Buprenorphine pharmacotherapy for the management of neonatal abstinence syndrome in methadone-exposed neonates.

We aimed to compare the outcomes of pharmacotherapy with either buprenorphine or methadone in infants treated for neonatal abstinence syndrome (NAS) secondary to intrauterine exposure to methadone. This is a multi-center, retrospective cohort study to assess length of treatment (LOT), hospital length of stay (LOS), and cumulative opioid exposure between infants treated with either methadone or buprenorphine for NAS secondary to in utero exposure to methadone. Infants delivered at a gestational age ≥35 weeks and a maternal history of opioid-use disorder and/or urine drug screen positive for methadone, and postnatal pharmacotherapy for NAS with either buprenorphine or methadone as first-line opioid replacement therapy, were eligible. Median LOT, LOS, and cumulative opioid exposure were compared between buprenorphine- and methadone-treated infants. A total of 156 infants (48 treated with buprenorphine and 108 with methadone) were identified. The median LOT and LOS for buprenorphine-treated infants was 8 and 13 days compared with 15 and 20 days for methadone-treated infants, respectively, P < .001 for both outcomes. Median cumulative opioid dose in morphine equivalents was 0.6 mg/kg for buprenorphine-treated infants vs 1.05 mg/kg for methadone-treated infants, P < .001. No adverse effects were noted among either group. Of infants treated with buprenorphine, 34 (71%) required the addition of adjunctive pharmacotherapy during the NICU stay, compared with 31 (32%) in the methadone-treated group, P = .0008. However, significantly fewer infants treated with buprenorphine required continuation of therapy beyond discharge as compared with those treated with methadone. The difference is most likely a reflection of the protocols used by the sites. In infants that required pharmacotherapy for NAS secondary to intrauterine exposure to methadone, treatment with buprenorphine, compared with methadone therapy, was associated with better outcomes. If confirmed with prospective data, buprenorphine could be considered first-line therapy for the two medication-assisted treatment regimens recommended by the American College of Obstetricians and Gynecologists.

Comparison of Neonatal Abstinence Syndrome Treatment with Sublingual Buprenorphine versus Conventional Opioids.

OBJECTIVE: The objective of this study was to compare duration of opioid treatment and length of stay outcomes for neonatal abstinence syndrome (NAS) using sublingual buprenorphine versus traditional weaning with methadone or morphine. STUDY DESIGN: This retrospective cohort analysis evaluated infants treated for NAS at a single community hospital from July 2013 through June 2017. A standardized weaning protocol was introduced in June 2015, allowing for treatment with sublingual buprenorphine regardless of type of intrauterine opioid exposure. General linear models were used to calculate adjusted mean duration of opioid treatment and length of hospitalization with 95% confidence intervals for infants treated with buprenorphine compared with traditional weaning with either methadone or morphine. RESULTS: A total of 360 infants were treated with either buprenorphine (n = 174) or a traditional opioid (n = 186). Infants treated with buprenorphine experienced a 3.0-day reduction in opioid treatment duration of 7.4 (6.3-8.5) versus 10.4 (9.3-11.5) days (p < 0.001) and a 2.8-day reduction in length of stay of 12.4 (11.3-13.6) versus 15.2 (14.1-16.4) days (p < 0.001). CONCLUSION: Our study provides an independent confirmation that among infants experiencing NAS following a wide array of intrauterine opioid exposures, buprenorphine weaning supports a shortened treatment duration compared with conventional weaning agents.

Nedd4-2-mediated ubiquitination facilitates processing of surfactant protein-C.

We previously proposed a model of surfactant protein (SP)-C biosynthesis in which internalization of the proprotein from the limiting membrane of the multivesicular body to internal vesicles represents a key step in the processing and secretion of SP-C. To test this hypothesis, alanine mutagenesis of the N-terminal propeptide of SP-C was performed. Adenoviruses encoding mutant proproteins were infected into type II cells isolated from Sftpc(-/-) mice, and media analyzed for secreted SP-C 24 hours after infection. Mutation of S(12)PPDYS(17) completely blocked secretion of SP-C. PPDY (PY motif) has previously been shown to bind WW domains of neural precursor cell-expressed developmentally down-regulated (Nedd) 4-like E3 ubiquitin ligases. Purified recombinant glutathione S-transferase-SP-C propeptide (residues 1-35) bound recombinant Nedd4-2 strongly, and Nedd4 weakly; the S(12)PPDYS(17)mutation abrogated binding of SP-C to Nedd4-2. Immobilized recombinant Nedd4-2 WW domain captured SP-C proprotein from mouse type II cell lysates; in the reverse pulldown, endogenous SP-C in type II cells was captured by recombinant Nedd4-2. To determine if the interaction of Nedd4-2 and SP-C resulted in ubiquitination, the SP-C proprotein was immunoprecipitated from transiently transfected human embryonic kidney 293 cells, and analyzed by SDS-PAGE/Western blotting with ubiquitin antibody. Two ubiquitinated forms of SP-C were detected; ubiquitination was blocked by mutation of K6, but not K34, in the SP-C propeptide. Mutation of K6 also inhibited processing of SP-C proprotein to the mature peptide in human embryonic kidney 293 cells. Nedd4-2-mediated ubiquitination regulates lumenal relocation of SP-C, leading to processing and, ultimately, secretion of SP-C.

Partial SP-B deficiency perturbs lung function and causes air space abnormalities.

Surfactant protein B (SP-B) is required for function of newborn and adult lung, and partial deficiency has been associated with susceptibility to lung injury. In the present study, transgenic mice were produced in which expression of SP-B in type II epithelial cells was conditionally regulated. Concentrations of SP-B were maintained at 60-70% of that normally present in control. Immunostaining for SP-B demonstrated cellular heterogeneity in expression of the protein. In subsets of type II cells in which SP-B staining was decreased, immunostaining for pro-SP-C was increased and lamellar body ultrastructure was disrupted, consistent with focal SP-B deficiency. Fluorescence-activated cell sorting analyses of freshly isolated type II cells identified a population of cells with low SP-B content and a smaller population with increased SP-B content, confirming nonuniform expression of the SP-B transgene. Focal air space enlargement, without cellular infiltration or inflammation, was observed. Pressure-volume curves indicated that maximal tidal volume was unchanged; however, hysteresis was modestly altered and residual volumes were significantly decreased in the SP-B-deficient mice. Chronic, nonuniform SP-B deficiency perturbed pulmonary function and caused air space enlargement.

Processing of pulmonary surfactant protein B by napsin and cathepsin H.

Surfactant protein B (SP-B) is an essential constituent of pulmonary surfactant. SP-B is synthesized in alveolar type II cells as a preproprotein and processed to the mature peptide by the cleavage of NH2- and COOH-terminal peptides. An aspartyl protease has been suggested to cleave the NH2-terminal propeptide resulting in a 25-kDa intermediate. Napsin, an aspartyl protease expressed in alveolar type II cells, was detected in fetal lung homogenates as early as day 16 of gestation, 1 day before the onset of SP-B expression and processing. Napsin was localized to multivesicular bodies, the site of SP-B proprotein processing in type II cells. Incubation of SP-B proprotein from type II cells with a crude membrane extract from napsin-transfected cells resulted in enhanced levels of a 25-kDa intermediate. Purified napsin cleaved a recombinant SP-B/EGFP fusion protein within the NH2-terminal propeptide between Leu178 and Pro179, 22 amino acids upstream of the NH2 terminus of mature SP-B. Cathepsin H, a cysteine protease also implicated in pro-SP-B processing, cleaved SP-B/EGFP fusion protein 13 amino acids upstream of the NH2 terminus of mature SP-B. Napsin did not cleave the COOH-terminal peptide, whereas cathepsin H cleaved the boundary between mature SP-B and the COOH-terminal peptide and at several other sites within the COOH-terminal peptide. Knockdown of napsin by small interfering RNA resulted in decreased levels of mature SP-B and mature SP-C in type II cells. These results suggest that napsin, cathepsin H, and at least one other enzyme are involved in maturation of the biologically active SP-B peptide.

Maintenance of the mouse type II cell phenotype in vitro.

The purpose of this study was to identify culture conditions for maintenance of isolated mouse type II cells with intact surfactant protein (SP) and phospholipid production. Type II cells were isolated from 6-wk-old mice and cultured on Matrigel matrix-rat tail collagen (70:30 vol/vol) in bronchial epithelial cell growth medium minus hydrocortisone plus 5% charcoal-stripped FBS and 10 ng/ml keratinocyte growth factor. Under these conditions, type II cells actively produced surfactant phospholipids and proteins for at least 7 days. Synthesis and secretion of surfactant phospholipids and SP-A, -B, -C, and -D declined on day 1 of culture but recovered by day 3, reaching levels comparable to or exceeding freshly isolated cells by day 5. Abundant lamellar bodies were readily apparent in cells examined on days 5 and 7, and a surfactant pellet was recovered by centrifugation of media harvested on each day of culture. Secretion of SP-B, SP-C, and phosphatidylcholine was stimulated by phorbol 12-myristate 13-acetate and was inhibited by compound 48/80. When tested with a bubble surfactometer, surfactant secreted by type II cells on day 5 of culture lowered surface tension to 5.2 +/- 2.3 mN/m. This is the first description of the synthesis and secretion of a functional surfactant complex by mouse type II cells after 7 days in primary culture.