Research News

A team led by Cleveland Clinic researchers Dennis Stuehr, PhD, staff, and Arnab Ghosh, PhD, staff scientist, both in the Department of Inflammation & Immunity in the Lerner Research Institute, uncovered key details in the role nitric oxide (NO) plays in cellular physiology and signaling. The research provides a new direction in the NO field and has significant implications for improving treatment of disease and outcomes in organ transplantation.

In the new study in Redox Biology, Drs. Stuehr and Ghosh examined how the body delivers heme, an essential precursor to hemoglobin that bonds oxygen to blood cells. The findings provide evidence that low NO doses can trigger heme maturation of hemoglobin and myoglobin.

“Our research is uncovering the underappreciated chemistry between NO and heme,” says Dr. Stuehr. “We’re learning how heme protein maturation is triggered, which will ultimately help us answer broader scientific questions about disease – and also improve outcomes in organ transplantation.”

Heme is essential for the transport and storage of oxygen throughout the body, which in turn generates cellular energy. The heme of hemeogloblin is the substance inside red blood cells that binds oxygen in the lungs and carries it to the tissues. Myoglobin is a protein found in striated muscle cells that supplies oxygen to the cells in muscles. The hemeproteins, hemoglobin and myoglobin are essential for life, and heme insertion is a critical step in their maturation.

This latest investigation from the team studies the interaction between heme and NO, demonstrates that NO levels that induce heme maturation were remarkably low, about the same levels the body would have in normal physiological functions. The researchers found even cells generating low amounts of NO produce enough to influence neighboring cells and have an effect on overall heme distribution.

Dr. Stuehr says the findings help determine the “sweet spot” for nitric oxide. If there’s too much, that can cause heme to be removed from proteins. In some diseases, the body is creating excess amounts of NO.

“People with asthma, for example, have higher levels of NO in their lungs and we are curious to know if these higher levels in asthmatics negate the beneficial effects of NO,” Dr. Stuehr says. “If that’s the case, we may be able to help people with asthma and bring them back to a healthy balance to alleviate airway inflammation by controlling how much heme is available.”

Organ transplantation is another field with potential implications for new therapies. Drs. Stuehr and Ghosh worked in collaboration with another Lerner Research Institute scientist, Toshihiro Okamoto, MD, PhD, to study oxygen and NO perfusion, which measures blood supply through the lungs and can detect abnormal circulation in the blood vessels of lungs. They measured the correlation between how well the lungs performed and any increases in the function of heme proteins that are important in enabling greater success in transplant functions.  The result was a higher performance score and functionality with the addition of NO. 

Earlier research by the team showed that low NO doses trigger a rapid cellular heme insertion into the protein target guanylyl cyclase β (sGCβ). Their current study revealed that this low NO phenomenon was not only limited to sGCβ but was also found to occur in the globins, all three NO synthases, and Myeloperoxidase. Interestingly, the study found that high NO doses were inhibitory to heme insertion for these hemeproteins, suggesting that NO has a dose-dependent dual effect and can act both ways to induce or inhibit heme maturation of key hemeproteins.

Next steps in the research include a gene activation study to investigate protein expression changes, mRNA sequencing and proteomics analysis to examine the differing ways proteins are expressed in cells and tissues when given the low beneficial levels of NO. 

“Our goal is to uncover the beneficial effects of NO that are tied to its effects on heme distribution,” says Dr. Stuehr.  “We believe there are dozens of downstream effects related to the presence of NO in the cells that help tissues function, and we want to further explore these questions.”