Novel C5a regulators in inflammatory disease

SARS-CoV-2 and Guillain-Barré Syndrome: Lessons from Viral Infections

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. COVID-19 has a broad clinical spectrum from asymptomatic patients to multiorgan dysfunction and septic shock. Most of the common symptoms of COVID-19 are classified as respiratory disorders, but some reports show neurological involvements. During the COVID-19 pandemic, a case series of neurological complications, such as Guillain-Barré syndrome (GBS), were reported. GBS is a neuroimmune disorder with acute inflammatory radicular polyneuropathy in different parts of the peripheral nerve. Some studies have reported GBS as an inflammatory neuropathy related to various viral infections, such as cytomegalovirus (CMV), Epstein-Barr Virus (EBV), herpes simplex virus (HSV), human immunodeficiency virus (HIV), influenza, and Zika virus. There are some immunomodulation approaches for the management of GBS. Studies have evaluated the effects of the various therapeutic approaches, including intravenous immunoglobulin (IVIG), plasma exchange (PE), complement inhibitors, and corticosteroids to regulate overactivation of immune responses during GBS in experimental and clinical studies. In this regard, the possible association between GBS and SARS-CoV-2 infection during the outbreak of the current pandemic and also the mentioned therapeutic approaches were reviewed.

Sequential Therapy of Acute Kidney Injury with a DNA Nanodevice

The high demand for acute kidney injury (AKI) therapy calls the development of multifunctional nanomedicine for renal management with programmable pharmacokinetics. Here, we developed a renal-accumulating DNA nanodevice with exclusive kidney retention for longitudinal protection of AKI in different stages in a renal ischemia-reperfusion (I/R) model. Due to the prolonged kidney retention time (>12 h), the ROS-sensitive nucleic acids of the nanodevice could effectively alleviate oxidative stress by scavenging ROS in stage I, and then the anticomplement component 5a (aC5a) aptamer loaded nanodevice could sequentially suppress the inflammatory responses by blocking C5a in stage II, which is directly related to the cytokine storm. This sequential therapy provides durable and pathogenic treatment of kidney dysfunction based on successive pathophysiological events induced by I/R, which holds great promise for renal management and the suppression of the cytokine storm in more broad settings including COVID-19.

Clinical and Pathophysiological Insights Into Immunological Mediated Glomerular Diseases in Childhood

The kidney is often the target of immune system dysregulation in the context of primary or systemic disease. In particular, the glomerulus represents the anatomical entity most frequently involved, generally as the expression of inflammatory cell invasion or circulant or in situ immune-complex deposition. Glomerulonephritis is the most common clinical and pathological manifestation of this involvement. There are no universally accepted classifications for glomerulonephritis. However, recent advances in our understanding of the pathophysiological mechanisms suggest the assessment of immunological features, biomarkers, and genetic analysis. At the same time, more accurate and targeted therapies have been developed. Data on pediatric glomerulonephritis are scarce and often derived from adult studies. In this review, we update the current understanding of the etiologic events and genetic factors involved in the pathogenesis of pediatric immunologically mediated primitive forms of glomerulonephritis, together with the clinical spectrum and prognosis. Possible new therapeutic targets are also briefly discussed.

Significance of Complement System in Ischemic Stroke: A Comprehensive Review

The complement system is an essential part of innate immunity, typically conferring protection via eliminating pathogens and accumulating debris. However, the defensive function of the complement system can exacerbate immune, inflammatory, and degenerative responses in various pathological conditions. Cumulative evidence indicates that the complement system plays a critical role in the pathogenesis of ischemic brain injury, as the depletion of certain complement components or the inhibition of complement activation could reduce ischemic brain injury. Although multiple candidates modulating or inhibiting complement activation show massive potential for the treatment of ischemic stroke, the clinical availability of complement inhibitors remains limited. The complement system is also involved in neural plasticity and neurogenesis during cerebral ischemia. Thus, unexpected side effects could be induced if the systemic complement system is inhibited. In this review, we highlighted the recent concepts and discoveries of the roles of different kinds of complement components, such as C3a, C5a, and their receptors, in both normal brain physiology and the pathophysiology of brain ischemia. In addition, we comprehensively reviewed the current development of complement-targeted therapy for ischemic stroke and discussed the challenges of bringing these therapies into the clinic. The design of future experiments was also discussed to better characterize the role of complement in both tissue injury and recovery after cerebral ischemia. More studies are needed to elucidate the molecular and cellular mechanisms of how complement components exert their functions in different stages of ischemic stroke to optimize the intervention of targeting the complement system.

Anti-C5a complementary peptide mitigates zymosan-induced severe peritonitis with fibrotic encapsulation in rats pretreated with methylglyoxal

In a previous study of fungal peritoneal injury in peritoneal dialysis patients, complement (C)-dependent pathological changes were developed in zymosan (Zy)-induced peritonitis by peritoneal scraping. However, the injuries were limited to the parietal peritoneum and did not show any fibrous encapsulation of the visceral peritoneum, which differs from human encapsular peritoneal sclerosis (EPS). We investigated peritoneal injury in a rat model of Zy-induced peritonitis pretreated with methylglyoxal (MGO) instead of scraping (Zy/MGO peritonitis) to clarify the role of C in the process of fibrous encapsulation of the visceral peritoneum. Therapeutic effects of an anti-C5a complementary peptide, AcPepA, on peritonitis were also studied. In Zy/MGO peritonitis, peritoneal thickness, fibrin exudation, accumulation of inflammatory cells, and deposition of C3b and C5b-9 with loss of membrane C regulators were increased along the peritoneum until day 5. On day 14, fibrous encapsulation of the visceral peritoneum was observed, resembling human EPS. Peritoneal injuries and fibrous changes were significantly improved with AcPepA treatment, even when AcPepA was administered following injection of Zy in Zy/MGO peritonitis. The data show that C5a might play a role in the development of encapsulation-like changes in the visceral peritoneum in Zy/MGO peritonitis. AcPepA might have therapeutic effects in fungal infection-induced peritoneal injury by preventing subsequent development of peritoneal encapsulation.

Anti-C5a complementary peptide ameliorates acute peritoneal injury induced by neutralization of Crry and CD59

In peritoneal dialysis (PD) therapy, physical stresses such as exposure to peritoneal dialysate, catheter trauma, and peritonitis may induce peritoneal injury that can prevent continued long-term PD therapy. Therefore, protection of the peritoneum is an important target to enable long-term PD therapy in patients with end-stage renal disease. We previously showed that neutralization of the membrane complement regulators (CRegs) Crry and CD59 in rat peritoneum provokes development of acute peritoneal injury due to uncontrolled complement activation. C5a is a key effecter molecule of the complement system released during acute inflammation. Control of C5a has been proposed as a strategy to suppress inflammatory reactions and, because peritoneal injury is accompanied by inflammation, we hypothesized that C5a targeted therapy might be an effective way to suppress peritoneal injury. In the present study we used an established acute peritonitis model induced by neutralization of CRegs to investigate the effects on acute peritoneal injury of inhibiting C5a. Intravenous administration of an anti-C5a complementary peptide (AcPepA) up to 4 h after induction of injury significantly and dose-dependently prevented accumulation of inflammatory cells and reduced tissue damage in the model, accompanied by decreased C3b deposition. We show that C5a contributed to the development of peritoneal injury. Our results suggest that C5a is a target for preventing or treating peritoneal injury in patients undergoing prolonged PD therapy or with infectious complications.

Modulation of the complement system in monocytes contributes to tuberculosis-associated immune reconstitution inflammatory syndrome

OBJECTIVE

Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is a common complication in HIV-TB co-infected patients receiving combined antiretroviral therapy (cART). This study investigated a putative contribution of monocytes to the development of TB-IRIS.

DESIGN

A prospective study was designed to compare gene expression between patients who developed TB-IRIS with matched non-TB-IRIS controls.

METHODS

We performed a hypothesis-generating transcriptome analysis on monocytes of HIV-TB co-infected patients. Identified pathways were subsequently analysed in patients' monocytes before and shortly after cART initiation, in a technically independent set-up (nCounter). Additionally, protein expression and enzymatic activities of specific factors were assessed at the systemic level.

RESULTS

Pathway analysis of microarray datasets and focused gene expression study revealed that, even before initiation of cART, the complement system is dysregulated in HIV-TB co-infected patients who are predisposed to developing TB-IRIS. Detailed analysis revealed differences between TB-IRIS patients and matched non-TB-IRIS cases, at the level of the balance between the effector C1Q and the inhibitor C1-INH, both before and 2 weeks after cART initiation. These differences were mirrored by increases in the downstream pro-inflammatory complement factor C5 over the course of 2 weeks of cART. Our results suggest that inappropriate control of complement activation could be associated with the 'flaring up' of inflammation observed during TB-IRIS.

CONCLUSION

The current study reveals a contribution of monocytes and the complement system to TB-IRIS development. An intriguing possibility is that the development of TB-IRIS may depend partially on the relative balance between C1Q and C1-INH.

Membrane complement regulators protect against fibrin exudation increases in a severe peritoneal inflammation model in rats

Peritonitis and the rare sequela of encapsulating peritoneal sclerosis (EPS) are serious problems in patients on peritoneal dialysis therapy. Chronic and persistent peritoneal injuries may be a risk factor of EPS. We previously reported that a chronic, proliferative peritonitis developed when zymosan was administered intraperitoneally following scraping injury of rat peritoneum (Mizuno M, Ito Y, Hepburn N, Mizuno T, Noda Y, Yuzawa Y, Harris CL, Morgan BP, Matsuo S. J Immunol 183: 1403–1412, 2009). Peritoneal membrane complement regulators (CRegs), especially Crry and CD59, protected from injury by inhibiting local complement activation, suggesting that CRegs play important roles in maintaining homeostasis in rat peritoneum. Here, we investigated roles of complement in the development of EPS by neutralizing CReg function with monoclonal antibodies (MAbs). Proliferative peritonitis was induced by scraping the peritoneum, followed by daily intraperitoneal administration of zymosan. When either Crry or CD59 alone was neutralized by MAb, the tissue injuries were not significantly changed compared with rats without neutralizing MAb. When both Crry and CD59 were neutralized in this model, severe fibrin exudation was observed on the peritoneal surface on day 5, accompanied by inflammatory cell infiltration, resembling the early stages of development of EPS. Dense peritoneal deposition of C3 fragments and membrane attack complex were observed, along with the fibrin exudates. Intravenous administration of cobra venom factor, which profoundly activates complement, further enhanced these pathological changes. Our results show that complement activation in injured peritoneum drives peritoneal inflammation, and that enhancement of complement activation by inhibiting CReg and/or enhancing systemic activation contributes to the initiation of EPS; therefore, anti-complement agents might be of therapeutic value in humans for the treatment of EPS.