Inflammation

Introduction

When your body suffers an injury or infection, inflammation is a normal part of the healing process. We are most familiar with short term (or acute) inflammation, such as when we get a cut and the skin swells up, turns red, and hurts. This effect usually goes away in a few hours.

Inflammation in your body’s cells or tissues may cause you to feel hot or lose function, or you may have no outward symptoms at all.

If inflammation fails to resolve itself and becomes chronic, it could contribute to further tissue injury and disease. Chronic inflammation can persist for months or years and is a contributing factor to more than half of deaths worldwide.

A review of scientific literature conducted by NIEHS-funded researchers affiliated with the National Toxicology Program found the environment plays a role in inflammation, which is associated with such diseases as:

• Autoimmune diseases, such as rheumatoid arthritis
• Cardiovascular diseases, such as high blood pressure and heart disease
• Gastrointestinal disorders like inflammatory bowel disease, Crohn's disease, and ulcerative colitis
• Lung diseases, such as chronic obstructive pulmonary disease (COPD) and asthma
• Mental illnesses, such as depression
• Metabolic diseases, such as Type 2 diabetes
• Neurodegenerative diseases, such as Parkinson’s disease
• Some cancers

Tissue inflammation may result from exposure to factors such as:

• Environmental chemicals
• Pathogens (germs) like bacteria, viruses, or fungi
• Radiation

What Is NIEHS Doing?

NIEHS supports a wide variety of research projects focused on inflammation and its role in health and disease. Questions addressed by NIEHS researchers and grantees include:

• Which environmental exposures, individually and in combination, affect inflammation?
• Which genetic and other susceptibility factors influence the inflammatory response?
• Which biological pathways are involved in environmentally induced inflammation? And how do they contribute to different diseases?
• What biomarkers can help identify cases of inflammation?

NIEHS researchers and grantees are studying the causes of inflammation and inflammatory diseases and testing novel strategies to treat inflammation. Some findings follow.

Air Pollution and Inflammatory Disease

• Exposure to ozone can worsen asthma by causing oxidative stress and airway inflammation, leading to cardiovascular disease even at levels lower than the current U.S. Environmental Protection Agency air quality standard.
• Exposure to air pollution is associated with an increased risk for development of Parkinson's disease, which is associated with systematic inflammation.
• The diabetes drug metformin may reduce inflammation triggered by air pollution exposure by preventing immune cells known as macrophages from releasing an inflammatory molecule called interleukin-6.
• Researchers have also identified mechanisms that may cause inflammatory bowel disease, including exposure to environmental neurotoxic pesticides.

Inflammation and Cancer

• Acute inflammation combats infection and stimulates tissue repair and regeneration. When it fails to improve quickly, it can turn chronic and lead to disease. Inflammation resolution failure is increasingly recognized as leading to cancer development. Controlling the body’s inflammatory response may be a way to reduce cancer deaths.
• Oxidative stress, an imbalance in the body’s ability to rid itself of toxins after an injury, is known to cause inflammation. NIEHS-funded scientists believe that certain proteins that act as intermediaries between inflammation and cancer hold promise for future therapies.
• By suppressing one of the body’s natural mechanisms to fight cancer, chronic liver inflammation can lead to a new tumor-promoting pathway. This discovery may aid in the development of future liver cancer treatments.
• Exposure to World Trade Center dust may have caused changes in the inflammation and immune regulation in some first responders, leading to an increase in prostate cancer.

Inflammation and COVID-19

• NIEHS-funded researchers have studied the role of hyperinflammation, which is enhanced in patients with respiratory diseases such as lung cancer, COPD, asthma, and acute respiratory distress syndrome (ARDS), in the progression and severity of COVID-19. The same study revealed a better understanding of the connection between environmental and genetic factors in inflammatory diseases could lead to the development of new therapies targeting COVID-19.

Inflammation, DNA Damage, and Aging

• Chemicals in the environment can cause inflammation-induced DNA damage and cell proliferation. The detection and response to this cellular harm can increase inflammation, creating a kind of feedback loop that can lead to mutations that initiate cancer.
• Certain environmental exposures deplete antioxidant defenses and induce inflammation, cell death, and DNA damage. The ability to respond to oxidative stress is a central determinant of aging and longevity and, thus, is implicated in many diseases, including cancer, atherosclerosis, and related cardiovascular diseases, respiratory diseases, and neurological diseases.
• Inflammatory responses to environmental stressors can reduce lifespan, supporting a theory that longevity depends on a balance between pro- and anti-inflammatory proteins.
• A study of pancreatic cancer revealed a mechanism by which inflammation can act in concert with DNA damage to induce mutations that drive cancer and cancer recurrence.
• The chemicals in vaping can cause lung cells to have less power to do their jobs, producing an inflammatory response that can increase lung aging.

Further Reading

Stories from the Environmental Factor (NIEHS newsletter)

• Vaping’s Respiratory Effects Traced by Leading Basic Researcher (April 2023)
• Falk Memorial Lecture Focuses on How Inflammation Ends (April 2022)
• Autoimmunity Origins May Lie in Defective Mitochondria (March 2021)
• Asthma Worsens When Signaling Pathway Is Triggered (March 2020)
• FDA Reviews Asbestos Testing in Cosmetics and Powders (March 2020)
• Prenatal Environment May Influence Brain Disorders Later in Life (February 2020)
• Parkinson’s Driven by Inflammation, Genetics, and the Environment (February 2020)
• Chronic Inflammation Needs Focused Research to Reduce Disease (January 2020)

Additional Resources

• Anemia of Inflammation or Chronic Disease – Information from the NIH National Institute of Diabetes and Digestive and Kidney Diseases
• Autoinflammatory Diseases – Information from the NIH National Institute of Arthritis and Musculoskeletal and Skin Diseases
• Heart Inflammation – Information from the NIH Heart, Lung, and Blood Institute
• Inflammatory Myopathies (muscle inflammation) – Information from the NIH National Institute of Neurological Disorders and Stroke

Related Health Topics

• Air Pollution
• Allergens & Irritants
• Asthma
• Autoimmune Diseases
• Lung Diseases
• Obesity