Intestinal Dysbiosis and the Developing Lung: The Role of Toll-Like Receptor 4 in the Gut-Lung Axis.

Background: In extremely premature infants, postnatal growth restriction (PNGR) is common and increases the risk of developing bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). Mechanisms by which poor nutrition impacts lung development are unknown, but alterations in the gut microbiota appear to play a role. In a rodent model, PNGR plus hyperoxia causes BPD and PH and increases intestinal Enterobacteriaceae, Gram-negative organisms that stimulate Toll-like receptor 4 (TLR4). We hypothesized that intestinal dysbiosis activates intestinal TLR4 triggering systemic inflammation which impacts lung development. Methods: Rat pups were assigned to litters of 17 (PNGR) or 10 (normal growth) at birth and exposed to room air or 75% oxygen for 14 days. Half of the pups were treated with the TLR4 inhibitor TAK-242 from birth or beginning at day 3. After 14 days, pulmonary arterial pressure was evaluated by echocardiography and hearts were examined for right ventricular hypertrophy (RVH). Lungs and serum samples were analyzed by western blotting and immunohistochemistry. Results: Postnatal growth restriction + hyperoxia increased pulmonary arterial pressure and RVH with trends toward increased plasma IL1ß and decreased IκBα, the inhibitor of NFκB, in lung tissue. Treatment with the TLR4 inhibitor attenuated PH and inflammation. Conclusion: Postnatal growth restriction induces an increase in intestinal Enterobacteriaceae leading to PH. Activation of the TLR4 pathway is a promising mechanism by which intestinal dysbiosis impacts the developing lung.

The developing gut-lung axis: postnatal growth restriction, intestinal dysbiosis, and pulmonary hypertension in a rodent model.

BACKGROUND: Postnatal growth restriction (PNGR) in premature infants increases risk of pulmonary hypertension (PH). In a rodent model, PNGR causes PH, while combining PNGR and hyperoxia increases PH severity. We hypothesized that PNGR causes intestinal dysbiosis and that treatment with a probiotic attenuates PNGR-associated PH. METHOD: Pups were randomized at birth to room air or 75% oxygen (hyperoxia), to normal milk intake (10 pups/dam) or PNGR (17 pups/dam), and to probiotic Lactobacillus reuteri DSM 17938 or phosphate-buffered saline. After 14 days, PH was assessed by echocardiography and right ventricular hypertrophy (RVH) was assessed by Fulton's index (right ventricular weight/left ventricle + septal weight). The small bowel and cecum were analyzed by high-throughput 16S ribosomal RNA gene sequencing. RESULTS: PNGR with or without hyperoxia (but not hyperoxia alone) altered the microbiota of the distal small bowel and cecum. Treatment with DSM 17938 attenuated PH and RVH in pups with PNGR, but not hyperoxia alone. DSM 17938 treatment decreased α-diversity. The intestinal microbiota differed based on oxygen exposure, litter size, and probiotic treatment. CONCLUSION: PNGR causes intestinal dysbiosis and PH. Treatment with DSM 17938 prevents PNGR-associated RVH and PH. Changes in the developing intestine and intestinal microbiota impact the developing lung vasculature and RV.

Postnatal growth restriction augments oxygen-induced pulmonary hypertension in a neonatal rat model of bronchopulmonary dysplasia.

BACKGROUND: Prematurity and fetal growth restriction are risk factors for pulmonary hypertension (PH) in infants with bronchopulmonary dysplasia (BPD). Neonatal rats develop PH and vascular remodeling when exposed to hyperoxia. We hypothesize that postnatal growth restriction (PNGR) due to under-nutrition increases the severity of PH induced by hyperoxia in neonatal rats. METHODS: Pups were randomized at birth to litters maintained in room air or 75% oxygen (hyperoxia), together with litters of normal milk intake (10 pups) or PNGR (17 pups). After 14 d, right ventricular hypertrophy (RVH) was assessed by Fulton's index (right ventricular weight/left ventricular plus septal weight) and PH by echocardiography. Lungs were analyzed by immunohistochemistry, morphometrics, western blotting, and metabolomics. RESULTS: Hyperoxia and PNGR each significantly increased pulmonary arterial pressure, RVH and pulmonary arterial medial wall thickness, and significantly decreased pulmonary vessel number. These changes were significantly augmented in pups exposed to both insults. Hyperoxia and PNGR both significantly decreased expression of proteins involved in lung development and vasodilation. CONCLUSION: PNGR induces right ventricular and pulmonary vascular remodeling and augments the effects of oxygen in neonatal rats. This may be a powerful tool to investigate the mechanisms that induce PH in low-birth-weight preterm infants with BPD.

Inflammation and Cardiometabolic Risk in African American Women Is Reduced by a Pilot Community-Based Educational Intervention.

BACKGROUND: Cardiovascular disease (CVD) is the leading cause of death for women, and African Americans have higher rates of CVD mortality than do other racio/ethnic groups. Women in community settings can benefit from preventive interventions, yet few investigations of successful programs have been conducted and evaluated in high-risk women, especially for metabolic syndrome. The purpose of our study was to pilot and assess the effectiveness of a 4-month pre-/post-CVD preventive educational intervention in improving knowledge, clinical risk profiles, adoption of heart-healthy lifestyles, inflammatory burden, and cardiometabolic risk in African American women in local communities. METHODS: Forty-two African American women (mean age 59 years) enrolled in the 4-month educational Cardiovascular Disease Preventive Intervention Program in Sacramento, CA, in 2010. Participants completed knowledge-based surveys pre-/postintervention, provided clinical measures (weight, waist circumference, body mass index (BMI), blood pressure and blood samples for analysis of fasting glucose and lipids, and inflammatory markers: tumor necrosis factor (TNF)-α±, high-sensitivity C-reactive protein (hs-CRP), and interleukin (IL)-12. RESULTS: The CVD risk profile of participants confirmed a high-risk cohort. Postintervention (n=31), there were significant (p<0.05) gains in knowledge for all symptoms of a heart attack and calling 911; improvements in clinical risk parameters, especially for waist circumference and low-density lipoprotein (LDL) cholesterol (p<0.05); and reductions in all the inflammatory markers assessed: TNF-α±by 16%, IL-12 by 20%, and hs-CRP by 26% (p<0.05). There was also a 60% reduction in the number of participants with metabolic syndrome (MetS) (p<0.05), driven primarily by reductions in triglycerides and glucose and a rise in high-density lipoprotein (HDL) cholesterol. CONCLUSIONS: We demonstrated the efficacy of a pilot community-based educational cardiovascular program in reducing cardiometabolic risk and inflammation in high-risk African American women. Our successful culturally appropriate and sustainable model could be implemented as part of comprehensive efforts to improve community-based health outcomes.