Anti-Inflammatory Properties of Drugs Used to Control COVID-19 and their Effects on the Renin-Angiotensin System and Angiotensin-Converting Enzyme-2

- COVID-19 infection is associated with systemic inflammation, and sometimes hyperinflammatory responses with cytokine storm. This plays a major role in COVID-19 severity and poor disease prognosis, even death. Higher levels of inflammatory hallmarks including C-reactive protein, ferritin, D-dimers, and cytokines such as interleukin (IL) -6, IL-10 and tumor necrosis factor- α (TNF-α) have been reported. Many anti-viral drugs have been tried, but none were proven fully effective. Supportive care and management of the complications that are caused mainly by inflammation might be the key to greater survival rates and shorter hospitalization (e.g., the use of remdesivir, lopinavir, ritonavir, umifenovir (arbidol), oseltamivir, ganciclovir, favipiravir, darunavir, hydroxychloroquine, chloroquine, colchicine, azithromycin, anakinra, canakinumab, tocilizumab, siltuximab, sarilumab, Type 1 interferon, interferon β-1a, interferon α-2b, baricitinib, ruxolitinib, fedratinib, methylprednisolone and dexamethasone). However, the efficacy of these treatments still needs well-planned clinical trials. In such trials, careful attention must be paid to the duration of the treatment, the onset of beneficial effects, and the severity of the disease, otherwise, the outcomes may still remain inconclusive. Herein, we present a review of the current drugs, which are being used in the management of the disease and their anti-inflammatory properties. We also investigated if these drugs directly interact with Angiotensin-Converting Enzyme (ACE 2), which is a crucial component of the virus entry to the cells.

COVID-19 is an acute respiratory infectious disease, which primarily spreads through the respiratory tract (3, 5, 6). The virus can be transmitted through the spread of droplets from patients to others or oral-fecal route (7-9). The common clinical symptoms of COVID-19 infection include cough and fever as the dominant symptoms, shortness of breath, fatigue, increased sputum production, sore throat, and headache. Additionally, up to 5 percent of the patients show gastrointestinal symptoms including diarrhea and vomiting (10-14).
In most cases, patients who develop acute respiratory distress syndrome are elderly patients or those with underlying disorders such as hypertension, chronic obstructive pulmonary disease, diabetes, and cardiovascular complications. Other symptoms include septic shock, metabolic acidosis, and coagulation dysfunction, which may lead to death (11-16).
Several studies have already published to frame how hyperinflammatory responses, which resemble the cytokine release syndrome (CRS), play a major role in COVID-19 severity and usually associated with poor disease prognosis (21, 23-25). Higher levels of inflammatory hallmarks including C-reactive protein, ferritin, D-dimers, and cytokines such as IL-6, IL-10, and TNF-α consistently occur in patients with CRS (4, 26, 27).
In general, inflammation is a fundamental and protective reaction of the body to infections and injuries, which has very complex and diverse patterns and has a significant role in the development of various diseases (28, 29). There are two types of inflammatory responses, acute and chronic. During acute inflammation, leukocytes infiltrate the damaged region to remove the stimulus and repair the tissue. This process results in healing in a short time. On the other hand, chronic inflammation is a prolonged and dysregulated process, which involves active inflammation and tissue destruction. Chronic inflammation is associated with many pathophysiological conditions such as atherosclerosis, cancer, arthritis, and autoimmune diseases (29). Inflammation often is associated with altered expression of metabolizing enzymes, transporters, receptors, and plasma proteins (30).
In some cases, the immune response that is triggered by SARS-CoV-2 goes out of control so that it may lead to pulmonary tissue damage, functional impairment, and reduced lung capacity (31). Although much of the attention has been paid to pulmonary complications, it is important to also focus on other pathophysiological aspects of COVID-19 such as cardiovascular complications. Cardiovascular events associated with COVID-19 are significant contributors to the mortality of the disease and include but not limited to myocardial injury and myocarditis, acute myocardial infarction, acute heart failure and cardiomyopathy, dysrhythmias (32-34), and thromboembolic events (35). Most of these complications are due to severe systemic inflammation that increases the risk of cardiovascular or other organ complications (22, 32). Arguably, female patients may be more tolerant of the complication of COVID-19 infection due to the anti-inflammatory actions of estrogen (36).
In addition, SARS-CoV-2 enters the lung alveolar epithelial cells through a receptormediated endocytosis mechanism. The virus utilizes the angiotensin-converting enzyme II (ACE2) as the entry receptor. The spike (S) protein of SARS-CoV-2 binds to Angiotensin-Converting Enzyme II (ACE 2), which leads to virus entry to the host cell. The virus uses the cellular protease TMPRSS2 (transmembrane protease serine 2) for priming the spike protein and its activation (37-39).
The Renin-Angiotensin System (RAS) regulates human physiology and controls cardiovascular homeostasis. The RAS exerts its effects through its components, the angiotensinconverting enzyme (ACE) and ACE2, their angiotensin (Ang) products (Ang II and Ang1-7), Ang II receptor type 1 (AT1R) and type 2 (AT2R) and G-coupled protein receptor of Ang1-7, Mas receptor. ACE metabolizes Ang I to Ang II which binds with AT1R and AT2R. RAS consists of two opposing arms. The first arm, ACE, Ang II, and AT1R causes inflammation, vasoconstriction, cell proliferation, and fibrosis. The second arm is antiinflammatory, antifibrotic, antiproliferative, and a vasodilator. It consists of ACE2, Ang1-7, and Mas receptor An imbalance of RAS components changes the system's role from a regulator to a harmful one (40-42). Inflammation causes such an imbalance (30, 43, 44), and being an inflammatory condition, COVID-19 seems to do the same (45).
To treat COVID-19 patients, various pharmacological interventions are suggested. The evidence to support beneficial effects is, however, mainly questionable (46). This review was carried out to test the hypothesis that the majority of drugs proposed to treat COVID-19 are anti-inflammatory in nature. Currently, there are no Food and Drug Administration (FDA)-approved drugs for the treatment of COVID-19, although remdesivir, which is an investigational antiviral drug is available through an FDA emergency use authorization (47-50). Other antiviral drugs such as a combination of lopinavir and ritonavir (47, 51, 52) and favipiravir (47, 53) have been also used in the treatment of COVID-19. However, in all cases, the FDA panel recommended against using them because solid clinical trial data are absent or no significant clinical benefit has been observed in patients with COVID-19.

Search and selection strategy Initial serch to identify the drug classes in the treatment of COVID-19
Since there are overwhelming number of the publications in regards to the treatment of COVID-19, initially we conducted a search to identify the drug classes which are mostly used in the treatment of the disease. The search was conducted using keywords "COVID-19" AND "Treatment" OR "Management" OR "Drug class" in PubMed and ScienceDirect databases and the US clinical trials registry (https://clinicaltrials.gov/ and https://www.covid19treatmentguidelines.nih.gov/ whats-new/). The initial search helped us to identify our keywords for step 1. For articles not in English, we used the web version of the Google Translate (https://translate.google.com/) Step 1: identification of the drugs used in the treatment of COVID- 19 We search for medications used to treat COVID-19 patients during January 1, to July 14, 2020 under the class of drugs identified in the initial search using the mentioned databases. Keywords consisted of "COVID-19" AND each of the following terms: "antiviral treatment", "macrolide", "antimalarial", "interleukin-1 (IL-1) inhibitor", "interleukin-6 (IL-6) inhibitor", "interferon treatment", "Janus Kinase (JAK) inhibitor", and "corticosteroid therapy". After trying several different combinations, the search keywords were selected among different possible combinations to find the most relevant results. Moreover, missing publications were identified by going through the reference lists of the selected articles. The articles that studied the current pharmacological options for the treatment of COVID-19 were selected for this review. Duplicates were excluded from the search results. For reporting the step 1 results, the name and category of the drugs, main therapeutic use, the mechanism(s) of action for the main therapeutic use, and references were presented. Figure 1 summarizes the study selection design for step 1.
Step 2: reviewing the anti-inflammatory properties of the drugs identified in step 1 and their possible effect on ACE2 We searched each drug, which was identified in step one for their anti-inflammatory properties and their possible effect on activation or inhibition of the ACE2. PubMed and ScienceDirect databases were selected as the search tools. Keywords for the search included "The name of the drug identified in step 1" AND "anti-inflammatory" or "The name of the drug identified in step 1" AND "ACE 2". The search conducted without any language or time restriction to identify the maximum number of published studies. Moreover, missing publications were identified by going through the reference lists of the selected articles. Duplicates were excluded from the search results.
In total, 1066 articles were found and screened and among those, 62 were selected based on the inclusion criteria ( Figure 1). Table 1 lists the drugs, which were identified as the current or potential pharmacotherapies for the treatment/management of COVID-19.
With the exception of a few, drugs used in treating COVID-19 infection have either direct or indirect anti-inflammatory actions ( Table 2).  Hydroxychloroquine, Chloroquine Direct. Inhibition of IL-1-alpha production by monocytes and IL-6 production by T cells and monocyte Inhibition of the alkaline cytosolic lysophospholipase and phospholipase A inhibition of T and B-cell receptors calcium signaling, inhibits toll-like receptors signaling, and inhibition of tumor necrosis factor (TNF)-alpha production (68, 111-124).
May prevent the viral S protein from binding to a newly discovered gangliosidebinding domain,   (171). Therefore, eradication of the virus with antiviral therapy is possibly not a sufficient strategy to reverse the side effects of the disease, mainly the damages caused by inflammation. Thus, during the disease, it is important to simultaneously fight the virus and manage the symptoms resulted from the inflammatory process. Indeed, as depicted in Table  2 all drugs used to treat COVID-19 patients have direct or indirect anti-inflammatory effects. With regard to the effect of the reninangiotensin system, it is important to point out that although the listed drugs may be void of direct effects on the, their anti-inflammatory effect indirectly influences the system (30, 43).
The data on the beneficial effects of the drugs used to treat COVID-19 patients are mainly unconvincing (60, 64). Many reports are only clinical observations that lack the inclusion of placebo or control arms. Thus, it is unclear whether the patient would have recuperated even without the use of those drugs.
In general, Inflammation is a fundamental and protective reaction of the body to infections and injuries. Acute inflammation is a beneficial function in a short time, which results in healing and could help eradicate infections. However, chronic inflammation is a prolonged and dysregulated process, which involves active inflammation and is associated with many pathophysiological conditions such as atherosclerosis, cancer, arthritis, and autoimmune diseases (28, 29). Inflammation is a complex condition with great inter-and intra-patient variability (172). As such, the severity of inflammation may play a role in therapeutic outcomes. In addition, anti-inflammatory properties of drugs are not always instantaneous, thus, the optimal effect may not appear in weeks and months. The exception being the most potent anti-inflammatory class of drugs, the corticosteroids that produce anti-inflammatory responses almost immediately. Indeed, in treating patients who are afflicted with arthritis, another inflammatory disease, initial and short-term therapy with corticosteroids is common while awaiting the optimal effects of other safer antiinflammatory drugs. Interestingly, early data suggest a significant beneficial effect of corticosteroid therapy in COVID-19 patients (104)(105)(106)(107)173). Such a beneficial effect may not only be due to the strong anti-inflammatory effect of corticosteroids but also, the quick onset of the action of these drugs. COVID-19 infection is an invasive inflammatory affliction that needs intervention with quick therapeutic outcomes that are not expected from most anti-inflammatory drugs. Indeed, the optimal anti-inflammatory effect of hydroxychloroquine is reported to take weeks (113,114,174), much longer than a quick multi-organ invasion of COVID-19.
The disease severity or the extent of inflammation may significantly influence the response to pharmacotherapy. This may not be a significant consideration when mere antiviral therapy is being used; but when attempting to combat inflammation associated with the viral infection, the disease severity can be of prime importance. Examples learned from other inflammatory conditions include the treatment of post-myocardial infarction patients whose survival rate depends significantly on the concentration of proinflammatory markers. Indeed, the higher the C-reactive protein concentration, the shorter will be the survival time ( Figure 2) (175). It is also been reported that patients with active inflammation do not respond well to some important cardiovascular drugs (176)(177)(178). Inflammation downregulate proteins involved in the metabolism of many drugs including the blockers of calcium channel (179,180), and the beta-adrenergic blocker antihypertension drugs (176). The downregulation causes high plasma concentrations of these medications. Interestingly, however, despite increased concentration, the efficacy of these drugs is reduced due to the downregulation of the receptors needed to exert effects. Controlling inflammation reverses these protein downregulations (177). The beneficial effects of drugs that interrupt angiotensin effects such as losartan (181) and valsartan (182) are not influenced by inflammation. Therefore, the influence of inflammation on response to cardiovascular drugs, and the choice of medication are important considerations in treating COVID-19 patients since the infection is associated with cardiovascular complications.
Currently, there is no specific pharmacological treatment for COVID-19 infection, thus, the therapy emphasizes the supportive care and management of the complications that are caused mainly by inflammation. In authors' opinion, treatment with anti-inflammatory drugs can be beneficial in COVID-19 patients with severe hyperinflammatory conditions. However, the efficacy of this treatment still needs well-planned clinical trials. There are several ongoing clinical trials on the treatment/management of COVID 19 (https://clinicaltrials.gov/ct2/who_table). In such trials, careful attention must be paid to the duration of the treatment, the onset of beneficial effects, and the severity of the disease, otherwise, the outcomes may still remain inconclusive. Additionally, it should be considered that the ongoing research efforts worldwide continuously provide more understanding of COVID-19 pathophisiology, which in turn provides us with more efficient treatment guidelines. This is a possibility that other drugs with no anti-inflammatory properties may prove beneficial, although the pathophysiology may suggest otherwise.

CONCLUSION
COVID-19 severe clinical manifestation is most likely due to the host immunologic reactions. The inflammatory processes consequently damage several patient's organs and may result in severe illness and death. Controlling the inflammation quickly and long enough with appropriate antiinflammatory drugs is the key to successfully manage the disease. In treating cardiovascular complications, the influence of inflammation must be considered.