Chemotherapy-induced peripheral neuropathy (CIPN) accompanied by chronic neuropathic pain is a major dose-limiting side effect of a large number of antitumoral agents including paclitaxel (Taxol). We also demonstrate the prevention of CIPN with our two new orally active PNDCs, SRI6 and SRI110. The improved chemical design of SRI6 and SRI110 also affords selectivity for PN over other reactive oxygen species (such as superoxide). Our findings identify PN as a critical determinant of CIPN, while providing the rationale toward development of superoxide-sparing and "PN-targeted" therapeutics.

Background: Chemotherapy-induced peripheral neuropathy (CIPN) is a critical dose-limiting side effect of many chemotherapeutic agents, including paclitaxel. Results: Spinal activation of the S1P-to-S1PR 1 axis contributes to the development and maintenance of paclitaxel-induced neuropathic pain through enhanced neuroinflammatory processes. Conclusion: Inhibition of S1PR 1 blocks and reverses paclitaxel-induced neuropathic pain without interfering with anticancer effects. Significance: Targeting the S1PR 1 signaling pathway could be an effective approach for the treatment of CIPN.

Clinical management of chronic neuropathic pain is limited by marginal effectiveness and unacceptable side effects of current drugs. We demonstrate A(3) adenosine receptor (A(3)AR) agonism as a new target-based therapeutic strategy. The development of mechanoallodynia in a well-characterized mouse model of neuropathic pain following chronic constriction injury of the sciatic nerve was rapidly and dose-dependently reversed by the A(3)AR agonists: IB-MECA, its 2-chlorinated analog (Cl-IB-MECA), and the structurally distinct MRS1898. These effects were naloxone insensitive and thus are not opioid receptor mediated. IB-MECA was ≥1.6-fold more efficacious than morphine and >5-fold more potent. In addition, IB-MECA was equally efficacious as gabapentin (Neurontin) or amitriptyline, but respectively >350- and >75-fold more potent. Besides its potent standalone ability to reverse established mechanoallodynia, IB-MECA significantly increased the antiallodynic effects of all 3 analgesics. Moreover, neuropathic pain development in rats caused by widely used chemotherapeutics in the taxane (paclitaxel), platinum-complex (oxaliplatin), and proteasome-inhibitor (bortezomib) classes was blocked by IB-MECA without antagonizing their antitumor effect. A(3)AR agonist effects were blocked with A(3)AR antagonist MRS1523, but not with A(1)AR (DPCPX) or A(2A)AR (SCH-442416) antagonists. Our findings provide the scientific rationale and pharmacological basis for therapeutic development of A(3)AR agonists for chronic pain.

Many of the widely used anticancer drugs induce dose-limiting peripheral neuropathies that undermine their therapeutic efficacy. Animal models of chemotherapy-induced painful peripheral neuropathy (CIPN) evoked by a variety of drug classes, including taxanes, vinca alkaloids, platinum-complexes, and proteasome-inhibitors, suggest that the common underlying mechanism in the development of these neuropathies is mitotoxicity in primary nerve sensory axons (PNSAs) arising from reduced mitochondrial bioenergetics [eg adenosine triphosphate (ATP) production deficits due to compromised respiratory complex I and II activity]. The causative mechanisms of this mitotoxicity remain poorly defined. However, peroxynitrite, an important pro-nociceptive agent, has been linked to mitotoxicity in several disease states and may also drive the mitotoxicity associated with CIPN. Our findings reveal that the development of mechano-hypersensitivity induced by paclitaxel, oxaliplatin, and bortezomib was prevented by administration of the peroxynitrite decomposition catalyst Mn(III) 5,10,15,20-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin (MnTE-2-PyP5+) without interfering with their anti-tumor effects. Peak CIPN was associated with the nitration and inactivation of superoxide dismutase in the mitochondria, but not in the cytosol, as well as a significant decrease in ATP production within the PNSAs; all of these events were attenuated by MnTE-2-PyP5+. Our results provide continued support for the role of mitotoxicity in the development of CIPN across chemotherapeutic drug classes, and identify peroxynitrite as a key mediator in these processes, thereby providing the rationale towards development of “peroxynitrite-targeted” therapeutics for CIPN.

The clinical efficacy of opiates for pain control is severely limited by analgesic tolerance and hyperalgesia. Herein we show that chronic morphine upregulates both the sphingolipid ceramide in spinal astrocytes and microglia, but not neurons, and spinal sphingosine-1-phosphate (S1P), the end-product of ceramide metabolism. Coadministering morphine with intrathecal administration of pharmacological inhibitors of ceramide and S1P blocked formation of spinal S1P and development of hyperalgesia and tolerance in rats. Our results show that spinally formed S1P signals at least in part by (1) modulating glial function because inhibiting S1P formation blocked increased formation of glial-related proinflammatory cytokines, in particular tumor necrosis factor-␣, interleukin-1␤␣, and interleukin-6, which are known modulators of neuronal excitability, and (2) peroxynitrite-mediated posttranslational nitration and inactivation of glialrelated enzymes (glutamine synthetase and the glutamate transporter) known to play critical roles in glutamate neurotransmission. Inhibitors of the ceramide metabolic pathway may have therapeutic potential as adjuncts to opiates in relieving suffering from chronic pain.

We report a new series of bis-cyclohexano-fused Mn(III) complexes of bis-hydroxyphenyldipyrromethenes (DIPYs) 4a-c as potent and orally active peroxynitrite scavengers. Complexes 4a-c have been shown to reduce peroxynitrite through a 2-electron mechanism thereby forming the corresponding Mn(V)O species, which have been characterized by UV, NMR, and LCMS methods. Mn(III) complex 4b and its strained BODIPY analogue 9b have been analyzed by x-ray crystallography. Finally, complex 4a has been shown to be an orally active and potent analgesic in a model carrageenan-induced hyperalgesia known to be driven by the overproduction of peroxynitrite.The overproduction of reactive oxygen species (ROS) in vivo is now widely recognized as a key contributor to numerous pathologies. 1 One particularly damaging situation results from the diffusion controlled radical coupling of the central ROS, superoxide, with nitric oxide to form peroxynitrite. 2 The highly reactive peroxynitrite is a powerful biological oxidant which leaves a trail of dysfunctional oxidized and nitrated proteins, lipids and nucleotides, in its wake. 3 From a pharmacological perspective, peroxynitrite is considered a potent proinflammatory and proapoptotic species which plays a critical role in pain of several etiologies as demonstrated initially by our team and then by others. [4][5][6] Accordingly, the discovery of pharmaceutically relevant agents which can effectively decompose peroxynitrite should have significant therapeutic value. 2,3 As a result of the early discoveries of Groves7 and Stern, 8 Mn(III) and Fe(III) porphyrins have emerged as an important class of peroxynitrite reductase and isomerase catalysts, respectively (Figure 1 A). Elegant mechanistic studies have revealed that the more pharmacologically-suitable Mn(III) porphyrins decompose peroxynitrite primarily in a oneelectron fashion and require a biological co-reductant such as ascorbate to complete the reductase catalytic cycle.9 One electron reduction of peroxynitrite produces the potentially damaging nitrogen dioxide radical which is also thought to undergo rapid reduction by Recently, Gross has reported that Mn(III) and Fe(III) corroles are also excellent peroxynitrite decomposition catalysts. 11 Remarkably, the Mn(III) corroles operate through a 2-electron cycle, reducing peroxynitrite to nitrite instead of nitrogen dioxide through a novel disproportionation mechanism. The most important finding from this work was that Mn(III) corroles can decompose peroxynitrite in a catalytic fashion (in contrast to Mn(III) porphyrins) and therefore do not require the assistance of endogenous co-reductants.Although Mn(III) porphyrins, such as Mn(III)-4-TMPyP 5+ 1, and Mn(III) corrole systems, such as compound 2, have proven to be powerful pharmacological tools in animal studies demonstrating the benefits of destroying peroxynitrite in vivo,11 -14 they are not optimal as therapeutic candidates. While these types of polycationic complexes have excellent catalytic activities and their high water so...

Trypanosoma cruzi is a protozoan parasite that can initiate mucosal infection after conjunctival exposure. The anatomical route of T. cruzi invasion and spread after conjunctival parasite contamination remains poorly characterized. In the present work we have identified the sites of initial invasion and replication after contaminative conjunctival challenges with T. cruzi metacyclic trypomastigotes using a combination of immunohistochemical and real-time PCR confirmatory techniques in 56 mice between 3 and 14 days after challenge. Our results demonstrate that the predominant route of infection involves drainage of parasites through the nasolacrimal duct into the nasal cavity. Initial parasite invasion occurs within the ductal and respiratory epithelia. After successive waves of intracellular replication and cell-to-cell spread, parasites drain via local lymphatic channels to lymph nodes and then disseminate through the blood to distant tissues. This model of conjunctival challenge was used to identify immune responses associated with protection against mucosal infection. Preceding mucosal infection induces mucosal immunity, resulting in at least 50-fold reductions in recoverable tissue parasite DNA in immune mice compared to controls 10 days after conjunctival challenge (P < 0.05). Antigen-specific gamma interferon production by T cells was increased at least 100-fold in cells harvested from immune mice (P < 0.05). Mucosal secretions containing T. cruzi-specific secretory immunoglobulin A harvested from immune mice were shown to protect against mucosal parasite infection (P < 0.05), demonstrating that mucosal antibodies can play a role in T. cruzi immunity. This model provides an important tool for detailed studies of mucosal immunity necessary for the development of mucosal vaccines.Trypanosoma cruzi is a protozoan intracellular parasite and the causative agent of Chagas disease. Approximately 16 to 18 million people in Central and South America are infected, and up to 40% will develop clinical manifestations of chronic infection (19). T. cruzi is transmitted by the reduviid bug when it takes a blood meal. Unlike most other insect-borne parasites, which are injected into the host while the insect feeds, the reduviid bug excretes the infective metacyclic trypomastigote in urine and feces in the process of concentrating its blood meal. Once deposited, the parasite can infect either through the wound created by the insect's bite or through mucosa after ingestion or contamination of conjunctival surfaces.The immunopathologic manifestations of Chagas' disease develop after years of chronic infection with T. cruzi. These manifestations were previously thought to be due to autoimmune responses triggered by parasite epitopes cross-reactive with self-proteins. However, the development of more sensitive tools that can detect low levels of parasite persistence have implicated chronic infection and the associated parasite-specific immunity in the development of disease pathology (20). Furthermore, chemotherapeutic treatmen...

The role of peroxynitrite (PN) as a mediator of nociceptive signaling is emerging. We recently reported that the development of central sensitization that follows the intraplantar injection of carrageenan in rats is associated with spinal PN synthesis. We now demonstrate that a significant pathway through which spinal PN modulates central sensitization is post-translational tyrosine nitration of key proteins involved in the glutamatergic pathway, namely glutamate transporter GLT-1 and glutamine synthetase (GS). We also reveal that spinal activation of the N-methyl-D-aspartate (NMDA) receptor provides a source of PN in this setting. Intraplantar injection of carrageenan led to the development of thermal hyperalgesia as well as nitration of GLT-1 and GS in dorsal horn tissues. Pretreatment with the PN decomposition catalyst FeTM-4-PyP5+ [Fe(III)5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin] or the NMDA receptor antagonist MK-801 blocked the development of hyperalgesia. Carrageenan-induced hyperalgesia was also associated with nitration and inactivation of spinal mitochondrial superoxide dismutase (MnSOD) known to provide a critical source of PN during central sensitization. Nitration of GLT1 and GS contributes to central sensitization by enhancing glutamateric neurotransmission. Our results support the critical role of nitroxidative stress in the development of hyperalgesia and suggest that post-translational nitration of enzymes and transporters linked to glutamatergic neurotransmission represent a novel mechanism of central sensitization.