4‐Hydroxy‐2‐Nonenal (HNE), a product of Lipid Peroxidation, Induces Tissue Factor Decryption by modulating Thioredoxin system and mitochondrial ROS generation independently
Authors: Ansari Shabbir Ahmed , Pendurthi Usha R. , Rao L. Vijay Mohan 
Published: November 2023

Oxidative stress plays a major role in the pathogenesis of various diseases such as atherosclerosis. Aberrant expression of a coagulation cofactor tissue factor (TF) is thought to contribute to the pathogenesis of atherosclerosis. Recently, we found that 4‐hydroxy‐2‐nonenal (HNE), a major aldehyde produced by oxidation of ω‐6 polyunsaturated fatty acids, increases the procoagulant activity of cell surface tissue factor (TF). These studies revealed that HNE generates ROS and decrypts TF through p38 MAPK‐dependent externalization of phosphatidylserine (PS). The present study is carried out to elucidate the detailed molecular mechanism involved in HNE‐induced TF decryption. Colocalization of ROS generation and mitochondrial staining indicated that mitochondria are the major source of HNE‐induced ROS generation. Inhibitors of the mitochondrial electron transport chain (ETC) complexes III and V significantly inhibited the HNE‐induced ROS generation. These inhibitors also attenuated the HNE‐induced PS externalization and TF activation, indicating that HNE‐induced ROS generation contributes to PS exposure critical for TF decryption. Interestingly, inhibition of ROS by these inhibitors did not block the HNE‐induced p38 MAPK activation. Additional studies showed that HNE inhibits thioredoxin (Trx) and thioredoxin reductase (TrxR) activities in a dose‐ and time‐dependent manner. Antioxidant N‐acetylcysteine (NAC) prevented the HNE‐induced inhibition of TrxR but the inhibitors of mitochondrial ETC that prevented HNE‐induced ROS generation failed to block the HNE‐induced TrxR inhibition. To investigate whether HNE‐induced inhibition of Trx or TrxR is responsible for HNE‐induced TF decryption, we determined whether inhibition of the activity of Trx or TrxR by their pharmacological inhibitors would also activate TF. Treatment of the cells with either curcumin, Auranofin or PMX‐464 (TrxR inhibitors) or PX‐12 (Trx inhibitor) markedly increased TF activity in a PS‐dependent manner. Inhibition of the TrxR/Trx also activated MKK3/6 and p38 MAPK as observed with HNE. Active Trx binds ASK1 and inactivation of Trx disrupts the complex, enabling ASK1 activation that leads to p38 MAPK activation. Therefore, we investigated whether HNE‐induced inactivation of Trx leads to ASK1 activation that could lead to p38 MAPK activation. Our data show HNE neither induces ASK1 activation nor ASK1 inhibitors block HNE‐induced TF decryption, suggesting that p38 MAPK activation is independent of ASK1. In additional experiments, we found that blockade of thiol groups by phenylarsine oxide (PAO) attenuated HNE‐induced PS exposure and TF decryption. In summary, our present data suggest that HNE induces TF decryption by two separate pathways – one is ROS‐dependent but independent of p38 MAPK activation and the second is via Trx‐TrxR‐ and p38 MAPK‐dependent. Both the mechanisms result in the exposure of PS at the cell surface that contributes to TF decryption. Blockade of thiol groups by PAO appears to inhibit HNE‐induced TF decryption by blocking the upstream signaling molecules that regulate HNE‐induced PS exposure.