Resolution of extravascular hemolysis with oral iptacopan monotherapy in a patient with treatment experienced paroxysmal nocturnal hemoglobinuria (PNH).

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematologic disorder characterized by a loss of glycosyl-phosphatidyl-inositol-linked (GPI) proteins on various hematopoietic cells. Some GPI proteins are involved in the regulation of the complement system, and their absence renders erythrocytes susceptible to complement-mediated lysis. Current standard of care in PNH is to block the complement system at the level of C5 using ravulizumab or eculizumab; however, some patients with PNH may develop extravascular hemolysis (EVH) during treatment with C5 inhibitors. The proximal complement inhibitor iptacopan has recently been shown to be efficacious in patients with PNH. This article reports on a 43-year-old female patient with PNH who was successfully treated with iptacopan. The patient had received ravulizumab for several years and developed a clinically relevant EVH. After obtaining informed consent, the patient received oral iptacopan 200 mg twice daily and ravulizumab was discontinued. Over the next few weeks hemoglobin levels and reticulocyte counts normalized. The patient reported mild flushes with erythema, chills, and mild muscle pain, all of which resolved during follow-up. No breakthrough hemolysis occurred, and no severe adverse events were recorded.

[Coagulation and complement crosstalk: molecular mechanisms of complement-mediated diseases].

The complement and coagulation systems are ancestrally related mechanisms of serine protease-induced protein activation. Recent studies have shown that the complement system enhances platelet aggregation by activating platelets and vascular endothelial cells. This system is also involved in the expression of tissue factor, which induces the coagulation reaction. Activated platelets and coagulation factors are also known to activate the complement system. In diseases involving the complement system, such as paroxysmal nocturnal hemoglobinuria, autoimmune hemolytic anemia, and atypical hemolytic uremic syndrome, excessive activation of this system contributes to complement-mediated thrombosis. The anti-C5 antibody eculizumab has shown a remarkable thromboprophylactic effect in these complement diseases. The recent surge in development of new anti-complement agents has raised expectations for the advancement of treatments and preventive measures for thrombosis associated with complement disorders. This review outlines the crosstalk between these two systems, and describes the mechanisms of several diseases featuring both thrombosis and complement activation.

Infantile Bullous Pemphigoid: A Case Report.

Background: Infantile bullous pemphigoid (IBP) is an exceptionally rare acquired autoimmune subepidermal bullous disorder characterized by vesicles, bullae, and additional manifestations, such as urticarial and infiltrated papules, plaques, or eczematous lesions. These skin lesions can lead to eroded and crusted regions after healing, and in some cases, rapid blister rupturing causes extensively eroded areas. Reporting these rare cases is crucial to improving our understanding, diagnosis, and treatment of IBP. Case Presentation: In this report, we present the clinical case of a 4-month-old male infant with generalized tense bullae causing irritability and sleeplessness. This case highlights the distinctive clinical features of IBP, including the development of multiple generalized tense bullae over 2 weeks. The pathological examination findings confirmed the diagnosis of IBP. Conclusion: This case emphasizes the significance of early identification and proper management of IBP. Our thorough assessment, which incorporates pathological verification and therapeutic interventions, has advanced our understanding of IBP. Additionally, this case underscores the vital need for timely diagnosis and personalized treatment approaches for affected infants.

Emerging treatment landscape for Guillain-Barré Syndrome (GBS): what's new?

INTRODUCTION: Guillain-Barré syndrome (GBS) is a monophasic immune neuropathic disorder characterized by acute paralysis. A significant portion of patients are left with residual deficits, which presents a considerable global healthcare challenge. The precise mechanisms underlying GBS pathogenesis are not fully elucidated. Recent studies have focused on postinfectious molecular mimicry and identified involvement of IgG autoantibodies and innate immune effectors in GBS. Intravenous immunoglobulins (IVIg) and plasma exchange (PE) are two established evidence-based immunomodulatory treatments for GBS, but a significant proportion of GBS patients fails to respond adequately to either therapy. This emphasizes an urgent need for novel and more potent treatments. AREAS COVERED: We discuss novel immunomodulatory therapies presently at different phases of preclinical and clinical investigation. Some drugs in development target pathophysiologic mechanisms such as IgG autoantibody catabolism and complement activation, which are relevant to GBS. EXPERT OPINION: There is an unmet need for more effective immune therapies for GBS. New immunomodulatory therapies under development may provide more potent options for GBS patients who do not respond to IVIg or PE. Future directions may include incorporating neuroprotective interventions based on evolving understanding of mechanisms underlying nerve injury and axonal degeneration.

Proangiogenic properties of complement protein C1q can contribute to endometriosis.

Endometriosis (EM) is defined as the engraftment and proliferation of functional endometrial-like tissue outside the uterine cavity, leading to a chronic inflammatory condition. While the precise etiology of EM remains elusive, recent studies have highlighted the crucial involvement of a dysregulated immune system. The complement system is one of the predominantly altered immune pathways in EM. Owing to its involvement in the process of angiogenesis, here, we have examined the possible role of the first recognition molecule of the complement classical pathway, C1q. C1q plays seminal roles in several physiological and pathological processes independent of complement activation, including tumor growth, placentation, wound healing, and angiogenesis. Gene expression analysis using the publicly available data revealed that C1q is expressed at higher levels in EM lesions compared to their healthy counterparts. Immunohistochemical analysis confirmed the presence of C1q protein, being localized around the blood vessels in the EM lesions. CD68+ macrophages are the likely producer of C1q in the EM lesions since cultured EM cells did not produce C1q in vitro. To explore the underlying reasons for increased C1q expression in EM, we focused on its established pro-angiogenic role. Employing various angiogenesis assays on primary endothelial endometriotic cells, such as migration, proliferation, and tube formation assays, we observed a robust proangiogenic effect induced by C1q on endothelial cells in the context of EM. C1q promoted angiogenesis in endothelial cells isolated from EM lesions (as well as healthy ovary that is also rich in C1q). Interestingly, endothelial cells from EM lesions seem to overexpress the receptor for the globular heads of C1q (gC1qR), a putative C1q receptor. Experiments with siRNA to silence gC1qR resulted in diminished capacity of C1q to perform its angiogenic functions, suggesting that C1q is likely to engage gC1qR in the pathophysiology of EM. gC1qR can be a potential therapeutic target in EM patients that will disrupt C1q-mediated proangiogenic activities in EM.

Systematic review of the complement components as potential biomarkers of pre-eclampsia: pitfalls and opportunities.

The complement system (C) is a crucial component of the innate immune system. An increasing body of research has progressively shed light on the pivotal role of C in immunological tolerance at the feto-maternal interface. Excessive C activation or impaired C regulation may determine the onset of pregnancy-related pathological conditions, including pre-eclampsia (PE). Thus, several studies have investigated the presence of C components or split products in blood matrixes (i.e., plasma, serum), urine, and amniotic fluid in PE. In the current study, we systematically reviewed the currently available scientific literature reporting measurements of C components as circulating biomarkers in PE, based on a literature search using Pubmed, Scopus, and Embase databases. A total of 41 out of 456 studies were selected after full-text analysis. Fourteen studies (34.1%) were identified as measuring the blood concentrations of the classical pathway, 5 (12.1%) for the lectin pathway, 28 (68.3%) for the alternative pathway, 17 (41.5%) for the terminal pathway components, and 16 (39%) for C regulators. Retrieved results consistently reported C4, C3, and factor H reduction, and increased circulating levels of C4d, Bb, factor D, C3a, C5a, and C5b-9 in PE compared to normal pregnancies, depicting an overall scenario of excessive C activation and aberrant C regulation. With evidence of C activation and dysregulation, C-targeted therapy is an intriguing perspective in PE management. Moreover, we also discussed emerging pitfalls in C analysis, mainly due to a lack of experimental uniformity and biased cohort selection among different studies and laboratories, aiming to raise a more comprehensive awareness for future standardization. Systematic review registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42024503070.

Efficacy and safety of eculizumab in Guillain-Barré syndrome: A phase 3, multicenter, double-blind, randomized, placebo-controlled clinical trial.

BACKGROUND AND AIMS: Guillain-Barré syndrome (GBS) is an acute, self-limited, immune-mediated peripheral neuropathy. Current treatments for GBS include intravenous immunoglobulin (IVIg) and plasma exchange, which may not sufficiently benefit severely affected patients. This study evaluated the efficacy and safety of eculizumab add-on therapy to IVIg (standard-of-care treatment) in patients with severe GBS. METHODS: This phase 3, multicenter, double-blind, randomized, placebo-controlled clinical trial (NCT04752566), enrolled Japanese adults (age ≥ 18 years) with severe GBS (Hughes functional grade [FG] score FG3 or FG4/FG5 within 2 weeks of onset of GBS). Participants were randomized 2:1 to receive intravenous infusion of eculizumab or placebo (once weekly for 4 weeks) with IVIg treatment with 20 weeks of follow-up. Primary efficacy endpoint was the time to first reach FG score ≤1 (able to run). Key secondary endpoints were proportion of participants achieving FG ≤1 at weeks 8 and 24 and FG improvement ≥3 at week 24. Pharmacodynamic analysis of serum free C5 concentration over time was performed. Safety was evaluated. RESULTS: The analysis included 57 participants (eculizumab, n = 37; placebo, n = 20). Primary endpoint was not achieved (hazard ratio, 0.9; 95% CI, 0.45-1.97; p = .89). Key secondary endpoints did not reach statistical significance. Serum C5 concentration was reduced by 99.99% at 1 h postdose and sustained to week 5 but returned to baseline at the end of follow-up period. No new safety signals for eculizumab were identified. INTERPRETATION: Although well tolerated, eculizumab treatment did not show significant effects on motor function recovery compared to placebo in patients with GBS.

Identification of disease phenotypes in acetylcholine receptor-antibody myasthenia gravis using proteomics-based consensus clustering.

BACKGROUND: The clinical heterogeneity of myasthenia gravis (MG), an autoimmune disease defined by antibodies (Ab) directed against the postsynaptic membrane, constitutes a challenge for patient stratification and treatment decision making. Novel strategies are needed to classify patients based on their biological phenotypes aiming to improve patient selection and treatment outcomes. METHODS: For this purpose, we assessed the serum proteome of a cohort of 140 patients with anti-acetylcholine receptor-Ab-positive MG and utilised consensus clustering as an unsupervised tool to assign patients to biological profiles. For in-depth analysis, we used immunogenomic sequencing to study the B cell repertoire of a subgroup of patients and an in vitro assay using primary human muscle cells to interrogate serum-induced complement formation. FINDINGS: This strategy identified four distinct patient phenotypes based on their proteomic patterns in their serum. Notably, one patient phenotype, here named PS3, was characterised by high disease severity and complement activation as defining features. Assessing a subgroup of patients, hyperexpanded antibody clones were present in the B cell repertoire of the PS3 group and effectively activated complement as compared to other patients. In line with their disease phenotype, PS3 patients were more likely to benefit from complement-inhibiting therapies. These findings were validated in a prospective cohort of 18 patients using a cell-based assay. INTERPRETATION: Collectively, this study suggests proteomics-based clustering as a gateway to assign patients to a biological signature likely to benefit from complement inhibition and provides a stratification strategy for clinical practice. FUNDING: CN and CBS were supported by the Forschungskommission of the Medical Faculty of the Heinrich Heine University Düsseldorf. CN was supported by the Else Kröner-Fresenius-Stiftung (EKEA.38). CBS was supported by the Deutsche Forschungsgemeinschaft (DFG-German Research Foundation) with a Walter Benjamin fellowship (project 539363086). The project was supported by the Ministry of Culture and Science of North Rhine-Westphalia (MODS, "Profilbildung 2020" [grant no. PROFILNRW-2020-107-A]).

The complement system as a target in cancer immunotherapy.

Malignant cells are part of a complex network within the tumor microenvironment, where their interaction with host cells and soluble mediators, including complement components, is pivotal. The complement system, known for its role in immune defense and homeostasis, exhibits a dual effect on cancer progression. This dichotomy arises from its antitumoral opsonophagocytosis and cytotoxicity versus its protumoral chronic inflammation mediated by the C5a/C5aR1 axis, influencing antitumor T-cell responses. Recent studies have revealed distinct co-expression patterns of complement genes in various cancer types, correlating with prognosis. Notably, some cancers exhibit co-regulated overexpression of complement genes associated with poor prognosis, while others show favorable outcomes. However, significant intra-patient heterogeneity further complicates this classification. Moreover, the involvement of locally produced and intracellular complement proteins adds complexity to the tumor microenvironment dynamics. This review highlights the unique interplay of complement components within different cancers and patient cohorts, showing that "one size does not fit all", for complement in cancer. It summarizes the clinical trials for complement targeting in cancer, emphasizing the need for tailored therapeutic approaches. By elucidating the mechanistic basis of complement's context-dependent role, this review aims to facilitate the development of personalized cancer therapies, ultimately improving patient care and outcomes.

Correlation between neuropsychiatric systemic lupus erythematosus and immunological markers: a real-world retrospective study.

OBJECTIVES: This study aimed to investigate disparities in clinical profiles and autoantibody patterns between patients with and without neuropsychiatric systemic lupus erythematosus (NPSLE) in a cohort and to identify risk factors associated with NPSLE in the Chinese population. METHODS: SLE patients were retrospectively reviewed from two tertiary hospitals. The relationships between NPSLE and immunological biomarkers were explored. RESULTS: Among the 945 SLE patients, 75 (7.94%) were diagnosed with NPSLE. The most prevalent NP manifestations involved cognitive disorder (30.67%), headache (26.67%), seizure disorder (26.67%), and psychosis (26.67%).We observed significant associations between psychosis and anti-ß2GPI antibodies (F = 6.092, p = 0.015), polyneuropathy and anti-Scl70 antibodies (F = 20.161, p < 0.001), demyelinating syndrome and anti-cardiolipin antibodies (F = 6.637, p = 0.011), myasthenia gravis and anti-RNP (F = 5.864, p = 0.017), and anti-Smith antibodies (F = 5.096, p = 0.026). Multivariate logistics analysis showed that anti-prothrombin (aPT) IgM antibodies (OR = 10.985, CI 1.279-94.343, p = 0.029), age (OR = 1.169, CI 1.032-1.325, p = 0.014), and serum creatinine (SCr) (OR = 1.014, CI 1.003-1.025, p = 0.009) were independent risk factors of NPSLE, while anti-Sjogren syndrome antigen B (SSB) antibodies (OR 0.023, CI 0.002-0.622, p = 0.023) and high complement C3 (OR = 0.001, CI 0-0.045, p < 0.001) indicated reduced risk of NPSLE. CONCLUSION: Various neuropsychiatric manifestations in SLE were found to be correlated with specific autoantibodies. Independent risk factors for NPSLE included aPT IgM antibodies, age, and elevated serum creatinine, while the absence of anti-SSB antibodies and low complement C3 levels were associated with increased risk. KEY POINTS: •Significant associations were found between specific autoantibodies and neuropsychiatric symptoms, shedding light on potential biomarkers for predicting and understanding NPSLE. •The study identifies independent risk factors for NPSLE in the Chinese population, including the presence of anti-prothrombin IgM antibodies, older age, elevated serum creatinine, and lower complement C3 levels.

Consensus recommendations for optimising the diagnosis and treatment of paroxysmal nocturnal haemoglobinuria in Singapore.

Introduction: Paroxysmal nocturnal haemoglobinuria (PNH) is a rare haematologic disease characterised by intravascular haemolysis, thrombophilia and bone marrow failure. There is a lack of established clinical guidance on the screening, diagnosis and manage-ment of PNH in Singapore. A relatively low level of awareness among healthcare professionals regarding PNH manifestations further contributes to diagnostic delays. Additionally, limited access to complement inhibitors, like eculizumab, may delay treatment and impact patient outcomes. Method: Nine haematologists from different institu-tions in Singapore convened to formulate evidence-based consensus recommendations for optimising the diagnosis and management of patients with PNH and improving access to novel treatments. The experts reviewed the existing literature and international guidelines published from January 2010 to July 2023, focusing on 7 clinical questions spanning PNH screening, diagnostic criteria, investigations, treatment and monitoring of subclinical and classic disease, PNH with underlying bone marrow disorders, and PNH in pregnancy. A total of 181 papers were reviewed to formulate the statements. All experts voted on the statements via 2 rounds of Delphi and convened for an expert panel discussion to finetune the recommendations. Results: Sixteen statements have been formulated for optimising the screening, diagnosis and management of PNH. Upon confirmation of PNH diagnosis, individuals with active haemolysis and/or thrombosis should be considered for anti-complement therapy, with eculizumab being the only approved drug in Singapore. Conclusion: The current recommendations aim to guide the clinicians in optimising the screening, diagnosis and management of PNH in Singapore.

Integrity of neural extracellular matrix is required for microglia-mediated synaptic remodeling.

Microglia continuously remodel synapses, which are embedded in the extracellular matrix (ECM). However, the mechanisms, which govern this process remain elusive. To investigate the influence of the neural ECM in synaptic remodeling by microglia, we disrupted ECM integrity by injection of chondroitinase ABC (ChABC) into the retrosplenial cortex of healthy adult mice. Using in vivo two-photon microscopy we found that ChABC treatment increased microglial branching complexity and ECM phagocytic capacity and decreased spine elimination rate under basal conditions. Moreover, ECM attenuation largely prevented synaptic remodeling following synaptic stress induced by photodamage of single synaptic elements. These changes were associated with less stable and smaller microglial contacts at the synaptic damage sites, diminished deposition of calreticulin and complement proteins C1q and C3 at synapses and impaired expression of microglial CR3 receptor. Thus, our findings provide novel insights into the function of the neural ECM in deposition of complement proteins and synaptic remodeling by microglia.

Sialic acids on T cells are crucial for their maintenance and survival.

Sialic acids are found as terminal sugars on glycan structures on cellular surfaces. T cells carry these sialoglycans abundantly, and they are thought to serve multiple functions in cell adhesion, cell migration, and protection from complement attack. We studied the role of sialoglycans on T cells in a mouse model with a T cell-specific deletion of cytidine monophosphate-sialic acid synthase (CMAS), the enzyme that is crucial for the synthesis of sialoglycans. These mice showed a T-cell deficiency in peripheral lymphoid organs. Many T cells with an undeleted Cmas allele were found in the periphery, suggesting that they escaped the Cre-mediated deletion. The remaining peripheral T cells of T cell-specific Cmas KO mice had a memory-like phenotype. Additional depletion of the complement factor C3 could not rescue the phenotype, showing that the T-cell defect was not caused by a host complement activity. Cmas-deficient T cells showed a high level of activated caspase 3, indicating an ongoing apoptosis. In bone marrow chimeric cellular transfer experiments, we observed a strong competitive disadvantage of Cmas-deficient T cells compared to wild-type T cells. These results show that sialoglycans on the surface of T cells are crucial for T-cell survival and maintenance. This function has not been recognized before and is similar to the function of sialoglycans on B cells.

Mass spectrometry-based proteomic profiling of extracellular vesicle proteins in diabetic and non-diabetic ischemic stroke patients: a case-control study.

Acute ischemic stroke is the most common cause of neurologic dysfunction caused by focal brain ischemia and tissue injury. Diabetes is a major risk factor of stroke, exacerbating disease management and prognosis. Therefore, discovering new diagnostic markers and therapeutic targets is critical for stroke prevention and treatment. Extracellular vesicles (EVs), with their distinctive properties, have emerged as promising candidates for biomarker discovery and therapeutic application. This case-control study utilized mass spectrometry-based proteomics to compare EVs from non-diabetic stroke (nDS = 14), diabetic stroke (DS = 13), and healthy control (HC = 12) subjects. Among 1288 identified proteins, 387 were statistically compared. Statistical comparisons using a general linear model (log2 foldchange ≥0.58 and FDR-p≤0.05) were performed for nDS vs HC, DS vs HC, and DS vs nDS. DS vs HC and DS vs nDS comparisons produced 123 and 149 differentially expressed proteins, respectively. Fibrinogen gamma chain (FIBG), Fibrinogen beta chain (FIBB), Tetratricopeptide repeat protein 16 (TTC16), Proline rich 14-like (PR14L), Inhibitor of nuclear factor kappa-B kinase subunit epsilon (IKKE), Biorientation of chromosomes in cell division protein 1-like 1 (BD1L1), and protein PR14L exhibited significant differences in the DS group. The pathway analysis revealed that the complement system pathways were activated, and blood coagulation and neuroprotection were inhibited in the DS group (z-score ≥2; p ≤ 0.05). These findings underscore the potential of EVs proteomics in identifying biomarkers for stroke management and prevention, warranting further clinical investigation.

Complement Factor B Inhibition or Deletion Is Not Sufficient to Prevent Neurodegeneration in a Murine Model of Glaucoma.

Purpose: Activation of the classical complement pathway is thought to contribute to the development and progression of glaucoma. The role of alternative complement or amplification pathways in glaucoma is not well understood. We evaluated complement factor B (FB) expression in postmortem human ocular tissues with or without glaucoma and the effect of FB inhibition and deletion in a mouse ocular hypertensive model of glaucoma induced by photopolymerized hyaluronic acid glycidyl methacrylate (HAGM). Methods: Human CFB mRNA in human eyes was assessed by RNAscope and TaqMan. HAGM model was performed on C57BL6/J mice. The effect of FB in HAGM model was evaluated with an oral FB inhibitor and Cfb-/- mice. Complement mRNA and proteins in mouse eyes were assessed by TaqMan and western blot, respectively. Results: CFB mRNA in human glaucomatous macular neural retina and optic nerve head was upregulated. Cfb mRNA is also upregulated in the HAGM model. Oral FB inhibitor, ED-79-GX17, dosed daily at 200 mg/kg for 3 days after intraocular pressure (IOP) induction in wild-type mice showed complement inhibition in ocular tissues and significantly inhibited systemic complement levels. Daily dosing of ED-79-GX17 for 30 days or Cfb deletion was also unable to prevent retinal ganglion cell or axon loss 30 days after IOP induction in mice. Conclusion: The alternative complement component FB may not substantially contribute to RGC loss in the HAGM mouse glaucoma model despite upregulation of Cfb expression and activation of the alternative pathway. The relevance of these findings to human glaucoma remains to be determined.

Infection and the Glycome─New Insights into Host Response.

Glycans play critical roles in the host-pathogen interactions leading to infection. However, we still understand very little about the dynamic nature of glycosylation in response to infection and its function in modulating host immunity. Many of the host proteins involved in immune defense are glycoproteins. Furthermore, the innate immune system recognizes glycans. The glycoform of a protein can impact proteolytic stability, receptor interactions, serum half-life, and other aspects. New, cutting-edge chemical biology tools are shedding light on the interplay between infection and the host glycome. In this review, we highlight new work on the importance of dynamic glycosylation of host proteins in the innate and adaptive immune pathways in response to infection. These include recent findings on altered glycoprofiles of mucins, complement components, and antibodies.

Glycogenolysis-Induced Astrocytic Serping1 Expression Regulates Neuroinflammatory Effects on Hippocampal neuron.

The bacterial pathogen, lipopolysaccharide (LPS), elicits microglial response and induces cytokine secretion that subsequently activates astrocytes. Recent findings have indicated that LPS-induced activation of postnatal glial cells has led to alterations in synapse formation in hippocampal and cortical neurons, thereby resulting in a prolonged increased risk for seizure or depression. Nevertheless, its mechanisms remain to be fully elucidated. Cellular metabolism has recently gained recognition as a critical regulatory mechanism for the activation of peripheral immune cells, as it supplies the requisite energy and metabolite for their activation. In the present study, we report that LPS did not change the expression of reported astrocyte-derived synaptogenic genes in the postnatal hippocampus; however, it induced upregulation of astrocytic complement component regulator Serping1 within the postnatal hippocampus. As a regulatory mechanism, activation of glycogen degradation (glycogenolysis) governs the expression of a subset of inflammatory-responsive genes including Serping1 through reactive oxygen species (ROS)-NF-κB axis. Our study further demonstrated that glycogenolysis is implicated in neurotoxic phenotypes of astrocytes, such as impaired neuronal synaptogenesis or cellular toxicity. These findings suggested that activation of glycogenolysis in postnatal astrocytes is an essential metabolic pathway for inducing responses in inflammatory astrocytes.

Complement Membrane Attack Complexes Disrupt Proteostasis to Function as Intracellular Alarmins.

Internalized pools of membrane attack complexes (MACs) promote NF-kB and dysregulated tissue inflammation. Here, we show that C9, a MAC-associated protein, promotes loss of proteostasis to become intrinsically immunogenic. Surface-bound C9 is internalized into Rab5 + endosomes whose intraluminal acidification promotes C9 aggregates. A region within the MACPF/CDC domain of C9 stimulates aggrephagy to induce NF-kB, inflammatory genes, and EC activation. This process requires ZFYVE21, a Rab5 effector, which links LC3A/B on aggresome membranes to RNF34-P62 complexes to mediate C9 aggrephagy. C9 aggregates form in human tissues, C9-associated signaling responses occur in three mouse models, and ZFYVE21 stabilizes RNF34 to promote C9 aggrephagy in vivo. Gene-deficient mice lacking ZFYVE21 in ECs showed reduced MAC-induced tissue injury in a skin model of chronic rejection. While classically defined as cytotoxic effectors, MACs may impair proteostasis, forming aggregates that behave as intracellular alarmins.

Mannan-Binding Lectin Is Associated with Inflammation and Kidney Damage in a Mouse Model of Type 2 Diabetes.

Autoreactivity of the complement system may escalate the development of diabetic nephropathy. We used the BTBR OB mouse model of type 2 diabetes to investigate the role of the complement factor mannan-binding lectin (MBL) in diabetic nephropathy. Female BTBR OB mice (n = 30) and BTBR non-diabetic WT mice (n = 30) were included. Plasma samples (weeks 12 and 21) and urine samples (week 19) were analyzed for MBL, C3, C3-fragments, SAA3, and markers for renal function. Renal tissue sections were analyzed for fibrosis, inflammation, and complement deposition. The renal cortex was analyzed for gene expression (complement, inflammation, and fibrosis), and isolated glomerular cells were investigated for MBL protein. Human vascular endothelial cells cultured under normo- and hyperglycemic conditions were analyzed by flow cytometry. We found that the OB mice had elevated plasma and urine concentrations of MBL-C (p < 0.0001 and p < 0.001, respectively) and higher plasma C3 levels (p < 0.001) compared to WT mice. Renal cryosections from OB mice showed increased MBL-C and C4 deposition in the glomeruli and increased macrophage infiltration (p = 0.002). Isolated glomeruli revealed significantly higher MBL protein levels (p < 0.001) compared to the OB and WT mice, and no renal MBL expression was detected. We report that chronic inflammation plays an important role in the development of DN through the binding of MBL to hyperglycemia-exposed renal cells.