MicroRNA-21 promotes fibrosis of the kidney by silencing metabolic pathways

Scarring of the kidney is a major public health concern, directly promoting loss of kidney function. To understand the role of microRNA (miRNA) in the progression of kidney scarring in response to injury, we investigated changes in miRNA expression in two kidney fibrosis models and identified 24 commonly up-regulated miRNAs. Among them, miR-21 was highly elevated in both animal models and in human transplanted kidneys with nephropathy. Deletion of miR-21 in mice resulted in no overt abnormality. However, miR-21(-/-) mice suffered far less interstitial fibrosis in response to kidney injury, a phenotype duplicated in wild-type mice treated with anti-miR-21 oligonucleotides. Global derepression of miR-21 target mRNAs was readily detectable in miR-21(-/-) kidneys after injury. Analysis of gene expression profiles up-regulated in the absence of miR-21 identified groups of genes involved in metabolic pathways, including the lipid metabolism pathway regulated by peroxisome proliferator-activated receptor-α (Pparα), a direct miR-21 target. Overexpression of Pparα prevented ureteral obstruction-induced injury and fibrosis. Pparα deficiency abrogated the antifibrotic effect of anti-miR-21 oligonucleotides. miR-21 also regulated the redox metabolic pathway. The mitochondrial inhibitor of reactive oxygen species generation Mpv17l was repressed by miR-21, correlating closely with enhanced oxidative kidney damage. These studies demonstrate that miR-21 contributes to fibrogenesis and epithelial injury in the kidney in two mouse models and is a candidate target for antifibrotic therapies.

MicroRNA-21 limits in vivo immune response-mediated activation of the IL-12/IFN-gamma pathway, Th1 polarization, and the severity of delayed-type hypersensitivity

An altered balance between Th1 and Th2 cytokines is responsible for a variety of immunoinflammatory disorders such as asthma, yet the role of posttranscriptional mechanisms, such as those mediated by microRNAs (miRs), in adjusting the relative magnitude and balance of Th cytokine expression have been largely unexplored. In this study, we show that miR-21 has a central role in setting a balance between Th1 and Th2 responses to Ags. Targeted ablation of miR-21 in mice led to reduced lung eosinophilia after allergen challenge, with a broadly reprogrammed immunoactivation transcriptome and significantly increased levels of the Th1 cytokine IFN-γ. Biological network-based transcriptome analysis of OVA-challenged miR-21(-/-) mice identified an unexpected prominent dysregulation of IL-12/IFN-γ pathways as the most significantly affected in the lungs, with a key role for miR-21 in IFN-γ signaling and T cell polarization, consistent with a functional miR-21 binding site in IL-12p35. In support of these hypotheses, miR-21 deficiency led dendritic cells to produce more IL-12 after LPS stimulation and OVA-challenged CD4(+) T lymphocytes to produce increased IFN-γ and decreased IL-4. Further, loss of miR-21 significantly enhanced the Th1-associated delayed-type hypersensitivity cutaneous responses. Thus, our results define miR-21 as a major regulator of Th1 versus Th2 responses, defining a new mechanism for regulating polarized immunoinflammatory responses.

Regulation of ion channel/neurotransmitter receptor function by RNA editing

RNA editing by select adenosine deamination (A-to-I editing) alters functional determinants in certain ion channels and neurotransmitter receptors in vertebrates and invertebrates. In most cases, edited and unedited versions of a given receptor/channel co-exist to expand the functional space of the receptor population. Recent studies have characterized K(+) channels in squid that are edited at multiple positions, revealed a role for Q/R site editing in AMPA receptor assembly, and demonstrated a link between serotonin levels and the extent of editing of a mammalian serotonin receptor.

Point mutation in an AMPA receptor gene rescues lethality in mice deficient in the RNA-editing enzyme ADAR2

RNA editing by site-selective deamination of adenosine to inosine alters codons and splicing in nuclear transcripts, and therefore protein function. ADAR2 (refs 7, 8) is a candidate mammalian editing enzyme that is widely expressed in brain and other tissues, but its RNA substrates are unknown. Here we have studied ADAR2-mediated RNA editing by generating mice that are homozygous for a targeted functional null allele. Editing in ADAR2-/- mice was substantially reduced at most of 25 positions in diverse transcripts; the mutant mice became prone to seizures and died young. The impaired phenotype appeared to result entirely from a single underedited position, as it reverted to normal when both alleles for the underedited transcript were substituted with alleles encoding the edited version exonically. The critical position specifies an ion channel determinant, the Q/R site, in AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptor GluR-B pre-messenger RNA. We conclude that this transcript is the physiologically most important substrate of ADAR2.

The effects of prenatal care utilization and maternal risk factors on pregnancy outcome between Mexican Americans and non-Hispanic whites

This study evaluates the effects of prenatal care classification and levels of maternal risk status on pregnancy outcomes in Mexican Americans and non-Hispanic whites in Arizona. All live birth certificates from 1986 and 1987 were reviewed yielding a total population of 101,206 (26,827 Mexican Americans). The adequacy of prenatal care was evaluated based on an index that includes six prenatal care groups. Two levels of maternal risk status (low and high) were defined based on a series of maternal risk factors. Overall, Mexican Americans had a greater proportion of maternal risk factors and a greater proportion of mothers with inadequate or no prenatal care compared with non-Hispanic whites. Prematurity and macrosomia were more prevalent than low birthweight in Mexican Americans. Low-risk status and adequate prenatal care regardless of ethnicity were found to be associated with a lower prevalence of low birthweight and preterm delivery. Whites, however, had a greater variation in the prevalence of low birthweight associated with changes in prenatal care utilization and maternal risk status compared with Mexican Americans. Finally, logistic regression analysis showed an independent effect of prenatal care, maternal risk status, maternal age, and maternal birthplace in predicting the overall low birthweight rate in Mexican Americans. The implications of these results are discussed relative to the usefulness of prenatal care as a health-care intervention in Mexican Americans.

Mexican-Americans' use of prenatal care and its relationship to maternal risk factors and pregnancy outcome

We evaluate the adequacy of prenatal care use and the association of use to a series of maternal risk factors and pregnancy outcomes, such as low birthweight, preterm delivery, and macrosomia in both Mexican-Americans and non-Hispanic whites in Arizona. The data came from all live-birth certificates from 1986 and 1987 for a total of 101,202 (26,826 Mexican-Americans). We evaluated the adequacy of prenatal care using a redesigned index that accounts for three factors: the month when prenatal care began, the number of prenatal care visits, and the duration of pregnancy. From this index we identified six prenatal care groups: intensive, adequate, intermediate, inadequate, no-care, and missing/unknown. Overall, we observed ethnic differences in patterns of prenatal care use, social profiles, and medical risk factors. Non-Hispanic whites, compared to Mexican-Americans, showed a greater risk for low birthweight and preterm delivery in those groups receiving poor prenatal care versus those who received adequate care. Within Mexican-Americans the risk of low birthweight was not the same for all subgroups. A higher overall prevalence of preterm delivery and macrosomia in comparison to low birthweight occurred in Mexican-Americans. We discuss the implications of the results for the identification, interpretation, evaluation, and public health significance of perinatal health problems of Mexican-Americans.

Breast-feeding policies and routines among Arizona hospitals and nursery staff: results and implications of a descriptive study

In 1988, Arizona's 61 hospitals providing obstetrical services were canvased with regard to hospital routines that favor either breast-feeding or bottle-feeding. Forty-five hospitals provided responses that were used in the survey. Practices favoring breast-feeding, which were reported by a majority of the hospitals (more than 50%), were demand feeding, staff assessment for "latch-on" (the action of nipple presentation and sucking initiation) and positioning, "rooming-in" (the practice of minimal mother-infant separation), and information about follow-up support services. Hospital practices suggested to promote bottle-feeding were the provision of pacifiers and supplemental water or glucose, issuance of formula packs at discharge, and a first feed of sterile water. A positive significant relationship was identified for policies advocating breast-feeding and the prevalence of breast-feeding encouragement from professional staff. Of 44 respondents, 41 indicated that their hospital's policies endorse breast-feeding as the ideal method of feeding healthy newborns. Hospital staff perceived that they encourage mothers to breast-feed and offer support to those who initiate breast-feeding. On the basis of this information, we conclude that dietetics practitioners should evaluate current breast-feeding practices and integrate policies supportive of breast-feeding into the health care system.

Stability of carmustine in the presence of sodium bicarbonate

The stability of carmustine in 5% dextrose injection and 0.9% sodium chloride injection, with and without added sodium bicarbonate, was studied at room temperature. Solutions of carmustine (0.1 mg/ml) in dextrose or saline with and without added sodium bicarbonate (1 meq/ml) were prepared. After 0, 15, 30, 60, and 90 minutes, aliquots of each test solution were analyzed for carmustine using the Bratton-Marshall test with absorbance at 540 nm. There was no significant decomposition of carmustine in dextrose or saline alone. However, the addition of sodium bicarbonate increased carmustine degradation; after 90 minutes, approximately 73% of the active drug remained. It is recommended that carmustine be neither admixed with nor administered piggyback with parenteral infusion solutions containing sodium bicarbonate.