Incorporation of ROS-Responsive Substance P-Loaded Zeolite Imidazolate Framework-8 Nanoparticles into a Ca2+-Cross-Linked Alginate/Pectin Hydrogel for Wound Dressing Applications.

PURPOSE: Wound healing, especially of extensive full-thickness wounds, is one of the most difficult problems in clinical studies. In this study, we prepared a novel substance P (SP)-delivery system using zeolite imidazolate framework-8 (ZIF-8) nanoparticles. METHODS: We synthesized ZIF-8 nanoparticles using a modified biomimetic mineralization method. We then coated SP-loaded ZIF-8 nanoparticles (SP@ZIF-8) with polyethylene glycol-thioketal (PEG-TK) to fabricate SP@ZIF-8-PEG-TK nanoparticles, and encapsulated them in injectable hydrogel composed of sodium alginate and pectin and cross-linked using calcium chloride. The final hydrogel wound dressing containing SP@ZIF-8-PEG-TK nanoparticles was called SP@ZIF-8-PEG-TK@CA. RESULTS: The fabricated ZIF-8 nanoparticles had high SP-loading efficiency. SP-release assay showed that the SP@ZIF-8-PEG-TK nanoparticles maintained drug activity and showed responsive release under stimulation by reactive oxygen species. The SP@ZIF-8-PEG-TK nanoparticles promoted proliferation of human dermal fibroblasts, up-regulated expression levels of inflammation-related genes in macrophages, and exhibited favorable cytocompatibility in vitro. Full-thickness excision wound models in vivo confirmed that SP@ZIF-8-PEG-TK@CA dressings had excellent wound-healing efficacy by promoting an early inflammatory response and subsequent M2 macrophage polarization in the wound-healing process. CONCLUSION: In conclusion, these findings indicated that SP@ZIF-8-PEG-TK@CA dressings might be useful for wound dressing applications in the clinic.

Substance-P Prevents Cardiac Ischemia-Reperfusion Injury by Modulating Stem Cell Mobilization and Causing Early Suppression of Injury-Mediated Inflammation.

BACKGROUND/AIMS: Therapies using stem/progenitor cells have been experimentally and clinically investigated to regenerate damaged hearts. Substance-P (SP) induces bone marrow (BM) stem cell mobilization and suppresses inflammation in ischemic injuries. This study investigated the role of SP in BM stem cell mobilization and immune responses for tissue repair after ischemic-reperfusion injury (IRI), in comparison with that of granulocyte colony-stimulating factor (GCSF). METHODS: SP was intravenously injected into IRI rats and its affect was evaluated by determining colony forming efficiency, immune cell/ cytokine profiles, histological changes, and heart function through echocardiography. RESULTS: In the rat cardiac IRI model, SP suppressed IRI-mediated tumor necrosis factor-α induction, but increased the levels of interleukin-10, CD206+ monocytes, and regulatory T cells in the blood; reduced myocardial apoptosis at day 1 post-IRI; and markedly stimulated colony forming unit (CFU)-e and (CFU)-f cell mobilization. Efficacy of SP in the recovery of cardiac function after IRI was demonstrated by increased cardiac contractility, accompanied by reduced infarction sizes and fibrosis, and increased revascularization of vessels covered with alpha smooth muscle actin. These effects of SP were confirmed in an acute myocardial infarction (AMI) model. All effects mediated by SP were superior to those mediated by GCSF. CONCLUSION: Systemic injection of SP decreased early inflammatory responses and promoted stem cell mobilization, leading to a compact vasculature and improved cardiac function in cardiac IRI and AMI.

Real-time near-infrared bioimaging of a receptor-targeted cytotoxic dendritic theranostic agent.

Efficient and site-specific delivery of anticancer drugs to tumors is important in the development of effective cancer chemotherapy. As an undecapeptide of the tachykinin neuropeptide family, the substance P (SP)/neurokinin-1 receptor (NK1R) system has been identified as a promising ligand-receptor pair in tumor-specific drug delivery. However, the rational design of suitable theranostic agents with high drug loading capacity and tumor targeting for cancer patients remains a great challenge. Herein, we report a dendritic strategy that utilizes the two amine functionalities of lysine to create branch points that allow conjugation of the anticancer drug 5-fluorouracil (5-FU) to the tumor-targeting ligand substance P, along with an additional near-infrared (NIR) squaraine dye, to construct a theranostic dendritic agent, P-FU 4. This cytotoxic theranostic agent, containing four carboxyl-modified 5-FU molecules, has several desirable advantages: i) the ability to self-assemble into nanoparticles; ii) enhanced cytotoxicity with high drug loading capacity (16%) and a specific receptor-targeted interaction with NK1R through the SP moiety; and iii) a high NIR squaraine fluorescence efficiency due to the specific dendron isolation, avoiding aggregation-mediated quenching. As demonstrated in this report, the cytotoxic activity of P-FU 4 is dose-dependent against the tested cancer cells. The improved drug loading capacity with dendritic branching distinctly enhanced cytotoxicity to tumor cells but had little effect on the viability of normal cells. P-FU 4 was preferentially taken up by tumor cells through a receptor-mediated interaction, which was monitored by effective NIR fluorescence with high tissue penetration. Studies using a mouse model revealed that P-FU 4 can significantly inhibit tumor progression, with a tumor-inhibition rate of 60.2%. The receptor-targeted cytotoxic dendritic theranostic agent is highly preferable to standard chemotherapeutic treatments and decreases the negative side effects of medications on healthy cells, which establishes its utility in drug delivery and cancer chemotherapy.

Lactoferrin- and antitransferrin-modified liposomes for brain targeting of the NK3 receptor agonist senktide: preparation and in vivo evaluation.

The aim of this work was to evaluate the capability of lactoferrin- and antitransferrin-modified long circulating liposomes to deliver the hydrophilic peptide senktide, a selective NK3 receptor agonist unable to cross the blood brain barrier, to central nervous system by using an indirect method based on in vivo microdialysis studies to estimate the responsiveness of nucleus accumbens shell dopamine to senktide. To this purpose, senktide was encapsulated in different targeted and not-targeted stealth liposomes prepared using film hydration method. Formulations were characterized in terms of morphology, size distribution, zeta potential, encapsulation efficiency, and antibody presence on the liposome surface. In vivo microdialysis studies were performed injecting intravenously the senktide-loaded liposomes and comparing obtained dopamine levels with those found with the free senktide given intracerebroventricularly. Results showed that all vesicles were spherical, small in size (around 120 nm), homogeneously dispersed, and slightly negatively charged. TEM analysis, using an anti IgG secondary antibody with 10nm gold nanoparticles at its distal end, demonstrated the successful linkage of the antibody on the liposomal surface. Intravenously administered in rats, senktide-loaded targeted stealth liposomes elicited a significant increase of dialysate dopamine in the nucleus accumbens shell, which was comparable to that of the free senktide given intracerebroventricularly when antitransferrin-targeted liposomes were tested. On the contrary, control stealth liposomes did not affect dopamine levels. Senktide brain levels were higher using the antitransferrin-targeted liposomes in comparison with the lactoferrin ones, while the opposite was obtained in the liver tissue where the highest senktide accumulation was always found.

Preparation and first biological evaluation of novel Re-188/Tc-99m peptide conjugates with substance-P.

INTRODUCTION: New (188)Re and (99m)Tc peptide conjugates with substance- P (SP) were prepared and biologically evaluated. The radiopharmaceuticals have been labelled with the [M≡N](2+) (M=(99m)Tc, (188)Re) core using a combination of π-donor tridentate and π-acceptor monodentate ancillary ligands. METHODS: The new radiopharmaceuticals have been prepared through a two-step reaction by simultaneous addition of the tridentate and monodentate ligands to a vial containing a preformed [M≡N](2+) core. The tridentate ligand was formed by linking two cysteine residues to the terminal arginine of the undecapeptide SP, whereas the monodentate ligand was a tertiary phosphine. The preparation of the corresponding Re-188 derivative required developing a more complex chemical procedure to obtain the [Re≡N](2+) core in satisfactory yields. Characterization of the resulting products was obtained by chromatographic methods. Biological evaluation was performed for both Tc-99m and Re-188 derivatives by in-vitro studies on isolated cells expressing NK1-receptors. In-vivo imaging in mice was carried out using a small-animal YAP(S)PET tomograph. CONCLUSION: New Tc-99m and Re-188 peptide radiopharmaceuticals with SP have been prepared in high-yield and with high-specific activity. Both Tc-99m and Re-188 peptide radioconjugates exhibit high affinity for NK1 receptors, thus giving further evidence to the empirical rule that structurally related Tc-99m and Re-188 radiopharmaceuticals exhibit identical biological properties.

Delivery of bone morphogenetic protein-2 and substance P using graphene oxide for bone regeneration.

In this study, we demonstrate that graphene oxide (GO) can be used for the delivery of bone morphogenetic protein-2 (BMP-2) and substance P (SP), and that this delivery promotes bone formation on titanium (Ti) implants that are coated with GO. GO coating on Ti substrate enabled a sustained release of BMP-2. BMP-2 delivery using GO-coated Ti exhibited a higher alkaline phosphatase activity in bone-forming cells in vitro compared with bare Ti. SP, which is known to recruit mesenchymal stem cells (MSCs), was co-delivered using Ti or GO-coated Ti to further promote bone formation. SP induced the migration of MSCs in vitro. The dual delivery of BMP-2 and SP using GO-coated Ti showed the greatest new bone formation on Ti implanted in the mouse calvaria compared with other groups. This approach may be useful to improve osteointegration of Ti in dental or orthopedic implants.

Intrathecal substance P-saporin in the dog: distribution, safety, and spinal neurokinin-1 receptor ablation.

BACKGROUND: Neurokinin-1 receptors (NK1-rs) located on superficial dorsal horn neurons are essential for integration of nociceptive input. Intrathecal injection of substance P-saporin (SP-SAP) leads to local loss of spinal NK1-r (+) neurons suggesting its potential as a therapeutic agent for chronic pain. The authors determined, in a canine model, effects of lumbar intrathecal SP-SAP. METHODS: Distribution of SP-SAP and Saporin was determined in plasma, lumbar cerebrospinal fluid, and tissue. Safety of intrathecal SP-SAP was determined in four groups (six dogs each) administered 0 (0.9% saline), 1.5, 15, or 150 µg SP-SAP through lumbar intrathecal catheters. Behavioral, physiologic, and biochemical variables were assessed. Spinal tissues were collected at 7 and approximately 90 days, or earlier if significant morbidity developed, and analyzed for NK1-r (+) neuron loss and histopathology. RESULTS: SP-SAP and Saporin were detectable in lumbar cerebrospinal fluid for up to 4 and 24 h, respectively. Animals receiving intrathecal saline, 1.5, or 15 µg of SP-SAP showed no persistent neurologic deficits. Three animals receiving 150 µg of SP-SAP developed pelvic limb paraparesis and were euthanized prematurely. Immunohistochemistry and in situ hybridization cell counts confirmed a significant reduction in NK1-r (+) in superficial dorsal horn neurons from lumbar spinal cord after intrathecal administration of 15 and 150 µg of SP-SAP. A significant loss of NK1-r neurons in the lumbar ventral horn occurred only with 150-µg SP-SAP. CONCLUSION: Intrathecal 15-µg SP-SAP reduced dorsal, but not ventral, NK1-r (+) neurons at the spinal level of delivery with minimal side effects, whereas 150-µg SP-SAP resulted in motor neuron toxicity.

LC-MS/MS quantification of a neuropeptide fragment kisspeptin-10 (NSC 741805) and characterization of its decomposition product and pharmacokinetics in rats.

The kisspeptins are critical regulators of mammalian reproduction. Kisspeptin-10 ((45)YNWNSFGLRF-NH2(54), kisspeptin-112-121 or metastin 45-54, NSC 741805), an active fragment of kisspeptin, has been shown to be a potent stimulator of gonadotropin-releasing hormone and secretion of luteinizing hormone in both rodents and primates. This shorter peptide fragment may have clinical utility potential and it is important to characterize its pharmacokinetic property. Recently, the pharmacokinetics of both kisspeptin-54 and kisspeptin-10 were characterized in humans using a radioimmunoassay (RIA), which measures only the immunoreactive kisspeptin (kisspeptin-IR). In this study, a highly sensitive and specific LC-MS/MS assay was developed to quantify kisspeptin-10 levels in rat plasma. The lower limit of quantitation (LLOQ) was 0.5 ng/mL, the within-day and between-day coefficient of variations (CVs) ranged from 5.2 to 15.4% and 1.3 to 14.2%, and the accuracy values ranged from 98 to 114% and 99 to 105%, respectively. With this method, stability studies demonstrated that kisspeptin-10 degraded rapidly with decomposition half-lives of 6.8 min, 2.9 min and 1.7 min at 4 °C, 25 °C, and 37 °C, respectively. The principal decomposition product was characterized as the N-terminal tyrosine deleted kisspeptin-10 (46)NWDSFGLRF-NH2(54). Pharmacokinetic study in rats showed that low ng/mL kisspeptin-10 was detected in the first few minutes, and eliminated rapidly and became undetectable 30 min after intravenous (i.v.) bolus administration of 1.0 mg/kg kisspeptin-10.

Combined systemic and local delivery of stem cell inducing/recruiting factors for in situ tissue regeneration.

Whereas the conventional tissue engineering strategy involves the use of scaffolds combined with appropriate cell types to restore normal functions, the concept of in situ tissue regeneration uses host responses to a target-specific scaffold to mobilize host cells to a site of injury without the need for cell seeding. For this purpose, local delivery of bioactive molecules from scaffolds has been generally used. However, this approach has limited stem cell recruitment into the implants. Thus, we developed a combination of systemic delivery of substance P (SP) and local release of stromal-derived factor-1α (SDF-1α) from an implant. In this study, we examined whether this combined system would significantly enhance recruitment of host stem cells into the implants. Flow cytometry and immunohistochemistry for CD29/CD45, CD146/α-smooth muscle actin, and c-kit demonstrated that this system significantly increased the number of stem cell-like cells within the implants when compared with other systems. In vitro culture of the cells that had infiltrated into the scaffolds from the combined system confirmed that host stem cells were recruited into these implants and indicated that they were capable of differentiation into multiple lineages. These results indicate that this combined system may lead to more efficient tissue regeneration.

Anti-HIV-1 activity of the neurokinin-1 receptor antagonist aprepitant and synergistic interactions with other antiretrovirals.

OBJECTIVES: Neurokinin-1 receptor (NK1R) antagonists interfere with binding of neuropeptide substance P to NK1R and exhibit novel anti-HIV-1 activities. Since NK1R antagonists effectively penetrate the blood-brain barrier to reduce the inflammatory response within the brain, we wished to evaluate their potential as anti-HIV-1 candidates for targeting HIV-1 infections of the central nervous system. DESIGN: A series of small molecule agents were evaluated for anti-NK1R and anti-HIV-1 activity using peripheral blood mononuclear cells (PBMCs). The most promising of these, aprepitant (Emend, Merck and Co. Inc.), was investigated for potential synergies with other antiretroviral drugs. METHODS: Anti-NK1R activity was tested by measuring intracellular calcium increase triggered by substance P. Anti-HIV-1 activity was evaluated by measuring p24 antigen in culture supernatants of PBMC following exposure to HIV. The concentration of drug which produced 50% reduction in intracellular calcium levels or viral production in 7-day PBMC cultures was determined. The combined effect of aprepitant with each of the major classes of anti-HIV-1 drugs was evaluated in synergy studies. RESULTS: Aprepitant had the highest anti-HIV-1 activity of the NK1R antagonists examined and was equally active against all major HIV-1 subtypes. Aprepitant acted synergistically with protease inhibitors (ritonavir and saquinavir), but not with nucleoside reverse transcriptase, non-nucleoside reverse transcriptase, or viral entry inhibitors. CONCLUSION: The ability of aprepitant to penetrate the blood-brain barrier, its safety record as an FDA-approved drug for reducing nausea and vomiting in chemotherapy, and synergistic activity with other anti-HIV-1 drugs make it a promising candidate for treatment of HIV infection.

Ensayos in-vitro e in-vivo del péptido marcado 177Lu-DOTA-Sustancia P y evaluación de los cálculos dosimétricos en la etapa preclínica / Tests in-vitro and in vivo of 177Lu-DOTA-SP labeled peptide and evaluation of the dosimetric calculations in the preclinical stage

Introducción: El péptido Sustancia P (SP) es el ligando principal de los receptores de neurokininas tipo 1, los cuales se encuentran sobreexpresados en los gliomas malignos. Método: Se obtuvo 177Lu-DOTA-SP con elevada pureza radioquímica. Se realizaron biodistribuciones en ratones normales a diferentes tiempos. Se calcularon las dosis absorbidas para los diferentes órganos del ratón (cGy/uCi). Utilizando los métodos de escalación por tiempo (A) y extrapolación directa (B), se obtuvieron las dosis en los diferentes órganos humanos. Se calcularon las máximas dosis tolerables en función de los órganos críticos (mCi/kg). Resultados: La máxima actividad tolerable que puede ser inyectada sin producir toxicidad en riñones es 11,2 mCi/kg (hombre adulto) y 11,4 mCi/kg (mujer adulta) según el método A y de 47,2 mCi/kg y 56,2 mCi/kg, respectivamente según el método B. Conclusiones: Hasta el momento se pudo obtener 177Lu-DOTA-SP con Ae= 0,05mCi/ ug de péptido. La misma puede aumentarse utilizando el 177LuCl3 de mayor actividad específica.

Introduction: Substance P (SP) is the main ligand of neurokin type 1 receptors, which are consistently overexpressed in malignant gliomas. Method: 177Lu-DOTA-SP was obtained with high radiochemical purity. Biodistribution in normal mice at different times, were done. Absorbed doses were calculated for different mice organs (cGy/uCi). Absorbed doses in human organs were calculated using two different methods, time scaling (A) and data extrapolation (B). Maximum tolerated doses were calculated according to critical organs (mCi/kg). Results: Maximum tolerated dose that can be injected without kidney toxicity is 11,2 mCi/kg (adult man) and 11,4 mCi/kg (adult woman) according to method A and 47,2 mCi/kg, 56,2 mCi/kg, respectively according to method B. Conclusion: So far, 177Lu-DOTA-SP was achieved with a specific activity (S.a) of 0,05 mCi/ ug of peptide. This S.a can be increased using 177LuCl3 of higher specific activity.

Targeted alpha-radionuclide therapy of functionally critically located gliomas with 213Bi-DOTA-[Thi8,Met(O2)11]-substance P: a pilot trial.

PURPOSE: Functionally critically located gliomas represent a challenging subgroup of intrinsic brain neoplasms. Standard therapeutic recommendations often cannot be applied, because radical treatment and preservation of neurological function are contrary goals. The successful targeting of gliomas with locally injected beta radiation-emitting (90)Y-DOTAGA-substance P has been shown previously. However, in critically located tumours, the mean tissue range of 5 mm of (90)Y may seriously damage adjacent brain areas. In contrast, the alpha radiation-emitting radionuclide (213)Bi with a mean tissue range of 81 microm may have a more favourable toxicity profile. Therefore, we evaluated locally injected (213)Bi-DOTA-substance P in patients with critically located gliomas as the primary therapeutic modality. METHODS: In a pilot study, we included five patients with critically located gliomas (WHO grades II-IV). After diagnosis by biopsy, (213)Bi-DOTA-substance P was locally injected, followed by serial SPECT/CT and MR imaging and blood sampling. Besides feasibility and toxicity, the functional outcome was evaluated. RESULTS: Targeted radiopeptide therapy using (213)Bi-DOTA-substance P was feasible and tolerated without additional neurological deficit. No local or systemic toxicity was observed. (213)Bi-DOTA-substance P showed high retention at the target site. MR imaging was suggestive of radiation-induced necrosis and demarcation of the tumours, which was validated by subsequent resection. CONCLUSION: This study provides proof of concept that targeted local radiotherapy using (213)Bi-DOTA-substance P is feasible and may represent an innovative and effective treatment for critically located gliomas. Primarily non-operable gliomas may become resectable with this treatment, thereby possibly improving the prognosis.

Neurokinin B/NK3 receptors exert feedback inhibition on L-DOPA actions in the 6-OHDA lesion rat model of Parkinson's disease.

Neurokinin B (NKB) and substance P (SP) act via NK(3) and NK(1) receptors. Using the unilateral 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson's disease (PD), it was found that chronic, but not acute, administration of L-DOPA increases striatal NKB expression in the dopamine-depleted hemisphere. In contrast, both acute and chronic administrations of L-DOPA restore reduced levels of SP mRNA. Co-treatment with the NK(3) receptor antagonist, SB222200, and L-DOPA increased contralateral rotations compared to L-DOPA alone in L-DOPA primed rats. The NK(3)R agonist, senktide, increased the phosphorylation of tyrosine hydroxylase (TH) at Ser(19)-TH, a CaMKII site, and of Thr(286)-CaMKII in striatal slices. Senktide had no effect on P-Ser(31)-TH, a MAPK site, but reduced P-Ser(217/221)-MEK. Amperometry demonstrated that senktide increased evoked dopamine release. SB222200 blocked the effects of senktide. In striatal slices prepared from 6-OHDA-lesioned rats repeatedly treated with L-DOPA, senktide no longer increased P-Thr(286)-CaMKII, suggesting a role of NK(3)R on dopamine terminals under normal conditions. SB222200 increased P-Ser(217/221)-MEK only in dopamine-depleted slices, indicating an increased NK(3)R tone under Parkinsonism conditions. Altogether, these data demonstrate a differential regulation of NKB and SP by L-DOPA in an animal model of PD and indicate a unique role of NKB in long-term effects of L-DOPA. Behavioural, biochemical and amperometric data indicate that NKB/NK(3)R signalling stimulates dopamine transmission at the presynaptic site, but inhibits it at the postsynaptic site. The inhibitory influence of NKB/NK(3)R on dopamine transmission dominates in an animal model of PD and provides a feedback inhibition on actions mediated via L-DOPA.

Safety evaluation of intrathecal substance P-saporin, a targeted neurotoxin, in dogs.

Intrathecal (IT) substance P-Saporin (SP-SAP), a 33-kDa-targeted neurotoxin, produces selective destruction of superficial neurokinin 1 receptor (NK1r)-bearing cells in the spinal dorsal horn. In rats, SP-SAP prevents the formation of hyperalgesia and can reverse established neuropathic pain behavior in rodents. To determine the safety of this therapeutic modality in a large animal model, beagles received bolus IT lumbar injections of vehicle, SP-SAP (1.5, 15, 45, or 150 microg), or a nontargeted preparation of saporin (SAP, 150 microg) for immunohistological analysis of spinal cords. Doses of 15 microg SP-SAP and above produced a significant and equivalent loss of NK1r-bearing cells and dendrites in lumbar laminae II and I compared to vehicle- or SAP-treated animals. Cervical regions in all animals displayed no loss of NK1r immunoreactivity as compared to controls. Total numbers of neurons in the lumbar dorsal horn or alpha-motor neurons in the ventral horn demonstrated no significant changes. No increases in the astrocytic marker glial fibrillary acidic protein were noted following treatment with SP-SAP, suggesting a lack of generalized neurotoxicity. Additional dogs received doses of 1.5-150 microg SP-SAP or SAP and were sacrificed after 28 or 90 days to assess behavioral and physiological parameters. Although some acute motor signs were observed with both SP-SAP and SAP, no long-lasting significant events were noted in any of these animals. These data indicate no adverse toxicity at doses up to 10 times those necessary for producing loss of superficial NK1r-bearing neurons in a large animal model.

Hemokinin-1 has Substance P-like function in U-251 MG astrocytoma cells: a pharmacological and functional study.

Substance P (SP) triggers responses in astrocytoma cells, which are considered important for proliferation and neuroimmunomodulatory activity. In this study, we compared the effects of SP with those of the novel tachykinin Hemokinin-1 (HK-1) in the human astrocytoma cell line U-251 MG. We show that U-251 MG cells express high levels of Neurokinin-1 (NK-1) receptors. The binding affinities of 125I-SP and 125I-mHK-1 to these receptors were in a similar, subnanomolar range. HK-1 and SP stimulated Ca2+ mobilization and induced increased cytokine mRNA expression. A specific NK-1 receptor antagonist blocked the observed effects. We conclude that there are no qualitative differences in SP and HK-1-evoked responses, suggesting that both peptides act through NK-1 receptors in U-251 MG cells. Moreover, we show TAC4 mRNA expression in gliomas, indicating a possible involvement of HK-1 in glioma biology.

Candidates for peptide receptor radiotherapy today and in the future.

Regulatory peptide receptors are overexpressed in numerous human cancers. These receptors have been used as molecular targets by which radiolabeled peptides can localize cancers in vivo and, more recently, to treat cancers with peptide receptor radiation therapy (PRRT). This review describes the candidate tumors eligible for such radiotherapy on the basis of their peptide receptor content and discusses factors in PRRT eligibility. At the present time, PRRT is performed primarily with somatostatin receptor- and cholecystokinin-2 (CCK2)-receptor-expressing neuroendocrine tumors with radiolabeled octreotide analogs or with radiolabeled CCK2-selective analogs. In the future, PRRT may be extended to many other tumor types, including breast, prostate, gut, pancreas, and brain tumors, that have recently been shown to overexpress several other peptide receptors, such as gastrin-releasing peptide-, neurotensin-, substance P-, glucagon-like peptide 1-, neuropeptide Y-, or corticotropin-releasing factor-receptors. A wide range of radiolabeled peptides is being developed for clinical use. Improved somatostatin or CCK(2) analogs as well as newly designed bombesin, neurotensin, substance P, neuropeptide Y, and glucagon-like peptide-1 analogs offer promise for future PRRT.

In vitro and in vivo evaluation of topical formulations of spantide II.

The purpose of this study was to develop and evaluate topical formulations of Spantide II, a neurokinin-1 receptor (NK-1R) antagonist, for the treatment of inflammatory skin disorders. Spantide II lotion and gel was formulated with and without n-methyl-2-pyrrolidone (NMP) as a penetration enhancer. The release of Spantide II from gels was evaluated using microporous polyethylene and polypropylene membranes in a Franz Diffusion cell setup. In vitro percutaneous absorption of Spantide II from lotion and gel formulations was evaluated using the above setup by replacing the membranes with hairless rat skin. The in vivo anti-inflammatory activity of Spantide II formulations was evaluated in an allergic contact dermatitis (ACD) mouse model. Among different gels studied, PF127 gel showed highest (70-fold) release of Spantide II compared with hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) gels. Lotion and gel formulations with or without NMP showed no detectable levels of Spantide II in the receiver compartment of the Franz diffusion cell until 24 hours. However, Spantide II showed significant retention in epidermis and dermis from lotion and gel formulations at 24 hours. The dermal levels increased approximately 3.5- and 2-fold when the lotion and gel formulations contained NMP as compared with the formulation with no NMP (P < .05). The in vivo studies indicated that Spantide II formulations with NMP were effective in significantly reducing ACD response, similar to dexamethasone (0.5 mM). In conclusion, Spantide II was stable as a topical formulation and delivered to target skin tissue (epidermis and dermis) for the treatment of ACD. In addition this study supports the role of cutaneous neurosensory system in modulating inflammatory responses in the skin.

Time course and substance P effects on the vascular and morphological changes in adjuvant-induced monoarthritic rats.

The aim of this study is to characterize the time course of the vascular and morphological changes in arthritic rat knee joints induced by Freund's complete adjuvant (FCA), and to investigate the effects of substance P on these changes. Single unilateral intra-articular injections of 0.1 ml FCA produced swelling of the ipsilateral knees for 4 weeks, blood vessel permeability was increased for 1 week, but blood flow was unaffected except for minor bilateral increases on day 28. The ipsilateral knees also showed marked accumulation of immune cells from day 3 to day 28, minor synovial tissue proliferation on week 2, and some cartilage erosions on weeks 1 and 2. Another group of rats was given additional injection of 1 nmol substance P in their adjuvant-treated knees at 4 h prior to assessments of inflammatory parameters on each specified day. This produced further swelling in their ipsilateral knees on day 3 and day 14, blood vessel permeability was augmented in the first 2 weeks, and blood flow was increased throughout the 4 weeks except on day 7. Parallel but smaller increases in vascular permeability and blood flow were also observed in their contralateral knees. Substance P did not affect FCA-induced changes in immune cell infiltration, synovial tissue proliferation, and cartilage erosion. These findings confirm that intra-articular injection of a low dose of FCA could elicit discrete monoarthritis in rat knees, and substance P could exacerbate and spread the early signs of this disease to the contralateral knees.

Percutaneous absorption and anti-inflammatory effect of a substance P receptor antagonist: spantide II.

PURPOSE: There is accumulating evidence that neurogenic mediators such as substance P (SP) and alpha-melanocyte stimulating hormone (alpha-MSH) contribute to inflammation following chemical and thermal injuries or in disease conditions such as psoriasis and contact dermatitis. Spantide II is a peptide with a molecular weight of 1670.2 which binds to neurokinin-1 receptor (NKR-1) and blocks proinflammatory activities associated with SP. The aim of this study was to investigate in vitro permeation and distribution of spantide II through hairless rat skin and the anti-inflammatory effect of topically delivered spantide II in an allergic contact dermatitis (ACD) mouse model. METHODS: The in vitro permeation and distribution of spantide II with or without cysteine HCl (CH) as a penetration enhancer through hairless rat skin was studied using Franz diffusion cells. The anti-inflammatory effect of spantide II was studied by measuring the reduction of ACD in C57BL/6 mice after application of spantide II as a topical solution. RESULTS: The skin permeation experiments with or without cysteine HCl (as penetration enhancer) showed no detectable levels of spantide II permeation across rat skin over a period of 48 h. Cysteine HCl significantly increased the distribution of spantide II in skin layers; also, the reduction in ACD response was significantly higher with the formulation containing cysteine HCl (p < 0.05). Spantide II at different concentrations showed a dose-dependent reduction of ACD response in mice. CONCLUSIONS: The current study demonstrates that spantide II can effectively be delivered to epidermis and dermis to exert a significant anti-inflammatory activity on the reduction of inflammation in a mouse model of ACD.

Direct interstitial infusion of NK1-targeted neurotoxin into the spinal cord: a computational model.

Convection-enhanced delivery of substance P (SP) nocitoxins to the spinal cord interstitium is under consideration for the treatment of chronic pain. To characterize treatment protocols, a three-dimensional finite-element model of infusion into the human dorsal column was developed to predict the distribution of SP-diphtheria toxin fusion protein (SP-DT') within normal and target tissue. The model incorporated anisotropic convective and diffusive transport through the interstitial space, hydrolysis by peptidases, and intracellular trafficking. For constant SP-DT' infusion (0.1 microl/min), the distribution of cytotoxicity in NK1 receptor-expressing neurons was predicted to reach an asymptotic limit at 6-8 h in the transverse direction at the level of the infusion cannula tip ( approximately 60% ablation of target neurons in lamina I/II). Computations revealed that SP-DT' treatment was favored by a stable SP analog (half-life approximately 60 min), high infusate concentration (385 nM), and careful catheter placement (adjacent to target lamina I/II). Sensitivity of cytotoxic regions to NK1 receptor density and white matter protease activity was also established. These data suggest that intraparenchymal infusions can be useful for treatment of localized chronic pain.