Porcine placenta hydrolysates regulate calcium disturbance in MC3T3-E1 osteoblastic cells

Background: In bone metabolism, Ca²⁺ disturbance and oxidative damage are the main biochemical factors related to pathology. Osteoblasts are bone-forming cells that also control bone endocrinology. Endocrine hormones and proteins are matured, folded, and secreted in the endoplasmic reticulum (ER). ER stress has emerged as a new pathological mechanism to explain bone disturbance. Here we studied the role of porcine placenta hydrolysates (PPHs) in the regulation of ER stress. Methods: Cell viability was determined in vitro using trypan blue dye exclusion. ER stress and apoptosis were evaluated using immunoblotting and a caspase kit. The fluorescent Ca²⁺-binding dye Fura-2/AM was used to measure changes in intracellular Ca²⁺ ([Ca²⁺]_i). ROS levels, NADPH oxidase activity, and superoxide dismutase (SOD) activity were also measured. Results: PPHs protected MC3T3-E1 osteoblastic cells against thapsigargin (Tg)-induced ER stress. Moreover, PPHs regulated caspase-12 and -3 activities, thereby protecting against cell death, and also regulated Tg-induced Ca²⁺ release. The Ca²⁺ chelator BAPT/AM also regulated caspase-12 and -3 activities and prevented Ca² stress-induced cell death. In the presence of PPHs or BAPTA/AM, Ca²⁺-related ROS were also regulated, as demonstrated by alterations in NADPH oxidase and SOD activity. Conclusions: PPHs appear to regulate bone metabolism disturbance by controlling Ca²⁺ concentrations, and thus ER stress and ROS, in osteoblasts cultured in vitro.