ACY-1083

Isoform-specific histone deacetylase inhibitors (HDACIs) MC1568 and ACY1083 are comparable to the non-selective HDACI valproic acid (VPA) in improving survival in rodents undergoing lethal hemorrhage. However, the organ-specific properties of isoform-specific HDACIs have not been fully evaluated. Also, whether they can act synergistically is not known. We hypothesized that isoform-specific HDACIs are superior to VPA in attenuating intestinal injury and act synergistically when coadministered.

Sprague Dawley rats were hemorrhaged (40% of total blood volume) and randomized to receive (n=4 per group) (1) MC1568 (5 mg/kg), (2) ACY1083 (30 mg/kg), (3) MC1568+ACY1083 (combination: 5 mg/kg + 30 mg/kg, respectively), (4) VPA (250 mg/kg), or (5) normal saline (NS; vehicle; 250 μL). Animals were observed for 3 hours, after which blood samples were collected and samples of the ileum were harvested. Expression of interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), and cytokine-induced neutrophil chemoattractant 1 (CINC-1) was assessed in the tissues using enzyme-linked immunosorbent assay. Intestinal cleaved caspase 3 (c-caspase 3) levels were assessed as a marker of apoptosis, and histologic sections of the ileum were examined for signs of bowel injury. Levels of IL-1β and TNF-α were also measured in the serum as global markers of inflammation.

Treatments with MC1568, ACY1083, MC1568+ACY1083, and VPA were associated with decreased IL-1β levels in the intestine and serum compared with NS. IL-1β and TNF-α levels were significantly lower in the ACY1083 group compared with the VPA group. CINC-1 levels were significantly lower in the isoform-specific HDACI groups compared with the NS; however, no significant differences were seen with VPA. All treatment groups had a lower expression of intestinal c-caspase 3 compared with NS. Furthermore, MC1568 and ACY1083 groups had lower apoptosis compared with the VPA group. Bowel injury scores were significantly lower in the isoform-specific HDACI groups compared with the NS group; however, the attenuation in the VPA-treated animals did not reach statistical significance.

Isoform-specific HDACIs provide superior intestinal protection compared with VPA in a rodent model of hemorrhagic shock.

Preclinical study.

Intestinal inflammation is a mediator of multiorgan failure in trauma. We have previously shown that histone deacetylase (HDAC6) inhibitors, including ACY1083, improve survival and preserve intestinal tight junction integrity in a rodent model of hemorrhagic shock (HS). However, mechanisms leading to this alleviation in intestinal injury remain poorly defined. In this study, we sought to determine whether HDAC6 inhibition by ACY1083 can attenuate intestinal inflammation and apoptosis in rats subjected to HS.

Sprague Dawley rats were subjected to hemorrhage (40% of total blood volume) followed by intravenous injection of either ACY1083 (30 mg/kg) dissolved in cyclodextrin or cyclodextrin only (vehicle group). Three hours after hemorrhage, blood samples were collected, and small bowel was harvested. Histological effects of ACY1083 on small bowel were examined. Myeloperoxidase (MPO) levels were assessed as a marker for neutrophil infiltration. Whole cell lysates were analyzed for acetylated α-tubulin, metalloproteinase (ADAM) 17, TNF-α, IL-6, and cleaved caspase 3 using Western blot. The levels of ADAM17, TNF-α, and IL-6 in serum were also examined using enzyme-linked immunosorbent assay.

ACY1083 treatment significantly attenuated HS-induced intestinal injury and MPO production. Both systemic and intestinal TNF-α and IL-6 levels were attenuated following ACY1083 administration. Increased acetylation of α-tubulin was observed in rats treated with ACY1083, along with a significantly decreased expression of cleaved caspase 3 following hemorrhage.

Inhibition of HDAC6 with ACY1083 provides intestinal protection by attenuating both the inflammatory and apoptotic responses during HS.