Involvement of the cynABDS Operon and the CO(2)-Concentrating Mechanism in the Light-Dependent Transport and Metabolism of Cyanate by Cyanobacteria

The cyanobacteria Synechococcus elongatus strain PCC7942 and Synechococcus sp. strain UTEX625 decomposed exogenously supplied cyanate (NCO(−)) to CO(2) and NH(3) through the action of a cytosolic cyanase which required HCO(3)(−) as a second substrate. The ability to metabolize NCO(−) relied on three essential elements: proteins encoded by the cynABDS operon, the biophysical activity of the CO(2)-concentrating mechanism (CCM), and light. Inactivation of cynS, encoding cyanase, and cynA yielded mutants unable to decompose cyanate. Furthermore, loss of CynA, the periplasmic binding protein of a multicomponent ABC-type transporter, resulted in loss of active cyanate transport. Competition experiments revealed that native transport systems for CO(2), HCO(3)(−), NO(3)(−), NO(2)(−), Cl(−), PO(4)(2−), and SO(4)(2−) did not contribute to the cellular flux of NCO(−) and that CynABD did not contribute to the flux of these nutrients, implicating CynABD as a novel primary active NCO(−) transporter. In the S. elongatus strain PCC7942 ΔchpX ΔchpY mutant that is defective in the full expression of the CCM, mass spectrometry revealed that the cellular rate of cyanate decomposition depended upon the size of the internal inorganic carbon (C(i)) (HCO(3)(−) + CO(2)) pool. Unlike wild-type cells, the rate of NCO(−) decomposition by the ΔchpX ΔchpY mutant was severely depressed at low external C(i) concentrations, indicating that the CCM was essential in providing HCO(3)(−) for cyanase under typical growth conditions. Light was required to activate and/or energize the active transport of both NCO(−) and C(i). Putative cynABDS operons were identified in the genomes of diverse Proteobacteria, suggesting that CynABDS-mediated cyanate metabolism is not restricted to cyanobacteria

Rat model of cancer-induced bone pain: changes in nonnociceptive sensory neurons in vivo

Abstract. Introduction:. Clinical data on cancer-induced bone pain (CIBP) suggest extensive changes in sensory function. In a previous investigation of an animal model of CIBP, we have observed that changes in intrinsic membrane properties and excitability of dorsal root ganglion (DRG) nociceptive neurons correspond to mechanical allodynia and hyperalgesia. Objectives:. To investigate the mechanisms underlying changes in nonnociceptive sensory neurons in this model, we have compared the electrophysiological properties of primary nonnociceptive sensory neurons at 2 weeks after CIBP model induction with properties in sham control animals. Methods:. Copenhagen rats were injected with 106 MAT-LyLu rat prostate cancer cells into the distal femur epiphysis to generate a model of CIBP. After von Frey tactile measurement of mechanical withdrawal thresholds, the animals were prepared for acute electrophysiological recordings of mechanically sensitive neurons in the DRG in vivo. Results:. The mechanical withdrawal threshold progressively decreased in CIBP model rats. At 2 weeks, the Aβ-fiber low-threshold mechanoreceptors (LTMs) in CIBP model rats exhibited a slowing of the dynamics of action potential (AP) genesis, including wider AP duration and lower AP amplitude compared with sham rats. Furthermore, enhanced excitability of Aβ-fiber LTM neurons was observed as an excitatory discharge in response to intracellular injection of depolarizing current into the soma. Conclusion:. After induction of the CIBP model, Aβ-fiber LTMs at >2 weeks but not <1 week had undergone changes in electrophysiological properties. Importantly, changes observed are consistent with observations in models of peripheral neuropathy. Thus, Aβ-fiber nonnociceptive primary sensory neurons might be involved in the peripheral sensitization and tumor-induced tactile hypersensitivity in CIBP

Evaluation of the preclinical analgesic efficacy of naturally derived, orally administered oil forms of Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and their 1:1 combination.

Chronic neuropathic pain (NP) is a growing clinical problem for which effective treatments, aside from non-steroidal anti-inflammatory drugs and opioids, are lacking. Cannabinoids are emerging as potentially promising agents to manage neuroimmune effects associated with nociception. In particular, Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), and their combination are being considered as therapeutic alternatives for treatment of NP. This study aimed to examine whether sex affects long-term outcomes on persistent mechanical hypersensitivity 7 weeks after ceasing cannabinoid administration. Clinically relevant low doses of THC, CBD, and a 1:1 combination of THC:CBD extracts, in medium chain triglyceride (MCT) oil, were orally gavaged for 14 consecutive days to age-matched groups of male and female sexually mature Sprague Dawley rats. Treatments commenced one day after surgically inducing a pro-nociceptive state using a peripheral sciatic nerve cuff. The analgesic efficacy of each phytocannabinoid was assessed relative to MCT oil using hind paw mechanical behavioural testing once a week for 9 weeks. In vivo intracellular electrophysiology was recorded at endpoint to characterize soma threshold changes in primary afferent sensory neurons within dorsal root ganglia (DRG) innervated by the affected sciatic nerve. The thymus, spleen, and DRG were collected post-sacrifice and analyzed for long-term effects on markers associated with T lymphocytes at the RNA level using qPCR. Administration of cannabinoids, particularly the 1:1 combination of THC, elicited a sustained mechanical anti-hypersensitive effect in males with persistent peripheral NP, which corresponded to beneficial changes in myelinated Aβ mechanoreceptive fibers. Specific immune cell markers associated with T cell differentiation and pro-inflammatory cytokines, previously implicated in repair processes, were differentially up-regulated by cannabinoids in males treated with cannabinoids, but not in females, warranting further investigation into sexual dimorphisms that may underlie treatment outcomes