Modulation of endogenous opioid signaling by inhibitors of puromycin sensitive aminopeptidase.

The endogenous opioid system regulates pain through local release of neuropeptides and modulation of their action on opioid receptors. However, the effect of opioid peptides, the enkephalins, is short-lived due to their rapid hydrolysis by enkephalin-degrading enzymes. In turn, an innovative approach to the management of pain would be to increase the local concentration and prolong the stability of enkephalins by preventing their inactivation by neural enkephalinases such as puromycin sensitive aminopeptidase (PSA). Our previous structure-activity relationship studies offered the S-diphenylmethyl cysteinyl derivative of puromycin (20) as a nanomolar inhibitor of PSA. This chemical class, however, suffered from undesirable metabolism to nephrotoxic puromycin aminonucleoside (PAN). To prevent such toxicity, we designed and synthesized 5'-chloro substituted derivatives. The compounds retained the PSA inhibitory potency of the corresponding 5'-hydroxy analogs and had improved selectivity toward PSA. In vivo treatment with the lead compound 19 caused significantly reduced pain response in antinociception assays, alone and in combination with Met-enkephalin. The analgesic effect was reversed by the opioid antagonist naloxone, suggesting the involvement of opioid receptors. Further, PSA inhibition by compound 19 in brain slices caused local increase in endogenous enkephalin levels, corroborating our rationale. Pharmacokinetic assessment of compound 19 showed desirable plasma stability and identified the cysteinyl sulfur as the principal site of metabolic liability. We gained additional insight into inhibitor-PSA interactions by molecular modeling, which underscored the importance of bulky aromatic amino acid in puromycin scaffold. The results of this study strongly support our rationale for the development of PSA inhibitors for effective pain management.

Strategy of pulseless pink supracondylar humerus fracture treatment in children: a comparison of two approaches.

PURPOSE: The appropriate treatment of pulseless pink supracondylar humerus fractures (SCHF) remains controversial. In this study, the outcomes of two treatment approaches (with and without vascular surgery) were compared. MATERIAL AND METHODS: This was a retrospective multicenter study of patients with pulseless pink SCHFs treated in ten pediatric surgery, trauma, or orthopedics departments in the Czech and Slovak Republic between 2014 and 2018. RESULTS: Of the total 3608 cases of displaced SCHF, 125 had the pulseless pink SCHF. Of those, 91% (114/125) did not undergo vascular surgery and 9% (11/125) underwent vascular surgery. The patients who did undergo vascular surgery had radial artery pulsation restored more frequently in the operating room (73% vs. 36%; p = 0.02), within 6 h (91% vs. 45%; p = 0.004), and within 24 h of surgery (91% vs. 57%; p = 0.05). However, 72 h after surgery, there was no significant difference in palpable radial artery pulsation between the vascular surgery and the non-vascular surgery groups (91% vs. 74%; p = 0.24). Additionally, no significant differences in long-term neurological (9% vs. 22%; p = 0.46) or circulatory (9% vs. 7%; p = 0.57) deficits were found between the two groups. CONCLUSION: While vascular surgery in patients with pulseless pink SCHFs is associated with a more prompt restoration of radial artery pulsation, no statistical significant differences in terms of the restoration of neurological deficits or the risks of long-term neurological or circulatory deficits were found between patients with and without vascular surgery.

Daily intermittent fasting in mice enhances morphine-induced antinociception while mitigating reward, tolerance, and constipation.

The opioid epidemic has plagued the United States with high levels of abuse and poor quality of life for chronic pain patients requiring continuous use of opioids. New drug discovery efforts have been implemented to mitigate this epidemic; however, new medications are still limited by low efficacy and/or high side effect and abuse potential. Intermittent fasting (IF) has recently been shown to improve a variety of pathological states, including stroke and neuroinflammation. Numerous animal and human studies have shown the benefits of IF in these disease states, but not in pain and opioid treatment. We thus subjected male and female CD-1 mice to 18-hour fasting intervals followed by 6-hour feed periods with standard chow for 1 week. Mice that underwent this diet displayed an enhanced antinociceptive response to morphine both in efficacy and duration using thermal tail-flick and postoperative paw incision pain models. While showing enhanced antinociception, IF mice also demonstrated no morphine reward and reduced tolerance and constipation. Seeking a mechanism for these improvements, we found that the mu-opioid receptor showed enhanced efficacy and reduced tolerance in the spinal cord and periaqueductal gray, respectively, from IF mice using a S-GTPγS coupling assay. These improvements in receptor function were not due to changes in mu-opioid receptor protein expression. These data suggest that a daily IF diet may improve the therapeutic index of acute and chronic opioid therapies for pain patients in the clinic, providing a novel tool to improve patient therapy and reduce potential abuse.

A new quasiclassical method for modeling the high-resolution spectra of polyatomic systems.

A new quasiclassical method for quantum autocorrelation functions based on the semiclassical limit in Wigner phase space has been derived. Unlike the existing quasiclassical method, the new method enables long-time simulations, thus making it possible to locate quantum spectral lines very precisely. The new method has been tested for a one-dimensional anharmonic oscillator fitted to the H(2) molecule and for a six-dimensional calculation of the Ar(2)I van der Waals cluster in adiabatic approximation. The obtained results compare well with the benchmark quantum-mechanical calculations and are also roughly comparable to the experimental Ar(2)I(-) zero-kinetic-energy photoelectron spectrum, which is available in the literature.