Inhibition of Fatty Acid Synthesis Aggravates Brain Injury, Reduces Blood-Brain Barrier Integrity and Impairs Neurological Recovery in a Murine Stroke Model.

Lisa Janssen,Dirk M Hermann,Thorsten R Doeppner,Xiaoyu Ai,Mathias Bähr,Xuan Zheng,Ertugrul Kilic,Ahmet B Caglayan,Ya-Chao Wang,Vivek Venkataramani,Wei Wei

doi:10.3389/fncel.2021.733973

Abstract

Inhibition of fatty acid synthesis (FAS) stimulates tumor cell death and reduces angiogenesis. When SH-SY5Y cells or primary neurons are exposed to hypoxia only, inhibition of FAS yields significantly enhanced cell injury. The pathophysiology of stroke, however, is not only restricted to hypoxia but also includes reoxygenation injury. Hence, an oxygen-glucose-deprivation (OGD) model with subsequent reoxygenation in both SH-SY5Y cells and primary neurons as well as a murine stroke model were used herein in order to study the role of FAS inhibition and its underlying mechanisms. SH-SY5Y cells and cortical neurons exposed to 10 h of OGD and 24 h of reoxygenation displayed prominent cell death when treated with the Acetyl-CoA carboxylase inhibitor TOFA or the fatty acid synthase inhibitor cerulenin. Such FAS inhibition reduced the reduction potential of these cells, as indicated by increased NADH2+/NAD+ ratios under both in vitro and in vivo stroke conditions. As observed in the OGD model, FAS inhibition also resulted in increased cell death in the stroke model. Stroke mice treated with cerulenin did not only display increased brain injury but also showed reduced neurological recovery during the observation period of 4 weeks. Interestingly, cerulenin treatment enhanced endothelial cell leakage, reduced transcellular electrical resistance (TER) of the endothelium and contributed to poststroke blood-brain barrier (BBB) breakdown. The latter was a consequence of the activated NF-κB pathway, stimulating MMP-9 and ABCB1 transporter activity on the luminal side of the endothelium. In conclusion, FAS inhibition aggravated poststroke brain injury as consequence of BBB breakdown and NF-κB-dependent inflammation.

Highlights

After more than twenty years of intensive research activities, the pathophysiology of cerebral ischemia is still poorly understood (Nakamura and Shichita, 2019)
Neuronal cells were exposed to OGD in a glucose-free medium (BSS0) for 10 h followed by 24 h of reoxygenation under standard cell culture conditions. Both SH-SY5Y cells and primary neurons revealed significantly increased levels of fatty acids when exposed to hypoxia (Supplementary Figures 1A,B)
The results of the tumor cell line were confirmed in primary cortical neurons, i.e., both cerulenin and TOFA increased cell death after OGD when compared to the corresponding controls (Figure 1B)

Summary

Introduction

After more than twenty years of intensive research activities, the pathophysiology of cerebral ischemia is still poorly understood (Nakamura and Shichita, 2019). Significant contributions have been made in the past, deciphering fundamental processes of the pathophysiology of cerebral ischemia such as excitotoxicity and inflammation (Dirnagl et al, 1999; Levine, 2004). These approaches display a mechanistic and oversimplified view of the complex signaling cascade that is activated upon induction of cerebral ischemia. Additional experimental research beyond analyzing injurious signaling cascades of the ischemic brain and its periphery is of uttermost importance, but both adaptation and preservation mechanisms of the ischemic neuron have long been neglected. Previous work by Brose et al (2016) sought out to study whether or not fatty acids are critically involved in the adaption process of neurons exposed to in vitro hypoxia

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Conclusion