cardiomyocyte cross-sectional area, improves cardiomyocyte injury, reduces serum BNP release, elevates LVEF and LVFS, improves cardiac function, and exerts myocardial protection.

Anticardiolipin Antibody Plays a More Important Role Than Anti-ß2-Glycoprotein I Antibody in Activating Complement in Patients with Lupus Nephritis.

Objective: This research aimed to explore the correlation between antiphospholipid antibodies (aPLs) and complement activation in lupus nephritis (LN) patients. Methods: A retrospective analysis was carried out on patients diagnosed with LN based on renal biopsy from June 2019 to June 2022. The study assessed levels of IgM, IgA, and IgG subtypes of anticardiolipin antibodies (aCLs) and anti-ß2-glycoprotein I (anti-ß2-GPI) antibodies. Pathological and clinical data were collected concurrently with the renal biopsy. Results: The analysis included 76 LN patients, with 44.7% testing positive for aPLs. LN patients with positive aPLs exhibited increased hematuria, higher SLEDAI scores, reduced serum C3 and C4 levels, and more C1q deposits in the glomerulus compared to those with negative aPLs (P<0.05). Correlation analysis demonstrated the inverse relationships between IgG-aCL levels and serum C3 and C4 levels (r=-0.29, P=0.005; r=-0.24, P=0.016, respectively), as well as a positive correlation with C4 deposits in the glomerulus (r=0.20, P=0.041). Conclusion: This investigation suggests that aPLs, particularly IgG-aCLs, may be associated with the severity of LN and could contribute to the activation of classical complement pathways.

Systematic Review of the Link Between Oxford MEST-C Classification and Complement Activation in IgA Nephropathy.

Introduction: IgA nephropathy's (IgAN's) MEST-C classification relationship with complement activation is still not fully understood because of limited and conflicting evidence. Our study aimed to delineate this relationship through a systematic review. Methods: We adhered to the Preferred Reporting Items for Systematic Review and Meta-analysis guidelines and conducted a systematic review, utilizing databases like MEDLINE (PubMed), Embase, Scopus, and Cochrane from January 2016 (year of updated MEST-C classification) to January 2023. We specifically selected studies that employed established methods to evaluate complement activation and the MEST-C classification. Results: A total of 34 studies with 10,082 patients were included. Among these, 7 studies focused on the pediatric population (500 patients), and 22 studies involved 8128 patients from Asian populations. C4d, C3, C5b9, MBL, C4, and factor H-related protein 5 (FHR5) were the most frequently studied complement proteins in relation to the MEST-C classification. Complement activation assessment was primarily conducted using immunofluorescence and immunohistochemistry on kidney biopsy specimens. All complement proteins investigated showed associations with the C1-2 class. Notably, FB, FH, MASP1/3, MASP2, C5a, and C5b9 from the alternative, lectin, and terminal pathways were uniquely present in the C1-2 class. Whereas C3, FHR5, C4, and C4d were associated with all the MEST-C classes. Conclusion: We found evidence supporting the involvement of alternative and lectin complement pathways across all MEST-C classes. All examined complement factors were associated with the C1-2 class, emphasizing the critical role of complement activation, possibly at the endothelial surface. These findings may guide the development of personalized treatment strategies targeting complement pathways in relation to the MEST-C lesions.

Serum Uric Acid Associates with Systemic Complement C3 Activation in Severe ANCA-Associated Renal Vasculitides.

Involvement of the complement system is key to the pathogenesis of antineutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis, but immunometabolic implications, especially on serum uric acid (UA) levels, still need to be elucidated. A total of 34 patients with biopsy-proven ANCA-associated renal vasculitis between 2015 and 2020 were retrospectively enrolled. Serum UA levels were correlated with clinical and histopathological characteristics, separated for critically ill (CI, n = 19), myeloperoxidase (MPO)-ANCA (n = 21) and proteinase 3 (PR3)-ANCA (n = 13) subgroups. We here identified inverse correlations of serum UA levels and complement C3 levels in the total cohort (p = 0.005) and the CI subgroup (p < 0.001). Intrarenal complement C4d deposition in venules correlated with serum UA levels in the total cohort (p = 0.007) and in the CI subgroup (p = 0.016). Significant associations of serum UA levels and tubulitis in areas of scarred cortex (t-IFTA) were identified in the total cohort (p = 0.008), and both subgroups of CI (p = 0.034) and MPO-ANCA (p = 0.029). In PR3-ANCA, interstitial fibrosis (ci) was observed as the strongest association with serum UA levels (p = 0.022). Our observations broaden our current understanding of contributory metabolic factors that influence the initial disease course in ANCA-associated renal vasculitis.

Storage of Transfusion Platelet Concentrates Is Associated with Complement Activation and Reduced Ability of Platelets to Respond to Protease-Activated Receptor-1 and Thromboxane A2 Receptor.

Platelet activation and the complement system are mutually dependent. Here, we investigated the effects of storage time on complement activation and platelet function in routinely produced platelet concentrates. The platelet concentrates (n = 10) were stored at 22 °C for seven days and assessed daily for complement and platelet activation markers. Additionally, platelet function was analyzed in terms of their responsiveness to protease-activated receptor-1 (PAR-1) and thromboxane A2 receptor (TXA2R) activation and their capacity to adhere to collagen. Complement activation increased over the storage period for all analyzed markers, including the C1rs/C1-INH complex (fold change (FC) = 1.9; p < 0.001), MASP-1/C1-INH complex (FC = 2.0; p < 0.001), C4c (FC = 1.8, p < 0.001), C3bc (FC = 4.0; p < 0.01), and soluble C5b-9 (FC = 1.7, p < 0.001). Furthermore, the levels of soluble platelet activation markers increased in the concentrates over the seven-day period, including neutrophil-activating peptide-2 (FC = 2.5; p < 0.0001), transforming growth factor beta 1 (FC = 1.9; p < 0.001) and platelet factor 4 (FC = 2.1; p < 0.0001). The ability of platelets to respond to activation, as measured by surface expression of CD62P and CD63, decreased by 19% and 24% (p < 0.05) for PAR-1 and 69-72% (p < 0.05) for TXA2R activation, respectively, on Day 7 compared to Day 1. The extent of platelet binding to collagen was not significantly impaired during storage. In conclusion, we demonstrated that complement activation increased during the storage of platelets, and this correlated with increased platelet activation and a reduced ability of the platelets to respond to, primarily, TXA2R activation.