Anti-Phospholipase A2 Receptor 1 and Anti-Cysteine Rich Antibodies, Domain Recognition and Rituximab Efficacy in Membranous Nephropathy: A Prospective Cohort Study.

RATIONALE & OBJECTIVE: Proteinuria and anti-phospholipase A2 receptor 1 (anti-PLA2R1) antibody titers are associated with primary membranous nephropathy (MN) outcomes. We evaluated the association of antibodies against the cysteine-rich (CysR) and C-type lectin 1, 7, and 8 (CTLD1, CTLD7, and CTLD8) domains of PLA2R1 with MN outcomes. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: One-hundred-thirteen consecutive, consenting patients referred to the Nephology Unit of the Azienda-Socio-Sanitaria-Territoriale (ASST) Papa Giovanni XXIII (Bergamo, Italy) with PLA2R1-related, biopsy-proven MN whose persistent nephrotic syndrome (NS) was managed conservatively for>6 months and were monitored with serial evaluations of proteinuria, autoantibodies (by enzyme-linked immunosorbent assay), and clinical outcomes. EXPOSURE: Rituximab. OUTCOME: Complete (proteinuria<0.3g/24h) or partial (proteinuria≥0.3g/24h and<3.0g/24h with>50% reduction vs basal) NS remission. ANALYTICAL APPROACH: Univariable and multivariable Cox regression analyses. RESULTS: All patients had anti-CysR antibodies; 62 (54.9%) were multidomain recognizers. Anti-PLA2R1 and anti-CysR antibody titers were strongly correlated at baseline (P<0.001, r=0.934), 6 months (P<0.001, r=0.964), and 12 months (P<0.001, r=0.944). During a median follow-up of 37.1 (IQR, 20.3-56.9) months, 71 patients (62.8%) achieved either complete or partial remission of their NS. Lower baseline anti-PLA2R1 (HR, 0.997 [95% CI, 0.996-0.999], P=0.002) and anti-CysR [HR, 0.996 [95% CI, 0.993-0.998], P=0.001) titers were associated with a higher probability of remission, along with female sex, lower proteinuria, and lower serum creatinine levels (P<0.05 for all comparisons). Anti-CTLD antibodies were not associated with outcomes. At 6 and 12 months, compared to baseline, anti-PLA2R1 and anti-CysR antibody titers decreased more in patients progressing to partial or complete remission than in those without remission (P<0.05 for all comparisons). LIMITATIONS: Observational design. CONCLUSIONS: In PLA2R1-related MN, anti-PLA2R1 and anti-CysR antibodies similarly predict rituximab efficacy independent of PLA2R1 domain recognition. The choice between these tests should be dictated by feasibility and costs. Evaluating anti-CTLD antibodies appears unnecessary. PLAIN-LANGUAGE SUMMARY: Primary membranous nephropathy (MN), a leading cause of nephrotic syndrome (NS) in adults, is an autoimmune disease caused by autoantibodies binding to the podocyte antigen phospholipase A2 receptor 1 (PLA2R1). We assessed whether the effects of anti-CD20 cytolytic therapy with the monoclonal antibody rituximab are associated with detection rates and levels of anti-PLA2R1 antibodies and antibodies against PLA2R1 domains such as cysteine-rich (CysR), and C-type lectin 1, 7, and 8 (CTLD1, 7, and 8), in patients with PLA2R1-related MN and persistent NS. The probability of rituximab-induced complete or partial NS remission was associated with baseline anti-PLA2R1 and anti-CysR antibody titers, but not with anti-CTLD1, 7 and 8 antibodies or multidomain recognition. Integrated evaluation of anti-PLA2R1 or anti-CysR antibodies with proteinuria and kidney function may play a role in monitoring the effects of rituximab in patients with PLA2R1-related NS and MN.

Angiotensin-converting enzyme 2: from a vasoactive peptide to the gatekeeper of a global pandemic.

PURPOSE OF REVIEW: We provide a comprehensive overview of angiotensin-converting enzyme 2 (ACE2) as a possible candidate for pharmacological approaches to halt inflammatory processes in different pathogenic conditions. RECENT FINDINGS: ACE2 has quickly gained prominence in basic research as it has been identified as the main entry receptor for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This novel pathogen causes Coronavirus Disease 2019 (COVID-19), a pathogenic condition that reached pandemic proportion and is associated with unprecedented morbidity and mortality. SUMMARY: The renin-angiotensin system is a complex, coordinated hormonal cascade that plays a pivotal role in controlling individual cell behaviour and multiple organ functions. ACE2 acts as an endogenous counter-regulator to the pro-inflammatory and pro-fibrotic pathways triggered by ACE through the conversion of Ang II into the vasodilatory peptide Ang 1-7. We discuss the structure, function and expression of ACE2 in different tissues. We also briefly describe the role of ACE2 as a pivotal driver across a wide spectrum of pathogenic conditions, such as cardiac and renal diseases. Furthermore, we provide the most recent data concerning the possible role of ACE2 in mediating SARS-CoV-2 infection and dictating COVID-19 severity.

The incessant search for renal biomarkers: is it really justified?

PURPOSE OF REVIEW: This review summarizes the most recent and relevant findings in the search for novel biomarkers for the most common renal diseases. RECENT FINDINGS: Unprecedented, fast-paced technical advances in biomedical research have offered an opportunity to identify novel and more specific renal biomarkers in several clinical settings. However, despite the huge efforts made, the molecules identified so far have generally failed to provide relevant information beyond what has already been generated by established biomarkers, such as serum creatinine and proteinuria, whereas the complexity and costs of these technology platforms hamper their widespread implementation. SUMMARY: No novel renal biomarkers have added clear-cut additional value in clinical decision-making. The only exception is anti-phospholipase A2 receptor antibodies, which have been implemented successfully as a diagnostic and prognostic biomarker of membranous nephropathy. This achievement, along with the large number of ongoing collaborative projects worldwide, should lead the renal community to be quite confident regarding the successful qualification of novel and effective diagnostic, prognostic and therapeutic response biomarkers for kidney diseases, hopefully in the next few years.

Sirtuins in Renal Health and Disease.

Sirtuins belong to an evolutionarily conserved family of NAD+-dependent deacetylases that share multiple cellular functions related to proliferation, DNA repair, mitochondrial energy homeostasis, and antioxidant activity. Mammalians express seven sirtuins (SIRT1-7) that are localized in different subcellular compartments. Changes in sirtuin expression are critical in several diseases, including metabolic syndrome, diabetes, cancer, and aging. In the kidney, the most widely studied sirtuin is SIRT1, which exerts cytoprotective effects by inhibiting cell apoptosis, inflammation, and fibrosis together with SIRT3, a crucial metabolic sensor that regulates ATP generation and mitochondrial adaptive response to stress. Here, we provide an overview of the biologic effects of sirtuins and the molecular targets thereof regulating renal physiology. This review also details progress made in understanding the effect of sirtuins in the pathophysiology of chronic and acute kidney diseases, highlighting the key role of SIRT1, SIRT3, and now SIRT6 as potential therapeutic targets. In this context, the current pharmacologic approaches to enhancing the activity of SIRT1 and SIRT3 will be discussed.

The long journey through renal filtration: new pieces in the puzzle of slit diaphragm architecture.

PURPOSE OF REVIEW: The podocyte slit diaphragm is probably the least understood component of the kidney filtration barrier. In this review, we aim to integrate the most recent findings on the molecular make-up and structural architecture of this specialized cell-cell junction into a current concept of glomerular filtration. RECENT FINDINGS: Analysis of cryopreserved mammalian tissue revealed a bipartite composition of the slit diaphragm. Single NEPH1 molecules span the lower part of the slit close to the glomerular basement membrane whereas NEPHRIN molecules are positioned in the apical part toward Bowman's space. This molecular arrangement could lead to heterogeneous ellipsoidal and circular pores, which are mainly located in the central region of the slit diaphragm. SUMMARY: Despite having been first identified in the 1970s, the slit diaphragm's structural architecture has not been fully elucidated to date and remains an area of intense research and scientific debate. The slit diaphragm has been initially described as a rigid 'zipper-like' structure in which periodic, rod-like units extend from a podocyte foot processes to a linear central bar, giving rise to homogeneous 4 × 14 nm pores. Several recent findings have challenged these long-held beliefs and instead pointed to an unanticipated complexity of slit diaphragm structure. High-resolution ultrastructural analysis found evidence that the slit diaphragm is a dynamic and adjustable cell-cell junction that forms a nonclogging barrier within the renal filtration system.

BRAF Signaling Pathway Inhibition, Podocyte Injury, and Nephrotic Syndrome.

Dabrafenib and trametinib, BRAF and MEK inhibitors, respectively, are effective targeted metastatic melanoma therapies, but little is known about their nephrotoxicity. Although tubulointerstitial injury has been the most widely reported renal side effect of targeted melanoma therapy, nephrotic syndrome has not been reported before. We report on a patient with metastatic melanoma who developed nephrotic syndrome during dabrafenib and trametinib treatment. Kidney biopsy showed diffuse loss of podocyte cytoarchitecture, extensive foot-process effacement, and glomerular endothelial injury. Kidney function and glomerular ultrastructural changes recovered fully after drug withdrawal. In vitro, BRAF inhibition decreased PLCε1 expression in podocytes, accompanied by a reduction in nephrin expression and an increase in permeability to albumin. Additionally, these drugs inhibited the podocyte-vascular endothelial growth factor (VEGF) system. In addition to implications for nephrotic syndrome pathophysiology, we suggest that patients given dabrafenib and trametinib be monitored closely for potential glomerular damage.

Shiga toxin promotes podocyte injury in experimental hemolytic uremic syndrome via activation of the alternative pathway of complement.

Shiga toxin (Stx)-producing Escherichia coli is the offending agent of postdiarrhea-associated hemolytic uremic syndrome (HUS), a disorder of glomerular ischemic damage and widespread microvascular thrombosis. We previously documented that Stx induces glomerular complement activation, generating C3a responsible for microvascular thrombosis in experimental HUS. Here, we show that the presence of C3 deposits on podocytes is associated with podocyte damage and loss in HUS mice generated by the coinjection of Stx2 and LPS. Because podocyte adhesion to the glomerular basement membrane is mediated by integrins, the relevance of integrin-linked kinase (ILK) signals in podocyte dysfunction was evaluated. Podocyte expression of ILK increased after the injection of Stx2/LPS and preceded the upregulation of Snail and downregulation of nephrin and α-actinin-4. Factor B deficiency or pretreatment with an inhibitory antibody to factor B protected mice against Stx2/LPS-induced podocyte dysregulation. Similarly, pretreatment with a C3a receptor antagonist limited podocyte loss and changes in ILK, Snail, and α-actinin-4 expression. In cultured podocytes, treatment with C3a reduced α-actinin-4 expression and promoted ILK-dependent nuclear expression of Snail and cell motility. These results suggest that Stx-induced activation of the alternative pathway of complement and generation of C3a promotes ILK signaling, leading to podocyte dysfunction and loss in Stx-HUS.

ß-arrestin-1 drives endothelin-1-mediated podocyte activation and sustains renal injury.

Activation of endothelin-A receptor (ET(A)R) by endothelin-1 (ET-1) drives epithelial-to-mesenchymal transition in ovarian tumor cells through ß-arrestin signaling. Here, we investigated whether this pathogenetic pathway could affect podocyte phenotype in proliferative glomerular disorders. In cultured mouse podocytes, ET-1 caused loss of the podocyte differentiation marker synaptopodin and acquisition of the mesenchymal marker α-smooth muscle actin. ET-1 promoted podocyte migration via ET(A)R activation and increased ß-arrestin-1 expression. Activated ET(A)R recruited ß-arrestin-1 to form a trimeric complex with Src leading to epithelial growth factor receptor (EGFR) transactivation and ß-catenin phosphorylation, which promoted gene transcription of Snail. Increased Snail expression fostered ET-1-induced migration as confirmed by Snail knockdown experiments. Silencing of ß-arrestin-1 prevented podocyte phenotypic changes and motility and inhibited ET(A)R-driven signaling. In vitro findings were confirmed in doxorubicin (Adriamycin)-induced nephropathy. Mice receiving Adriamycin developed renal injury with loss of podocytes and hyperplastic lesion formation; ß-arrestin-1 expression increased in visceral podocytes and in podocytes entrapped in pseudo-crescents. Administration of the selective ET(A)R antagonist sitaxsentan prevented podocyte loss, formation of the hyperplastic lesions, and normalized expression of glomerular ß-arrestin-1 and Snail. Increased ß-arrestin-1 levels in podocytes retrieved from crescents of patients with proliferative glomerulopathies confirmed the translational relevance of these findings and suggest the therapeutic potential of ET(A)R antagonism for a group of diseases still needing a specific treatment.

Angiotensin II contributes to diabetic renal dysfunction in rodents and humans via Notch1/Snail pathway.

In nondiabetic rat models of renal disease, angiotensin II (Ang II) perpetuates podocyte injury and promotes progression to end-stage kidney disease. Herein, we wanted to explore the role of Ang II in diabetic nephropathy by a translational approach spanning from in vitro to in vivo rat and human studies, and to dissect the intracellular pathways involved. In isolated perfused rat kidneys and in cultured human podocytes, Ang II down-regulated nephrin expression via Notch1 activation and nuclear translocation of Snail. Hairy enhancer of split-1 was a Notch1-downstream gene effector that activated Snail in cultured podocytes. In vitro changes of the Snail/nephrin axis were similar to those in renal biopsy specimens of Zucker diabetic fatty rats and patients with advanced diabetic nephropathy, and were normalized by pharmacological inhibition of the renin-angiotensin system. Collectively, the present studies provide evidence that Ang II plays a relevant role in perpetuating glomerular injury in experimental and human diabetic nephropathy via persistent activation of Notch1 and Snail signaling in podocytes, eventually resulting in down-regulation of nephrin expression, the integrity of which is crucial for the glomerular filtration barrier.

SARS-CoV-2 and the spike protein in endotheliopathy.

SARS-CoV-2, the causative agent of COVID-19, primarily affects the epithelial compartment in the upper and lower airways. There is evidence that the microvasculature in both the pulmonary and extrapulmonary systems is a major target of SARS-CoV-2. Consistent with this, vascular dysfunction and thrombosis are the most severe complications in COVID-19. The proinflammatory milieu triggered by the hyperactivation of the immune system by SARS-CoV-2 has been suggested to be the main trigger for endothelial dysfunction during COVID-19. More recently, a rapidly growing number of reports have indicated that SARS-CoV-2 can interact directly with endothelial cells through the spike protein, leading to multiple instances of endothelial dysfunction. Here, we describe all the available findings showing the direct effect of the SARS-CoV-2 spike protein on endothelial cells and offer mechanistic insights into the molecular basis of vascular dysfunction in severe COVID-19.

Sirtuins in kidney health and disease.

Sirtuins (SIRTs) are putative regulators of lifespan in model organisms. Since the initial discovery that SIRTs could promote longevity in nematodes and flies, the identification of additional properties of these proteins has led to understanding of their roles as exquisite sensors that link metabolic activity to oxidative states. SIRTs have major roles in biological processes that are important in kidney development and physiological functions, including mitochondrial metabolism, oxidative stress, autophagy, DNA repair and inflammation. Furthermore, altered SIRT activity has been implicated in the pathophysiology and progression of acute and chronic kidney diseases, including acute kidney injury, diabetic kidney disease, chronic kidney disease, polycystic kidney disease, autoimmune diseases and renal ageing. The renoprotective roles of SIRTs in these diseases make them attractive therapeutic targets. A number of SIRT-activating compounds have shown beneficial effects in kidney disease models; however, further research is needed to identify novel SIRT-targeting strategies with the potential to treat and/or prevent the progression of kidney diseases and increase the average human healthspan.

Bi-specific autoantigen-T cell engagers as targeted immunotherapy for autoreactive B cell depletion in autoimmune diseases.

Introduction: In autoimmune diseases, autoreactive B cells comprise only the 0.1-0.5% of total circulating B cells. However, current first-line treatments rely on non-specific and general suppression of the immune system, exposing patients to severe side effects. For this reason, identification of targeted therapies for autoimmune diseases is an unmet clinical need. Methods: Here, we designed a novel class of immunotherapeutic molecules, Bi-specific AutoAntigen-T cell Engagers (BiAATEs), as a potential approach for targeting the small subset of autoreactive B cells. To test this approach, we focused on a prototype autoimmune disease of the kidney, membranous nephropathy (MN), in which phospholipase A2 receptor (PLA2R) serves as primary nephritogenic antigen. Specifically, we developed a BiAATE consisting of the immunodominant Cysteine-Rich (CysR) domain of PLA2R and the single-chain variable fragment (scFv) of an antibody against the T cell antigen CD3, connected by a small flexible linker. Results: BiAATE creates an immunological synapse between autoreactive B cells bearing an CysR-specific surface Ig+ and T cells. Ex vivo, the BiAATE successfully induced T cell-dependent depletion of PLA2R-specific B cells isolated form MN patients, sparing normal B cells. Systemic administration of BiAATE to mice transgenic for human CD3 reduced anti-PLA2R antibody levels following active immunization with PLA2R. Discussion: Should this approach be confirmed for other autoimmune diseases, BiAATEs could represent a promising off-the-shelf therapy for precision medicine in virtually all antibody-mediated autoimmune diseases for which the pathogenic autoantigen is known, leading to a paradigm shift in the treatment of these diseases.

Sirt3 deficiency promotes endothelial dysfunction and aggravates renal injury.

Sirtuin 3 (SIRT3), the main deacetylase of mitochondria, modulates the acetylation levels of substrates governing metabolism and oxidative stress. In the kidney, we showed that SIRT3 affects the proper functioning of high energy-demanding cells, such as tubular cells and podocytes. Less is known about the role of SIRT3 in regulating endothelial cell function and its impact on the progression of kidney disease. Here, we found that whole body Sirt3-deficient mice exhibited reduced renal capillary density, reflecting endothelial dysfunction, and VEGFA expression compared to wild-type mice. This was paralleled by activation of hypoxia signaling, upregulation of HIF-1α and Angiopietin-2, and oxidative stress increase. These alterations did not result in kidney disease. However, when Sirt3-deficient mice were exposed to the nephrotoxic stimulus Adriamycin (ADR) they developed aggravated endothelial rarefaction, altered VEGFA signaling, and higher oxidative stress compared to wild-type mice receiving ADR. As a result, ADR-treated Sirt3-deficient mice experienced a more severe injury with exacerbated albuminuria, podocyte loss and fibrotic lesions. These data suggest that SIRT3 is a crucial regulator of renal vascular homeostasis and its dysregulation is a predisposing factor for kidney disease. By extension, our findings indicate SIRT3 as a pharmacologic target in progressive renal disease whose treatments are still imperfect.

SARS-CoV-2 spike protein induces lung endothelial cell dysfunction and thrombo-inflammation depending on the C3a/C3a receptor signalling.

The spike protein of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can interact with endothelial cells. However, no studies demonstrated the direct effect of the spike protein subunit 1 (S1) in inducing lung vascular damage and the potential mechanisms contributing to lung injury. Here, we found that S1 injection in mice transgenic for human angiotensin converting enzyme 2 (ACE2) induced early loss of lung endothelial thromboresistance at 3 days, as revealed by thrombomodulin loss and von Willebrand factor (vWF) increase. In parallel, vascular and epithelial C3 deposits and enhanced C3a receptor (C3aR) expression were observed. These changes preceded diffuse alveolar damage and lung vascular fibrin(ogen)/platelets aggregates at 7 days, as well as inflammatory cell recruitment and fibrosis. Treatment with C3aR antagonist (C3aRa) inhibited lung C3 accumulation and C3a/C3aR activation, limiting vascular thrombo-inflammation and fibrosis. Our study demonstrates that S1 triggers vascular dysfunction and activates complement system, instrumental to lung thrombo-inflammatory injury. By extension, our data indicate C3aRa as a valuable therapeutic strategy to limit S1-dependent lung pathology.

Long-term adaptive response in COVID-19 vaccine recipients and the effect of a booster dose.

We examined the immune response in subjects previously infected with SARS-CoV2 and infection-naïve 9 months after primary 2-dose COVID-19 mRNA vaccination and 3 months after the booster dose in a longitudinal cohort of healthcare workers. Nine months after primary vaccination, previously infected subjects exhibited higher residual antibody levels, with significant neutralizing activity against distinct variants compared to infection-naïve subjects. The higher humoral response was associated with higher levels of receptor binding domain (RBD)-specific IgG+ and IgA+ memory B cells. The booster dose increased neither neutralizing activity, nor the B and T cell frequencies. Conversely, infection-naïve subjects needed the booster to achieve comparable levels of neutralizing antibodies as those found in previously infected subjects after primary vaccination. The neutralizing titer correlated with anti-RBD IFNγ producing T cells, in the face of sustained B cell response. Notably, pre-pandemic samples showed high Omicron cross-reactivity. These data show the importance of the booster dose in reinforcing immunological memory and increasing circulating antibodies in infection-naïve subjects.

SARS-CoV-2 Spike Protein 1 Activates Microvascular Endothelial Cells and Complement System Leading to Platelet Aggregation.

Microvascular thrombosis is associated with multiorgan failure and mortality in coronavirus disease 2019 (COVID-19). Although thrombotic complications may be ascribed to the ability of SARS-CoV-2 to infect and replicate in endothelial cells, it has been poorly investigated whether, in the complexity of viral infection in the human host, specific viral elements alone can induce endothelial damage. Detection of circulating spike protein in the sera of severe COVID-19 patients was evaluated by ELISA. In vitro experiments were performed on human microvascular endothelial cells from the derma and lung exposed to SARS-CoV-2-derived spike protein 1 (S1). The expression of adhesive molecules was studied by immunofluorescence and leukocyte adhesion and platelet aggregation were assessed under flow conditions. Angiotensin converting enzyme 2 (ACE2) and AMPK expression were investigated by Western Blot analysis. In addition, S1-treated endothelial cells were incubated with anti-ACE2 blocking antibody, AMPK agonist, or complement inhibitors. Our results show that significant levels of spike protein were found in the 30.4% of severe COVID-19 patients. In vitro, the activation of endothelial cells with S1 protein, via ACE2, impaired AMPK signalling, leading to robust leukocyte recruitment due to increased adhesive molecule expression and thrombomodulin loss. This S1-induced pro-inflammatory phenotype led to exuberant C3 and C5b-9 deposition on endothelial cells, along with C3a and C5a generation that further amplified S1-induced complement activation. Functional blockade of ACE2 or complement inhibition halted S1-induced platelet aggregates by limiting von Willebrand factor and P-selectin exocytosis and expression on endothelial cells. Overall, we demonstrate that SARS-CoV-2-derived S1 is sufficient in itself to propagate inflammatory and thrombogenic processes in the microvasculature, amplified by the complement system, recapitulating the thromboembolic complications of COVID-19.

Low Nephron Number Induced by Maternal Protein Restriction Is Prevented by Nicotinamide Riboside Supplementation Depending on Sirtuin 3 Activation.

A reduced nephron number at birth, due to critical gestational conditions, including maternal malnutrition, is associated with the risk of developing hypertension and chronic kidney disease in adulthood. No interventions are currently available to augment nephron number. We have recently shown that sirtuin 3 (SIRT3) has an important role in dictating proper nephron endowment. The present study explored whether SIRT3 stimulation, by means of supplementation with nicotinamide riboside (NR), a precursor of the SIRT3 co-substrate nicotinamide adenine dinucleotide (NAD+), was able to improve nephron number in a murine model of a low protein (LP) diet. Our findings show that reduced nephron number in newborn mice (day 1) born to mothers fed a LP diet was associated with impaired renal SIRT3 expression, which was restored through supplementation with NR. Glomerular podocyte density, as well as the rarefaction of renal capillaries, also improved through NR administration. In mechanistic terms, the restoration of SIRT3 expression through NR was mediated by the induction of proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α). Moreover, NR restored SIRT3 activity, as shown by the reduction of the acetylation of optic atrophy 1 (OPA1) and superoxide dismutase 2 (SOD2), which resulted in improved mitochondrial morphology and protection against oxidative damage in mice born to mothers fed the LP diet. Our results provide evidence that it is feasible to prevent nephron mass shortage at birth through SIRT3 boosting during nephrogenesis, thus providing a therapeutic option to possibly limit the long-term sequelae of reduced nephron number in adulthood.

Sexual dimorphic response to rituximab treatment: A longitudinal observational study in a large cohort of patients with primary membranous nephropathy and persistent nephrotic syndrome.

Rituximab is one of the first-line therapies for patients with membranous nephropathy (MN) at high risk of progression towards kidney failure. We investigated whether the response to Rituximab was affected by sex and anti-PLA2R antibody levels in 204 consecutive patients (148 males and 56 females) with biopsy-proven MN who were referred to the Nephrology Unit of the Azienda Socio Sanitaria Territoriale Papa Giovanni XXIII from March 2001 to October 2016 and managed conservatively for at least 6 months. The primary outcome was a combined endpoint of complete (proteinuria <0.3 g/24 h) or partial (proteinuria <3.0 g/24 h and >50% reduction vs. baseline) remission. Patients gave written informed consent to Rituximab treatment. The study was internally funded. No pharmaceutical company was involved. Anti-PLA2R antibodies were detectable in 125 patients (61.3%). At multivariable analyses, female gender (p = 0.0198) and lower serum creatinine levels (p = 0.0108) emerged as independent predictors of better outcome (p = 0.0198). The predictive value of proteinuria (p = 0.054) and anti-PLA2R titer (p = 0.0766) was borderline significant. Over a median (IQR) of 24.8 (12.0-36.0) months, 40 females (71.4%) progressed to the combined endpoint compared with 73 males (49.3%). Anti-PLA2R titers at baseline [127.6 (35.7-310.8) vs. 110.1 (39.9-226.7) RU/ml] and after Rituximab treatment were similar between the sexes. However, the event rate was significantly higher in females than in males [HR (95%): 2.12 (1.44-3.12), p = 0.0001]. Forty-five of the 62 patients (72.3%) with anti-PLA2R titer below the median progressed to the combined endpoint versus 35 of the 63 (55.6%) with higher titer [HR (95%): 1.97 (1.26-3.07), p < 0.0029]. The highest probability of progressing to the combined endpoint was observed in females with anti-PLA2R antibody titer below the median (86.7%), followed by females with anti-PLA2R antibody titer above the median (83.3%), males with titer below the median (68.1%), and males with titer above the median (44.4%). This trend was statistically significant (p = 0.0023). Similar findings were observed for complete remission (proteinuria <0.3 g/24 h) and after analysis adjustments for baseline serum creatinine. Thus, despite similar immunological features, females were more resilient to renal injury following Rituximab therapy. These findings will hopefully open new avenues to identify the molecular pathways underlying sex-related nephroprotective effects.