Resilience to acute kidney injury in offspring of maternal protein restriction

Renal, but not platelet or skin, extracellular vesicles decrease oxidative stress, enhance nascent peptide synthesis, and protect from ischemic renal injury

Acute kidney injury (AKI) is deadly and expensive, and specific, effective therapy remains a large unmet need. We have demonstrated the beneficial effects of transplanted adult tubular cells and extracellular vesicles (EVs; exosomes) derived from those renal cells on experimental ischemic AKI, even when administered after renal failure is established. To further examine the mechanisms of benefit with renal EVs, we tested the hypothesis that EVs from other epithelia or platelets (a rich source of EVs) might be protective, using a well-characterized ischemia-reperfusion model. When given after renal failure was present, renal EVs, but not those from skin or platelets, markedly improved renal function and histology. The differential effects allowed us to examine the mechanisms of benefit with renal EVs. We found significant decreases in oxidative stress postischemia in the renal EV-treated group with preservation of renal superoxide dismutase and catalase as well as increases in anti-inflammatory interleukin-10. In addition, we propose a novel mechanism of benefit: renal EVs enhanced nascent peptide synthesis following hypoxia in cells and in postischemic kidneys. Although EVs have been used therapeutically, these results serve as "proof of principle" to examine the mechanisms of injury and protection.NEW & NOTEWORTHY Acute kidney injury is common and deadly, yet the only approved treatment is dialysis. Thus, a better understanding of injury mechanisms and potential therapies is needed. We found that organ-specific, but not extrarenal, extracellular vesicles improved renal function and structure postischemia when given after renal failure occurred. Oxidative stress was decreased and anti-inflammatory interleukin-10 increased with renal, but not skin or platelet, exosomes. We also propose enhanced nascent peptide synthesis as a novel protective mechanism.

Developmental Programming-Aging Interactions Have Sex-Specific and Developmental Stage of Exposure Outcomes on Life Course Circulating Corticosterone and Dehydroepiandrosterone (DHEA) Concentrations in Rats Exposed to Maternal Protein-Restricted Diets

The steroids corticosterone and dehydroepiandrosterone (DHEA) perform multiple life course functions. Rodent life-course circulating corticosterone and DHEA trajectories are unknown. We studied life course basal corticosterone and DHEA in offspring of rats fed protein-restricted (10% protein, R) or control (20% protein, C), pregnancy diet first letter, and/or lactation second letter, producing four offspring groups-CC, RR, CR, and RC. We hypothesize that 1. maternal diet programs are sexually dimorphic, offspring life course steroid concentrations, and 2. an aging-related steroid will fall. Both changes differ with the plastic developmental period offspring experienced R, fetal life or postnatally, pre-weaning. Corticosterone was measured by radioimmunoassay and DHEA by ELISA. Steroid trajectories were evaluated by quadratic analysis. Female corticosterone was higher than male in all groups. Male and female corticosterone were highest in RR, peaked at 450 days, and fell thereafter. DHEA declined with aging in all-male groups. DHEA: corticosterone fell in three male groups but increased in all-female groups with age. In conclusion, life course and sexually dimorphic steroid developmental programming-aging interactions may explain differences in steroid studies at different life stages and between colonies experiencing different early-life programming. These data support our hypotheses of sex and programming influences and aging-related fall in rat life course serum steroids. Life course studies should address developmental programming-aging interactions.

Repeated Episodes of Ischemia/Reperfusion Induce Heme-Oxygenase-1 (HO-1) and Anti-Inflammatory Responses and Protects against Chronic Kidney Disease

Preconditioning episodes of ischemia/reperfusion (IR) induce protection against acute kidney injury (AKI), however their long-term effect still unknown. We evaluated AKI to chronic kidney disease (CKD) transition, after three-mild or three-severe episodes of IR. AKI was induced by single bilateral IR (1IR), or three episodes of IR separated by 10-day intervals (3IR) of mild (20 min) or severe (45 min) ischemia. Sham-operated rats served as controls. During 9-months, the 1IR group (20 or 45 min) developed CKD evidenced by progressive proteinuria and renal fibrosis. In contrast, the long-term adverse effects of AKI were markedly ameliorated in the 3IR group. The acute response in 3IR, contrasted with the 1IR group, that was characterized by an increment in heme oxygenase-1 (HO-1) and an anti-inflammatory response mediated by a NFkB-p65 phosphorylation and IL-6 decrease, together with an increase in TGF-β, and IL-10 expression, as well as in M2-macrophages. In addition, three episodes of IR downregulated endoplasmic reticulum (ER) stress markers expression, CHOP and BiP. Thus, repeated episodes of IR with 10-day intervals induced long-term renal protection accompanied with HO-1 overexpression and M2-macrophages increase.

Sirtuin 7 Deficiency Reduces Inflammation and Tubular Damage Induced by an Episode of Acute Kidney Injury

Acute kidney injury (AKI) is a public health problem worldwide. Sirtuins are a family of seven NAD+-dependent deacylases, Overexpression of Sirtuin 1, 3, and 5 protect against AKI. However, the role of Sirtuin 7 (Sirt7) in AKI is not known. Here, we analyzed how Sirt7 deficient mice (KO-Sirt7) were affected by AKI. As expected, wild-type and Sirt7 heterozygotes mice that underwent renal ischemia/reperfusion (IR) exhibited the characteristic hallmarks of AKI: renal dysfunction, tubular damage, albuminuria, increased oxidative stress, and renal inflammation. In contrast, the KO-Sirt7+IR mice were protected from AKI, exhibiting lesser albuminuria and reduction in urinary biomarkers of tubular damage, despite similar renal dysfunction. The renoprotection in the Sirt7-KO+IR group was associated with reduced kidney weight, minor expression of inflammatory cytokines and less renal infiltration of inflammatory cells. This anti-inflammatory effect was related to diminished p65 expression and in its active phosphorylation, as well as by a reduction in p65 nuclear translocation. Sirt7 deficient mice are protected from AKI, suggesting that this histone deacetylase promotes tubular damage and renal inflammation. Therefore, our findings indicate that Sirt7 inhibitors may be an attractive therapeutic target to reduce NFκB signaling.

Transient response of serpinA3 during cellular stress

We demonstrated that serpinA3c/k relocates from the cytoplasm to the apical tubular membrane (ATM) in chronic kidney disease (CKD), suggesting its secretion in luminal space in pathophysiological contexts. Here, we studied serpinA3c/k expression and secretion under different stressful conditions in vitro and in vivo. HEK-293 cells were transfected with a FLAG-tagged serpinA3c/k clone and exposed to H₂ O₂ or starvation. Both stressors induced serpinA3c/k secretion but with a higher molecular weight. Glycanase treatment established that serpinA3c/k is glycosylated. Site-directed mutagenesis for each of the four glycosylation sites was performed. During cellular stress, serpinA3c/k secretion increased with each mutant except in the quadruple mutant. In rats and patients suffering acute kidney injury (AKI), an atypical urinary serpinA3c/k excretion (uSerpinA3c/k) was observed. In rats with AKI, the greater the induced kidney damage, the greater the uSerpinA3 c/k, together with relocation toward ATM. Our findings show that: (1) serpinA3c/k is glycosylated and secreted, (2) serpinA3c/k secretion increases during cellular stress, (3) its appearance in urine reveals a pathophysiological state, and (4) urinary serpinA3 excretion could become a potential biomarker for AKI.

Early triggers of moderately high-fat diet-induced kidney damage

Most of the obesity murine models inducing renal injury use calorie-enriched foods, where fat represents 60% of the total caloric supply, however, this strategy doubles the standard proportion of fat ingestion in obese patients. Therefore, it is crucial to study the impact of a high-fat intake on kidney physiology that resembles common obesity in humans to understand the trigger mechanisms of the long-term consequences of overweight and obesity. In this study, we analyzed whether chronic feeding with a moderately high fat diet (MHFD) representing 45% of total calories, may induce kidney function and structural injury compared to C57BL/6 mice fed a control diet. After 14 weeks, MHFD induced significant mice obesity. At the functional level, obese mice showed signs of kidney injury characterized by increased albuminuria/creatinine ratio and higher excretion of urinary biomarkers of kidney damage. While, at the structural level, glomerular hypertrophy was observed. Although, we did not detect renal fibrosis, the obese mice exhibited a significant elevation of Tgfb1 mRNA levels. Kidney damage caused by the exposure to MHFD was associated with greater oxidative stress, renal inflammation, higher endoplasmic reticulum (ER)-stress, and disruption of mitochondrial dynamics. In summary, our data demonstrate that obesity induced by a milder fat content diet is enough to establish renal injury, where oxidative stress, inflammation, ER-stress, and mitochondrial damage take relevance, pointing out the importance of opportune interventions to avoid the long-term consequences associated with obesity and metabolic syndrome.