JAK-STAT Pathway Inhibition And Their Implications: In COVID-19 Therapy

The emergence of SARS CoV-2 in December 2019 in Wuhan city, Hubei province, China is the present global pandemic. SARS CoV was the first CoV to be outbreaked on 2003 in China with fatality rate of 9.5%.According to WHO’s coronavirus situation reports of August 10, US (United States), Brazil and India remained to be the top 3 countries for past 7 days, being affected with COVID – 19. The onset of COVID- 19 is sudden, 2-4 days after exposure is considered as the incubation period and takes about 2-8 weeks for recovery, where the patient is presented with symptoms like fever, cough, shortness of breath and more.

Major cells involved in SARS –COV-2

1.Pneumocytes

Ø SARS-COV-2 infects type 2 pneumocytes in the alveolar epithelium, since they are rich in ACE-2 in the lung tissue

 2.Endothelial cells

Ø SARS CoV resulted in endothelial cell dysfunction leading to micro circulation disorder

Ø Capillary leak, hemodynamic   instability and consumptive coagulopathy occurs as a result of endothelial activation in CSS

3.Macrophages, Monocytes and Neutrophils

Ø  Macrophage is the potent source of inflammatory cytokine

Ø Macrophages and neutrophils are responsible for the destruction and phagocytosis of infected cell. Neutrophils entrap and kill microbes through neutrophils extracellular traps (NET) and this leads to demise of neutrophil., which is called “NETosis.”

4.Lymphoctes

Ø In COVID-19 patients 80% of them revealed peripheral blood lymphopenia and unexpected infiltration in the airways due to the dysfunction of innate T cells

5.NK Cells and Dendritic Cells

Ø In severe COVID-19 patient, NK cells in peripheral blood were declined

Ø NK cells destroy virus infected cells by degranulation, receptor mediated apoptosis, and antibody-dependent cell-mediated cytotoxicity

Ø Dendritic cells help to release pro-inflammatory mediators like TNFα, and aid in activation of T Lymphocyte and B Lymphocyte

SARS-CoV-2 and cytokine storm

Cytokines are necessary for combating viral infections but hyper inflammation conditions created by SARS-CoV-2 infection due to cytokine storm could lead to ARDS and even death. Cytokine storm created by SARS-CoV-2 infection also known as cytokine release syndrome (CRS)/hypercytokinemia characterized by the hyper production of inflammatory cytokines which results in the immune cells biological activity(infection) and at the same time, immune systemic negative feedback gets lost. Cytokine storm releases inflammatory responses that results in local initiation, systematic spreading, and tissue damage.

COVID -19 patients are identified with CSS, based on:

 (i) Unexpected or quick development with multiple organ collaboration (liver, Cardiac, renal injury); 

(ii) Systematic inflammatory indicators (serum ferritin, ESR, CRP) gets elevated considerably;

 (iii) Remarkable deterioration of peripheral blood lymphocyte counts; and

(iv)  Multiple cytokines (IL-1b, IL-2R, IL-6, IFN-c, IP-10, MCP-1, TNF-a) gets upraised

Small Molecules Modulating Jak/Stat Signaling Pathway

Manipulation of JAK/STAT pathway with specific inhibitors or drugs for its regulation is a promise for the upcoming therapeutic intervention for the treatment of numerous diseases.Various regulatory agencies now uphold JAK inhibitors (JAKinibs) for the treatment of immune mediated diseases. It is FERM and SH2 like domains of JAKs that regulate the kinase activity whereas classic transcription factors STAT1-4, STAT5A, STAT5B, STAT6 modulate gene transcription. Inhibitory mechanism of SOCS protein family or auto inhibition of JH1-JH2 interactions are few driving techniques in controlling the anomalous activation of the pathway. Another mechanism of regulation includes the dephosphorylation of activated JAKs and STATs by multiple Protein Tyrosine Phosphates (PTP) including SHP1; SHP2 (both activator and suppressor) and TC-PTP for STAT1, STAT3, STAT5; PTPRT for STAT3; CD45 for JAKs. Upon evidence, inhibition of activated STAT dimers by Protein Inhibitors of Activated STATs (PIAS)- PIAS1, PIAS2 (PIASx), PIAS3, PIAS4 (PIASy)- also play an important role in modulating JAK/STAT signaling. Existing evidence suggest that both activating and inactivating mutation of JAKs and STATs can impair the pathway resulting in numerous pathological conditions including malignancies and immune mediated diseases.The role of cytokines in COVID-19 has been a contributor to the worsening of the disease and inhibiting these cytokines to reduce inflammation has been a strategy to keep the disease under check.The JAK/STAT signaling inhibition looks to be a promising approach to reduce inflammation in COVID-19 patients yet falls short of concrete conclusions due to a lack of understanding of mechanism occurring at molecular levels thus warranting further studies.

Ruxolitinib, Baricitinib, Tofacitinib In Clinical Trial Against Covid-19

Ruxolitinib : It is both JAK 1 & JAK 2 inhibitor that act by terminating the kinase activity, thereby preventing nuclear translocation and STAT activation. Studies proved that inhibition of IL6/JAK/STAT3 pathway by the same can result in significant reduction of IL-6 level.                                                               Side-effects like purpuric lesions on the skin of limbs and erythrodermic rashes were identified from the examination of two SARs-Cov-2 infected patients. Anemia was also observed. Common side effects include black tarry stools, bladder pain, bleeding gum, blood in the urine or stool, coughing up blood and more.

Baricitinib is a kinase inhibitor that competes with ATP to effectively and reversibly inhibit both JAK1 and JAK2 with high selectivity hindering the pro-inflammatory signals of several cytokines like IL-6, IL-12, IL-23. It also plays a vital role in blocking proteins of the host cell responsible for the viral reproduction, and being an anti-inflammatory agent, also reduces the inflammation in ARDS patients as well. Side effects like headache, upper respiratory tract infection, nasopharyngitis are common. Long term use may increase the risks of developing serious infections and thromboembolic events in patients.

Tofacitinib inhibits JAK1, JAK3 initially & then JAK 2 at a lesser extent to modulate both immune &inflammatory responses. Common side effects include Abdominal pain, acne vulgaris, anemia, angioedema, diarrhea, dehydration, dyspepsia, headache, hepatotoxicity, hyperlipidemia, hepatitis, lymphoma, lymphopenia, nausea, neutropenia, pulmonary embolism, rashes, vomiting, blood clots, GI perforations.

 Ms. ROSHITHA ANN SHAJI, AAJA ALOSIOUS, MARIYA LUVIS- Vth PHARM -D

POST COVID COMPLICATIONS

Corona is a pandemic that we are going through this situation. The pandemic has affected the worldwide so adversely that not having much protection poses a great risk for all. The vaccine has been developed and been used widely to provide immunizations. Almost 95% of immunization is provided by these vaccines. But unfortunately, the nation is now facing a 2^nd wave which happens to be a mutant species of the SARS CoV- 2.

The real question is whether we are still in danger after the infection? And sadly, the answer is yes, we are still in danger. This is the basis of the topic “post covid complications.” The coronavirus almost affects all the organs in our body from the brain to the skin due to which the risk of facing a lot of post covid complications rises.

The pathophysiology of corona virus involves the target receptor ACE2. Upon entering the healthy human body via the infected air droplets released from a sick patient, the corona virus penetrates the cell after fusion with the ACE2 receptor. The corona virus consists of spike glycoproteins on its cell surface, which helps in the penetration. There are two subunits S1 and S2. The S1 subunit gets cleaved by the TMPRSS2 and the S2 subunit fuses with the fusion protein on the ACE2 receptor. This helps the genetic material of the virus to be transferred into the cell membrane of the human host. The genetic material of the virus is recognized as its own by the human cell. The process is proceeded by the formation of new viral RNA and its package to form new viruses. It then gets released out to the cell and infects other cells and organs, thus resulting in the proven signs and symptoms and leading to a variety of complications.

Let’s begin with Neurologic complications: The coronavirus affects the brain by two hypothesized mechanisms.:

1.  Via the olfactory nerve: the olfactory nerve is the only cranial nerve which is exposed into the environment, which makes it the perfect route through which the virus gains entry to the brain. Upon entering the brain, the virus interacts with the ACE2 receptor and causes inflammation.

2.    Via blood brain barrier: the endothelial cells consist of ACE2 receptor and hence after interacting with the receptor, the virus gets transported into the brain, crossing the BBB.

After entering the brain, the virus goes on to infect the brain cells causing brain encephalitis, stroke, hallucinations, delirium, Seizures, brain fog, anosmia, ageusia, and in rare cases gullian barre syndrome and bell’s palsy.

Next, we have Respiratory complications: acute respiratory distress syndrome and post covid fibrosis.

The SARS- CoV2 affects the lungs by interacting with the ACE2 receptor and causing inflammation of the lungs. This leads to the decreased production of oxygen, because of which the infected person has to breath frequently to cope with the lack of oxygen, which results in symptoms like breathlessness. Increased inflammation leads to scarring of the lungs which causes fibrosis and accumulation of fluid in the air sacs of the lungs leading to ARDS.

Cardiopulmonary Complications

The corona virus is known to cause a lot of cardiological complications ranging from heart attack to myocardial infarction. The mechanism by which the SARS- CoV 2 causes these complications is due to its interaction with the ACE 2 receptors present in the heart cells. The virus causes inflammation in the heart muscle, decreasing its capacity to pump the blood efficiently, disruption in the heart signalling, interfering with the conduction of abnormal heart rhythms, leading to arrythmia or worsening of the pre-existing condition. When the lungs get inflamed due to the infection, which decreases the amount of oxygen for respiration. This leads to increased burden for the lungs which pumps more rapidly to cope up with the decreased oxygen. This results in the inflammation of the heart cells. Also, the upon interacting with the endothelial cells, there occurs the formation of blood clots which goes on to clog the blood vessels leading to myocardial infarction.

Renal Complications

The corona virus infection leads to acute kidney injury. This is due to the interaction of the virus with the ACE 2 receptors in the tubular epithelial cells, podocytes, and endothelial cells which gets inflamed and lead to acute tubular necrosis (ATN), collapsing focal segmental glomerulonephritis (FSGS) and endotheliitis of the glomerular capillaries respectively. All these eventually lead to acute kidney injury.

Hepatobiliary Complications

Although its known that the covid usually affects the lungs, it can also lead to liver inflammation. The virus affects the liver since there are ACE 2 receptors present in the liver. The liver inflammation in signified by the elevation in the liver enzymes such as ALT and AST.

Musculoskeletal Complications

Although not much has been studied about the musculoskeletal complications, but it has been hypothesised that due to the pulmonary inflammation it can lead to systemic inflammation and release of chemokines and cytokines like CXCL 10, IFN gamma, IFN 1 beta, IL 6, IL 8, IL 17, TNF alpha …etc. This can lead to skeletal muscle and bone and muscle complications like myalgias, atrophy, weakness, fatigue, bone mineral loss, osteonecrosis and chondrolysis. It has also been reported that rhabdomyolysis may occur as a result of acute kidney injury.

Dermatologic Complications

Most reported complication is the incidence of covid toes post infection. It is a chilblain like skin infection which not only occur in the toes but also other extremities like the finger. Covid toes begin with a red coloration on the fingers and toes which then gradually turns purple in colour.it can also form blisters, itch or pain. Some people develop painful raised bumps or areas of rough skin. Sometimes there can be pus under the skin.

Ms. ANJALI AMBROSE, Vth PHARM-D