Erythropoietin Reduces Auto- and Alloantibodies by Inhibiting T Follicular Helper Cell Differentiation

A systematic review and meta-analysis of factors contributing to post-kidney transplant anemia and the effect of erythropoietin-stimulating agents

BACKGROUND

The effects of various risk and associated factors on post-kidney transplant anemia (PTA) have not been fully compared and estimated. This meta-analysis aims to elucidate factors contributing to PTA and determine the influence of erythropoietin-stimulating agents (ESAs) on renal outcomes, thus offering potential pathways for enhanced management strategies post-transplant.

METHODS

A systematic review was conducted in electronical database. Studies reporting on risk factors (with cause-effect relationships) and associated factors (without definite cause-effect relationships) of PTA, and the effects of ESAs on post-kidney transplant outcomes, were included. Pooled odds ratios (ORs) and weighted mean differences (WMDs) were analyzed using random-effects models.

RESULTS

This systematic review encompassed 38,233 patients from 85 studies. Factors increased PTA risk included African American, older donor age, human antigen leukocyte mismatches, and low pre-transplant hemoglobin levels. Poor allograft function, high interleukine-6, Cytomegalovirus, delayed graft function, allograft rejections, immunosuppressive medications, and renin-angiotensin system blockades were associated with PTA. Native autosomal dominant polycystic kidney disease was a protective factor against PTA. Administration of ESAs with the aim of normalizing hemoglobin levels in patients with chronic allograft dysfunction slowed the decline in eGFR and reduce the risk of death, with a pooled OR of 0.36 (95% CI: 0.14 to 0.89; p = 0.040).

CONCLUSIONS

The risks and associated factors for PTA have been elucidated, underscoring the need for individualized treatment approaches. Late ESA therapy, aimed at hemoglobin normalization, suggests a renal-protective effect and reduced mortality, which should be considered in the management of PTA.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42024545330.

The differentiation courses of the Tfh cells: a new perspective on autoimmune disease pathogenesis and treatment

The follicular helper T cells are derived from CD4+T cells, promoting the formation of germinal centers and assisting B cells to produce antibodies. This review describes the differentiation process of Tfh cells from the perspectives of the initiation, maturation, migration, efficacy, and subset classification of Tfh cells, and correlates it with autoimmune disease, to provide information for researchers to fully understand Tfh cells and provide further research ideas to manage immune-related diseases.

Injectable thermosensitive hydrogel loading erythropoietin and FK506 alleviates gingival inflammation and promotes periodontal tissue regeneration

Background: Periodontitis is a chronic multifactorial inflammatory disease associated with dysbiotic plaque biofilms and characterized by progressive destruction of the tooth-supporting apparatus. Therefore, there is significant potential in the discovery of drugs that inhibit periodontal inflammatory responses and promote periodontal regeneration. Methods: In this study, we generated a periodontitis rat model to detect the effects of chitosan/β-sodium glycerophosphate (β-GP)/glycolic acid (GA) hydrogel carried Erythropoietin and FK506 (EPO-FK506-CS/β-GP/GA). A total of forty-eight male Wistar rats were used to establish the periodontitis model. Drug injection was administered every 3 days for a total of five times over a 2-week period. After a period of 2 weeks following implantation, the rats underwent anesthesia, and a section of their maxillae encompassing the maxillary first and second molars, along with the alveolar bone, was obtained. micro-CT scanning, histopathology, immunohistochemistry and reverse transcription-quantitative PCR (RT-qPCR) assays were performed. Meanwhile, ELISA assay was performed to detect the levels of inflammatory mediators (TNF-α, IL-6 and IL-1β). Results: The synthesis and characterization of EPO-FK506-CS/β-GP/GA revealed that the hydrogel has stability and sustained release of drugs. The application of FK506+EPO was found to significantly enhance new bone formation in the defect area, as evidenced by the results of HE staining. Additionally, the use of FK506+EPO in the treated groups led to a notable increase in the density of alveolar bone, as observed through micro-CT analysis, when compared to the Model group. EPO-FK506-CS/β-GP/GA hydrogel exhibited notable efficacy in modulating inflammatory mediators (TNF-α, IL-6 and IL-1β). Furthermore, the osteoinductive properties of the EPO-FK506-CS/β-GP/GA hydrogel were extensive, as evidenced by a significant upregulation in the expression of key markers (Collagen I, Runx2, OPN, and OCN) associated with osteoblastic differentiation. Conclusion: Taken together, EPO-FK506-CS/β-GP/GA hydrogel alleviates gingival inflammation and promotes periodontal tissue regeneration in the periodontitis.

Endogenous erythropoietin has immunoregulatory functions that limit the expression of autoimmune kidney disease in mice

Background

Administration of recombinant erythropoietin (EPO), a kidney-produced hormone with erythropoietic functions, has been shown to have multiple immunoregulatory effects in mice and humans, but whether physiological levels of EPO regulate immune function in vivo has not been previously evaluated.

Methods

We generated mice in which we could downregulate EPO production using a doxycycline (DOX)-inducible, EPO-specific silencing RNA (shEPOrtTA^POS), and we crossed them with B6.MRL-Fas^lpr/J mice that develop spontaneous lupus. We treated these B6.MRL/lpr shEPOrtTA^POS with DOX and serially measured anti-dsDNA antibodies, analyzed immune subsets by flow cytometry, and evaluated clinical signs of disease activity over 6 months of age in B6.MRL/lpr shEPOrtTA^POS and in congenic shEPOrtTA^NEG controls.

Results

In B6.MRL/lpr mice, Epo downregulation augmented anti-dsDNA autoantibody levels and increased disease severity and percentages of germinal center B cells compared with controls. It also increased intracellular levels of IL-6 and MCP-1 in macrophages.

Discussion

Our data in a murine model of lupus document that endogenous EPO reduces T- and B-cell activation and autoantibody production, supporting the conclusion that EPO physiologically acts as a counterregulatory mechanism to control immune homeostasis.

A protective erythropoietin evolutionary landscape, NLRP3 inflammasome regulation, and multisystem inflammatory syndrome in children

The low incidence of pediatric severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and the associated multisystem inflammatory syndrome (MIS-C) lack a unifying pathophysiological explanation, impeding effective prevention and therapy. Activation of the NACHT, LRR, and PYD domains-containing protein (NLRP) 3 inflammasome in SARS-CoV-2 with perturbed regulation in MIS-C, has been reported. We posit that, early age physiological states and genetic determinants, such as certain polymorphisms of renin-angiotensin aldosterone system (RAAS) molecules, promote a controlled RAAS hyperactive state, and form an evolutionary landscape involving an age-dependent erythropoietin (EPO) elevation, mediating ancestral innate immune defenses that, through appropriate NLRP3 regulation, mitigate tissue injury and pathogen invasion. SARS-CoV-2-induced downregulation of angiotensin-converting enzyme (ACE)2 expression in endothelial cells (EC), impairment of endothelial nitric oxide (NO) synthase (eNOS) activity and downstream NO bioavailability, may promote a hyperactive RAAS with elevated angiotensin II and aldosterone that, can trigger, and accelerate NLRP3 inflammasome activation, while EPO-eNOS/NO abrogate it. Young age and a protective EPO evolutionary landscape may successfully inhibit SARS-CoV-2 and contain NLRP3 inflammasome activation. By contrast, increasing age and falling EPO levels, in genetically susceptible children with adverse genetic variants and co-morbidities, may lead to unopposed RAAS hyperactivity, NLRP3 inflammasome dysregulation, severe endotheliitis with pyroptotic cytokine storm, and development of autoantibodies, as already described in MIS-C. Our haplotype estimates, predicted from allele frequencies in population databases, are in concordance with MIS-C incidence reports in Europeans but indicate lower risks for Asians and African Americans. Targeted Mendelian approaches dissecting the influence of relevant genetic variants are needed.

Role of T follicular helper and T follicular regulatory cells in antibody-mediated rejection: new therapeutic targets?

PURPOSE OF REVIEW

Antibody-mediated rejection (AbMR) after solid organ transplantation is tightly controlled by multiple cells of the immune system. Tfh and Tfr cells are essential controllers of antibody responses making them putative targets for therapeutics. However, the mechanisms of how Tfh and Tfr cells regulate B cell and antibody responses are not completely understood. Here, we summarize recent studies elucidating the functions of T follicular helper (Tfh) and T follicular regulatory (Tfr) cells as well as their possible roles in regulating AbMR in solid organ transplantation.

RECENT FINDINGS

New tools have been developed to study the roles of Tfh and Tfr cells in specific disease states, including AbMR after solid organ transplantation. These tools suggest complex roles for Tfh and Tfr cells in controlling antibody responses. Nevertheless, studies in solid organ transplant rejection suggest that Tfh and Tfr cells may be high value targets for therapeutics. However, specific strategies to target these cells are still being investigated.

SUMMARY

AbMR is still a substantial clinical problem that restricts long-term survival after solid organ transplantation. Growing evidence has demonstrated a pivotal role for Tfh and Tfr cells in controlling AbMR. In addition to providing an early indication of rejection as a biomarker, targeting Tfh and Tfr cells as a therapeutic strategy offers new hope for alleviating AbMR.

Linking erythropoietin to regulatory T-cell-dependent allograft survival through myeloid cells

Erythropoietin (EPO) has multiple nonerythropoietic functions, including immune modulation, but EPO’s effects in transplantation remain incompletely understood. We tested the mechanisms linking EPO administration to prolongation of murine heterotopic heart transplantation using WT and conditional EPO receptor–knockout (EPOR-knockout) mice as recipients. In WT controls, peritransplant administration of EPO synergized with CTLA4-Ig to prolong allograft survival (P < 0.001), reduce frequencies of donor-reactive effector CD8⁺ T cells in the spleen (P < 0.001) and in the graft (P < 0.05), and increase frequencies and total numbers of donor-reactive Tregs (P < 0.01 for each) versus CTLA4-Ig alone. Studies performed in conditional EPOR-knockout recipients showed that each of these differences required EPOR expression in myeloid cells but not in T cells. Analysis of mRNA isolated from spleen monocytes showed that EPO/EPOR ligation upregulated macrophage-expressed, antiinflammatory, regulatory, and pro-efferocytosis genes and downregulated selected proinflammatory genes. Taken together, the data support the conclusion that EPO promotes Treg-dependent murine cardiac allograft survival by crucially altering the phenotype and function of macrophages. Coupled with our previous documentation that EPO promotes Treg expansion in humans, the data support the need for testing the addition of EPO to costimulatory blockade-containing immunosuppression regimens in an effort to prolong human transplant survival.

Age and genotype dependent erythropoietin protection in COVID-19

Erythropoietin (EPO) is the main mediator of erythropoiesis and an important tissue protective hormone that appears to mediate an ancestral neuroprotective innate immune response mechanism at an early age. When the young brain is threatened-prematurity, neonatal hyperbilirubinemia, malaria- EPO is hyper-secreted disproportionately to any concurrent anemic stimuli. Under eons of severe malarial selection pressure, neuroprotective EPO augmenting genetic determinants such as the various hemoglobinopathies, and the angiotensin converting enzyme (ACE) I/D polymorphism, have been positively selected. When malarial and other cerebral threats abate and the young child survives to adulthood, EPO subsides. Sustained high ACE and angiotensin II (Ang II) levels through the ACE D allele in adulthood may then become detrimental as witnessed by epidemiological studies. The ubiquitous renin angiotensin system (RAS) influences the α-klotho/fibroblast growth factor 23 (FGF23) circuitry, and both are interconnected with EPO. Here we propose that at a young age, EPO augmenting genetic determinants through ACE D allele elevated Ang II levels in some or HbE/beta thalassemia in others would increase EPO levels and shield against coronavirus disease 2019, akin to protection from malaria and dengue fever. Human evolution may use ACE2 as a “bait” for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) to gain cellular entry in order to trigger an ACE/ACE2 imbalance and stimulate EPO hypersecretion using tissue RAS, uncoupled from hemoglobin levels. In subjects without EPO augmenting genetic determinants at any age, ACE2 binding and internalization upon SARS-CoV-2 entry would trigger an ACE/ACE2 imbalance, and Ang II oversecretion leading to protective EPO stimulation. In children, low nasal ACE2 Levels would beneficially augment this imbalance, especially for those without protective genetic determinants. On the other hand, in predisposed adults with the ACE D allele, ACE/ACE2 imbalance, may lead to uncontrolled RAS overactivity and an Ang II induced proinflammatory state and immune dysregulation, with interleukin 6 (IL-6), plasminogen activator inhibitor, and FGF23 elevations. IL-6 induced EPO suppression, aggravated through co-morbidities such as hypertension, diabetes, obesity, and RAS pharmacological interventions may potentially lead to acute respiratory distress syndrome, cytokine storm and/or autoimmunity. HbE/beta thalassemia carriers would enjoy protection at any age as their EPO stimulation is uncoupled from the RAS system. The timely use of rhEPO, EPO analogs, acetylsalicylic acid, bioactive lipids, or FGF23 antagonists in genetically predisposed individuals may counteract those detrimental effects.