Agonistic anti-CD148 monoclonal antibody attenuates diabetic nephropathy in mice

CD148 agonistic antibody alleviates renal injury induced by chronic angiotensin II infusion in mice

BACKGROUND

Angiotensin II (Ang II) plays a critical role in the progression of kidney disease. In addition to its direct signaling events, Ang II transactivates epidermal growth factor receptor (EGFR) and causes renal injury. CD148 is a transmembrane protein tyrosine phosphatase that dephosphorylates EGFR and strongly inhibits its activity. In this study, we have asked if CD148 agonistic antibody 18E1 mAb attenuates renal injury induced by chronic Ang II infusion to explore its therapeutic application.

METHODS

Hypertensive nephropathy was induced in mice subjected to unilateral nephrectomy (UNx) by infusing Ang II (1.4 mg/kg per day) for 6 weeks using an osmotic minipump. The 18E1 mAb or isotype control IgG were intraperitoneally injected (15 mg/kg, three times per week) to the UNx + Ang II mice for 6 weeks, and their renal phenotype was investigated.

RESULTS

Chronic Ang II infusion induced evident hypertension and renal injury that is indicated by elevation of plasma creatinine, urinary albumin excretion, renal hypertrophy, podocyte injury, macrophage infiltration, and the expression of alpha smooth muscle actin and collagen deposition. As compared with isotype control antibody, 18E1 mAb significantly reduced these renal changes, while it showed no effects on blood pressure. Furthermore, phospho-EGFR immunohistochemistry and immunoblotting demonstrated renal EGFR is activated in the mice that were subjected to UNx and Ang II infusion and 18E1 mAb significantly reduces EGFR phosphorylation in these kidneys as compared with isotype control treatment.

CONCLUSION

Agonistic CD148 antibody attenuates UNx + Ang II-induced renal injury, in part by reducing EGFR activity.

Defining and Harnessing the Megakaryocyte/Platelet Checkpoint

Platelets, or thrombocytes are anucleate cell fragments of megakaryocytes (MKs) that are highly reactive to sites of vascular injury and implicated in many pathologies. However, the molecular mechanisms regulating the number and activity of platelets in the circulation remain undefined. The primary outstanding question remains what is the triggering mechanism of platelet production, or thrombopoiesis? Putative stimulatory factors and mechanical forces are thought to drive this process, but none induce physiological levels of thrombopoiesis. Intrinsic inhibitory mechanisms that maintain MKs in a refractory state in sites of thrombopoiesis are conspicuously overlooked, as well as extrinsic cues that release this brake system, allowing asymmetric platelet production to proceed toward the vascular lumen. Here we introduce the novel concept of a MK/platelet checkpoint, putative components and a working model of how it may be regulated. We postulate that the co-inhibitory receptor G6b-B and the non-transmembrane protein-tyrosine phosphatases (PTPs) Shp1 and Shp2 form an inhibitory complex that is the primary gatekeeper of this checkpoint, which is spatiotemporally regulated by the receptor-type PTP CD148 and vascular heparan sulfate proteoglycans. By advancing this alternative model of thrombopoiesis, we hope to stimulate discourse and a shift in how we conceptualize and address this fundamental question.

Meis1 Targets Protein Tyrosine Phosphatase Receptor J in Fibroblast to Retard Chronic Kidney Disease Progression

Renal fibrosis is a common pathological feature of chronic kidney disease (CKD) with the proliferation and activation of myofibroblasts being definite effectors and drivers. Here, increased expression of Meis1 (myeloid ecotropic viral integration site 1) is observed, predominantly in the nucleus of the kidney of CKD patients and mice, and negatively correlates with serum creatinine. Fibroblast-specific knock-in of Meis1 inhibits myofibroblast activation and attenuates renal fibrosis and kidney dysfunction in CKD models. Overexpression of Meis1 in NRK-49F cells suppresses the pro-fibrotic response induced by transforming growth factor-β1 but accelerates by its knockdown. Mechanistically, Meis1 targets protein tyrosine phosphatase receptor J (Ptprj) to block renal fibrosis by inhibiting the proliferation and activation of fibroblasts. Finally, a new activator of Ptprj is identified through computer-aided virtual screening, which has the effect of alleviating renal fibrosis. Collectively, these results illustrate that the Meis1/Ptprj axis has therapeutic potential for clinically treating CKD.

Identification of Novel Genetic Risk Factors for Focal Segmental Glomerulosclerosis in Children: Results From the Chronic Kidney Disease in Children (CKiD) Cohort

RATIONALE & OBJECTIVE

Focal segmental glomerulosclerosis (FSGS) is a major cause of pediatric nephrotic syndrome, and African Americans exhibit an increased risk for developing FSGS compared with other populations. Predisposing genetic factors have previously been described in adults. Here we performed genomic screening of primary FSGS in a pediatric African American population.

STUDY DESIGN

Prospective cohort with case-control genetic association study design.

SETTING & PARTICIPANTS

140 African American children with chronic kidney disease from the Chronic Kidney Disease in Children (CKiD) cohort, including 32 cases with FSGS.

PREDICTORS

Over 680,000 common single-nucleotide polymorphisms (SNPs) were tested for association. We also ran a pathway enrichment analysis and a human leucocyte antigen (HLA)-focused association study.

OUTCOME

Primary biopsy-proven pediatric FSGS.

ANALYTICAL APPROACH

Multivariate logistic regression models.

RESULTS

The genome-wide association study revealed 169 SNPs from 14 independent loci significantly associated with FSGS (false discovery rate [FDR]<5%). We observed notable signals for genetic variants within the APOL1 (P=8.6×10^-7; OR, 25.8 [95% CI, 7.1-94.0]), ALMS1 (P=1.3×10^-7; 13.0% in FSGS cases vs 0% in controls), and FGFR4 (P=4.3×10^-6; OR, 24.8 [95% CI, 6.3-97.7]) genes, all of which had previously been associated with adult FSGS, kidney function, or chronic kidney disease. We also highlighted novel, functionally relevant genes, including GRB2 (which encodes a slit diaphragm protein promoting podocyte structure through actin polymerization) and ITGB1 (which is linked to renal injuries). Our results suggest a major role for immune responses and antigen presentation in pediatric FSGS through (1) associations with SNPs in PTPRJ (or CD148, P=3.5×10^-7), which plays a role in T-cell receptor signaling, (2) HLA-DRB1∗11:01 association (P=6.1×10^-3; OR, 4.5 [95% CI, 1.5-13.0]), and (3) signaling pathway enrichment (P=1.3×10^-6).

LIMITATIONS

Sample size and no independent replication cohort with genomic data readily available.

CONCLUSIONS

Our genetic study has identified functionally relevant risk factors and the importance of immune regulation for pediatric primary FSGS, which contributes to a better description of its molecular pathophysiological mechanisms.

The Emergence of Senescent Surface Biomarkers as Senotherapeutic Targets

Senescence is linked to a wide range of age-associated diseases and physiological declines. Thus, senotherapeutics are emerging to suppress the detrimental effects of senescence either by senomorphics or senolytics. Senomorphics suppress the traits associated with senescence phenotypes, while senolytics aim to clear senescent cells by suppressing their survival and enhancing the apoptotic pathways. The main goal of these approaches is to suppress the proinflammatory senescence-associated secretory phenotype (SASP) and to promote the immune recognition and elimination of senescent cells. One increasingly attractive approach is the targeting of molecules or proteins specifically present on the surface of senescent cells. These proteins may play roles in the maintenance and survival of senescent cells and hence can be targeted for senolysis. In this review, we summarize the recent knowledge regarding senolysis with a focus on novel surface biomarkers of cellular senescence and discuss their emergence as senotherapeutic targets.

Macrophage Phenotype and Fibrosis in Diabetic Nephropathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease globally. The primary initiating mechanism in DN is hyperglycemia-induced vascular dysfunction, but its progression is due to different pathological mechanisms, including oxidative stress, inflammatory cells infiltration, inflammation and fibrosis. Macrophages (Mφ) accumulation in kidneys correlates strongly with serum creatinine, interstitial myofibroblast accumulation and interstitial fibrosis scores. However, whether or not Mφ polarization is involved in the progression of DN has not been adequately defined. The prevalence of the different phenotypes during the course of DN, the existence of hybrid phenotypes and the plasticity of these cells depending of the environment have led to inconclusive results. In the same sense the role of the different macrophage phenotype in fibrosis associated or not to DN warrants additional investigation into Mφ polarization and its role in fibrosis. Due to the association between fibrosis and the progressive decline of renal function in DN, and the role of the different phenotypes of Mφ in fibrosis, in this review we examine the role of macrophage phenotype control in DN and highlight the potential factors contributing to phenotype change and injury or repair in DN.