From hydralazine to CGRP to man?

Hydralazine augmented ultrasound hyperthermia for the treatment of hepatocellular carcinoma

This study investigates the use of hydralazine to enhance ultrasound hyperthermia for the treatment of hepatocellular carcinoma (HCC) by minimizing flow-mediated heat loss from the tumor. Murine HCC tumors were treated with a continuous mode ultrasound with or without an intravenous administration of hydralazine (5 mg/kg). Tumor blood flow and blood vessels were evaluated by contrast-enhanced ultrasound (CEUS) imaging and histology, respectively. Hydralazine markedly enhanced ultrasound hyperthermia through the disruption of tumor blood flow in HCC. Ultrasound treatment with hydralazine significantly reduced peak enhancement (PE), perfusion index (PI), and area under the curve (AUC) of the CEUS time-intensity curves by 91.9 ± 0.9%, 95.7 ± 0.7%, and 96.6 ± 0.5%, compared to 71.4 ± 1.9%, 84.7 ± 1.1%, and 85.6 ± 0.7% respectively without hydralazine. Tumor temperature measurements showed that the cumulative thermal dose delivered by ultrasound treatment with hydralazine (170.8 ± 11.8 min) was significantly higher than that without hydralazine (137.7 ± 10.7 min). Histological assessment of the ultrasound-treated tumors showed that hydralazine injection formed larger hemorrhagic pools and increased tumor vessel dilation consistent with CEUS observations illustrating the augmentation of hyperthermic effects by hydralazine. In conclusion, we demonstrated that ultrasound hyperthermia can be enhanced significantly by hydralazine in murine HCC tumors by modulating tumor blood flow. Future studies demonstrating the safety of the combined use of ultrasound and hydralazine would enable the clinical translation of the proposed technique.

Gender-specific effects of calcitonin gene-related peptide and substance P on coronary blood flow in an experimental model

BACKGROUND

Calcitonin gene-related peptide (CGRP) and substance P (SP) play counter-regulatory roles in coronary flow. This study is to assess whether effects of CGRP and SP are gender-specific.

METHODS

Langendorff-perfused hearts were used to compare coronary flow rates among 119 wild-type, alpha-CGRP and SP receptor knockout mice under various perfusion pressures (20, 30, 40, 50 mmHg).

RESULTS

For mouse heart coronary flow rate, deletion of alpha-CGRP gene resulted in significant reduction for both genders at all pressures; female CGRP knockout showed 15.3% reduction (P < .01); male CGRP knockout showed 13.8% reduction (P < .01); no significant difference between male and female CGRP knockout; female SP receptor knockout showed 13.9% increase (P < .01); female SP receptor knockout had a greater percentage decrease than male (P < .01).

CONCLUSIONS

CGRP plays similar roles as a vasodilator in males and females. SP seems to act as a vasoconstrictor in females.

Issues in flow and oxygenation dependent contrast (FLOOD) imaging of tumours

The sensitivity of blood oxygenation level dependent (BOLD) contrast techniques to changes to tumour deoxyhaemoglobin concentration is of relevance to many strategies in cancer treatments. In the context of tumour studies, which frequently involve the use of agents to modify blood flow, there are underlying physiological changes different to those of BOLD in the brain. Hence we use the term, flow and oxygenation dependent (FLOOD) contrast, to emphasize this difference and the importance of flow effects. We have measured the R(2)* changes in a prolactinoma tumour model for a variety of vasoactive challenges [carbogen, 100% oxygen and 100% nitrogen as different breathing gases, and administration of tumour blood flow modifiers such as calcitonin gene related peptide (CGRP), hydralazine and nicotinamide]. In addition we have measured other relevant physiological parameters, such as bioenergetic status from (31)P MRS, and blood pH and glucose, that may change during a vasoactive challenge. Here we discuss how they relate to our understanding of FLOOD contrast in tumours. We frequently observe R(2)* changes that match the expected action of the vascular stimulus: R(2)* decreases with agents expected to improve tumour oxygenation and blood flow, and increases with agents designed to increase tumour hypoxia. Unlike most normal tissues, tumours have a chaotic and poorly regulated blood supply, and a mix of glycolytic and oxidative metabolism; thus the response to a vasoactive challenge is not predictable. Changes in blood volume can counteract the effect of blood oxygenation changes, and changes in blood pH and glucose levels can alter oxygen extraction. This can lead to R(2)* changes that are smaller or the reverse of those expected. To properly interpret FLOOD contrast changes these effects must be accounted for.

The use of a hypoxic cell radiosensitizer AK-2123 gave no improvement in thermoradiotherapy combined with hydralazine

An electron-affinic compound, AK-2123, and the anti-hypertensive agent, hydralazine, were combined with radiation and hyperthermia for treatment of murine SCC-VII tumours. Hydralazine markedly decreased tumour perfusion while AK-2123 had no influence on it. Hydralazine enhanced the tumouricidal effects of hyperthermia alone and in combination with radiation. AK-2123 provided a radiosensitization which was significant only in tumours irradiated without supplementary hyperthermia. The greatest tumour response was achieved when thermoradiotherapy was combined with hydralazine alone; the additional use of AK-2123 with this treatment combination did not further increase the effect. It is concluded that hydralazine plus heat virtually eliminated a hypoxia-related radioresistance in tumours, thus removing the requirement for AK-2123 administration.

Modification of tumour perfusion and oxygenation monitored by gradient recalled echo MRI and 31P MRS

Gradient recalled echo (GRE) 1H images can be used to monitor changes in blood oxygenation via the dephasing effects of paramagnetic deoxyhaemoglobin (Hb). We have modulated the blood flow/oxygenation of GH3 rat tumours by i.v. calcitonin gene-related peptide (CGRP) or carbogen (95% O2, 5% CO2) inhalation, and obtained GRE 1H images interleaved with 31P spectra before, during and after the insult. With CGRP the GRE image intensity decreased (6/10) by > 10% with a concomitant 40% decrease (4/4) in beta NTP/P1 and a small decrease in pH. Both the image intensity and 31P spectra returned to near their pre-CGRP levels after 50 min, consistent with a transient episode of hypoxia. Carbogen breathing (5/5) caused > 40% increases in average GRE image intensity, with no significant changes in the 31P spectra (4/4). Three-dimensional GRE images were obtained to confirm that a T2* increase, rather than just an 'in-flow' effect due to increased blood flow, was responsible for the GRE enhancement. Increases in average image intensity > 40% were observed for the three-dimensional GRE images (2/2), indicating a T2* increase. Using Hb as an endogenous contrast agent, the high sensitivity of the GRE technique may provide a method of monitoring heterogeneous tumour perfusion and oxygenation, both in the laboratory and the clinic.