Perinatal Arterial Ischemic Stroke Is Associated to Materno-Fetal Immune Activation and Intracranial Arteritis.

The medium-size intra-cranial arteries arising from the carotid bifurcation are prone to perinatal arterial ischemic strokes (PAIS). PAIS' physiopathology needs to be better understood to develop preventive and therapeutic interventions that are currently missing. We hypothesized that materno-fetal inflammation leads to a vasculitis affecting selectively the carotidian tree and promoting a focal thrombosis and subsequent stroke. Dams were injected with saline or lipopolysaccharide (LPS) from Escherichia coli. A prothrombotic stress was applied on LPS-exposed vs. saline (S)-exposed middle cerebral arteries (MCA). Immunolabeling detected the inflammatory markers of interest. In S-exposed newborn pups, a constitutive higher density of macrophages combined to higher expressions of tumor necrosis factor-α (TNF-α), and interleukin 1ß (IL-1ß) was observed within the wall of intra- vs. extra-cranial cervicocephalic arteries. LPS-induced maternal and placental inflammatory responses mediated by IL-1ß, TNF-α and monocyte chemotactic protein 1 (MCP-1) were associated with: (i) increased density of pro-inflammatory macrophages (M1 phenotype); and (ii) pro-inflammatory orientation of the IL-1 system (IL-1ß/IL-1 receptor antagonist (IL-1Ra) ratio) within the wall of LPS-, vs. S-exposed, intra-cranial arteries susceptible to PAIS. LPS plus photothrombosis, but not sole photothrombosis, triggered ischemic strokes and subsequent motor impairments. Based on these preclinical results, the combination of pro-thrombotic stress and selective intra-cranial arteritis arising from end gestational maternal immune activation seem to play a role in the pathophysiology of human PAIS.

Deciphering PDT-induced inflammatory responses using real-time FDG-PET in a mouse tumour model.

Dynamic positron emission tomography (PET), combined with constant infusion of 2-deoxy-2-[(18)F]fluoro-d-glucose (FDG), enables real-time monitoring of transient metabolic changes in vivo, which can serve to understand the underlying physiology. Here we investigated characteristic changes in the tumour FDG-uptake profiles in relation to acute localized inflammatory responses induced by photodynamic therapy (PDT). Dynamic PET imaging with constant FDG infusion was used with EMT-6 tumour bearing mice. FDG time-activity uptake curves were measured simultaneously, in treated and reference tumours, for 3 hours, before, during and after PDT light treatment. Inflammation was studied when evoked, either by PDT using a trisulfonated porphyrazine photosensitizer, or lipopolysaccharide (LPS), and inhibited using indomethacin. The distinct transient patterns, characterized by drops and subsequent recovery of tumour FDG uptake rates, were also analysed using immunohistochemical markers for apoptosis, necrosis, and inflammation. Typical profiles for tumour FDG-uptake, consisted of a drop during PDT, followed by a gradual recovery period. Tumours treated with LPS, but not with light, showed a continuous increase in FDG-uptake during the 3 h experimental period. Treatment with indomethacin, inhibited the rise in FDG-uptake observed with either LPS or PDT. Tumour FDG-uptake profiles correlated with necrosis markers during PDT, and inflammatory response markers post-PDT, but not with an apoptosis marker at any time during or after PDT. Dynamic FDG-PET imaging combined with indomethacin reveals that, the drop in the tumour FDG-uptake rate during the PDT illumination phase reflects vascular collapse and necrosis, while the increased tumour FDG-uptake rate immediately post-illumination involves an acute localized inflammatory response. Dynamic FDG infusion and PET imaging, combined with the use of selective inhibitors, provides unique insight for deciphering the complex underlying processes leading to tumour response in PDT, and allows for rapid as well as cost effective optimization of PDT protocols.

Phthalocyanine-peptide conjugates: receptor-targeting bifunctional agents for imaging and photodynamic therapy.

The synthesis of a series of new zinc phthalocyanine-peptide conjugates targeting the gastrin-releasing peptide (GRP) and integrin receptors is reported. Two alternative synthetic methods based on Sonogashira cross-coupling of an iodinated zinc phthalocyanine with acetylenic bombesin or arginine-glycine-aspartic acid (RGD) derivatives, either in solution or on solid phase, are presented. The water-soluble conjugates were screened for their photodynamic efficacy against several cancer cell lines expressing different levels of GRP and integrin receptors, and their intracellular localization was evaluated via confocal fluorescence microscopy. Variations in photocytotoxicity between the conjugates correlate to differences in hydrophobicity as well as receptor-mediated cell uptake. In the case of the phthalocyanine-bombesin conjugate, competition experiments confirm the involvement of the GRP receptor in both the phototherapeutic activity as well as intracellular localization. These findings warrant further in vivo studies to evaluate the potential of this conjugate as photosensitizer for photodynamic therapy (PDT) of cancers overexpressing the GRP receptor.

Predicting efficacy of photodynamic therapy by real-time FDG-PET in a mouse tumour model.

Dynamic positron emission tomography (PET) combined with the constant infusion of 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) as a tracer permits real-time monitoring of systemic transient metabolic changes resulting from photodynamic therapy (PDT) in tumour bearing animals. The effect of PDT on tumour FDG uptake rates was evaluated using four different sulfonated phthalocyanine analogs as photosensitizers (PS) in combination with either continuous or fractionated illumination protocols. Mice bearing two EMT-6 tumours were infused with FDG to start PDT 30 min later. Dynamic images were acquired to produce FDG uptake over time for the treated and reference tumours. Practically all PDT protocols induced a reduction in the FDG uptake rates in the treated tumour during PDT, except for the zinc tetrasulfophthalocyanine, when using fractionated light, reflecting the low photodynamic efficacy of this PS. In general, the response to PDT was characterized by a rebound in the FDG uptake rate after illumination. A strong drop in FDG tumour uptake rates during PDT, followed by a strong rebound, together with short delay-to-response times, corresponded to optimal long-term tumour response outcomes. This dynamic FDG-PET protocol provides real-time observations to predict long-term PDT efficacy, while using fewer animals than conventional methods, thus making possible the rapid optimization of treatment parameters.

PET imaging using 64Cu-labeled sulfophthalocyanines: synthesis and biodistribution.

Sulfonated metallo phthalocyanines (MPcS(n)) are second generation photosensitizers advanced for photodynamic therapy of various medical applications. A series of ZnPcS(n) was demetallated and subsequently converted to the corresponding [(64)Cu]CuPcS(n) in 40-50% isolated yields and >98% radiochemical purities. Tumor-bearing mice were injected with the (64)Cu-labeled products and subjected to 3-h dynamic PET imaging studies. Biodistribution patterns showed characteristic differences between the various derivatives. Tumor uptake was detected only for the amphiphilic derivatives [(64)Cu]CuPcS(2) and [(64)Cu]CuPcS(3)C(6) (1-1.5%ID/g). The biological data suggest that PET imaging with [(64)Cu]CuPc can be used to establish structure-PDT efficacy relationships for Pc-based photosensitizers.

Mono- and tri-cationic porphyrin-monoclonal antibody conjugates: photodynamic activity and mechanism of action.

Two cationic porphyrins bearing an isothiocyanate group for conjugation to monocolonal antibodies have been synthesized. The two porphyrins conjugated efficiently to three monoclonal antibodies (anti-CD104, anti-CD146 and anti-CD326), which recognize antigens commonly over-expressed on a range of tumour cells. In vitro, all conjugates retained the phototoxicity of the porphyrin and the immunoreactivity of the antibody. Mechanistic studies showed that conjugates formed from the mono- and tri-cationic porphyrin and anti-CD104 antibody mediated apoptosis following irradiation with non-thermal red light of 630 ± 15 nm wavelength. In vivo antibody conjugates caused suppression of human LoVo tumour growth in immunodeficient NIH III mice, similar to the commercial photodynamic therapy (PDT) agent Photofrin, but at administered photosensitizer doses that were more than two orders of magnitude lower. Positron emission tomography (PET) following PDT showed a large, early increase in uptake of (18) fluorodeoxyglucose (FDG) by tumours treated with the anti-CD104 conjugates. This effect was not observed with Photofrin or with conjugates formed from the same photosensitizers conjugated to an irrelevant antibody.

Structure-activity relationships of mono-substituted trisulfonated porphyrazines for the photodynamic therapy (PDT) of cancer.

The impact of lipophilicity on biological parameters critical to photodynamic efficacy was analyzed for a new generation of trisulfobenzo(mononaphtho)porphyrazines. The porphyrazines were substituted on the naphtho ring with linear alkynyl side chains of various lengths. When compared to the analogous phthalocyanine structures, the added benzo ring in the porphyrazine structures increased the lipophilicity for analogs with short alkynyl chains, while this effect disappeared for analogs with longer side chains. In aqueous media, the analogous phthalocyanine series showed aggregation tendencies. In contrast, no correlation between aggregate formation and the length of the alkynyl side chain was evident in the porphyrazine series. At low concentrations, the length of the side chain did not affect cell uptake, while phototoxicity towards EMT-6 mouse tumour cells showed a parabolic relationship, where the hexynyl derivative showed the highest activity. The trisulfonated porphyrazines localized at intracellular organelles, plasma and perinuclear membranes, but could not be found in the nucleus. Total cell uptake of dye did not correlate with phototoxicity, suggesting that localization in certain intracellular organelles, and distribution into critical intracellular sites are important determinants of their photodynamic activity. The hexynyl trisulfonated zinc porphyrazine derivative (ZnNPcS(3)C(6)) showed the strongest in vitro photodynamic activity and therefore was further studied in an EMT-6 mouse tumour model. An i.v. dose of 1 micromol of ZnNPS(3)C(6) per kg, followed 24 h later by activation with light, induced 100% tumour necrosis within 24 h post-PDT. This treatment delayed tumour volume doubling time from 5 days to >2 weeks, and gave 41% tumour cure >3 weeks post-PDT. Applying the same light dose fractionated (5 min on, 2 min off), further improved tumour response, leading to a doubling time of 26 days and a 73% tumour cure. At the administered 1 micromol kg(-1) dye dose, no skin phototoxicity was observed and >90% blood clearance was observed within 5 h post-injection. Compared to the analogous trisulfo monohexynyl zinc phthalocyanine, the new trisulfobenzo(mononaphthohexynyl)porphyrazine provided a broader range of excitation wavelengths, and improved photodynamic potency, while apparently being free of unwanted systemic side effects.

Pd-catalyzed Heck reaction for the synthesis of isomeric metallo tetravinylsulfo phthalocyanines and their photosensitizing properties.

Tetrasulfonated zinc phthalocyanine (ZnPcS(4)) is a potent sensitizer for photodynamic therapy of various medical conditions. Depending on its mode of preparation the material consists of mixtures of ortho and meta sulfonated derivatives as well as regioisomers with different photodynamic potency. To study the effect of the site of substitution on biological parameters that contribute to overall photodynamic efficacy, a series of pure ortho- and meta-tetravinylsulfonated metallo phthalocyanines MPc-o/m-(VS)(4) were prepared from the corresponding tetraiodo phthalocyanines using the palladium-catalyzed cross-coupling reaction (Heck reaction). Compared to the tetrasulfonated phthalocyanines, the tetravinylsulfonated derivatives are more hydrophobic and their Q-band absorption maxima are red-shifted. While their in vitro phototoxicity is in the same range as the mixed isomeric sulfonated derivatives, ortho-substituted MPc-o-(VS)(4) are more photocytotoxic as compared to their corresponding meta analogs. Although the central metal ion and site of substitution affect aggregation, the tendency to aggregate did not correlate with photodynamic potency nor did overall cell uptake. Instead, intracellular localization at both mitochondrial and lysosomal membranes appears to be the major factor explaining the augmented activity of the ortho substituted derivatives.

Trisulfonated porphyrazines: new photosensitizers for the treatment of retinal and subretinal edema.

A new series of water-soluble, mononaphthotrisulfobenzoporphyrazines, bearing an alkynyl side chain of varying lengths on the naphtho ring, were prepared and tested for their efficacy to inhibit plasma extravasation when used as photosensitizers during photodynamic therapy (PDT) of the retina in the rat. The hexynyl substituted photosensitizer was the most potent, and was able to produce complete inhibition, at low doses of photosensitizer and light.

Targeting gastrin-releasing peptide receptors of prostate cancer cells for photodynamic therapy with a phthalocyanine-bombesin conjugate.

Sulfonated aluminum phthalocyanines (AlPcS) are potent photosensitizers for the photodynamic therapy (PDT) of cancer. In this study we evaluate the possibility to improve the efficacy of AlPcS-PDT for prostate cancer by targeting tetrasulfonated aluminum phthalocyanines (AlPcS(4)) to the gastrin-releasing peptide receptor (GRPR) through coupling to bombesin. A mono-carbohexyl derivative of AlPcS(4) is attached to 8-Aoc-bombesin(7-14)NH(2) via an amide bridge to yield a bombesin-AlPcS(4) conjugate linked by a C-14 spacer chain. The conjugate is characterized by mass spectroscopy and shown to bind to the GRPR with a relative binding affinity (RBA) of 2.3, taking bombesin (RBA=100) as unity. The in vitro photodynamic efficacy of the conjugate against PC-3 human prostate cancer cells is improved by a factor 2.5 over the non-conjugated mono-carbohexyl derivative of AlPcS(4).

PET imaging of apoptosis with (64)Cu-labeled streptavidin following pretargeting of phosphatidylserine with biotinylated annexin-V.

PURPOSE: In vivo detection of apoptosis is a diagnostic tool with potential clinical applications in cardiology and oncology. Radiolabeled annexin-V (anxV) is an ideal probe for in vivo apoptosis detection owing to its strong affinity for phosphatidylserine (PS), the molecular flag on the surface of apoptotic cells. Most clinical studies performed to visualize apoptosis have used (99m)Tc-anxV; however, its poor distribution profile often compromises image quality. In this study, tumor apoptosis after therapy was visualized by positron emission tomography (PET) using (64)Cu-labeled streptavidin (SAv), following pre-targeting of apoptotic cells with biotinylated anxV. METHODS: Apoptosis was induced in tumor-bearing mice by photodynamic therapy (PDT) using phthalocyanine dyes as photosensitizers, and red light. After PDT, mice were injected i.v. with biotinylated anxV, followed 2 h later by an avidin chase, and after another 2 h with (64)Cu-DOTA-biotin-SAv. PET images were subsequently recorded up to 13 h after PDT. RESULTS: PET images delineated apoptosis in treated tumors as early as 30 min after (64)Cu-DOTA-biotin-SAv administration, with tumor-to-background ratios reaching a maximum at 3 h post-injection, i.e., 7 h post-PDT. Omitting the administration of biotinylated anxV or the avidin chase failed to provide a clear PET image, confirming that all three steps are essential for adequate visualization of apoptosis. Furthermore, differences in action mechanisms between photosensitizers that target tumor cells directly or via initial vascular stasis were clearly recognized through differences in tracer uptake patterns detecting early or delayed apoptosis. CONCLUSION: This study demonstrates the efficacy of a three-step (64)Cu pretargeting procedure for PET imaging of apoptosis. Our data also confirm the usefulness of small animal PET to evaluate cancer treatment protocols.

Photodynamic activity of substituted zinc trisulfophthalocyanines: role of plasma membrane damage.

We recently reported that variations in cellular phototoxicity among a series of alkynyl-substituted zinc trisulfophthalocyanines (ZnPcS3Cn) correlates with their hydrophobicity, with the most amphiphilic derivatives showing the highest cell uptake and phototoxicity. In this study we address the role of the plasma membrane in the photodynamic response as it relates to the overall hydrophobicity of the photosensitizer. The membrane tracker dye 1-[4(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), which is incorporated into plasma membranes by endocytosis, was used to establish plasma membrane uptake by EMT-6 cells of the ZnPcS3C, by colocalization, and TMA-DPH membrane uptake rates after photodynamic therapy were used to quantify membrane damage. TMA-DPH colocalization patterns show plasma membrane uptake of the photosensitizers after short 1 h incubation periods. TMA-DPH plasma membrane uptake rates after illumination of the photosensitizer-treated cells show a parabolic relationship with photosensitizer hydrophobicity that correlates well with the phototoxicity of the ZnPcS3C,. After a 1 h incubation period, overall phototoxicity correlates closely with the postillumination rate of TMA-DPH incorporation into the cell membrane, suggesting a major role of plasma membrane damage in the overall PDT effect. In contrast, after a 24 h incubation, phototoxicity shows a stronger but imperfect correlation with total cellular photosensitizer uptake rather than TMA-DPH membrane uptake, suggesting a partial shift in the cellular damage responsible for photosensitization from the plasma membrane to intracellular targets. We conclude that plasma membrane localization of the amphiphilic ZnPcS3C6-C9 is a major factor in their overall photodynamic activity.

Structure-photodynamic activity relationships of substituted zinc trisulfophthalocyanines.

To identify optimal features of metalated sulfophthalocyanine dyes for their use as photosensitizers in the photodynamic therapy of cancer, we synthesized a series of alkynyl-substituted trisulfonated phthalocyanines and compared their amphiphilic properties to a number of parameters related to their photodynamic potency. Varying the length of the substituted alkynyl side-chain modulates the hydrophobic/hydrophilic properties of the dyes providing a linear relationship between their n-octanol/water partition coefficients and retention times on reversed-phase HPLC. Aggregate formation of the dyes in aqueous solution increased with increasing hydrophobicity while monomer formation was favored by the addition of serum proteins or organic solvent. Trisulfonated zinc phthalocyanines bearing hexynyl and nonynyl substituents exhibited high cellular uptake with strong localization at the mitochondrial membranes, which coincided with effective photocytotoxicity toward EMT-6 murine mammary tumor cells. Further increase in the length of the alkynyl chains (dodecynyl, hexadecynyl) did not improve their phototoxicity, likely resulting from extensive aggregation of the dyes in aqueous medium and reduced cell uptake. Aggregation was evident from shifts in the electronic spectra and reduced capacity to generate singlet oxygen. When monomerized through the addition of Cremophor EL all sulfonated zinc phthalocyanines gave similar singlet oxygen yields. Accordingly, differences in the tendency of the dyes to aggregate do not appear to be a determining factor in their photodynamic potency. Our results confirm that the latter in particular relates to their amphiphilic properties, which facilitate cell uptake and intracellular localization at photosensitive sites such as the mitochondria. Combined, these factors play a significant role in the overall photodynamic potency of the dyes.