In conclusion we report that the widely prescribed

In conclusion, we report that the widely prescribed drug VPA exerts therapeutic effects on optic nerve demyelination and retinal degeneration in a mouse model of MS. Our findings raise an interesting possibility that combination therapy of VPA and ASK1 inhibition may be useful for treatment of autoimmune demyelinating disorders including optic neuritis and MS. We are planning to utilize an ASK1 inhibitor [7] in combination with VPA, especially after the onset of EAE, in our future studies.
Conflict of interest statement
Introduction Obese sub-phenotypes associated with increased cardio-metabolic risk are characterized by metabolically and endocrinologically dysfunctional AT that is thought to contribute to the development of obesity-associated morbidities [1], [2], [3]. As an underlying mechanism for dysfunctional AT, various AT stresses have been recognized in obesity, including inflammation, endoplasmic reticulum stress, hypoxia, and oxidative stress [4], [5], [6], [7], [8]. Much effort has been invested in understanding which types of besity-induced AT stress is most significant, and the emerging picture is of an inter-connected “network of stresses” [9]. Yet, the molecular pathways activated by these stresses, linking them with the functional alterations they are claimed to induce, are incompletely mapped. The interest in this extends beyond understanding the basic pathogenic mechanisms; such AT stress-response network(s), particularly when identified in human-AT, may constitute a molecular signature that could be used for improved patient stratification and identification of targets of future pharmacological therapies. Several signaling pathways were reported to be activated in AT in obesity, mostly in mouse models [10], [11], [12], [13], [14], [15], [16], [17]. In human-AT in obesity, one such stress-responsive pathway activated particularly in the intra-abdominal visceral fat is a MAP kinase signaling cascade comprised of MAP3K ASK1 (MAP3K5), MAP2Ks MKK4 and 3/6, MAPKs p38MAPK, and JNK [18], [19]. We demonstrated that ASK1 NSC74859 (both mRNA and protein levels) was up-regulated in obesity and, more importantly, that ASK1 mRNA levels in omental fat constituted, by multivariate analysis, a statistical predictor of whole-body insulin resistance independent of age, sex, BMI, and additional confounders [18]. In cellular systems, ASK1 has been recognized to respond to the same stresses that are implicated in AT in obesity, in particular to inflammation, oxidative and ER stresses [20], [21], [22]. Functionally related to obesity, genetic variants of ASK1 that resulted in decreased ASK1 expression in muscle were associated with insulin resistance in Pima Indians [23]. In mice, whole-body knockout of ASK1 predisposed to obesity, potentially by interfering with brown fat function [24]. These two studies assign a potential role for ASK1 in whole-body metabolic (dys)regulation. Yet, the impact of ASK1 over-expression in humans, particularly in white adipose tissue, and the molecular underpinnings for its elevated expression, remain unknown. As a MAP kinase, ASK1 was mainly shown to be regulated by phosphorylation and/or oxidation of its inhibitory partner thioredoxin [22], [25], [26]. Yet, transcriptional regulation of ASK1 was also reported. The transcription factor E2F1, mainly known as a cell cycle regulator, binds directly to the ASK1 promoter and up-regulates its expression in cancer cells [27], [28], [29]. Recently, we reported significant gene regulatory functions for E2F1 in adipocytes, cells that are post-mitotic [30]. E2F1 was up-regulated in omental AT in obesity in the adipocyte cell fraction, increasing not only the expression of several autophagy genes but also the autophagy process itself [30]. This finding is consistent with other studies implicating non-cell-cycle related, including metabolic, functions of E2F1 (and of other classical cell-cycle regulators) [31], [32], [33], [34], [35]. In the present study, we test the hypothesis that ASK1 expression and its downstream signals are regulated by E2F1 in human-AT in obesity. Both clinically and mechanistically, we systematically investigated the possibility that the E2F1-ASK1 network molecularly defines an obese sub-phenotype characterized by AT stress and metabolic dysfunction.