Table 1.

Pathological roles of MPO in tissue inflammation and disease.

Disease	MPO Activity	References
Cardiovascular Disease	Elevated MPO in atherosclerosis associated with disease severity MPO oxidizes low density lipoproteins, promoting the formation of atherosclerotic lesions MPO binds the ECM of smooth muscle cells and alters ECM composition MPO alters the rigidity of platelets, promoting aggregation and vascular inflammation	[60,77,89,90,91,92]
Neurodegenerative Disorders	MPO modulates neuronal, microglial cells, and astrocyte activity MPO-derived ROS cause vascular inflammation in the brain MPO accumulation is observed Alzheimer’s disease and contributes to severity of symptoms (demonstrated via improved health in KO mice) MPO levels positively correlate with MS severity	[69,70,71,93,94,95]
Cancer	MPO induces DNA damage and promotes mutational burden MPO enhances breast cancer progression in murine models MPO converts procarcinogens into carcinogens	[96,97,98]
Inflammatory Bowel Disease	Elevated MPO levels associated with increased morbidity MPO levels are higher in the stool of patients with active IBD MPO impairs resolution of mucosal injury via suppression of IEC migration and proliferation MPO inhibition limits severity of colitis MPO released on NETs exacerbates colitis, promotes tissue damage, and is positively correlated with severity of Crohn’s disease	[42,57,75,76,99]
Obesity	Obese individuals have significantly increased MPO in serum MPO participates in the regulation of obesity, however the specific function remains to be determined MPO inhibition attenuates liver damage associated with obesity	[65,100,101]
Pulmonary Inflammation	MPO degrades the glycocalyx, which is important in neutrophil adhesion and lung injury MPO deficiency promotes or suppresses inflammation in the lung in different models of pulmonary infection MPO inhibition shows limited efficacy as a potential therapeutic for tuberculosis	[82,102,103,104]
Arthritis	Experimentally induced arthritis is attenuated in MPO deficient individuals Elevated MPO levels promote oxidative stress in patients with arthritis	[68,105,106]
Ischemic Stroke	MPO levels positively correlate with the risk for recurrent acute stroke MPO inhibition is protective against inflammation-associated cell death following stroke	[107,108]