Pulmonary hypertension is a progressive and life-threatening condition that remains untreatable. In its severe form, patients experience excessive proliferation of endothelial and smooth muscle cells within pulmonary blood vessels, leading to vascular narrowing, increased pulmonary arterial pressure, and right ventricular hypertrophy.
Laboratory studies have revealed that the proliferative behavior of vascular cells in pulmonary hypertension shares similarities with cancer cells. Both exhibit monoclonality, resistance to programmed cell death, and altered energy metabolism.
In oncology, interferon alpha-2b (IFN-α2b) is widely used as an anticancer agent. Given its antiproliferative and tumor-suppressing effects, researchers in the United States hypothesized that IFN-α2b might also mitigate the development and progression of pulmonary hypertension. Their laboratory study demonstrated that IFN-α2b injections not only alleviated pulmonary hypertension symptoms but also reversed disease progression by restoring vascular lumen size, reducing vascular wall thickness, and decreasing right ventricular hypertrophy. The study was conducted on rats, mice, and cultured human pulmonary hypertension cells.
Study Design
A series of experiments were conducted on rats, as their pulmonary endothelial and smooth muscle cell abnormalities closely mimic those observed in human pulmonary hypertension.
Three groups of rats were included in the study: a preventive group, a therapeutic group, and a control group. The control group was maintained under normal conditions. The preventive and therapeutic groups were exposed to three weeks of hypoxia, which induced severe pulmonary hypertension.
In the preventive group, half of the rats received daily injections of human IFN-α2b, while the other half received a placebo. IFN-α2b injections significantly mitigated pulmonary hypertension symptoms, reducing systolic pressure and right ventricular hypertrophy compared to the placebo group.
In the therapeutic group, the experiment lasted five weeks. Initially, all rats were subjected to three weeks of hypoxia without any treatment. After this period, the rats were returned to normal oxygen conditions for two weeks. Half of the rats received daily injections of human IFN-α2b, while the other half received a placebo.
In the placebo group, pulmonary hypertension continued to progress despite the return to normal oxygen conditions. The number and severity of vascular lesions continued to increase.
In contrast, the therapeutic group that received IFN-α2b exhibited substantial vascular improvement compared to both the preventive and placebo groups. The extent of vascular recovery is illustrated in the following images:
Image Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC4024039/
Figure A: Vessel lumen narrowing after three weeks of hypoxia. 0% represents normal conditions; <50% indicates less than a twofold reduction in lumen size; >50% suggests a more than twofold reduction.
Figure B: Degree of vascular narrowing across different groups.
Figure C: Photographs of vascular wall thickness showing marked improvement in the IFN-α2b treatment group.
Figure D: Average vascular wall thickness in the preventive, therapeutic, and control groups.
The findings were further validated in mice. Wild-type mice exhibited similar responses to hypoxia as the rats. However, immunodeficient mice, which lack functional IFN receptors, responded similarly to the placebo group, suggesting that endogenous IFN does not significantly influence pulmonary hypertension progression.
To understand the cellular mechanisms underlying IFN-α2b’s effects, researchers analyzed how hypoxia influences metabolic activity in endothelial and smooth muscle cells.
Under hypoxia, genes associated with monoclonal cell proliferation became highly active. This phenomenon was observed in both rats with induced hypoxia and cultured human pulmonary hypertension cells. Adding IFN-α2b significantly reduced the activity of these genes, indicating its ability to prevent excessive vascular cell proliferation.
While these findings explain the preventive effects of IFN-α2b, they do not fully account for the therapeutic improvements observed in vascular structure. To investigate this further, researchers examined the role of programmed cell death (apoptosis) in pulmonary hypertension.
Hypoxia inhibited apoptosis, leading to uncontrolled endothelial and smooth muscle cell proliferation within the pulmonary vasculature. However, when IFN-α2b was introduced, apoptosis was restored both in rat models of hypoxia and in cultured human pulmonary arterial cells from pulmonary hypertension patients.
Conclusions
Human interferon alpha-2b effectively slows the progression of pulmonary hypertension and reverses vascular damage associated with the disease. Its preventive effects stem from two key mechanisms: Suppressing the abnormal proliferation of endothelial and smooth muscle cells within pulmonary vessels and restoring apoptosis, thereby improving vascular integrity in pulmonary hypertension. These findings highlight IFN-α2b as a promising therapeutic candidate for pulmonary hypertension, warranting further clinical investigation.
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Reference
Recombinant Human Interferon Alpha 2b Prevents and Reverses Experimental Pulmonary Hypertension
