# Inhibition of the JAK and MEK Pathways Limits Mitochondrial ROS Production in Human Saphenous Vein Smooth Muscle Cells

## TL;DR

This study shows that blocking JAK and MEK pathways reduces harmful ROS production in vein cells from diabetic patients, which could help prevent vein graft failure.

## Contribution

The study identifies JAK and MEK pathways as novel therapeutic targets for reducing mitochondrial ROS in diabetic saphenous vein smooth muscle cells.

## Key findings

- Ruxolitinib and trametinib significantly reduce mitochondrial ROS in HSVSMCs from both T2DM and non-diabetic patients.
- HSVSMCs from T2DM patients have higher basal mitochondrial ROS levels compared to non-diabetic controls.
- Inhibition of JAK/STAT and MAPK/ERK1,2 pathways reduces ROS-driven proliferation and migration in HSVSMCs.

## Abstract

What are the main findings?
Ruxolitinib and trametinib, JAK and MEK inhibitors, respectively, limit mitochondrial-derived ROS (mROS) production in human saphenous vein smooth muscle cells (HSVSMC), which is responsible for the maladaptive remodelling leading to saphenous VGF.Basal mROS level is higher in HSVSMCs from type 2 diabetic patients (T2DM) compared with non-diabetic patients.

Ruxolitinib and trametinib, JAK and MEK inhibitors, respectively, limit mitochondrial-derived ROS (mROS) production in human saphenous vein smooth muscle cells (HSVSMC), which is responsible for the maladaptive remodelling leading to saphenous VGF.

Basal mROS level is higher in HSVSMCs from type 2 diabetic patients (T2DM) compared with non-diabetic patients.

What are the implications of the main findings?
The JAK and MEK pathways are potential targets to reduce T2DM-dependent increased mROS production.The JAK and MEK pathways present viable targets for drug development to limit ROS-driven VGF.

The JAK and MEK pathways are potential targets to reduce T2DM-dependent increased mROS production.

The JAK and MEK pathways present viable targets for drug development to limit ROS-driven VGF.

Activation of JAK/STAT and MAPK/ERK1,2 signalling pathways has been shown to increase the production of reactive oxygen species (ROS) in multiple cell types involved in cardiovascular diseases (CVDs), including vascular smooth muscle cells (VSMCs). However, these have not yet been studied in human saphenous vein SMCs (HSVSMCs) responsible for the maladaptive remodelling leading to saphenous vein graft failure (VGF), to which patients with type 2 diabetes mellitus (T2DM) are more susceptible. Therefore, this study aimed to evaluate the contributions of the JAK/STAT and MAPK/ERK1,2 pathways towards production of mitochondrial ROS (mROS) in HSVSMCs from T2DM patients versus non-diabetic controls. HSVSMCs explanted from surplus HSV tissues from consenting patients undergoing coronary artery bypass graft surgery were stimulated in vitro with mitogenic stimuli known to be involved in neointimal hyperplasia (NIH) and VGF, which are known activators of the JAK/STAT and the MAPK/ERK1,2 signalling pathways. Flow cytometry was then used to analyse the production of mROS (superoxide) in MitoSOX-stained HSVSMCs. Additionally, we examined the effect of ruxolitinib and trametinib, selective inhibitors of JAK1/2 and MEK1/2 signalling pathways, respectively, on mROS levels in these cells. From our findings, mROS production was significantly higher in HSVSMCs from T2DM patients versus non-diabetic controls. Activation of either the JAK/STAT or MAPK/ERK1,2 signalling pathways did not significantly alter the production of mROS in HSVSMCs from both T2DM and non-diabetic patients. However, inhibition of JAK/STAT and MAPK/ERK1,2 signalling pathways with ruxolitinib and trametinib, respectively, resulted in a significant reduction in mROS in HSVSMCs from both T2DM and non-diabetic patients. Our findings demonstrate a JAK/STAT- and MAPK/ERK1,2-mediated production of mROS in HSVSMCs. Hence, they are potential targets for drug development to limit ROS production in ROS-driven proliferation and migration of HSVSMCs responsible for VGF.