Neutrophil peptidylarginine deiminase 4 is essential for detrimental age-related cardiac remodelling and dysfunction in mice

Nets in fibrosis: Bridging innate immunity and tissue remodeling

Fibrosis, a complex pathological process characterized by excessive deposition of extracellular matrix components, leads to tissue scarring and dysfunction. Emerging evidence suggests that neutrophil extracellular traps (NETs), composed of DNA, histones, and antimicrobial proteins, significantly contribute to fibrotic diseases pathogenesis. This review summarizes the process of NETs production, molecular mechanisms, and related diseases, and outlines the cellular and molecular mechanisms associated with fibrosis. Subsequently, this review comprehensively summarizes the current understanding of the intricate interplay between NETs and fibrosis across various organs, including the lung, liver, kidney, skin, and heart. The mechanisms by which NETs contribute to fibrogenesis, including their ability to promote inflammation, induce epithelial-mesenchymal transition (EMT), activate fibroblasts, deposit extracellular matrix (ECM) components, and trigger TLR4 signaling were explored. This review aimed to provide insights into the complex relationship between NETs and fibrosis via a comprehensive analysis of existing reports, offering novel perspectives for future research and therapeutic interventions.

Neuroinflammatory Responses and Blood-Brain Barrier Injury in Chronic Alcohol Exposure: Role of Purinergic P2X7 Receptor Signaling

Alcohol consumption leads to neuroinflammation and blood-brain barrier (BBB) damage, resulting in neurological impairment. We previously demonstrated that ethanol-induced disruption of barrier function in human brain endothelial cells was associated with mitochondrial injury, increased ATP and extracellular vesicle (EV) release, and purinergic receptor P2X7R activation. Therefore, we aimed to evaluate the effect of P2X7r blockade on peripheral and neuro-inflammation in EtOH-exposed mice. In a chronic intermittent ethanol (CIE)-exposed mouse model, P2X7R was inhibited by two different methods: Brilliant Blue G (BBG) or gene knockout. We assessed blood ethanol concentration (BEC), plasma P2X7R and P-gp, number of extra-cellular vesicles (EV), serum ATP and EV-ATP levels. Brain microvessel gene expression and EV mtDNA copy numbers were measured by RT2 PCR array and digital PCR, respectively. A RT2 PCR array of brain microvessels revealed significant upregulation of proinflammatory genes involved in apoptosis, vasodilation, and platelet activation in CIE-exposed animals, which were decreased 15-50-fold in BBG-treated CIE-exposed animals. Plasma P-gp levels and serum P2X7R shedding were significantly increased in CIE-exposed animals. Pharmacological or genetic suppression of P2X7R decreased P2X7R shedding to levels equivalent to those in control group. The increase in EV number and EV-ATP content in the CIE-exposed mice was significantly reduced by P2X7R inhibition. CIE mice showed augmented EV-mtDNA copy numbers which were reduced in EVs after P2X7R inhibition or receptor knockout. These observations suggested that P2X7R signaling plays a critical role in ethanol-induced brain injury. Increased eATP, EV-ATP, EV numbers, and EV-mtDNA copy numbers highlight a new mechanism of brain injury during alcohol exposure via P2X7R and biomarkers of such damage. In this study, for the first time, we report the in vivo involvement of P2X7R signaling in CIE-induced brain injury.

Neutrophil peptidylarginine deiminase 4 plays a systemic role in obesity-induced chronic inflammation in mice

BACKGROUND

Obesity is an increasing problem in our current society and is expected to keep rising in incidence. With its multiorigin, complex pathophysiology, it is difficult to treat and easy to acquire unnoticeably. During obesity, it has been established that the body is in a constant state of low-grade inflammation, thereby causing changes in immune cell physiology.

OBJECTIVES

Here, we investigated the influence of neutrophils, more specifically as a result of peptidylarginine deiminase 4 (PAD4) activity and the release of neutrophil extracellular traps (NETs), during obesity-induced chronic inflammation.

METHODS

Wild-type mice were placed on a high-fat diet (HFD) and investigated over a period of 10 weeks for NET formation and its impact on the heart. Neutrophil-selective PAD4 knockout (Ne-PAD4-/-) mice were studied in parallel.

RESULTS

As a result of high fat intake, we observed clear alteration in the priming status of isolated neutrophils toward NET release, including early stages of speck formation and histone citrullination of apoptosis-associated speck-like protein containing a CARD. Ne-PAD4-/- mice deficient in NET formation did not increase bodyweight to the same extent as their littermate controls, with Ne-PAD4-/- mice being leaner after 10 weeks of HFD feeding. Interestingly, obesity progression led to cardiac remodeling and diastolic dysfunction in wild-type mice after 10 weeks, while this remodeling and subsequent decrease in function were absent in Ne-PAD4-/- mice. Surprisingly, HFD did not alter NET content or thrombus formation in the inferior vena cava stenosis model.

CONCLUSION

Detrimental physiological effects, the result of obesity progression, can in part be attributed to neutrophil PAD4 and NETs in response to chronic inflammation.