Noninvasive optical cytochrome c oxidase redox state measurements using diffuse optical spectroscopy

Area of Science:

• Physiology
• Biophysics
• Medical Imaging

Background:

• Assessing organ oxidative metabolic states in vivo is crucial but challenging.
• Cytochrome c oxidase (CcO) is a key enzyme in cellular respiration, and its redox state reflects metabolic activity.
• Noninvasive methods are needed to monitor CcO redox state in real-time.

Purpose of the Study:

• To demonstrate that diffuse optical spectroscopy (DOS) can detect CcO redox states in vivo.
• To differentiate CcO redox state changes from hemoglobin concentration changes under physiological stress.
• To establish a method for assessing organ oxidative metabolism.

Main Methods:

• Utilized diffuse optical spectroscopy (DOS) to continuously measure muscle total hemoglobin, oxyhemoglobin, deoxyhemoglobin, and oxidized/reduced CcO in rabbits.
• Applied intermittent decreases in inspired oxygen (100% to 21%).
• Induced physiological perturbations through cyanide (CN) poisoning and hemorrhage/resuscitation.

Main Results:

• Hemorrhage led to reduced CcO redox state and decreased oxyhemoglobin, indicating hypoxia.
• Cyanide poisoning resulted in reduced CcO redox state but increased oxyhemoglobin, due to direct CcO inhibition.
• DOS measurements successfully decoupled CcO redox state changes from hemoglobin concentration changes.

Conclusions:

• Diffuse optical spectroscopy (DOS) can effectively distinguish CcO redox states from hemoglobin dynamics in vivo.
• This technique offers a promising noninvasive approach to assess organ oxidative metabolic states.
• Understanding CcO redox state changes is vital for diagnosing and managing conditions involving metabolic dysfunction.