Antioxidative properties of human milk and spermine are not related to expression of Hsp 70

Role of intestinal Hsp70 in barrier maintenance: contribution of milk to the induction of Hsp70.2

BACKGROUND

Necrotizing enterocolitis (NEC) is a gastrointestinal disease of complex etiology resulting in devastating systemic inflammation and often death in premature newborns. We previously demonstrated that formula feeding inhibits ileal expression of heat shock protein-70 (Hsp70), a critical stress protein within the intestine. Barrier function for the premature intestine is critical. We sought to determine whether reduced Hsp70 protein expression increases neonatal intestinal permeability.

METHODS

Young adult mouse colon cells (YAMC) were utilized to evaluate barrier function as well as intestine from Hsp70-/- pups (KO). Sections of intestine were analyzed by Western blot, immunohistochemistry, and real time PCR. YAMC cells were sub-lethally heated or treated with expressed milk (EM) to induce Hsp70.

RESULTS

Immunostaining demonstrates co-localized Hsp70 and tight junction protein zona occludens-1 (ZO-1), suggesting physical interaction to protect tight junction function. The permeability of YAMC monolayers increases following oxidant injury and is partially blocked by Hsp70 induction either by prior heat stress or EM. RT-PCR analysis demonstrated that the Hsp70 isoforms, 70.1 and 70.3, predominate in WT pup; however, Hsp70.2 predominates in the KO pups. While Hsp70 is present in WT milk, it is not present in KO EM. Hsp70 associates with ZO-1 to maintain epithelial barrier function.

CONCLUSION

Both induction of Hsp70 and exposure to EM prevent stress-induced increased permeability. Hsp70.2 is present in both WT and KO neonatal intestine, suggesting a crucial role in epithelial integrity. Induction of the Hsp70.2 isoform appears to be mediated by mother's milk. These results suggest that mother's milk feeding modulates Hsp70.2 expression and could attenuate injury leading to NEC.

LEVEL OF EVIDENCE

Level III.

Gut epithelial inducible heat-shock proteins and their modulation by diet and the microbiota

The epidemic of metabolic diseases has raised questions about the interplay between the human diet and the gut and its microbiota. The gut has two vital roles: nutrient absorption and intestinal barrier function. Gut barrier defects are involved in many diseases. Excess energy intake disturbs the gut microbiota and favors body entry of microbial compounds that stimulate chronic metabolic inflammation. In this context, the natural defense mechanisms of gut epithelial cells and the potential to boost them nutritionally warrant further study. One such important defense system is the activation of inducible heat-shock proteins (iHSPs) which protect the gut epithelium against oxidative stress and inflammation. Importantly, various microbial components can induce the expression of iHSPs. This review examines gut epithelial iHSPs as the main targets of microbial signals and nutrients and presents data on diseases involving disturbances of gut epithelial iHSPs. In addition, a broad literature analysis of dietary modulation of gut epithelial iHSPs is provided. Future research aims should include the identification of gut microbes that can optimize gut-protective iHSPs and the evaluation of iHSP-mediated health benefits of nutrients and food components.

Prooxidant-antioxidant balance in perinatal asphyxia

OBJECTIVE

To determine the prooxidant-antioxidant balance (PAB) in neonatal asphyxia and compare it with values for PAB in healthy neonates.

METHODS

In a prospective observational study, serum PAB of umbilical cord blood of 30 neonates with asphyxia [pH < 7.2, low Apgar score, signs of respiratory distress syndrome (RDS)] as the case group and 35 healthy neonates (without an abnormal clinical event at birth and after the first week) as the control group were compared.

RESULTS

Among the 35 neonates in the control group, the average level of serum PAB was 20.00 HK units, which was significantly lower than for the 30 neonates within the case group (40.46 HK units; p = 0.019). The blood pH in the case group was significantly lower than for control group (P < 0.001). In controls, HCO3 (-) and pCO2 were 18.6 mmol/L and 38.5 mmHg respectively, whilst in the case group these values were 15.5 mmol/L and 45.7 mmHg respectively (p < 0.05).

CONCLUSIONS

Determination of PAB may be useful in the early diagnosis of perinatal asphyxia and is consistent with HCO3 (-), pCO2 and Apgar score.

Mother's milk-induced Hsp70 expression preserves intestinal epithelial barrier function in an immature rat pup model

Preterm infants face many challenges in transitioning from the in utero to extrauterine environment while still immature. Failure of the preterm gut to successfully mature to accommodate bacteria and food substrate leads to significant morbidity such as neonatal necrotizing enterocolitis. The intestinal epithelial barrier plays a critical role in gut protection. Heat shock protein 70 (Hsp70) is an inducible cytoprotective molecule shown to protect the intestinal epithelium in adult models. To investigate the hypothesis that Hsp70 may be important for early protection of the immature intestine, Hsp70 expression was evaluated in intestine of immature rat pups. Data demonstrate that Hsp70 is induced by exposure to mother's milk. Hsp70 is found in mother's milk, and increased Hsp70 transcription is induced by mother's milk. This Hsp70 colocalizes with the tight junction protein ZO-1. Mother's milk-induced Hsp70 may contribute to maintenance of barrier function in the face of oxidant stress. Further understanding of the means by which mother's milk increases Hsp70 in the ileum will allow potential means of strengthening the intestinal barrier in at-risk preterm infants.