Inflammation Acute and Chronic

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton, Bruno Serra, Rishika Babburu, Temitope Olowoyeye, Kim Jackson, Vidya Acharya and Sehriban Ozmen  

Introduction

Inflammation is the immune system's response to harmful stimuli eg. pathogens, damaged cells, toxic compounds, or irradiation, and acts by removing injurious stimuli and initiating the healing process.

• Inflammation is a defense mechanism that is vital to health. During acute inflammatory responses, cellular and molecular events and interactions efficiently minimize impending injury or infection. This process contributes to restoration of tissue homeostasis and resolution of the acute inflammation.
• Uncontrolled acute inflammation may become chronic, contributing to a variety of chronic inflammatory diseases. Inflammation can be hence be either acute or chronic.

1. Acute Inflammation - Tissue damage due to trauma, microbial invasion, or noxious compounds can induce acute inflammation. It starts rapidly, becomes severe in a short time and symptoms may last for a few days eg. cellulitis; acute pneumonia. Subacute inflammation is the period between acute and chronic inflammation and may last 2 to 6 weeks.
2. Chronic Inflammation - Chronic inflammation is also referred to as slow, long-term inflammation lasting for prolonged periods of several months to years. Generally, the extent and effects of chronic inflammation vary with the cause of the injury and the ability of the body to repair and overcome the damage.

Process and Resolution of Inflammation.

At the tissue level, inflammation is characterized by redness, swelling, heat, pain, and loss of tissue function, which result from local immune, vascular and inflammatory cell responses to infection or injury. Important microcirculatory events that occur during the inflammatory process include vascular permeability changes, leukocyte recruitment and accumulation, and inflammatory mediator release.

• In chronic inflammation most of the features of acute inflammation continue eg. the expansion of blood vessels (vasodilation), increase in blood flow, capillary permeability and migration of neutrophils into the infected tissue through the capillary wall (diapedesis). However, the composition of the white blood cells changes soon and the macrophages and lymphocytes begin to replace short-lived neutrophils.
• Thus the hallmarks of chronic inflammation are the infiltration of the primary inflammatory cells such as macrophages, lymphocytes, and plasma cells in the tissue site, producing inflammatory cytokines, growth factor, enzymes and contributing to the progression of tissue damage and secondary repair including fibrosis and granuloma formation.  
• To prevent progression from acute inflammation to persistent chronic inflammation, the inflammatory response must be suppressed to prevent additional tissue damage. Inflammation resolution is a well-managed process involving the controlled production of mediators, during which chemokine gradients are diluted over time. Circulating white blood cells eventually no longer sense these gradients and are not recruited to sites of injury.
• Dysregulation of this process can lead to uncontrolled chronic inflammation. Inflammation resolution processes that rectify tissue homeostasis include reduction or cessation of tissue infiltration by neutrophils and apoptosis of spent neutrophils, counter-regulation of chemokines and cytokines, macrophage transformation from classically to alternatively activated cells, and initiation of healing.

Causes

Chronic inflammation is not obvious and often insidious and often begins without an apparent cause. The immune system becomes activated and then stays on all the time at a low level. Chronic inflammation can develop if a person has:

• Sensitivity: Inflammation happens when the body senses something that should not be there. Hypersensitivity to an external trigger can result in an allergy.
• Exposure: Sometimes, long-term, low-level exposure to an irritant, such as an industrial chemical, can result in chronic inflammation.
• Autoimmune disorders: The immune system mistakenly attacks normal healthy tissue, as in psoriasis.
• Autoinflammatory diseases: A genetic factor affects the way the immune system works, as in Behçet’s disease.
• Persistent acute inflammation: In some cases, a person may not fully recover from acute inflammation. Sometimes, this can lead to chronic inflammation.

Factors that may increase the risk of chronic inflammation include:

• older age
• obesity
• a diet that is rich in unhealthful fats and added sugar
• smoking
• low sex hormones
• stress
• sleep

Damage

Scientists think chronic inflammation causes oxidative stress in the body, which is an imbalance between the production of dangerous free radicals, molecules that harm healthy tissue in the body, and antioxidants, substances that clean up waste products and neutralize them. This can damage DNA as well as proteins and fatty tissue, which in turn accelerates biological aging.

Chronic inflammation is involved in not just a few select disorders but a wide variety of very serious physical and mental health conditions. Indeed, chronic inflammatory diseases are the most significant cause of death in the world today, with more than 50 percent of all deaths being attributable to inflammation-related diseases.

Chronic Inflammatory Complications

It is important to note that chronic inflammation is not a specific disease but a mechanistic process. Chronic inflammation progresses silently. It is the cause of most chronic diseases and presents a major threat to the health and longevity of individuals. The diseases associated with chronic inflammation are multiple.

• Cardiovascular diseases: Many clinical studies have shown strong and consistent relationships between markers of inflammation such as hsCRP and cardiovascular disease prediction. Furthermore, Atherosclerosis is a pro-inflammatory state with all the features of chronic low-grade inflammation and leads to increase cardiovascular events such as myocardial infarction, stroke, among others.
• Cancer: Chronic low-level inflammation also appears to participate in many types of cancer such as kidney, prostate, ovarian, hepatocellular, pancreatic, colorectal, lung, and mesothelioma.
• Diabetes: Immune cells like macrophages infiltrate pancreatic tissues releasing pro-inflammatory molecules in diabetic individuals. Both circulating and cellular biomarkers underscore that diabetes is a chronic inflammatory disease. Chronic complications linked to diabetes include both microvascular and macrovascular complications. Diabetes not only increases the risk of macrovascular complications like strokes and heart attacks but also microvascular complications like diabetic retinopathy, neuropathy, and nephropathy.
• Rheumatoid arthritis
• IBD: a group of chronic inflammatory disorders of the digestive tract. It can develop as ulcerative colitis causing long-lasting inflammation and ulcers in the lining of large intestine and rectum or Crohn's disease characterized by inflammation of the lining of digestive tract dispersing into affected tissues such as mouth, esophagus, stomach and the anus.
• Chronic kidney disease:  Low-grade inflammation is a common feature of chronic kidney disease. It can lead to the retention of several pro-inflammatory molecules in the blood and contributes to the progression of CKD and mortality.
• Allergic asthma
• COPD
• Alzheimer’s:  In older adults, chronic low-level inflammation is linked to cognitive decline and dementia.

Physiotherapy

A physical therapists can be an educator on reduction of risk and lifestyle modifications .

• Emphasis is on diet and lifestyle modification eg weight loss, regular exercises, smoking cessation, healthy diet, and good sleep hygiene. 
• Physical Exercise: In human clinical trials, it is shown that energy expenditure through exercise lowers multiple pro-inflammatory molecules and cytokines independently of weight loss.

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