Oxaliplatin, a platinum-based chemotherapeutic agent, has become a standard treatment for advanced colorectal cancer. The dose-limiting toxicity of this compound is the development of peripheral ...neuropathy. A tangled panel of symptoms, sensory loss, paresthesia, dysesthesia and pain, may be disabling for patients and adversely affect their quality of life.
Recently, we described a characteristic glial activation profile in a rat model of oxaliplatin-induced neuropathy. Glial cells are considered a new pharmacological target for neuropathic pain relief but its relevance in chemotherapy-dependent neuropathies is debated. Aimed to evaluate the significance of glial activation in pain generated by oxaliplatin, the microglial inhibitor minocycline or the astrocyte inhibitor fluorocitrate were continuously infused by intrathecal route in oxaliplatin-treated rats. Both compounds significantly reduced oxaliplatin-evoked pain though the efficacy of fluorocitrate was higher revealing a prominent role of astrocytes.
Immunohistochemical analysis of the dorsal horn confirmed the specific Iba1-positive cell inhibition caused by minocycline as well as the selectivity of fluorocitrate on GFAP-positive cells. The activation of astrocytes in minocycline-treated rats suggests a microglia-independent modulation of astrocytes by oxaliplatin neurotoxicity. Neither the selective activation of astrocyte after minocycline treatment nor the exclusive microglial response after fluorocitrate is able to evoke pain.
Morphometric and morphological determinations performed on dorsal root ganglia evidenced that the glial inhibitors did not prevent the oxaliplatin-dependent increase of eccentric nucleoli and multinucleolated neurons. The decrease of soma area was also unaltered.
In summary, these data highlight the role of central glial cells in oxaliplatin-dependent neuropathic pain. On the other hand, glial inhibition is not associated with neuroprotective effects suggesting the need for careful modulation of glial signaling to prevent the pathophysiology that leads to persistent neuropathic pain.
•Prevention of microglia or astrocyte activation reduces oxaliplatin-dependent pain.•Astrocytes have a preponderant role.•Astrocyte number increase is not consequential to microglial activation.•Oxaliplatin induces pain by the synergistic signal of microglia and astrocytes.•Glial cell inhibition is not associated with neuroprotection.
Accumulating evidence suggests that opioid analgesics can lead to paradoxical sensitization to pain when delivered in different administration patterns. Although opioid tolerance-induced hyperalgesia ...is largely studied, little is known about the mechanisms underlying acute ultra-low-dose morphine hyperalgesia. Activation of spinal glial cells is reported to regulate pain hypersensitivity. To elucidate the mechanism involved in acute ultra-low-dose morphine hyperalgesia, we tested whether an opioid agonist promoted the activation of spinal astrocytes and microglia and investigated the cellular pathways involved. Ultra-low-dose morphine activated spinal astrocytes with no effect on microglia. The astrocyte activation was selectively prevented by the opioid antagonist naloxone, the μ-opioid receptor (MOR) silencing and the JNK inhibitor SP600125. Morphine elevated spinal JNK1, JNK2, and c-Jun phosphorylation. Conversely, phosphorylation of cAMP response element-binding protein (CREB) and signal transducer and activator of transcription-1 (STAT-1) was not elevated, and nuclear factor kappa B (NF-κB) levels remained unmodified. Administration of SP600125 and the N-methyl-D-aspartate (NMDA) antagonist MK801 prevented morphine hyperalgesia. Ultra-low-dose morphine increased protein kinase C (PKC) γ phosphorylation. Pretreatment with a PKC inhibitor prevented morphine hyperalgesia and JNK and c-Jun overphosphorylation, indicating PKC is a JNK upstream modulator and illustrating the presence of a pathway involving PKC, NMDA, and JNK activated by morphine. Immunofluorescence experiments indicated the neuronal localization of spinal MOR. However, JNK was not detected in MOR-expressing cells, showing the presence of a neuron-astrocyte signaling pathway. These results illustrate the selective activation of an astrocyte JNK pathway after the stimulation of neuronal MOR, which contributes to ultra-low-dose morphine hyperalgesia.
Magnetic nanoparticles, MNPs, mineralized within a human ferritin protein cage, HFt, can represent an appealing platform to realize smart therapeutic agents for cancer treatment by drug delivery and ...magnetic fluid hyperthermia, MFH. However, the constraint imposed by the inner diameter of the protein shell (ca. 8 nm) prevents its use as heat mediator in MFH when the MNPs comprise pure iron oxide. In this contribution, we demonstrate how this limitation can be overcome through the controlled doping of the core with small amount of Co(II). Highly monodisperse doped iron oxide NPs with average size of 7 nm are mineralized inside a genetically modified variant of HFt, carrying several copies of α-melanocyte-stimulating hormone peptide, which has already been demonstrated to have excellent targeting properties toward melanoma cells. HFt is also conjugated to poly(ethylene glycol) molecules to increase its in vivo stability. The investigation of hyperthermic properties of HFt-NPs shows that a Co doping of 5% is enough to strongly enhance the magnetic anisotropy and thus the hyperthermic efficiency with respect to the undoped sample. In vitro tests performed on B16 melanoma cell line demonstrate a strong reduction of the cell viability after treatment with Co doped HFt-NPs and exposure to the alternating magnetic field. Clear indications of an advanced stage of apoptotic process is also observed from immunocytochemistry analysis. The obtained data suggest this system represents a promising candidate for the development of a protein-based theranostic nanoplatform.
Oxaliplatin is the standard treatment for advanced colorectal cancer. Its dose-limiting toxicity is the development of a painful neuropathic syndrome sustained by unclear mechanisms. Although the ...oxidative hypothesis is a matter of debate, direct data about oxidative damage induced in vivo by anticancer agents are lacking and the efficacy of the available antioxidant compounds are unsatisfactory. In a rat model of painful oxaliplatin-induced neuropathy (2.4 mgkg(-1) i.p., daily for 21 days), we described an important component of oxidative stress. In the plasma of oxaliplatin-treated rats, the increases in carbonylated protein and thiobarbituric acid reactive substances were the index of the resultant protein oxidation and lipoperoxidation, respectively. The same pattern of oxidation was revealed also in the sciatic nerve, and in the spinal cord where the damage reached the DNA level. The antioxidant compound silibinin (100 mgkg(-1) per os), administered once a day, starting from the first day of oxaliplatin injection until the 20th, prevented oxidative damage as did α-tocopherol. Repetitive administration of silibinin, as well as α-tocopherol, reduced oxaliplatin-dependent pain induced by mechanical and thermal stimuli. Antioxidants were also able to improve motor coordination. The antineuropathic effect of both molecules improved by about 50% oxaliplatin-induced behavioral alterations.
This study characterizes oxidative stress parameters in a rat model of oxaliplatin-induced neuropathy. A relationship between the improvement of oxidative alterations and pain relief is established in rats treated with natural antioxidant compounds like α-tocopherol and silibinin. Silibinin could be a valid therapeutic option for chemotherapy-induced neuropathy.
Opioids are first-line drugs for moderate to severe acute pain and cancer pain. However, these medications are associated with severe side effects, and whether they are efficacious in treatment of ...chronic nonmalignant pain remains controversial.Medications that act through alternative molecular mechanisms are critically needed. Antagonists of α9α10 nicotinic acetylcholine receptors (nAChRs) have been proposed as an important nonopioidmechanism based on studies demonstrating prevention of neuropathology after trauma-induced nerve injury. However, the key α9α10 ligands characterized to date are at least two orders of magnitude less potent on human vs. rodent nAChRs, limiting their translational application. Furthermore, an alternative proposal that these ligands achieve their beneficial effects by acting as agonists of GABAB receptors has caused confusion over whether blockade of α9α10 nAChRs is the fundamental underlying mechanism. To address these issues definitively, we developed RgIA4, a peptide that exhibits high potency for both human and rodent α9α10 nAChRs, and was at least 1,000-fold more selective for α9α10 nAChRs vs. all other molecular targets tested, including opioid and GABAB receptors. A daily s.c. dose of RgIA4 prevented chemotherapy-induced neuropathic pain in rats. In wild-type mice, oxaliplatin treatment produced cold allodynia that could be prevented by RgIA4. Additionally, in α9 KO mice, chemotherapy-induced development of cold allodynia was attenuated and the milder, temporary cold allodynia was not relieved by RgIA4. These findings establish blockade of α9-containing nAChRs as the basis for the efficacy of RgIA4, and that α9-containing nAChRs are a critical target for prevention of chronic cancer chemotherapy-induced neuropathic pain.
Neurotoxicity is the limiting side effect of the anticancer agent oxaliplatin. A tangled panel of symptoms, sensory loss, paresthesia, dysesthesia, and pain may be disabling for patients and ...adversely affect their quality of life. To elucidate the morphologic and molecular alterations that occur in the nervous system during neuropathy, rats were daily injected with 2.4 mg kg(-1) oxaliplatin intraperitoneally. A progressive decrease in the pain threshold and hypersensitivity to noxious and nonnoxious stimuli were evidenced during the treatment (7, 14, 21 days). On day 21, morphometric alterations were detectable exclusively in the dorsal root ganglia, whereas the activating transcription factor 3 and neurofilament (heavy-chain) expression changed dramatically in both the nerves and ganglia. Inflammatory features were not highlighted. Interestingly, satellite cells exhibited signs of activation. Glial modulation was characterized in the spinal cord and brain areas involved in pain signaling. On the 21st day, spinal astrocytes increased numerically whereas the microglial population was unaltered. The number of glial cells in the brain differed according to the zone and treatment time points. In particular, on day 21, a significant astrocyte increase was measured in the anterior cingulate cortex, somatosensory area 1, neostriatum, ventrolateral periaqueductal gray, and nucleus raphe magnus.
These data highlight the relevance of glial cells in chemotherapy-induced neurotoxicity as part of the investigation of the role that specific brain areas play in neuropathy.
The hydrochlorothiazide (HCT) low solubility and permeability give rise to limited and variable bioavailability; its low stability makes it difficult to develop stable aqueous liquid formulations; ...its low dose makes the achievement of a homogeneous drug distribution very difficult. Thus, the aim of this study was to investigate the effectiveness of a strategy based on the development of nanostructured lipid carriers (NLC) as an innovative oral pediatric formulation of HCT with improved therapeutic efficacy. The performance of various synthetic and natural liquid lipids was examined and two different preparation methods were employed, i.e. homogenization-ultrasonication (HU) and microemulsion (ME), in order to evaluate their influence on the NLC properties in terms of size, polydispersity index, ζ-potential, entrapment efficiency, gastric stability, and drug release properties. Precirol®ATO5 was used as solid lipid and Tween
®
80 and Pluronic
®
F68 as surfactants, formerly selected in a previous study focused on the development of HCT-solid lipid nanoparticles (SLNs). The presence of Pluronic
®
F68 did not allow ME formation. On the contrary, using Tween
®
80, the ME method enabled a higher entrapment efficiency than the HU. Regardless of the preparation method, NLCs exhibited great entrapment efficiency values clearly higher than previous SLNs. Moreover, NLC-ME formulations provided a prolonged release, which lasted for 6 h. In particular, NLC-ME containing Tween
®
20 as Co-Surfactant showed the best performances, giving rise to a complete drug release, never achieved with previous SLN formulations, despite their successful results. In vivo studies on rats confirmed these results, displaying their best diuretic profile. Moreover, all HCT-loaded NLC formulations showed higher stability than the corresponding SLNs.
The gut-brain axis and the intestinal microbiota are emerging as key players in health and disease. Shifts in intestinal microbiota composition affect a variety of systems; however, evidence of their ...direct impact on cognitive functions is still lacking. We tested whether faecal microbiota transplant (FMT) from aged donor mice into young adult recipients altered the hippocampus, an area of the central nervous system (CNS) known to be affected by the ageing process and related functions.
Young adult mice were transplanted with the microbiota from either aged or age-matched donor mice. Following transplantation, characterization of the microbiotas and metabolomics profiles along with a battery of cognitive and behavioural tests were performed. Label-free quantitative proteomics was employed to monitor protein expression in the hippocampus of the recipients. We report that FMT from aged donors led to impaired spatial learning and memory in young adult recipients, whereas anxiety, explorative behaviour and locomotor activity remained unaffected. This was paralleled by altered expression of proteins involved in synaptic plasticity and neurotransmission in the hippocampus. Also, a strong reduction of bacteria associated with short-chain fatty acids (SCFAs) production (Lachnospiraceae, Faecalibaculum, and Ruminococcaceae) and disorders of the CNS (Prevotellaceae and Ruminococcaceae) was observed. Finally, the detrimental effect of FMT from aged donors on the CNS was confirmed by the observation that microglia cells of the hippocampus fimbria, acquired an ageing-like phenotype; on the contrary, gut permeability and levels of systemic and local (hippocampus) cytokines were not affected.
These results demonstrate that age-associated shifts of the microbiota have an impact on protein expression and key functions of the CNS. Furthermore, these results highlight the paramount importance of the gut-brain axis in ageing and provide a strong rationale to devise therapies aiming to restore a young-like microbiota to improve cognitive functions and the declining quality of life in the elderly. Video Abstract.
Anti-cancer therapy based on the repeated administration of oxaliplatin is limited by the development of a disabling neuropathic syndrome with detrimental effects on the patient’s quality of life. ...The lack of effective pharmacological approaches calls for the identification of innovative therapeutic strategies based on new targets. We focused our attention on the imidazoline I
1
receptor (I
1
-R) and in particular on the selective I
1
-R agonist 2-(1-(1,1′-biphenyl-2-yl)propan-2-yl)-4,5-dihydro-1
H
-imidazole) (carbophenyline). The purpose of this work was the preclinical evaluation of the efficacy of carbophenyline on oxaliplatin-induced neuropathic pain in mice. Carbophenyline, acutely per os administered (0.1–10 mg kg
−1
), induced a dose-dependent anti-hyperalgesic effect that was completely blocked by the pre-treatment with the I
1
-R antagonist
3
or the I
1
/α
2
receptor antagonist efaroxan, confirming the I
1
-R-dependent mechanism. Conversely, pre-treatment with the I
2
-R antagonist BU224 did not block the anti-nociceptive effect evoked by carbophenyline. Repeated oral administrations of carbophenyline (1 mg kg
−1
) for 14 days, starting from the first day of oxaliplatin injection, counteracted the development of neuropathic pain in all behavioral tests (cold plate, Von Frey, and paw pressure tests) carried out 24 h after the last carbophenyline treatment on days 7 and 14. In the dorsal horn of the spinal cord, carbophenyline significantly decreased the oxaliplatin-induced astrocyte activation detected by immunofluorescence staining by the specific labelling with GFAP antibody. In conclusion, carbophenyline showed anti-neuropathic properties both after acute and chronic treatment with preventive effect against oxaliplatin-induced astrocyte activation in the spinal cord. Therefore, I
1
-R agonists emerge as a new class of candidates for the management of oxaliplatin-induced neuropathic pain.
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