© Carestream Health, Inc.

IMAGING AND NON-INVASIVE MEASUREMENT OF CAPSAICIN INDUCED DERMAL BLOOD FLOW.

Rao V. L. Papineni*, Sunil Reddy#, Sean Orton, William McLaughlin, Douglas Vizard, John Pizzonia, and M.U.R. Naidu#.

Carestream Molecular Imaging, 4 Research Dr., Woodbridge, CT, 06525, USA and # NIMS, Hyderabad, India. * rao.papineni1@carestreamhealth.com

"Molecular Imaging - Wisdom To See For Maladies To Flee"Dr. Rao V. L. Papineni

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AbstractCapsaicin effects neurogenic inflammation and a localized vasodilation by activating transient receptor potential vanilloid type 1 receptor (TRPV1). Topical application of capsaicin on the human forearm results in increased dermal blood flow (DBF). Capsaicin induced changes in the microvascular dynamics at the dermis, is mainly driven through the calcitonin gene-related peptide (CGRP) receptor activation. There is growing evidence suggesting that endothelial dysfunction is an important and an early event in the pathogenesis of major cardiovascular diseases. Novel sensitive and robust methodologies are becoming essential in clinics to determine endothelial function in dermal circulation non-invasively. Here, we have utilized two approaches to both compare and validate the methodologies in determination of the DBF. In the method-1, RBC perfusion was carried out in healthy human subjects using Laser Doppler Flowmetry. Measurements were made after 30 min of topical application of capsaicin (0.075%) on one arm and saline on the other arm (control). Significant change in the DBF was observed in the arm applied with capsaicin- the mean blood flow increased from 25.7 bpu to 83.5 bpu. The mean blood flow change in the control arm however showed negligible changes (26.1 bpu to 26.6 bpu). In the second method, we determined the dermal blood flow in response to the topical application of capsaicin using a planar optical imaging setup. Fluorescence images were captured to determine the capsaicin-induced dermal blood flow. The results indicate the possibility of utilizing inexpensive optical imaging in the clinical and pharmaceutical fields in microvascular dynamic analysis and testing endothelial function in clinical studies. Also, provides opportunity for rapid screening of novel compound antagonists of CGRP receptor that block the capsaicin-induced DBF.

ConclusionsDermal blood flow in response to capsaicin treatment

is determined by planar optical imaging utilizing

natural fluorescence.

Data indicates a circadian rhythmic nature in dermal

microvascular dynamics when responding to

capsaicin treatment- a direction we are currently

pursing.

The feasibility of utilizing the imaging approach in

measuring dermal blood flow provides promise and

opportunity to adapt the methodology in detection of

endothelial dysfunction.

Carestream is a trademark of Carestream Health, Inc. The Kodak trademark is used under license from Kodak. Carestream

Molecular Imaging is a division of Carestream Health, Inc. LDF100C is the trademark of BIOPAC Systems Inc. Capzasin-HP is the

trademark of CHATTEM.

Capsaicin Action in Dermal Vasodilation

Capsaicin Induced Dermal Blood Flow. The cartoon shows the activation of transient receptor potential vanilloid type I receptor (TRPV1) by capsaicin. The resultant neurogenic inflammation and vasodilation are evoked by the release of calcitonin gene-related peptide (CGRP), NO, Substance P and prostaglandins. The neuropeptide CGRP is the major player in the capsaicin induced dermal blood flow.

Changes in Dermal Microvascular Dynamics

The data from 24 healthy human subjects (Upper Left Panel) were obtained using LDF to validate the blood perfusion Unit (BPU) measurement technique. The data from left arm (dark red Bar) and the Right arm (orange Bar) show negligible changes in BPU. In response to the capsaicin (0.075%) treatment (Upper Right Panel), the ten individuals show significant changes in the dermal blood flow (BPU). Capsaicin was applied to non-dominant arm while cold cream was applied to dominant arm. The changes also seem to be related to the time (AM or PM) of capsaicin application. The violet sections of the stacked bars represent the baseline, and the blue regions represent post pharmacological treatment.

Optical Imaging: The microcirculation was determined using Carestream Developmental Phase-Planar Optical Imaging Set-up (Left Two Panels).Non-invasive imaging of healthy subject’s hand: pre (left-upper panel) and post-capsaicin treatment (left- lower panel) were performed. The surface plots of the natural fluorescence with the raw images (inset) are shown here. Ex 620 EM 700; F-Stop: 2.8, no binning.

The above schematic describes the Carestream Developmental phase “Planar Optical Imaging set-up” designed to image human hand. A 400-Watt Xenon illuminator has been applied to image the natural fluorescence at the interphalangeal joints and the whole Arm.

TRPV1

CGRP

Substance PProstaglandinsNitric OxideNeurokinin AHistamine

Vasodilation Neurogenic Inflammation Activation

Dermal Vasodilation

Capsaicin

400 watt

CCD

EX 620

Hand

Laser Doppler Flowmetry (LDF) from BIOPAC was used to measure dermal blood flow. The Llaser Doppler microvascularperfusion module monitors the red blood cell perfusion in the microcirculation. Laser Doppler signals are recorded as BPU (Blood Perfusion units).

Pea size capsaicin was applied to the skin to evoke the pharmacological response in healthy individuals. The time ofincubation was for 30 min before measurement. In the case of

optical imaging, 15 min incubation protocol was observed. Baseline measurements were performed prior to capsaicin application.

Caucasians, Asian Chinese, South Asian, adult volunteers wereenrolled after full explanation of the studies. All individuals completed the study per protocol.

Materials and Methods

Dermal Imaging – Optical Imager

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Dr. Papineni