Low-intensity light therapy (LILT) appears to be working through newly recognized photoacceptor systems. The mitochondrial electron transport chain has been shown to be photosensitive to red and near-infrared (NIR) light. Although the underlying mechanisms have not yet been clearly elucidated, mitochondrial photostimulation has been shown to increase ATP production and cause transient increases in reactive oxygen species (ROS). In some cells, this process appears to participate in reduction/oxidation (redox) signaling. Redox mechanisms are known to be involved in cellular homeostasis and proliferative control. In plants, photostimulation of the analogous photosynthetic electron transport chain leads to redox signaling known to be integral to cellular function. In gene therapy research, ultraviolet lasers are being used to photostimulate cells through a process that also appears to involve redox signaling. It seems that visible and near visible low-intensity light can be used to modulate cellular physiology in some nonphotosynthetic cells, acting through existing redox mechanisms of cellular physiology. In this manner, LILT may act to promote proliferation and/or cellular homeostasis. Understanding the role of redox state and signaling in LILT may be useful in guiding future therapies, particularly in conditions associated with pro-oxidant conditions. 323

Objective To examine the impact of mood states on endothelial function, as measured noninvasively by brachial artery flow-mediated dilation (FMD). Substantial literature indicates that negative mood is linked to cardiovascular disease (CVD). However, the mechanisms underlying this relationship are not well defined. CVD is often preceded by dysfunction of the endothelium. Methods Healthy adults (n = 70; mean age, 36 years) completed the Profile of Mood States (POMS), which contains six subscales (depression/dejection; tension/anxiety; anger/hostility; confusion/bewilderment; fatigue/inertia; vigor/activity) that are used to compute a total mood disturbance score for overall psychological distress. FMD was calculated (maximum percentage change in brachial artery diameter) from ultrasound assessment of arterial diameter at baseline and for 10 minutes after occlusion. Results Regressions showed that increases in POMS total mood disturbance scores were associated with decreases in endothelial function. Mood disturbance explained 10% of the variance in FMD (p < .01), after controlling for age, sex, mean arterial pressure, body mass index, and socially desirable response bias. An exploratory set of separate regressions conducted to decompose the link between FMD and total mood disturbance revealed that the following POMS subscales were inversely correlated with FMD: depression/dejection, tension/anxiety, anger/hostility, fatigue/inertia (p’s < .05), and confusion/bewilderment (p < .01). Conclusions Mood disturbance could contribute to CVD via impaired vasodilation. These preliminary results show that even mild levels of adverse psychological states, particularly depressed, anxious, angry, confused, and fatigued states, might be linked to increased cardiovascular risk.

Low-intensity light therapy (LILT) is showing promise in the treatment of a wide variety of medical conditions. Concurrently, our knowledge of LILT mechanisms continues to expand. We are now aware of LILT's potential to induce cellular effects through, for example, accelerated ATP production and the mitigation of oxidative stress. In clinical use, however, it is often difficult to predict patient response to LILT. It appears that cellular reduction= oxidation (redox) state may play a central role in determining sensitivity to LILT and may help explain variability in patient responsiveness. In LILT, conditions associated with elevated reactive oxygen species (ROS) production, e.g. diabetic hyperglycemia, demonstrate increased sensitivity to LILT. Consequently, assessment of tissue redox conditions in vivo may prove helpful in identifying responsive tissues. A noninvasive redox measure may be useful in advancing investigation in LILT and may one day be helpful in better identifying responsive patients. The detection of biophotons, the production of which is associated with cellular redox state and the generation of ROS, represents just such an opportunity. In this review, we will present the case for pursuing further investigation into the potential clinical partnership between biophoton detection and LILT.

Mills, P J (2008). Depressive symptoms are associated with soluble P-selectin reactivity to acute exercise in heart failure. Depressive symptoms are associated with soluble P-selectin reactivity to acute exercise in heart failure Abstract BACKGROUND: To determine the effects of depressive symptom severity on the circulating soluble adhesion molecule response to an acute exercise challenge in patients with heart failure (HF) compared with control subjects. METHODS: Thirty-eight male HF patients and 19 male control subjects (mean age +/-SEM: 55.5 +/-1.9) completed the Beck Depression Inventory (BDI) before undergoing a moderate 20-minute bicycle exercise at approximately 65% to 70% VO(2peak). Plasma levels of the soluble adhesion molecules P-selectin (sP-selectin) (sCD62P) and soluble intercellular adhesion molecule-1 (sICAM-1) were determined immediately before and after and 10 minutes after exercise. RESULTS: Higher BDI scores moderated greater increases in sP-selectin levels in response to exercise over time in HF patients as compared with control subjects [F(1.8/84.5) = 3.25, p = .05]. Post hoc testing revealed that in HF patients, but not in control subjects, higher BDI scores were significantly associated with greater increases in sP-selectin levels over time in response to exercise [BDI by exercise interaction: F(1.6/49.6) = 5.67, p = .010]. Also, in HF patients, but not in control subjects, higher BDI scores were associated with higher sP-selectin levels at pre-exercise and postexercise time points [main effect BDI: F(1/31) = 4.86, p = .035]. CONCLUSIONS: Our findings suggest that in male HF patients with increasing depressive symptom severity, levels of the adhesion molecule sP-selectin are higher before and after exercise and have greater increases in response to exercise. This could have implications for acute coronary syndromes associated with exercise and thereby may impact mortality.