Apple phenolic extracts ameliorate lead-induced cognitive impairment and depression- and anxiety-like behavior in mice by abating oxidative stress, inflammation and apoptosis via the miR-22-3p/SIRT1 axis.

Lead can lead to neurotoxicity and cognitive impairment. In this study, for the first time, the protective effects and working mechanisms of apple phenolic extracts (APEs) against lead acetate (Pb(Ac)2)-induced cognitive impairment and depression- and anxiety-like behavior were examined in vivo. Forty male mice were administered daily (via gastric gavage; 8 weeks) with 0.9% normal saline (control), Pb(Ac)2 (20 ppm), APE (200 ppm) or Pb(Ac)2 (20 ppm) + APE (200 ppm). The APE contained five major phenolic compounds: chlorogenic acid, proanthocyanidin B2, epicatechin, phloridzin and phloretin. Behavioral tests, histopathological examinations and biochemical analyses revealed that Pb(Ac)2-treated mice exhibited cognitive and behavioral deficits (i.e. a reduced percentage of spontaneous alternation, prolonged duration of immobility and decreased open field test scores compared with the control. Pb(Ac)2 exposure significantly increased cellular oxidative damage and the levels of pro-inflammatory cytokines (interleukin (IL)-1ß, IL-6 and tumor necrosis factor-α (TNF-α), ionized calcium binding adaptor molecule 1 (Iba1) and pro-apoptotic proteins (caspase 3, caspase 9 and Bax), while downregulating the expression of Bcl-2 in the brain. APE administration alleviated these Pb(Ac)2-induced changes through regulating oxidative stress, neuroinflammation and apoptosis via the miR-22-3p/Sirtuin 1 (SIRT1) signaling pathway. Taken together, the APE has the potential to treat lead-induced neurotoxicity and neurodegenerative disorders via antioxidant, anti-inflammatory and anti-apoptotic actions.

ZMYND11 links histone H3.3K36me3 to transcription elongation and tumour suppression.

Recognition of modified histones by 'reader' proteins plays a critical role in the regulation of chromatin. H3K36 trimethylation (H3K36me3) is deposited onto the nucleosomes in the transcribed regions after RNA polymerase II elongation. In yeast, this mark in turn recruits epigenetic regulators to reset the chromatin to a relatively repressive state, thus suppressing cryptic transcription. However, much less is known about the role of H3K36me3 in transcription regulation in mammals. This is further complicated by the transcription-coupled incorporation of the histone variant H3.3 in gene bodies. Here we show that the candidate tumour suppressor ZMYND11 specifically recognizes H3K36me3 on H3.3 (H3.3K36me3) and regulates RNA polymerase II elongation. Structural studies show that in addition to the trimethyl-lysine binding by an aromatic cage within the PWWP domain, the H3.3-dependent recognition is mediated by the encapsulation of the H3.3-specific 'Ser 31' residue in a composite pocket formed by the tandem bromo-PWWP domains of ZMYND11. Chromatin immunoprecipitation followed by sequencing shows a genome-wide co-localization of ZMYND11 with H3K36me3 and H3.3 in gene bodies, and its occupancy requires the pre-deposition of H3.3K36me3. Although ZMYND11 is associated with highly expressed genes, it functions as an unconventional transcription co-repressor by modulating RNA polymerase II at the elongation stage. ZMYND11 is critical for the repression of a transcriptional program that is essential for tumour cell growth; low expression levels of ZMYND11 in breast cancer patients correlate with worse prognosis. Consistently, overexpression of ZMYND11 suppresses cancer cell growth in vitro and tumour formation in mice. Together, this study identifies ZMYND11 as an H3.3-specific reader of H3K36me3 that links the histone-variant-mediated transcription elongation control to tumour suppression.