No abstract

Protoberberines represent a structural class of organic cations that induce topoisomerase I-mediated DNA cleavage, a behavior termed topoisomerase I poisoning. We have employed a broad range of biophysical, biochemical, and computer modeling techniques to characterize and cross-correlate the DNA-binding and topoisomerase poisoning properties of four protoberberine analogues that differ with respect to the substituents on their A- and/or D-rings. Our data reveal the following significant features: (i) The binding of the four protoberberines unwinds duplex DNA by approximately 11 degrees, an observation consistent with an intercalative mode of interaction. (ii) Enthalpically favorable interactions, such as stacking interactions between the intercalated ligand and the neighboring base pairs, provide <50% of the thermodynamic driving force for the complexation of the protoberberines to duplex DNA. Computer modeling studies on protoberberine-DNA complexes suggest that only rings C and D intercalate into the host DNA helix, while rings A and B protrude out of the helix interior into the minor groove. (iii) All four protoberberine analogues are topoisomerase I-specific poisons, exhibiting little or no topoisomerase II poisoning activity. (iv) Modifications of the D-ring influence both DNA binding and topoisomerase I poisoning properties. Specifically, transference of a methoxy substituent from the 11- to the 9-position diminishes both DNA binding affinity and topoisomerase I poisoning activity, an observation suggesting that DNA binding is important in the poisoning of topoisomerase I by protoberberines. (v) Modifications of the A-ring have a negligible impact on DNA binding affinity, while exerting a profound influence on topoisomerase I poisoning activity. Specifically, protoberberine analogues containing either 2,3-dimethoxy; 3,4-dimethoxy; or 3, 4-methylenedioxy substituents all bind DNA with a similar affinity. By contrast, these analogues exhibit markedly different topoisomerase I poisoning activities, with these activities following the hierarchy: 3,4-methylenedioxy > 2,3-dimethoxy >> 3, 4-dimethoxy. These differences in topoisomerase I poisoning activity may reflect the differing abilities of the analogues to interact with specific functionalities on the enzyme, thereby stabilizing the enzyme in its cleavable state. In the aggregate, our results are consistent with a mechanistic model in which both ligand-DNA and ligand-enzyme interactions are important for the poisoning of topoisomerase I by protoberberines, with the DNA-directed interactions involving ring D and the enzyme-directed interactions involving ring A. It is reasonable to suggest that the poisoning of topoisomerase I by a broad range of other naturally occurring and synthetic ligands may entail a similar mechanism.

Purpose: Social and economic factors have been shown to affect health outcomes. In particular, social determinants of health (SDH) are linked to poor health outcomes in children. Research and some professional academies support routine social needs screening during primary care visits. Translating this recommendation into practice remains challenging due to the resources required and dearth of evidence-based research to guide health center level implementation. We describe our experience implementing a novel social needs screening program at an academic pediatric clinic. Methods: The Community Linkage to Care (CLC) pilot program integrates social needs screening and referral support using community health workers (CHWs) as part of routine primary care visits. Our multidisciplinary team performed process mapping, developed workflows, and led ongoing performance improvement activities. We established key elements of the CLC program through an iterative process We conducted social needs screens at 65% of eligible well-child visits from May 2017 to April 2018; 19.7% of screens had one or more positive responses. Childcare (48.8%), housing quality and/or availability (39.9%), and food insecurity (22.8%) were the most frequently reported needs. On average, 76% of providers had their patients screened on more than half of eligible well-child visits. Discussion: Our experience suggests that screening for social needs at well-child visits is feasible as part of routine primary care. We attribute progress to leveraging resources, obtaining provider buy-in, and defining program components to sustain activities.

Social determinants of health (SDH) significantly affect the health of children and thus, screening is important in pediatric primary care. We assessed the use of a formal social history taking tool after a 2-phase intervention. The first phase (P1) was a teaching module describing SDH and community resources and the second phase (P2) consisted of visual reminders to use the tool. Patient charts (n = 322) were reviewed pre- and postintervention. Residents had higher documentation rates of Women, Infants, and Children (WIC) program use and housing subsidies at post-P1 and at post-P(1 + 2) (WIC, P = .01 and P = .03, respectively; housing, P = .02 and P = .04, respectively), and higher documentation rates of food stamp utilization at post-P(1 + 2) ( P = .04), as compared with baseline. Implementation of a simple teaching tool in the outpatient setting enabled residents to document income benefits and housing. Further studies should be done to evaluate effective teaching methods to elicit other important SDH.