SIRT1 in forebrain excitatory neurons produces sexually dimorphic effects on depression-related behaviors and modulates neuronal excitability and synaptic transmission in the medial prefrontal cortex

Abstract

Sirtuin 1 (SIRT1), an NAD +-dependent deacetylase, is a key regulator of cellular metabolism. Recent genome-wide association studies identified genetic variants of SIRT1 linked to major depressive disorders. SIRT1 is widely expressed in the brain; however, neuronal substrates that mediate SIRT1 action on depressive behaviors remain largely unknown. Here we show that selective deletion of SIRT1 in forebrain excitatory neurons causes depression-like phenotypes in male but not female mice. AAV-Cre-mediated SIRT1 knockdown in the medial prefrontal cortex (mPFC) of adult male mice induces depressive-like behaviors. Whole-cell patch-clamp recordings demonstrate that loss of SIRT1 decreases intrinsic excitability and spontaneous excitatory synaptic transmission in layer V pyramidal neurons in the prelimbic mPFC. Consistent with neuronal hypoexcitability, SIRT1 knockout reduces mitochondrial density and expression levels of genes involved in mitochondrial biogenesis and dynamics in the prelimbic mPFC. When a SIRT1 activator (SRT2104) is injected into the mPFC or lateral ventricle of wild-type mice, it reverses chronic unpredictable stress-induced anhedonia and behavioral despair, indicating an antidepressant-like effect. These results suggest that SIRT1 in mPFC excitatory neurons is required for normal neuronal excitability and synaptic transmission and regulates depression-related behaviors in a sex-specific manner.

Modulation of depression-related behaviors by adiponectin AdipoR1 receptors in 5-HT neurons

“…The DRN was dissected from five to six 100-μm-thick coronal midbrain slices (from −4.36 to −4.96 mm from bregma) on ice according to the mouse brain atlas [38]. Total RNA was extracted from each tissue sample to generate cDNA using a protocol reported elsewhere [39,40]. First, total RNA was treated with 4× gDNA wiper mix at 42°C for 2 min to remove genomic DNA contamination, then reversely transcribed into cDNAs with 5× HiScript II QRT SuperMix that was added to the reaction mixture and incubated at 25°C for 10 min followed by 50°C for 30 min and 85°C for 5 min.…”

“…The resulting cDNA was used for real-time PCR detection using the StepOnePlus real-time PCR system (Applied Biosystems, Waltham, MA, USA). The condition for PCR was 95°C for 5 min, followed by 40 cycles of 95°C for 10 s and 60°C for 30 s. The primer sequences used to amplify each desired product were as follows: mouse AdipoR1 exon 2 [23], forward-5′-CCCGTATCCACCAGACACCGG-3′, reverse-5′-GGCAATGGGGCTCCTTCTGG-3′; mouse β-tubulin [39], forward-5′-AGCAACATGAATGACCTGGTG-3′, reverse-5′-GCTTTCCCTAACCTGCTTGG-3′. The housekeeping gene β-tubulin was used as a reference gene for normalization of gene expression.…”

“…Mice were subjected to two different stressors daily at different times of the day and housed singly for five consecutive days [39]. The stressors included 2-h restraint, 15-min tail pinch, 24-h constant light, 24-h wet bedding, and 45°cage tilt, 10-min inescapable foot shocks, 30-min elevated platform, and social isolation.…”

“…This test was used to assess sex-related reward-seeking behavior based upon interest of male rodents in pheromonal odors from estrus female urine [39,42]. Female mice were maintained in a separate room, and the estrous cycle was assessed by microscopic evaluation of vaginal smears as previously described [43].…”

“…The locomotor activity was measured in an open-field box (40 × 40 × 40 cm). Mice were placed in the open-field area and allowed to freely explore for 30 min [39,40]. A CCD camera was mounted above the open box for recording locomotor activity.…”