Erythrocyte Membrane Camouflaged Nanotheranostics for Optical Molecular Imaging-Escorted Self-Oxygenation Photodynamic Therapy.

Hypoxic tumor microenvironment (TME) hampers the application of oxygen (O2)-dependent photodynamic therapy (PDT) in solid tumors. To address this problem, a biomimetic nanotheranostics (named MMCC@EM) is developed for optical molecular imaging-escorted self-oxygenation PDT. MMCC@EM is synthesized by encapsulating chlorin e6 (Ce6) and catalase (CAT) in metal-organic framework (MOF) nanoparticles with erythrocyte membrane (EM) camouflage. Based on the biomimetic properties of EM, MMCC@EM efficiently accumulates in tumor tissues. The enriched MMCC@EM achieves TME-activatable drug release, thereby releasing CAT and Ce6, and this process can be monitored through fluorescence (FL) imaging. In addition, endogenous hydrogen peroxide (H2O2) will be decomposed by CAT to produce O2, which can be reflected by the measurement of intratumoral oxygen concentration using photoacoustic (PA) imaging. Such self-oxygenation nanotheranostics effectively mitigate tumor hypoxia and improve the generation of singlet oxygen (1O2). The 1O2 disrupts mitochondrial function and triggers caspase-3-mediated cellular apoptosis. Furthermore, MMCC@EM triggers immunogenic cell death (ICD) effect, leading to an increased infiltration of cytotoxic T lymphocytes (CTLs) into tumor tissues. As a result, MMCC@EM exhibits good therapeutic effects in 4T1-tumor bearing mice under the navigation of FL/PA duplex imaging.

D-serine in the midbrain periaqueductal gray contributes to morphine tolerance in rats.

BACKGROUND: The N-methyl-D-aspartate subtype of glutamate receptor plays a critical role in morphine tolerance. D-serine, a co-agonist of N-methyl-D-aspartate receptor, participates in many physiological and pathophysiological processes via regulating N-methyl-D-aspartate receptor activation. The purinergic P2X7 receptor activation can induce the D-serine release in the central nervous system. This study aimed to investigate the role of the ventrolateral midbrain periaqueductal gray D-serine in the mechanism of morphine tolerance in rats. The development of morphine tolerance was induced in normal adult male Sprague-Dawley rats through subcutaneous injection of morphine (10 mg/kg). The analgesic effect of morphine (5 mg/kg, i.p.) was assessed by measuring mechanical withdrawal thresholds in rats with an electronic von Frey anesthesiometer. The D-serine concentration and serine racemase expression levels in the ventrolateral midbrain periaqueductal gray were evaluated through enzyme-linked immunosorbent assay and Western blot analysis, respectively. The effects of intra-ventrolateral midbrain periaqueductal gray injections of the D-serine degrading enzyme D-amino acid oxidase and antisense oligodeoxynucleotide targeting the P2X7 receptor on chronic morphine-treated rats were also explored. RESULTS: We found that repeated morphine administrations decreased the antinociceptive potency of morphine evidenced by the percent changes in mechanical pain threshold in rats. By contrast, the D-serine contents and the expression levels of the serine racemase protein were upregulated in the ventrolateral midbrain periaqueductal gray in morphine-tolerant rats. The development of morphine tolerance was markedly alleviated by intra-ventrolateral midbrain periaqueductal gray injections of D-amino acid oxidase or antisense oligodeoxynucleotide targeting the P2X7 receptor. CONCLUSIONS: Our data indicate that the development of antinociceptive tolerance to morphine is partially mediated by ventrolateral midbrain periaqueductal gray D-serine content, and the activation of the ventrolateral midbrain periaqueductal gray P2X7 receptor is an essential prelude to D-serine release. These results suggest that a cascade involving P2X7 receptor-D-serine-N-methyl-D-aspartate receptor mediated signaling pathway in the supraspinal mechanism of morphine tolerance.

A Versatile Cryomicroneedle Patch for Traceable Photodynamic Therapy.

Photodynamic therapy (PDT) continues to encounter multifarious hurdles, stemming from the ineffectual preservation and delivery system of photosensitizers, the dearth of imaging navigation, and the antioxidant/hypoxic tumor microenvironment. Herein, a versatile cryomicroneedle patch (denoted as CMN-CCPH) is developed for traceable PDT. The therapeutic efficacy is further amplified by catalase (CAT)-induced oxygen (O2) generation and Cu2+-mediated glutathione (GSH) depletion. The CMN-CCPH is composed of cryomicroneedle (CMN) as the vehicle and CAT-biomineralized copper phosphate nanoflowers (CCP NFs) loaded with hematoporphyrin monomethyl ether (HMME) as the payload. Importantly, the bioactive function of HMME and CAT can be optimally maintained under the protection of CCPH and CMN for a duration surpassing 60 days, leading to bolstered bioavailability and notable enhancements in PDT efficacy. The in vivo visualization of HMME and oxyhemoglobin saturation (sO2) monitored by fluorescence (FL)/photoacoustic (PA) duplex real-time imaging unveils the noteworthy implications of CMN-delivered CCPH for intratumoral enrichment of HMME and O2 with reduced systemic toxicity. This versatile CMN patch demonstrates distinct effectiveness in neoplasm elimination, underscoring its promising clinical prospects.

Activation of P2X7 receptors in the midbrain periaqueductal gray of rats facilitates morphine tolerance.

Opiates such as morphine exhibit analgesic effect in various pain models, but repeated and chronic morphine administration may develop resistance to antinociception. The purinergic signaling system is involved in the mechanisms of pain modulation and morphine tolerance. This study aimed to determine whether the P2X7 receptor in the ventrolateral midbrain periaqueductal gray (vlPAG) is involved in morphine tolerance. Development of tolerance to the antinociceptive effect of morphine was induced in normal adult male Sprague-Dawley (SD) rats through subcutaneous injection of morphine (10mg/kg). The analgesic effect of morphine (5mg/kg, i.p.) was assessed by measuring mechanical withdrawal thresholds (MWTs) in rats with an electronic von Frey anesthesiometer. The expression levels and distribution of the P2X7 receptor in the vlPAG was evaluated through Western blot analysis and immunohistochemistry. The acute effects of intra-vlPAG injection of the selective P2X7 receptor agonist Bz-ATP, the selective P2X7 receptor antagonist A-740003, or antisense oligodeoxynucleotide (AS ODN) targeting the P2X7 receptor on morphine-treated rats were also observed. Results demonstrated that repeated morphine administration decreased the mechanical pain thresholds. By contrast, the expression of the P2X7 receptor protein was up-regulated in the vlPAG in morphine tolerant rats. The percent changes in MWT were markedly but only transiently attenuated by intra-vlPAG injection of Bz-ATP (9nmol/0.3µL) but elevated by A-740003 at doses of 10 and 100nmol/0.3µL. AS ODN (15nmol/0.3µL) against the P2X7 receptor reduced the development of chronic morphine tolerance in rats. These results suggest that the development of antinociceptive tolerance to morphine is partially mediated by activating the vlPAG P2X7 receptors. The present data also suggest that the P2X7 receptors may be a therapeutic target for improving the analgesic effect of morphine in treatments of pain when morphine tolerance occurs.

Antihyperalgesic effect of 5-HT7 receptor activation on the midbrain periaqueductal gray in a rat model of neuropathic pain.

The 5-HT7 receptor is the most recently discovered receptor for 5-hydroxytryptamine (5-HT), and only little is known about the analgesic potential of this receptor. Adenosine triphosphate (ATP) modulates pain transmission by activating P2X/P2Y receptors, in which the P2X3 subtype is an important target for this effect. This study examined the antihyperalgesic effect of the 5-HT7 receptors in the ventrolateral midbrain periaqueductal gray (vlPAG), a crucial site for endogenous pain inhibition. This study also explored the importance of the interactions between the 5-HT7 and P2X3 receptors in this effect. To address this issue, neuropathic pain was induced through chronic constriction injury (CCI) of the sciatic nerve in Sprague-Dawley (SD) rats. The expression level and distribution of the 5-HT7 receptor were evaluated through Western blot and immunohistochemistry. The mechanical withdrawal threshold (MWT) was measured by using an electronic pressure meter test. Different doses (3, 6, and 12µmol) of AS-19, a selective agonist of the 5-HT7 receptor, were administered in the vlPAG of CCI rats. The effects of pretreatment with the selective 5-HT7 receptor antagonist SB-269970 or the selective P2X3 receptor antagonist A-317491 on the analgesic effect of AS-19 were observed. Results showed that CCI decreased the MWT values of the rats. The injury also increased the protein level of the 5-HT7 receptor in the vlPAG of neuropathic pain rats. AS-19 microinjection significantly elevated the MWT values in a dose-dependent manner, but SB-269970 pretreatment attenuated the antihyperalgesic effect of AS-19. Furthermore, the antihyperalgesic effect of the 5-HT7 receptor was partially but significantly blocked by A-317491 pretreatment. These data indicate that the 5-HT7 receptor in the vlPAG exerts an antihyperalgesic effect on rats with neuropathic pain. The 5-HT7 and P2X3 receptors interact in the vlPAG and exhibit an analgesic action through the enhanced function of the endogenous analgesic system.