# High-Power Laser Therapy Modulates Mitochondrial Function and Redox Balance Without Cytotoxicity: An In Vitro Study in BV-2 Microglial Cells

## TL;DR

High-power laser therapy affects mitochondrial function and redox balance in microglial cells without causing cell death.

## Contribution

This is the first study to evaluate the safety and redox modulation of high-power laser therapy in BV-2 microglial cells.

## Key findings

- Protocol A increased cell viability and ATP levels while reducing apoptosis and ROS.
- Protocol C induced transient oxidative stress and reduced mitochondrial membrane potential.
- NO levels increased selectively under Protocol A, indicating anti-inflammatory effects.

## Abstract

Background: Recent technological advances have sparked growing interest in high-power laser devices due to their capacity for energy delivery and therapeutic potential, especially in deeper tissues. This promising approach may be comparable to photobiomodulation for modulating inflammatory and redox processes in various tissues. However, to our knowledge, this is the first study to evaluate the safety profile and redox modulation capacity of high-power laser therapy in BV-2 microglial cells. Methods: This study investigated the cellular responses of BV-2 microglial cells exposed to three laser irradiation protocols using a high-power laser device (650/810/915/980 nm, 657 J total dose), applied at variable distances to simulate in vivo power attenuation. Cell viability, apoptosis, adenosine triphosphate(ATP) levels, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), nitric oxide (NO), and intracellular calcium levels were assessed at multiple time points (5 min to 24 h). Results: Protocol-dependent effects were observed. Protocol A promoted early increases in cell viability and ATP levels, along with decreased apoptotic markers and ROS production, suggesting a protective bioenergetic response. In contrast, Protocol C showed transient increases in oxidative stress and reduced MMP, suggesting possible mitochondrial stress. A selective increase in NO levels under Protocol A also suggests modulation of inflammatory pathways without cytotoxicity. Conclusions: High-power laser therapy modulates redox balance, mitochondrial function, and inflammatory mediators (e.g., NO) in a dual-phase manner in BV-2 microglial cells. These findings contribute to defining safe and effective parameters for potential musculoskeletal and neurological applications.