Long COVID-19 and Peripheral Serotonin: A Commentary and Reconsideration

Abstract:

We believe there are serious problems with a recently published and highly publicized paper entitled “Serotonin reduction in post-acute sequelae of viral infection.” The blood centrifugation procedure reportedly used by Wong et al would produce plasma that is substantially (over 95%) depleted of platelets. Given this, their published mean plasma serotonin values of 1.2 uM and 2.4 uM for the control/contrast groups appear to be at least 30 to 60 times too high and should be disregarded. The plasma serotonin values reported for the long COVID and viremia patients also should be disregarded, as should any comparisons to the control/contrast groups.

We also note that the plasma serotonin means for the two control/contrast groups are not in good agreement. In the “Discussion” section, Wong et al state that their results tend to support the use of selective serotonin reuptake inhibitors (SSRIs) for the treatment of COVID-19, and they encourage further clinical trials of SSRIs. While they state that, “Our animal models demonstrate that serotonin levels can be restored and memory impairment reversed by precursor supplementation or SSRI treatment”, it should be noted that no data are presented showing an increase or restoration in circulating serotonin with SSRI administration.

In fact, one would expect a marked decline in platelet serotonin due to SSRIs’ effective inhibition of the platelet serotonin transporter. Wong et al hypothesize that problems of long COVID arise from too little peripheral serotonin. However, given the frequent presence of a hyperaggregation state in long COVID, and the known augmenting effects of platelet serotonin on platelet aggregation, it is plausible to suggest that reductions in platelet serotonin might be associated with a lessening of the cardiovascular sequelae of COVID-19.

Source: Anderson GM, Cook EH, Blakely RD, Sutcliffe JS, Veenstra-VanderWeele J. Long COVID-19 and Peripheral Serotonin: A Commentary and Reconsideration. J Inflamm Res. 2024 Apr 11;17:2169-2172. doi: 10.2147/JIR.S456000. PMID: 38628604; PMCID: PMC11019386. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11019386/ (Full text)

SSRI Use During Acute COVID-19 Infection Associated with Lower Risk of Long COVID Among Patients with Depression

Abstract:

Background Long COVID, also known as post-acute sequelae of COVID-19 (PASC), is a poorly understood condition with symptoms across a range of biological domains that often have debilitating consequences. Some have recently suggested that lingering SARS-CoV-2 virus in the gut may impede serotonin production and that low serotonin may drive many Long COVID symptoms across a range of biological systems. Therefore, selective serotonin reuptake inhibitors (SSRIs), which increase synaptic serotonin availability, may prevent or treat Long COVID. SSRIs are commonly prescribed for depression, therefore restricting a study sample to only include patients with depression can reduce the concern of confounding by indication.

Methods In an observational sample of electronic health records from patients in the National COVID Cohort Collaborative (N3C) with a COVID-19 diagnosis between September 1, 2021, and December 1, 2022, and pre-existing major depressive disorder, the leading indication for SSRI use, we evaluated the relationship between SSRI use at the time of COVID-19 infection and subsequent 12-month risk of Long COVID (defined by ICD-10 code U09.9). We defined SSRI use as a prescription for SSRI medication beginning at least 30 days before COVID-19 infection and not ending before COVID-19 infection. To minimize bias, we estimated the causal associations of interest using a nonparametric approach, targeted maximum likelihood estimation, to aggressively adjust for high-dimensional covariates.

Results We analyzed a sample (n = 506,903) of patients with a diagnosis of major depressive disorder before COVID-19 diagnosis, where 124,928 (25%) were using an SSRI. We found that SSRI users had a significantly lower risk of Long COVID compared to nonusers (adjusted causal relative risk 0.90, 95% CI (0.86, 0.94)).

Conclusion These findings suggest that SSRI use during COVID-19 infection may be protective against Long COVID, supporting the hypothesis that serotonin may be a key mechanistic biomarker of Long COVID.

Source: Zachary Butzin-DozierYunwen JiSarang DeshpandeEric HurwitzJeremy CoyleJunming (Seraphina) ShiAndrew MertensMark J. van der LaanJohn M. Colford Jr.Rena C. PatelAlan E. Hubbardthe National COVID Cohort Collaborative (N3C) Consortium. SSRI Use During Acute COVID-19 Infection Associated with Lower Risk of Long COVID Among Patients with Depression.  

Assessing the effect of selective serotonin reuptake inhibitors in the prevention of post-acute sequelae of COVID-19

Abstract:

Background: Post-acute sequelae of COVID-19 (PASC) produce significant morbidity, prompting evaluation of interventions that might lower risk. Selective serotonin reuptake inhibitors (SSRIs) potentially could modulate risk of PASC via their central, hypothesized immunomodulatory, and/or antiplatelet properties although clinical trial data are lacking.

Materials and methods: This retrospective study was conducted leveraging real-world clinical data within the National COVID Cohort Collaborative (N3C) to evaluate whether SSRIs with agonist activity at the sigma-1 receptor (S1R) lower the risk of PASC, since agonism at this receptor may serve as a mechanism by which SSRIs attenuate an inflammatory response. Additionally, determine whether the potential benefit could be traced to S1R agonism. Presumed PASC was defined based on a computable PASC phenotype trained on the U09.9 ICD-10 diagnosis code.

Results: Of the 17,908 patients identified, 1521 were exposed at baseline to a S1R agonist SSRI, 1803 to a non-S1R agonist SSRI, and 14,584 to neither. Using inverse probability weighting and Poisson regression, relative risk (RR) of PASC was assessed. A 29% reduction in the RR of PASC (0.704 [95% CI, 0.58-0.85]; P = 4 ×10-4) was seen among patients who received an S1R agonist SSRI compared to SSRI unexposed patients and a 21% reduction in the RR of PASC was seen among those receiving an SSRI without S1R agonist activity (0.79 [95% CI, 0.67 – 0.93]; P = 0.005).Thus, SSRIs with and without reported agonist activity at the S1R were associated with a significant decrease in the risk of PASC.

Source: Sidky H, Hansen KA, Girvin AT, Hotaling N, Michael SG, Gersing K, Sahner DK; N3C consortium. Assessing the effect of selective serotonin reuptake inhibitors in the prevention of post-acute sequelae of COVID-19. Comput Struct Biotechnol J. 2024 Jan 9;24:115-125. doi: 10.1016/j.csbj.2023.12.045. PMID: 38318198; PMCID: PMC10839808. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10839808/ (Full text)

Central 5-HTergic hyperactivity induces myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like pathophysiology

Abstract:

Objectives: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a significant medical challenge, with no indisputable pathophysiological mechanism identified to date.

Methods: Based on clinical clues, we hypothesized that 5-hydroxytryptamine (5-HT) hyperactivation is implicated in the pathogenic causes of ME/CFS and the associated symptoms. We experimentally evaluated this hypothesis in a series of mouse models.

Results: High-dose selective serotonin reuptake inhibitor (SSRI) treatment induced intra- and extracellular serotonin spillover in the dorsal raphe nuclei of mice. This condition resulted in severe fatigue (rota-rod, fatigue rotating wheel and home-cage activity tests) and ME/CFS-associated symptoms (nest building, plantar and open field test), along with dysfunction in the hypothalamic-pituitary-adrenal (HPA) axis response to exercise challenge. These ME/CFS-like features induced by excess serotonin were additionally verified using both a 5-HT synthesis inhibitor and viral vector for Htr1a (5-HT1A receptor) gene knockdown.

Conclusions: Our findings support the involvement of 5-HTergic hyperactivity in the pathophysiology of ME/CFS. This ME/CFS-mimicking animal model would be useful for understanding ME/CFS biology and its therapeutic approaches.

Source: Lee JS, Kang JY, Park SY, Hwang SJ, Bae SJ, Son CG. Central 5-HTergic hyperactivity induces myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like pathophysiology. J Transl Med. 2024 Jan 8;22(1):34. doi: 10.1186/s12967-023-04808-x. PMID: 38191373. https://translational-medicine.biomedcentral.com/articles/10.1186/s12967-023-04808-x (Full text)

Treatment of 95 post-Covid patients with SSRIs

Abstract:

After Covid-19 infection, 12.5% develops post-Covid-syndrome (PCS). Symptoms indicate numerous affected organ systems. After a year, chronic fatigue, dysautonomia and neurological and neuropsychiatric complaints predominate. In this study, 95 PCS patients were treated with selective serotonin reuptake inhibitors (SSRIs). This study used an exploratory questionnaire and found that two-thirds of patients had a reasonably good to strong response on SSRIs, over a quarter of patients had moderate response, while 10% reported no response.

Overall, patients experienced substantial improved well-being. Brainfog and sensory overload decreased most, followed by chronic fatigue and dysautonomia. Outcomes were measured with three different measures that correlated strongly with each other. The response to SSRIs in PCS conditions was explained by seven possible neurobiological mechanisms based on recent literature on PCS integrated with already existing knowledge.

Important for understanding these mechanisms is the underlying biochemical interaction between various neurotransmitter systems and parts of the immune system, and their dysregulation in PCS. The main link appears to be with the metabolic kynurenine pathway (KP) which interacts extensively with the immune system. The KP uses the same precursor as serotonin: tryptophan. The KP is overactive in PCS which maintains inflammation and which causes a lack of tryptophan. Finally, potential avenues for future research to advance this line of clinical research are discussed.

Source: Rus CP, de Vries BEK, de Vries IEJ, Nutma I, Kooij JJS. Treatment of 95 post-Covid patients with SSRIs. Sci Rep. 2023 Nov 2;13(1):18599. doi: 10.1038/s41598-023-45072-9. PMID: 37919310; PMCID: PMC10622561. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10622561/ (Full text)

Comments to “Fluvoxamine and long COVID-19: a new role for sigma-1 receptor (S1R) agonists” by Khani and Entezari-Maleki

To the Editor:

The coronavirus disease 2019 (COVID-19) pandemic causes short-term and long-term health problems in survivors after infection of SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2). A recent systematic review using 57 studies with 250,351 survivors of COVID-19 shows that the median proportion of COVID-19 survivors experiencing at least 1 PASC (post-acute sequelae of COVID-19) was 54% at 1 month (short-term), 55% at 2–5 months (intermediate-term), and 54% at 6 or more months (long-term) [1]. The most common sequelae involved neurologic symptoms (i.e., headaches, memory deficits, difficulty concentrating, cognitive impairment), psychiatric symptoms (i.e., depression, anxiety, sleep disorders), pulmonary abnormalities (i.e., dyspnea, cough, increased oxygen requirement, pulmonary diffusion abnormalities, chest imaging abnormalities), and functional mobility impairment (i.e., impairment in general functioning, mobility decline, reduced exercise tolerance). However, there are no therapeutic drugs for long-term symptoms in survivors of COVID-19.

The precise mechanisms underlying SARS-CoV-2 induced long-term detrimental effects remain unclear. Infection of SARS-CoV-2 can damage endothelial cells leading to inflammation, thrombi and brain damage. SARS-CoV-2-associated systemic inflammation leads to decreased monoamines and neurotrophic factors, and microglial activation in the brain, resulting in long-term neurological and psychiatric symptoms in COVID-19 survivors [2]. A retrospective study of Wuhan University (Wuhan, China) reported that patients with Epstein-Barr virus (EBV)/SARS-CoV-2 coinfection have about 3-fold risk of having a fever symptom than patients with SARS-CoV-2 infection alone, and that levels of C-reactive protein and aspartate aminotransferase in patients with EBV/SARS-CoV-2 coinfection were higher than those in patients with SARS-CoV-2 infection alone [3]. This report suggests that EBV reactivation may be associated with the severity of clinical symptoms after SARS-CoV-2 infection.

Interestingly, approximately 67% of patients (20/30) with long-term sequelae of COVID-19 were positive for EBV reactivation based on positive titers for EBV early antigen-diffuse IgG or EBV viral capsid antigen IgM [4]. Thus, EBV reactivation may play a role in long-term symptoms in COVID-19 survivors although further study using a large sample size is needed. The authors suggest that most of long-lasting symptoms in COVID-19 survivors following the recovery from SARS-CoV-2 infection might not be directly affected by the virus but probably result from SARS-CoV-2-associated inflammation and EBV reactivation [4].

In the issue, Khani and Entezari-Maleki proposed that fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), may be a new therapeutic drug for long-term consequences of COVID-19 survivors [5]. Fluvoxamine has been demonstrated to prevent clinical deterioration in early-stage subjects with COVID-19 [6]. In addition of serotonin transporter inhibition, sigma-1 receptor chaperone in the endoplasmic reticulum (ER) and acid sphingomyelinase might play a role in the mechanisms of beneficial action of fluvoxamine for patients with SARS-CoV-2 infection [6,7,8]. It is also reported that sigma-1 receptor agonists such as fluvoxamine could produce potent anti-inflammatory actions by the prevention of inositol requiring enzyme 1α (IRE1) and X-box binding protein-1 (XBP-1) pathway [9]. Collectively, it is likely that sigma-1 receptor agonists such as fluvoxamine could produce potent anti-inflammatory effects through sigma-1 receptor/IRE1/XBP-1 pathway in the ER [6,7,8,9].

Among the SSRIs, fluvoxamine was the most potent at sigma-1 receptor in the brain [6,7,8]. Given the link between EBV reactivation and XBP-1 [10], it is possible that the potent sigma-1 receptor agonist fluvoxamine may have beneficial effects for long-term consequences in COVID-19 survivors through sigma-1 receptor/IRE1/XBP-1 pathway [4]. Therefore, it is of great interest to examine whether fluvoxamine can improve long-term sequelae in COVID-19 survivors.

Source: Hashimoto Y, Suzuki T, Hashimoto K. Comments to “Fluvoxamine and long COVID-19: a new role for sigma-1 receptor (S1R) agonists” by Khani and Entezari-Maleki. Mol Psychiatry. 2022 Apr 6:1–2. doi: 10.1038/s41380-022-01546-2. Epub ahead of print. PMID: 35388183; PMCID: PMC8985059. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8985059/ (Full text)

Selective serotonin reuptake inhibitor combined with dengzhanshengmai capsule improves the fatigue symptoms: a 12-week open-label pilot study

Abstract:

OBJECTIVE: This study was to assess the efficacy and safety of selective serotonin reuptake inhibitor (SSRI) plus Dengzhanshengmai capsule in patients with chronic fatigue syndrome (CFS).

METHODS: SSRI at a moderate dose plus Dengzhanshengmai (n = 134) with SSRI alone (n = 134) were compared for the efficacy and safety in the treatment of CFS. The therapeutic efficacy and safety were evaluated.

RESULTS: As compared to monotherapy group, the efficacy in combined therapy group was better and characterized by the improvement of general fatigue (0.8±0.6 vs. 1.3±0.7), physical fatigue (0.6±0.3 vs. 1.0±0.4) and reduced activity (1.0±0.5 vs. 1.3±0.6) since the 2nd week (P<0.01) and in reduced motivation (2.1±0.8 vs. 2.4±1.0) since the 8th week (P<0.01) and the improvement continued thereafter. The mental fatigue score and HAD score were comparable between two groups (P>0.05). No significant difference was found in the drop-out rate between SSRI group (15.7%) and SSRI plus Dengzhanshengmai group (18.0%). The reasons for drop out were adverse events (7.5% vs. 9.7%), requests of the patients or career requirement (3.7% vs. 4.5%), loss to follow-up and others (2.2% vs. 3.0%) and lack of efficacy (2.2% vs. 0.7%). Although the patients in combined therapy group experienced a higher rate of hypertension than (5.8% vs. 1.5%), no significant difference was observed (P = 0.08).

CONCLUSION: SSRI combined with Dengzhanshengmai capsule may significantly improve the general fatigue, physical fatigue, reduced activity and reduced motivation of CFS patients as compared to monotherapy with SSRI. Furthermore, this combined therapy is safe and tolerable.

 

Source: Li DQ, Li ZC, Dai ZY. Selective serotonin reuptake inhibitor combined with dengzhanshengmai capsule improves the fatigue symptoms: a 12-week open-label pilot study. Int J Clin Exp Med. 2015 Jul 15;8(7):11811-7. eCollection 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4565405/ (Full article)