Background Bursopentin (BP5) is a multifunctional pentapeptide found in the chicken bursa of Fabricius. Recent study indicated that BP5 significantly stimulates expression of p53 protein in colon cancer HCT116 cells. However, the effects and underlying mechanisms of BP5 on HCT116 cell proliferation remain largely unclear. Methods Analyses of cell viability, cell cycle arrest as well as apoptosis were performed to study the actions of BP5 on HCT116 cells. Western blot analyse was assayed to measure the cell cycle-related and apoptosis-related proteins. Specific siRNAs targeting IRE1, ATF-6, and PERK were used for IRE1, ATF-6, and PERK knockdown, respectively. Cellular reactive oxygen species (ROS) were detected using a H 2 DCF-DA green fluorescence probe. Cytosolic free Ca 2+ concentrations and mitochondrial membrane potential (ΔΨm) were measured using Fluo-3 AM and JC-1 stains, respectively. Results BP5 possessed strong inhibitory effects on the cell growth and induced apoptosis in HCT116 cells. Mechanistically, BP5 arrested the cell cycle at G1 phase by increasing p53 and p21 expression and decreasing cyclin E1-CDK2 complex expression. BP5 treatment dramatically activated the endoplasmic reticulum (ER) stress-mediated apoptotic pathway, as revealed by the significantly enhanced expression of unfolded protein response (UPR) sensors (IRE1α, ATF6, PERK) as well as downstream signaling molecules (XBP-1s, eIF2α, ATF4 and CHOP), and by the significantly altered the BP5-induced phenotypic changes in IRE1, ATF6, and PERK knockdown cells. Additionally, BP5-induced ER stress was accompanied by the accumulation of cytosolic free Ca 2+ and intracellular ROS. Furthermore, BP5 treatment resulted in the increase of Bax expression, the decrease of Bcl-2 expression and the reduction of ΔΨm, subsequently causing a release of cytochrome c from the mitochondria into the cytoplasm and finally enhancing the activities of caspase-9 and -3. In addition, z-VAD-fmk, a pan-caspase inhibitor, markedly rescued BP5-induced cell viability reduction and reduced BP5-induced apoptosis. Conclusions Our present results suggest that BP5 has an anticancer capacity to arrest cell cycle at G1 phase and to trigger ER stress/mitochondria-mediated caspase-dependent apoptosis in HCT116 cells. Therefore, our findings provide insight into further investigations of the anticancer activities of BP5. Electronic supplementary material The online version of this article (10.1186/s12935-019-0849-3) contains supplementary material, which is available to authorized users.

No abstract

No abstract

No abstract

Polylactide (PLA) was melt blended with low amounts of poly(butylene adipate-co-terephthalate) (PBAT) using a simple reactive extrusion process herein, aiming to address the inherent brittleness of PLA without significantly compromising its stiffness. PLA/PBAT (90/10) blends with a small amount of peroxide (0.02 phr) and a second crosslinker agent TAIC (triallyl isocyanurate) were produced to explore the structure-performance relationship evolution in reactive extrusion. The results showed that the PLA blend with an appropriate amount of TAIC (i.e., 1.0 phr) exhibited a remarkable increase in elongation at break, reaching as high as 76.8%, which was 22 times higher compared to pure PLA and 6.8 times higher than unmodified PLA/PBAT blends. Furthermore, the sample with high elongation also demonstrated a high stiffness, boasting a Young's modulus of 1.6 GPa and a yield strength of 43 MPa. It was evident that both interfacial adhesion and PBAT size significantly influenced the stretchability of the PLA/PBAT blends. The combination of enhanced compatibility and optimized PBAT phase size of approximately 1.0 µm worked synergistically to enhance the toughness of PLA. Notably, either larger or smaller particle sizes did not contribute favorably to enhancing the toughness of PLA, even if compatibility was improved. The addition of small amounts of TAIC successfully reduced the PBAT phase size but did not enhance compatibility, leading to subpar mechanical performance. Conversely, higher TAIC contents resulted in over-crosslinking, despite considerable improvements in compatibility. This study offers a versatile, scalable, and practical method to prepare fully biodegradable PLA blends with high toughness.