Endoplasmic reticulum stress in bone marrow-derived cells prevents acute cardiac inflammation and injury in response to angiotensin II.

Inflammation plays an important role in hypertensive cardiac injury. The endoplasmic reticulum (ER) stress pathway is involved in the inflammatory response. However, the role of ER stress in elevated angiotensin II (Ang II)-induced cardiac injury remains unclear. In this study, we investigated the role of ER stress in Ang II-induced hypertensive cardiac injury. Transcriptome analysis and quantitative real-time PCR showed that Ang II infusion in mice increased ER stress-related genes expression in the heart. C/EBP homologous protein (CHOP) deficiency, a key mediator of ER stress, increased infiltration of inflammatory cells, especially neutrophils, the production of inflammatory cytokines, chemokines in Ang II-infused mouse hearts. CHOP deficiency increased Ang II-induced cardiac fibrotic injury: (1) Masson trichrome staining showed increased fibrotic areas, (2) immunohistochemistry staining showed increased expression of α-smooth muscle actin, transforming growth factor β1 and (3) quantitative real-time PCR showed increased expression of collagen in CHOP-deficient mouse heart. Bone marrow transplantation experiments indicated that CHOP deficiency in bone marrow cells was responsible for Ang II-induced cardiac fibrotic injury. Moreover, TUNEL staining and flow cytometry revealed that CHOP deficiency decreased neutrophil apoptosis in response to Ang II. Taken together, our study demonstrated that hypertension induced ER stress after Ang II infusion. ER stress in bone marrow-derived cells protected acute cardiac inflammation and injury in response to Ang II.