12 research outputs found
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Targeting the Cystine/Glutamate Antiporter System xc⁻ in Cancer-Induced Bone Pain
Many common cancers, including breast, prostate and lung cancers, have a propensity to metastasize to bone. Although these cancers go undetected in their native tissues, bone metastases often produce excruciating pain, the etiology of which is poorly understood. Cancer-induced bone pain (CIBP) is not well-controlled with existing medications, severely compromising patient quality of life. While CIBP is multifaceted, increased level of the excitatory neurotransmitter glutamate in the bone-tumor microenvironment may contribute to the pain state. Here, we demonstrate for the first time a relationship between reactive oxygen/nitrogen species, glutamate in the bone-tumor microenvironment and pain behaviors. The murine mammary adenocarcinoma cell line 66.1 is found to release glutamate via the cystine/glutamate antiporter system xc⁻. In a syngeneic model of breast CIBP in which 66.1 cells are inoculated into the femur intramedullary space, administration of sulfasalazine, an established system xc⁻ inhibitor and anti-inflammatory agent, reduces femur glutamate level and attenuates CIBP-related behaviors. Peroxynitrite, a reactive nitrogen species known to be generated in breast tumors, is shown to drive 66.1 system xc⁻ functional expression and tumor cell glutamate release. The elimination of peroxynitrite with the redox modulators FeTMPyP or SRI10 not only modulates tumor cell system xc⁻ functional expression in vitro and in vivo, significantly altering glutamate levels, but also assuages CIBP. In sum, we demonstrate that pharmacological inhibition of system xc⁻ transport attenuates CIBP-related behaviors. These data support a role for tumor-derived glutamate in CIBP and validate system xc⁻ an analgesic target in this pain state.Release 01-Aug-201
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Neurotensin receptor 1-biased ligand attenuates neurotensin-mediated excitation of ventral tegmental area dopamine neurons and dopamine release in the nucleus accumbens.
Strong expression of the G protein-coupled receptor (GPCR) neurotensin receptor 1 (NTR1) in ventral tegmental area (VTA) dopamine (DA) neurons and terminals makes it an attractive target to modulate DA neuron activity and normalize DA-related pathologies. Recent studies have identified a novel class of NTR1 ligand that shows promising effects in preclinical models of addiction. A lead molecule, SBI-0654553 (SBI-553), can act as a positive allosteric modulator of NTR1 β-arrestin recruitment while simultaneously antagonizing NTR1 Gq protein signaling. Using cell-attached recordings from mouse VTA DA neurons we discovered that, unlike neurotensin (NT), SBI-553 did not independently increase spontaneous firing. Instead, SBI-553 blocked the NT-mediated increase in firing. SBI-553 also antagonized the effects of NT on dopamine D2 auto-receptor signaling, potentially through its inhibitory effects on G-protein signaling. We also measured DA release directly, using fast-scan cyclic voltammetry in the nucleus accumbens and observed antagonist effects of SBI-553 on an NT-induced increase in DA release. Further, in vivo administration of SBI-553 did not notably change basal or cocaine-evoked DA release measured in NAc using fiber photometry. Overall, these results indicate that SBI-553 blunts NT's effects on spontaneous DA neuron firing, D2 auto-receptor function, and DA release, without independently affecting these measures. In the presence of NT, SBI-553 has an inhibitory effect on mesolimbic DA activity, which could contribute to its efficacy in animal models of psychostimulant use
Angiotensin-(1-7)/Mas receptor as an antinociceptive agent in cancer-induced bone pain
Many cancerous solid tumors metastasize to the bone and induce pain (cancer-induced bone pain [CIBP]). Cancer-induced bone pain is often severe because of enhanced inflammation, rapid bone degradation, and disease progression. Opioids are prescribed to manage this pain, but they may enhance bone loss and increase tumor proliferation, further compromising patient quality of life. Angiotensin-(1-7) (Ang-(1-7)) binds and activates the Mas receptor (MasR). Angiotensin-(1-7)/MasR activation modulates inflammatory signaling after acute tissue insult, yet no studies have investigated whether Ang-(1-7)/MasR play a role in CIBP. We hypothesized that Ang-(1-7) inhibits CIBP by targeting MasR in a murine model of breast CIBP. 66.1 breast cancer cells were implanted into the femur of BALB/cAnNHsd mice as a model of CIBP. Spontaneous and evoked pain behaviors were assessed before and after acute and chronic administration of Ang-(1-7). Tissues were collected from animals for ex vivo analyses of MasR expression, tumor burden, and bone integrity. Cancer inoculation increased spontaneous pain behaviors by day 7 that were significantly reduced after a single injection of Ang-(1-7) and after sustained administration. Preadministration of A-779 a selective MasR antagonist prevented this reduction, whereas pretreatment with the AT(2) antagonist had no effect; an AT(1) antagonist enhanced the antinociceptive activity of Ang-(1-7) in CIBP. Repeated Ang-(1-7) administration did not significantly change tumor burden or bone remodeling. Data here suggest that Ang-(1-7)/MasR activation significantly attenuates CIBP, while lacking many side effects seen with opioids. Thus, Ang-(1-7) may be an alternative therapeutic strategy for the nearly 90% of patients with advanced-stage cancer who experience excruciating pain.College of Medicine at the University of Arizona; NIH- NCI [R01 CA142115-01]Open access article.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
P-glycoprotein modulates morphine uptake into the CNS: a role for the non-steroidal anti-inflammatory drug diclofenac.
Our laboratory has previously demonstrated that peripheral inflammatory pain (PIP), induced by subcutaneous plantar injection of λ-carrageenan, results in increased expression and activity of the ATP-dependent efflux transporter P-glycoprotein (P-gp) that is endogenously expressed at the blood-brain barrier (BBB). The result of increased P-gp functional expression was a significant reduction in CNS uptake of morphine and, subsequently, reduced morphine analgesic efficacy. A major concern in the treatment of acute pain/inflammation is the potential for drug-drug interactions resulting from P-gp induction by therapeutic agents co-administered with opioids. Such effects on P-gp activity can profoundly modulate CNS distribution of opioid analgesics and alter analgesic efficacy. In this study, we examined the ability of diclofenac, a non-steroidal anti-inflammatory drug (NSAID) that is commonly administered in conjunction with the opioids during pain therapy, to alter BBB transport of morphine via P-gp and whether such changes in P-gp morphine transport could alter morphine analgesic efficacy. Administration of diclofenac reduced paw edema and thermal hyperalgesia in rats subjected to PIP, which is consistent with the known mechanism of action of this NSAID. Western blot analysis demonstrated an increase in P-gp expression in rat brain microvessels not only following PIP induction but also after diclofenac treatment alone. Additionally, in situ brain perfusion studies showed that both PIP and diclofenac treatment alone increased P-gp efflux activity resulting in decreased morphine brain uptake. Critically, morphine analgesia was significantly reduced in animals pretreated with diclofenac (3 h), as compared to animals administered diclofenac and morphine concurrently. These novel findings suggest that administration of diclofenac and P-gp substrate opioids during pain pharmacotherapy may result in a clinically significant drug-drug interaction
Diclofenac administration following λ-carrageenan injection attenuates PIP-induced paw edema and hyperalgesia.
<p>Animals received subcutaneous injections of saline (Sal) or λ-carrageenan (Carr) into the plantar surface of the right hind paw (injected). 15 min after paw treatment animals received saline (Sal, 1 mL/kg, i.p.) or diclofenac (Diclo, 30 mg/kg, i.p.) <b>A</b>) Administration of diclofenac resulted in a significant decrease in paw edema in λ-carrageenan treated animals 3 h post paw treatment. Edema of the untreated left hind paw (contralateral) was comparable in all treatment groups. <b>B</b>) Administration of diclofenac attenuated λ-carrageenan -induced hyperalgesia 3 h post paw treatment. Data are reported as mean ± SEM from at least nine animals per treatment group. Asterisks represent data points that are statically different as indicated (*p<0.05).</p
Diclofenac increases P-gp immunofluorescence.
<p>Animals received subcutaneous injections of saline (Sal) or λ-carrageenan (Carr) into the plantar surface of the right hind paw. 15 min after paw treatment animals received saline (Sal, 1 mL/kg, i.p.) or diclofenac (Diclo, 30 mg/kg, i.p.). 3 h after paw treatment animals were sacrificed and brain microvessels were isolated, plated on glass slides and fixed. Vessels were probed with mouse monoclonal anti-P-glycoprotein antibody and rabbit polyclonal antibody directed against von Willebrand factor (VWF). All slides were then incubated with appropriate Alexa Fluor-conjugated secondary antibodies. <b>A</b>. Representative immunofluorescent images from animals treated with saline paw and saline i.p. (Sal/Sal), saline paw and diclofenac i.p. (Sal/Diclo), λ-carrageenan paw and saline i.p. (Carr/Sal) or λ-carrageenan paw and diclofenac i.p. (Carr/Diclo). <b>B</b>. Semiquantitative analysis of the mean fluorescent intensity of P-gp. Microvessels isolated from treated and control animals were randomly selected for image analysis. Each bar represents the mean ± SEM of 75 microvessels from 3 separate experiments. Asterisks represent data points that are significantly different from Sal/Sal (*p<0.05).</p
PIP increases P-gp-mediated transport of morphine at the BBB.
<p>The effect of λ-carrageenan treatment on brain uptake [<sup>3</sup>H]morphine (36.7 µg/rat) was determined by <i>in situ</i> brain perfusion. Animals received subcutaneous injections of saline or λ-carrageenan into the plantar surface of the right hind paw. 3 h post paw treatment animals were perfused with [<sup>3</sup>H]morphine (0.5 mCi/mL) for 10 min. As previously shown, λ-carrageenan treatment induced an increase in P-gp function as exemplified by decreased brain morphine uptake. P-gp specific efflux of morphine was confirmed using the P-gp selective inhibitory peptide reversin 205. Animals were perfused with reversin 205 for 10 min prior to perfusion with [<sup>3</sup>H]morphine. Animals were then perfused with [<sup>3</sup>H]morphine (.5 mCi/mL) for 10 min in the presence of reversin 205. Results are expressed as mean ± SEM of at least 6 individual animals per treatment group. Asterisks represent data points that are significantly different (*p<0.05).</p
Diclofenac increases P-gp-mediated transport of morphine at the BBB.
<p>The effect of λ-carrageenan treatment on brain uptake [<sup>3</sup>H]morphine (36.7 µg/rat) was determined by <i>in situ</i> brain perfusion. Animals received subcutaneous injections of saline or λ-carrageenan into the plantar surface of the right hind paw. 15 min after paw treatment animals received saline (1 mL/kg, i.p.) or diclofenac (30 mg/kg, i.p.). 3 h post paw treatment animals were perfused with [<sup>3</sup>H]morphine (0.5 mCi/mL) for 10 min. Morphine brain accumulation was significantly decreased in animals that received saline paw injections with diclofenac i.p. injections (Sal/Diclo) and in animals that received λ-carrageenan paw injections with saline i.p. injections (Carr/Sal) as compared to saline treated (Sal/Sal) animals. Results are expressed as mean ± SEM of at least 6 individual animals per treatment group. Asterisks represent data points that are significantly different (*p<0.05).</p
Diclofenac treatment increases P-gp expression in rat brain microvessels.
<p>Animals received subcutaneous injections of saline (Sal) or λ-carrageenan (Carr) into the plantar surface of the right hind paw. 15 min after paw treatment animals received saline (Sal, 1 mL/kg, i.p.) or diclofenac (Diclo, 30 mg/kg, i.p.). 3 h after paw treatment, animals were sacrificed and brain microvessels were isolated and prepared for Western blot analysis. Whole microvessels (10 µg) were resolved on a 10% SDS-polyacrylamide gel and transferred to a PVDF membrane. Samples were analyzed for expression of P-gp. <b>A</b>) Representative blot illustrating increased P-gp expression in animals treated with λ-carrageenan, diclofenac or both λ-carrageenan and diclofenac. <b>B</b>) Relative levels of P-gp expression in samples from <b>A</b> were determined by densitometric analysis. Results are expressed as mean ± SEM of three separate experiments (9 animals per group). Asterisks represent data points that are significantly different from saline control (*p<0.05).</p