Single-cell transcriptomic analyses reveal distinct immune cell contributions to epithelial barrier dysfunction in checkpoint inhibitor colitis.

Immune checkpoint inhibitor (ICI) therapy has revolutionized oncology, but treatments are limited by immune-related adverse events, including checkpoint inhibitor colitis (irColitis). Little is understood about the pathogenic mechanisms driving irColitis, which does not readily occur in model organisms, such as mice. To define molecular drivers of irColitis, we used single-cell multi-omics to profile approximately 300,000 cells from the colon mucosa and blood of 13 patients with cancer who developed irColitis (nine on anti-PD-1 or anti-CTLA-4 monotherapy and four on dual ICI therapy; most patients had skin or lung cancer), eight controls on ICI therapy and eight healthy controls. Patients with irColitis showed expanded mucosal Tregs, ITGAEHi CD8 tissue-resident memory T cells expressing CXCL13 and Th17 gene programs and recirculating ITGB2Hi CD8 T cells. Cytotoxic GNLYHi CD4 T cells, recirculating ITGB2Hi CD8 T cells and endothelial cells expressing hypoxia gene programs were further expanded in colitis associated with anti-PD-1/CTLA-4 therapy compared to anti-PD-1 therapy. Luminal epithelial cells in patients with irColitis expressed PCSK9, PD-L1 and interferon-induced signatures associated with apoptosis, increased cell turnover and malabsorption. Together, these data suggest roles for circulating T cells and epithelial-immune crosstalk critical to PD-1/CTLA-4-dependent tolerance and barrier function and identify potential therapeutic targets for irColitis.

Prevalence and Appropriateness of Polypharmacy in Older Adults with Inflammatory Bowel Diseases.

BACKGROUND: Despite the growing prevalence of older adults with inflammatory bowel diseases (IBD), polypharmacy, an important geriatric construct, is poorly understood. We described polypharmacy and its implications in older adults with IBD. METHODS: In a cross sectional study of adults ≥ 60 years with IBD, we obtained medication lists from the medical record and patients. We assessed medications by the Beer's criteria, anti-cholinergic burden and drug-drug interactions. We constructed multi-variate logistic regression models to assess association between polypharmacy with low quality-of-life, controlling for age, sex, IBD-type, number of comorbidities and depression. RESULTS: In 100 adults ≥ 60 years with IBD, with a median age of 68 years, 56% met criteria for remission by a validated disease activity index. Polypharmacy, defined as ≥ 5 concomitant medications, was noted in 86% of the cohort and 45% had severe polypharmacy, defined as ≥ 10 concomitant medications. In this cohort, 48% were on ≥ 1 medication that met Beer's criteria for potentially inappropriate in older adults and 24% had a cumulative anti-cholinergic drug burden score of ≥ 3, the threshold for serious adverse events attributed to anti-cholinergic burden. Serious drug-drug interactions were found in 26% with 7% involving an IBD medication. Controlling for potential confounders, polypharmacy, defined both numerically (OR 22.79, p < 0.01) and by medication appropriateness (OR 1.95, p < 0.01), was significantly associated with low quality of life. CONCLUSION: Polypharmacy is prevalent in older adults with IBD and independently associated with low quality of life. Describing polypharmacy can guide de-prescription strategies tailored to GI clinic for older adults with IBD.

Why Are Gly31, Gly33, and Gly35 Highly Conserved in All Fluorescent Proteins?

Green fluorescent protein (GFP)-like fluorescent proteins have been found in more than 120 species. Although the proteins have little sequence identity, Gly31, 33, and 35 are 87, 100, and 95% conserved across all species, respectively. All GFP-like proteins have a ß-barrel structure composed of 11 ß-sheets, and the 3 conserved glycines are located in the second ß-sheet. Molecular dynamics (MD) simulations have shown that mutating one or more of the glycines to alanines most likely does not reduce chromophore formation in correctly folded immature fluorescent proteins. MD and protein characterization of alanine mutants indicate that mutation of the conserved glycines leads to misfolding. Gly31, 33, and 35 are essential to maintain the integrity of the ß1-3 triad that is the last structural element to slot in place in the formation of the canonical fluorescent protein ß-barrel. Glycines located in ß-sheets may have a similar role in the formation of other non-GFP ß-barrels.