Transglutaminase inhibition protects against oxidative stress-induced neuronal death downstream of pathological ERK activation.

Molecular deletion of transglutaminase 2 (TG2) has been shown to improve function and survival in a host of neurological conditions including stroke, Huntington's disease, and Parkinson's disease. However, unifying schemes by which these cross-linking or polyaminating enzymes participate broadly in neuronal death have yet to be presented. Unexpectedly, we found that in addition to TG2, TG1 gene expression level is significantly induced following stroke in vivo or due to oxidative stress in vitro. Forced expression of TG1 or TG2 proteins is sufficient to induce neuronal death in Rattus norvegicus cortical neurons in vitro. Accordingly, molecular deletion of TG2 alone is insufficient to protect Mus musculus neurons from oxidative death. By contrast, structurally diverse inhibitors used at concentrations that inhibit TG1 and TG2 simultaneously are neuroprotective. These small molecules inhibit increases in neuronal transamidating activity induced by oxidative stress; they also protect neurons downstream of pathological ERK activation when added well after the onset of the death stimulus. Together, these studies suggest that multiple TG isoforms, not only TG2, participate in oxidative stress-induced cell death signaling; and that isoform nonselective inhibitors of TG will be most efficacious in combating oxidative death in neurological disorders.

Mithramycin is a gene-selective Sp1 inhibitor that identifies a biological intersection between cancer and neurodegeneration.

Oncogenic transformation of postmitotic neurons triggers cell death, but the identity of genes critical for degeneration remain unclear. The antitumor antibiotic mithramycin prolongs survival of mouse models of Huntington's disease in vivo and inhibits oxidative stress-induced death in cortical neurons in vitro. We had correlated protection by mithramycin with its ability to bind to GC-rich DNA and globally displace Sp1 family transcription factors. To understand how antitumor drugs prevent neurodegeneration, here we use structure-activity relationships of mithramycin analogs to discover that selective DNA-binding inhibition of the drug is necessary for its neuroprotective effect. We identify several genes (Myc, c-Src, Hif1α, and p21(waf1/cip1)) involved in neoplastic transformation, whose altered expression correlates with protective doses of mithramycin or its analogs. Most interestingly, inhibition of one these genes, Myc, is neuroprotective, whereas forced expression of Myc induces Rattus norvegicus neuronal cell death. These results support a model in which cancer cell transformation shares key genetic components with neurodegeneration.

Perineural Methylprednisolone Depot Formulation Decreases Opioid Consumption After Total Knee Arthroplasty.

Purpose: Opioid consumption after total knee arthroplasty (TKA) remains a challenge with single injection nerve blocks even with common local anesthetic adjuvants dexamethasone (DEX). This study aimed to investigate the effects of adding methylprednisolone acetate (MPA) to adductor canal blocks (ACB) and interspace between the popliteal artery and capsule of the posterior knee (iPACK) blocks on postoperative opioid consumption. Methods: A retrospective analysis was conducted on 100 consecutive TKA patients equally assigned into two groups, with one group receiving DEX through ACB and iPACK block and the other group receiving DEX and methylprednisolone acetate (DEX/MPA) through the same nerve blocks. The primary outcome was cumulative opioid consumption (oral milligram morphine equivalent, OME) during hospitalization for up to three days. Secondary outcomes included daily opioid consumption, highest rest and active pain scores, prosthetic knee joint active range of motion (AROM), laboratory studies including fasting serum glucose (FSG) and white blood cell count (WBC) on each postoperative day (POD), and length of hospital stay. Results: Cumulative opioid consumption was significantly lower in the DEX/MPA group vs DEX group (median difference (95% CI) = -45.3 (-80.5 to -10), P = 0.011). The highest rest and active pain scores were both significantly lower in the DEX/MPA group than in DEX group on POD 2 (least square mean difference (95% CI) = -1.3 (-2.3 to -0.4), P = 0.005 and -0.9 (-1.8 to -0.1), P = 0.031, respectively). Except on POD 1, FSG values were significantly lower in the DEX/MPA group (median difference (95% CI) = -22.5 (-36 to -8.9), P = 0.001). AROM, WBC, and length of stay were comparable between both groups. Conclusion: Compared to perineural DEX alone, the addition of MPA further decreases postoperative opioid consumption without clinically significant changes on FSG and WBC. Level of Evidence: III.

Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis.

Hypercalcemia in sarcoidosis is due to three mechanistic reasons: (1) systemic conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by the enzyme 1-α hydroxylase produced by activated monocyte/macrophage system, (2) production of parathormone-related peptide (PTHrP) by the sarcoid granuloma, (3) tissue-level conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by 1-αhydroxylase produced by local monocyte/macrophage system in the sarcoid granuloma. We report two cases of one proposed mechanism of hypercalcaemia in sarcoidosis (mechanism 3). Both individuals presented with sarcoidosis and 25-hydroxyvitamin D deficiency and developed symptomatic hypercalcaemia with vitamin D replacement. Given their low serum parathormone and parathormone-related peptide levels, low serum 25-hydroxy vitamin D and normal serum 1,25-dihydroxyvitamin D, the systemic 25-hydroxy vitamin D deficiency may not have reflected an increased activity of vitamin D at the local granulomatous tissue level.

Histone Deacetylase Inhibitors and Mithramycin A Impact a Similar Neuroprotective Pathway at a Crossroad between Cancer and Neurodegeneration.

Mithramycin A (MTM) and histone deacetylase inhibitors (HDACi) are effective therapeutic agents for cancer and neurodegenerative diseases. MTM is a FDA approved aureolic acid-type antibiotic that binds to GC-rich DNA sequences and interferes with Sp1 transcription factor binding to its target sites (GC box). HDACi, on the other hand, modulate the activity of class I and II histone deacetylases. They mediate their protective function, in part, by regulating the acetylation status of histones or transcription factors, including Sp1, and in turn chromatin accessibility to the transcriptional machinery. Because these two classes of structurally and functionally diverse compounds mediate similar therapeutic functions, we investigated whether they act on redundant or synergistic pathways to protect neurons from oxidative death. Non-protective doses of each of the drugs do not synergize to create resistance to oxidative death suggesting that these distinct agents act via a similar pathway. Accordingly, we found that protection by MTM and HDACi is associated with diminished expression of the oncogene, Myc and enhanced expression of a tumor suppressor, p21(waf1/cip1). We also find that neuroprotection by MTM or Myc knockdown is associated with downregulation of class I HDAC levels. Our results support a model in which the established antitumor drug MTM or canonical HDACi act via distinct mechanisms to converge on the downregulation of HDAC levels or activity respectively. These findings support the conclusion that an imbalance in histone acetylase and HDAC activity in favor of HDACs is key not only for oncogenic transformation, but also neurodegeneration.