Faculty Bibliography

Photosensitivity, or skin sensitivity to ultraviolet radiation (UVR), is a feature of lupus erythematosus and other autoimmune and dermatologic conditions, but the mechanistic underpinnings are poorly understood. We identify a Langerhans cell (LC)-keratinocyte axis that limits UVR-induced keratinocyte apoptosis and skin injury via keratinocyte epidermal growth factor receptor (EGFR) stimulation. We show that the absence of LCs in Langerin-diphtheria toxin subunit A (DTA) mice leads to photosensitivity and that, in vitro, mouse and human LCs can directly protect keratinocytes from UVR-induced apoptosis. LCs express EGFR ligands and a disintegrin and metalloprotease 17 (ADAM17), the metalloprotease that activates EGFR ligands. Deletion of ADAM17 from LCs leads to photosensitivity, and UVR induces LC ADAM17 activation and generation of soluble active EGFR ligands, suggesting that LCs protect by providing activated EGFR ligands to keratinocytes. Photosensitive systemic lupus erythematosus (SLE) models and human SLE skin show reduced epidermal EGFR phosphorylation and LC defects, and a topical EGFR ligand reduces photosensitivity. Together, our data establish a direct tissue-protective function for LCs, reveal a mechanistic basis for photosensitivity, and suggest EGFR stimulation as a treatment for photosensitivity in lupus erythematosus and potentially other autoimmune and dermatologic conditions.

Nonadherence to treatment is a major cause of lupus flares. Hydroxychloroquine (HCQ), a major medication in systemic lupus erythematosus, has a long half-life and can be quantified by HPLC. This international study evaluated nonadherence in 305 lupus patients with flares using drug levels (HCQ<200ng/ml or undetectable desethylchloroquine), and self-administered questionnaires (MASRI<80% or MMAS-8<6). Drug levels defined 18.4% of the patients as severely nonadherent. In multivariate analyses, younger age, non-use of steroids, higher BMI and unemployment were associated with nonadherence by drug level. Questionnaires classified 39.9% of patients as nonadherent. Correlations between adherence measured by questionnaires, drug level, and physician assessment were moderate. Both methods probably measured two different patterns of nonadherence: self-administered questionnaires mostly captured relatively infrequently missed tablets, while drug levels identified severe nonadherence (i.e., interruption or erratic tablet intake). The frequency with which physicians miss nonadherence, together with under-reporting by patients, suggests that therapeutic drug monitoring is useful in this setting.

OBJECTIVES: The presence of tubulointerstitial damage (TID) on renal biopsy is considered to be a late sequela of lupus nephritis (LN). The objective of this study was to determine if TID predicts progression to end stage renal disease (ESRD) in LN patients without advanced kidney disease. METHODS: All SLE patients with an index biopsy consistent with LN between January 2005 and July 2015, and eGFR >/= 30mL/min/1.73m2 were included. Moderate-to-severe TID was defined as the presence of moderate-to-severe tubular atrophy and/or interstitial fibrosis. Time to ESRD was defined as time from the index biopsy date to incident ESRD date; non-ESRD patients were censored at the time of death or the last visit before December 2015. Time-dependent analyses were conducted to evaluate whether moderate-to-severe TID was predictive of ESRD progression. RESULTS: Of the 131 LN patients with eGFR >/= 30mL/min/1.73m2, 17 (13%) patients progressed to ESRD. Moderate-to-severe TID was present in 13% of biopsies with eGFR >/= 60mL/min/1.73m2 and in 33% of biopsies with eGFR between 30 and 60mL/min/1.73m2. Moderate-to-severe TID was associated with a higher risk of ESRD progression: adjusted hazard ratio (HR) = 4.1, 95% CI: 1.4-12.1, p = 0.01 for eGFR >/= 30mL/min/1.73m2; HR = 6.2, 95% CI: 1.7-23.2, p = 0.008 for eGFR >/= 60mL/min/1.73m2. There was no association between tubulointerstitial inflammation (TII) and ESRD progression. CONCLUSIONS: Moderate-to-severe TID, but not TII, was a strong predictor of ESRD progression independent of eGFR or glomerular findings, therefore, providing an important window for potential early interventions.

Lupus nephritis is a leading cause of mortality among systemic lupus erythematosus (SLE) patients, and its heterogeneous nature poses a significant challenge to the development of effective diagnostics and treatments. Single cell RNA sequencing (scRNA-seq) offers a potential solution to dissect the heterogeneity of the disease and enables the study of similar cell types distant from the site of renal injury to identify novel biomarkers. We applied scRNA-seq to human renal and skin biopsy tissues and demonstrated that scRNA-seq can be performed on samples obtained during routine care. Chronicity index, IgG deposition, and quantity of proteinuria correlated with a transcriptomic-based score composed of IFN-inducible genes in renal tubular cells. Furthermore, analysis of cumulative expression profiles of single cell keratinocytes dissociated from nonlesional, non-sun-exposed skin of patients with lupus nephritis also revealed upregulation of IFN-inducible genes compared with keratinocytes isolated from healthy controls. This indicates the possible use of scRNA-seq analysis of skin biopsies as a biomarker of renal disease. These data support the potential utility of scRNA-seq to provide new insights into the pathogenesis of lupus nephritis and pave the way for exploiting a readily accessible tissue to reflect injury in the kidney.