A review of laboratory-based methods to investigate second messengers in low-level laser therapy (LLLT)

Second messengers are chemical signals or intracellular molecules (cyclic AMP or inositide) or ions (calcium ions) that are regulated by extracellular signaling agents such as neurotransmitters and hormones (first messengers). Second messengers typically operate by activating protein kinases that phosphorylate various target proteins, thereby altering the function of these proteins. In order to understand the cellular and molecular responses of cells, for example, in response to treatment such as low-level laser therapy (LLLT), it is important to determine firstly, if there is an effect on the intracellular molecules and ions and secondly, if that effect can be directly linked to a change in cellular function such as cell viability or proliferation. More research is needed to determine the exact mechanism whereby photonic energy can stimulate injured or wounded cells to restore homeostasis and stimulate cell functions such as DNA, RNA and protein syntheses. This review discusses selected laboratory methods that can be employed to investigate the role of second messengers in LLLT.