View Brian L. Lin's publications

The overarching goal of my research is to investigate mechanosensitive ion channel signaling in cardiac and skeletal muscle diseases. Full description My current research focuses on testing novel therapies in mouse and human models of Duchenne muscular dystrophy (DMD). DMD is caused by a loss of dystrophin, resulting in progressive muscle weakness and immobility, severe spinal deformities, pathological fibrosis, heart failure, and early mortality. The muscle weakness and loss of the ability to walk are the symptoms most commonly associated with DMD. However, most DMD patients eventually succumb to cardiac failure, as the heart is also a muscle. In muscle cells, loss of dystrophin destabilizes the sarcolemma membrane which hyperactivates mechanosensitive cation (notably Ca2+) channels and downstream fibrotic signaling, cell damage and death, and cardiac arrhythmia. We identified TRPC6 (transient receptor potential – canonical 6) as one such mechanosensitive ion channel hyperactivated in DMD. TRPC6-dependent excess Ca2+ influx resulted in hypercontraction and arrhythmia in beating DMD cardiomyocytes subjected to acute mechanical load. Breeding severe mdx/utrn-/- DMD mice into the TRPC6-null background improves cardiac and skeletal muscle function, and extended the lifespan of by 2-3 fold. Using new and specific TRPC6 inhibitors in mouse models and in vitro human stem cell models of DMD show normalization of Ca2+ transients and improvement in cardiac contraction. We show TRPC6 inhibition works to treat DMD. Our goal is to determine how. Mechanosensative Ion Channels and Inflammation One striking discovery was the localization of myocardial damage in DMD hearts that was attenuated with TRPC6 inhibition. Using traditional histology as a guide, I applied spatial transcriptomics and proteomics to these hearts to investigate potential causes. Gene set enrichment analysis identified signaling associated with inflammatory cytokines. Circulating cytokines in DMD mice show that systemic inflammatory signaling is indeed mediated by TRPC6 in DMD. TRPC6 inhibition reduces classic pro-inflammatory cytokines, such as TNFα, and promoted anti-inflammatory cytokines such as IL-10. Therefore, we seek to determine the precise source and localization of these cytokines and their impact on myocyte function. The Role of Copper in Myocytes Furthermore, signaling involving copper (Cu+) or use Cu+ as a cofactor was identified enriched within areas of myocardial damage. Preliminary analysis using laser-ablated mass spec shows elevated Cu+ in the muscles of our DMD mice, and is consistent with human DMD biopsy data that shows only two elevated ions – Cu+ and Ca2+. While Ca2+ has been well-studied in DMD, the role of Cu+ in DMD hearts remains unknown. Therefore, we seek to combine traditional histology with spatial -omics and mass spectrometry to elucidate the role of Cu+ in DMD and determine the therapeutic efficacy of TRPC6 inhibition to attenuate excess Cu+ in DMD. Mechanical Stress Mechanisms in the Heart Finally, we demonstrate a link between Ca2+/calmodulin-dependent protein kinase II (CaMKII) and TRPC6-mediated mechanosensitive signaling. CaMKII and TRPC6 appear to require one another to regulate mechanical stress responses in the heart, and the dysregulation of one is thought to exacerbate the pathological signaling of the other. Therefore, using both mouse and human induced pluripotent stem cell-derived cardiomyocytes, we seek to determine the impact of TRPC6 inhibition on mitigating the vicious feed-forward signaling between CaMKII and TRPC6.