Indian scientists have discovered a previously unknown mechanism underlying life-threatening sepsis and proposed a new treatment strategy centered upon cell-free chromatin (cfCh), they reported in the March 4, 2020, edition of PLOS ONE.
Notably, they showed that sepsis could be caused by cfCh released from dying host cells following microbial infection, integrating into and disrupting the DNA of healthy cells, causing them to die and release more cfCh, leading to a vicious cycle of cell death and sepsis-related pathologies, which theoretically could be targeted therapeutically.
Sepsis represents a major global health burden, affecting an estimated 49 million people annually with approximately 11 million deaths, but current treatment options are at best suboptimal.
In fact, “there are no specific treatments for sepsis,” said study leader Indraneel Mittra, a professor in the Advanced Centre for Treatment, Research and Education in Cancer at the Tata Memorial Centre in Mumbai.
“All patients are managed in the intensive care unit (ICU) with supportive care including antibiotics and maintaining the fluid balance, but 40%-50% die despite ICU treatment,” said Mittra.
Triggered by an immune response to infection or injury, sepsis is characterized by hyperinflammation, impaired immune response, cell death, liver and kidney failure, thrombosis and hemorrhage.
However, despite extensive research, the pathophysiology of sepsis remains poorly understood, which has restricted the discovery and development of effective new treatments.
In the new PLOS ONE study, which was supported by the Department of Atomic Energy of the Government of India, Mittra and his research team reported having made significant advances toward a novel therapeutic modality for sepsis.
“We had previously found that cfCh from dying cells and those circulating in blood could freely enter healthy cells, integrate into their genomes to induce DNA double-strand breaks, apoptosis and activation of proinflammatory cytokines,” said Mittra.
Therefore, “we hypothesized that sepsis may be caused by release of cfCh from dying host cells following microbial infection to trigger DNA damage, apoptotic and inflammatory responses in healthy host cells.
“The cfCh released from dying host cells may then trigger a vicious cycle with release of more cfCh thereby perpetuating and amplifying the pathological complications of sepsis,” he told BioWorld.
The researchers tested this hypothesis using cfCh inactivators including anti-histone antibodies complexed with nanoparticles (CNPs) which inactivate cfCh by binding to the histone component of cfCh; DNase I, which inactivates cfCh by degrading its DNA component; and a combination of the plant antioxidant, resveratrol, and copper (R-Cu2+), which degrades cfCh DNA via free radicals.
They then induced sepsis in mice by injecting the bacterial endotoxin, lipopolysaccharide (LPS), while administering CNPs, DNase I or R-Cu2+ in the other groups, to investigate if they could reduce LPS-induced sepsis/death.
The three cfCh-inactivating agents were similarly effective at ameliorating all the pathophysiological parameters related to sepsis, which had initially been increased by LPS.
The treatments had a particularly marked effect on survival, just 10% of mice in the LPS-only group survived, compared to 50% survival in the R-Cu2+ and DNase I treatment groups, while CNPs improved survival to 30%.
A job for…. Resveratrol?
Of the three agents, “the most promising was resveratrol-copper, since both are inexpensive and widely available as health supplements that can be safely and readily administered orally, requiring minimal regulatory clearance,” said Mittra.
“Resveratrol is a well-known antioxidative plant polyphenol, which has been widely tested for multiple indications, but with marginal effects. However, in the presence of copper, resveratrol becomes a pro-oxidant due to its ability to reduce Cu++ to Cu+ thereby generating free radicals, which can degrade the DNA component of cfCh,” said Mittra
“While both resveratrol and copper have been extensively tested in a variety of conditions, we are the first to show that resveratrol and copper in combination is of marked therapeutic benefit.”
In contrast, as a protein molecule, “CNPs would require extensive regulatory clearances and, while DNase1 has been tried in autoimmune disease in humans, it is expensive and has side effects,” he said.
The researchers then injected the three cfCh inactivators into mice without any LPS, in which no DNA damage was seen, confirming that they were non-toxic as monotherapy.
“Our new findings suggest that previous clinical trials of anti-inflammatory drugs to treat sepsis might have failed because the drugs attempted to treat the symptoms of inflammation rather than attacking the root cause, which is integration of cfCh into DNA of healthy cells and disruption of DNA," said Mittra
"Our group has also previously shown that the toxic side effects of chemotherapy stem from cfCh generated by healthy cells killed by the drugs; this creates a vicious cycle of more cell death that underlies the toxicity of chemotherapy.
"This study has now shown that the inexpensive combination of resveratrol and copper is a highly effective cfCh-inactivator,” said Mittra
Although this is a pre-clinical study, based on its findings, Mittra’s group has started phase 1 and 2 clinical trials of R-Cu2+ in patients receiving high-dose chemotherapy and bone marrow transplant for multiple myeloma, and in those with advanced gastric or oral cancer receiving chemotherapy.
Looking forward, said Mittra, “although a proposed trial in sepsis patients using R-Cu2+ has already received institutional ethics committee approval, we have been held up due to the COVID-19 pandemic. Nevertheless, we believe that the potential therapeutic use of R-CU2+ is enormous and our group is now actively studying the effects of R-CU2+ in the retardation of aging and the prevention and treatment of cancer.”