Abstract Body: Background: Cannabis use has been linked to increased cardiovascular risk, yet the cellular mechanisms underlying Δ⁹-tetrahydrocannabinol (Δ⁹-THC)-induced vascular dysfunction remain poorly understood. Vascular fibrosis and endothelial dysfunction are key drivers of cardiovascular disease and pathological vascular remodeling, but whether Δ⁹-THC directly promotes pro-fibrotic cellular states has not been established.
Aims: To investigate the effects of Δ⁹-THC on fibroblast and endothelial cell phenotype and function using complementary in vitro and in vivo models.
Approach: Primary human fibroblasts and human coronary artery endothelial cells (HCAECs) were treated with Δ⁹-THC (5 µM, 48 hours) or vehicle control. Phenotypic changes were assessed by immunofluorescence (α-SMA, SM22, PDGFRβ, CD31), EdU proliferation assays, and qRT-PCR for inflammatory markers (IL1B, CXCL8). For in vivo studies, healthy wild-type C57BL/6J mice received Δ⁹-THC (1 mg/kg, i.p.) or vehicle for 8 weeks. Cardiovascular function was evaluated by Doppler echocardiography (coronary flow velocity reserve, CFVR) and ex vivo aortic wire myography in response to acetylcholine (ACh) and sodium nitroprusside (SNP).
Results: Δ⁹-THC significantly upregulated pro-fibrotic markers in fibroblasts (α-SMA: 1.48±0.12 vs. vehicle, p=0.028; SM22: 1.31±0.07 vs. vehicle, p=0.036), comparable to TGF-β stimulation. Δ⁹-THC also induced a pro-inflammatory response (IL-1β protein: p=0.004; IL1B and CXCL8 mRNA: 4-fold and 18-fold increases, respectively; p=0.029) and reduced fibroblast proliferation (EdU+ cells: 0.67±0.03 vs. vehicle 0.83±0.02, p=0.0029). In HCAECs, Δ⁹-THC increased SM22 expression (p=0.0001) without altering CD31, indicating acquisition of a mesenchymal-like signature. Chronic Δ⁹-THC exposure in vivo impaired coronary flow velocity reserve (CFVR: 1.73±0.07 vs. vehicle 2.26±0.08, p=0.0004) and reduced endothelium-dependent (ACh: p<0.01 at 10^-7–10^-5 M) and endothelium-independent (SNP: p<0.0001 at 10^-8 M, p<0.05 at 10^-7–10^-6 M) vasorelaxation.
Conclusion: These findings demonstrate that Δ⁹-THC promotes pro-fibrotic, pro-inflammatory phenotypic shifts in vascular cells and impairs coronary and endothelial function in vivo. The convergence of cellular remodeling and functional deficits highlights a critical mechanism linking cannabis use to cardiovascular disease. Further studies are needed to elucidate the pathways underlying these observations and to assess their translational relevance.