Changes in beta(1) integrin in renal tubular epithelial cells after intrauterine asphyxia of rabbit pups

Predictive ability of 2-h serum neutrophil gelatinase-associated lipocalin for perinatal asphyxia-induced acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a common cause of mortality and morbidity in asphyxiated newborns. Recent research suggests serum neutrophil gelatinase-associated lipocalin (sNGAL) as an early biomarker of AKI in newborns with perinatal asphyxia. The prospect of sNGAL is yet to be studied in Nigeria, with a huge burden of asphyxia-related neonatal deaths.

METHODS

A cross-sectional analytic study was conducted on 53 asphyxiated term newborns and 53 healthy babies at the newborn unit of the Wesley Guild Hospital Ilesa, Nigeria. sNGAL was assessed in all neonates with perinatal asphyxia at baseline (within 30 min of delivery), 2 h, and 48 h of life.

RESULTS

Mean sNGAL was significantly higher in asphyxiated newborns than in the control group, 81.4 (45.9) vs. 53.7 (29.2), p < 0.001. However, the mean 2-h sNGAL levels were similar in asphyxiated babies with and without AKI 100.5 (36.7) ng/ml vs. 85.3 (31.4) ng/ml, p = 0.115. The 2-h sNGAL with an AUC of 0.61 at an 83.0 ng/ml cut-off had an acceptable discriminating capability of predicting AKI. The sensitivity, specificity, positive predictive value, and negative predictive value were 80%, 51.5%, 50%, and 81%, respectively.

CONCLUSION

This study shows that sNGAL levels were significantly elevated in newborns with perinatal asphyxia compared to healthy neonates, but the 2-h sNGAL is less predictive of AKI in newborns with perinatal asphyxia. The negative predictive value is high, and this may find some relevance in the attempts at early exclusion of asphyxiated babies prone to AKI. A higher resolution version of the Graphical abstract is available as Supplementary information.

Hypoxia Decreases Invasin-Mediated Yersinia enterocolitica Internalization into Caco-2 Cells

Yersinia enterocolitica is a major cause of human yersiniosis, with enterocolitis being a typical manifestation. These bacteria can cross the intestinal mucosa, and invade eukaryotic cells by binding to host β₁ integrins, a process mediated by the bacterial effector protein invasin. This study examines the role of hypoxia on the internalization of Y. enterocolitica into intestinal epithelial cells, since the gastrointestinal tract has been shown to be physiologically deficient in oxygen levels (hypoxic), especially in cases of infection and inflammation. We show that hypoxic pre-incubation of Caco-2 cells resulted in significantly decreased bacterial internalization compared to cells grown under normoxia. This phenotype was absent after functionally blocking host β₁ integrins as well as upon infection with an invasin-deficient Y. enterocolitica strain. Furthermore, downstream phosphorylation of the focal adhesion kinase was also reduced under hypoxia after infection. In good correlation to these data, cells grown under hypoxia showed decreased protein levels of β₁ integrins at the apical cell surface whereas the total protein level of the hypoxia inducible factor (HIF-1) alpha was elevated. Furthermore, treatment of cells with the HIF-1 α stabilizer dimethyloxalylglycine (DMOG) also reduced invasion and decreased β₁ integrin protein levels compared to control cells, indicating a potential role for HIF-1α in this process. These results suggest that hypoxia decreases invasin-integrin-mediated internalization of Y. enterocolitica into intestinal epithelial cells by reducing cell surface localization of host β₁ integrins.