Major depressive disorder (MDD) is a psychiatric illness that presents as a deficit of serotonergic neurotransmission in the central nervous system. MDD patients also experience alterations in cortisol and cytokines levels. Treatment with selective serotonin reuptake inhibitors (SSRIs) is the first-line antidepressant regimen for MDD. The aim of this study was to determine the effect of a combination of SSRIs and an immunomodulator—human dialyzable leukocyte extract (hDLE)—on cortisol and cytokines levels. Patients received SSRIs or SSRIs plus hDLE. The proinflammatory cytokines IL-1
Clinical and epidemiological studies have established that major depressive disorder (MDD) is a cause of chronic stress [
Various studies have linked variations in cytokine and cortisol levels in MDD [
MDD patients have high levels of cortisol in bodily fluids, such as saliva, blood, cerebrospinal fluid, and urine [
SSRIs are designed to compensate for alterations in serotonin levels (5-HT) and are usually administered over 1 year [
Our group has reported that without pharmacological intervention, MDD patients have a predominantly anti-inflammatory cytokine profile that is associated with high cortisol levels [
Controlled trials have reported that 30% to 40% of MDD patients become resistant to pharmacological treatments due to medical comorbidities, unavailability of appropriate services, and poor adherence to therapies [
Although the mechanisms of action are not fully understood, we used a dual pharmacological therapy SSRI plus human dialyzable leukocyte extracts (hDLEs) and measured cortisol and cytokines levels for 52 weeks of followup in depressed patients. hDLEs comprise many peptide sequences below 17 kDa [
The outpatient clinic of Instituto Nacional de Psiquiatria “Ramón de Fuente,” Mexico City, assessed 434 individuals and recruited 65 Mexican patients. Patient recruitment was made according to the clinical experimental procedures set out in the INPRF-NC092318.0 research protocol, approved by the ethics committee of the Instituto Nacional de Psiquiatría, México. All subjects were diagnosed by psychiatrists who applied the Mini-International Neuropsychiatric Interview, a standardized diagnostic interview that is based on DSM-IV-TR criteria. Clinical status was measured using the Hamilton Depression Scale (HDRS) and Beck Depression Inventory (BDI). Patients who met the inclusion criteria were free of antidepressants for at least 3 weeks before the study. Each subject underwent laboratory screens to rule out other medical illnesses. After receiving a detailed explanation of the study aims, all participants signed written consent forms.
All patients were administered SSRIs (19 fluoxetine, 7 paroxetine, and 5 Sertraline) or SSRIs plus hDLEs (23 fluoxetine, 9 paroxetine, 1 sertraline, and 1 escitalopram). All patients were evaluated monthly by their psychiatrist, based on the HDRS and BDI. Blood and urine samples were obtained at weeks (W) 0, 5, 20, 36, and 52 of treatment. Figure
Demographic characteristics in depressed subjects and healthy volunteers.
Age (years) | Gender (male/female) | BMI (kg/m2) | Education (years) | Family history (positive/negative) | First episode | Recurrent episode | |
---|---|---|---|---|---|---|---|
Healthy volunteers ( |
32 ± 6 | 10/20 | 24.3 ± 0.4 | 15 ± 3 | NA | NA | NA |
Patients/SSRIs ( |
35 ± 9 | 10/21 | 24.6 ± 0.7 | 13 ± 2 | 10/21 | 15 | 16 |
Patients/SSRIs plus DLE ( |
33 ± 9 | 6/28 | 24.0 ± 4.0 | 12 ± 3 | 16/18 | 22 | 12 |
Values are given as mean ± standard deviation. Education refers to the number of years of schooling. Family history is expressed as the number of patients with depressive antecedents (positive) versus the number of patients without depressive antecedents (negative). NA: nonapplicable. BMI: body mass index.
Flowchart of 52 week SSRIs and SSRIs plus hDLEs treatment in MDD patients. The numbers in parenthesis refer to the number of patients evaluated throughout the study, the changes in patient numbers for a pharmacological treatment, and the changes in patient numbers for treatment types withdrawn from the protocol. Change in prescription refers to the symbol >.
The doses of SSRIs (mg/day) were as follows: fluoxetine, 20; paroxetine, 20; sertraline, 100; and escitalopram, 10. SSRI doses were established for each patient by his physician and adjusted when it was necessary throughout the study; the drugs were paid for by the patients (Figure
hDLEs (Tranferon) were kindly provided by the Proyecto Factor de Transferencia, Escuela Nacional de Ciencias Biológicas, Instituto Politecnico Nacional (Mexico City, MX). For the group that was given SSRIs plus hDLEs, 30 units of hDLEs were administered to each patient for the 52 weeks of followup as follows: 3 units in week 1, 2 units in week 2, 1 unit each in weeks 3 and 4, and 1 unit every 2 weeks from Week 5 to the end of the study, as described [
Participants were instructed to collect their urine for 24 hours, in which total cortisol was measured by radioimmunoassay (RIA). Circulatory levels of IL-1
Human IL-1
Nonspecific binding was prevented with 3% bovine serum albumin (BSA) in phosphate-buffered saline (PBS). Standards and samples were pipetted, and secondary antibodies were added to the plate. The secondary antibody concentrations were as follows (ng/mL): IFN-
Data were analyzed using Prisma 6 for Mac OS X (GraphPad Software, La Jolla, CA, USA,
Clinical and laboratory parameters, as measured by the Institute’s clinical laboratory, such as complete blood count, blood chemistry, thyroid function test (T3, T4, and TSH), and complete urinalysis, fell within normal ranges of reference values in MDD patients and healthy volunteers; no parameter differed significantly between groups (data not shown). Table
Hamilton depression rate score in depressive patients.
W0 | W5 | W20 | W36 | W52 | |
---|---|---|---|---|---|
Patients/SSRIs |
20 ± 2 |
10 ± 2 |
3.3 ± 2 |
4 ± 2 |
2.6 ± 1.9 |
Patients/SSRIs |
24 ± 4 |
13 ± 4 |
2.8 ± 3 |
2 ± 1 |
2.4 ± 1 |
Values are given as mean ± standard deviation.
The concentrations of urinary cortisol in healthy volunteers and depressed patients before and throughout the 52 weeks of treatment are shown in Figure
24 h urinary cortisol levels detected by RIA in healthy volunteers and MDD patients. Patients were treated with SSRIs or SSRIs plus hDLEs during 52 weeks of study. The statistical analyses were as follows. First, the patient group before antidepressant treatment (W0) was compared with the control group (HVs). Second, the values before the antidepressant treatment (W0) were compared with those during the treatment (W5, W20, W36, or W52) in patients. Third, the data of patients at W52 versus HVs were compared. *
Variations in circulating proinflammatory cytokine levels were determined by ELISA using antibodies against cytokines specific. The levels expressed in pg/mL are shown in Figure
Serum proinflammatory cytokines detected by capture ELISSA assay in HVs and MDD patients. Patients were treated with SSRIs or SSRIs plus hDLEs during 52 weeks of study. The statistical analyses were as follows. First, the patient group before antidepressant treatment (W0) was compared with the control group (HVs). Second, the values before the antidepressant treatments (W0) were compared with those during the treatment (W5, W20, W36, or W52) in patients. Third, the data of patients at W52 versus HVs were compared. IL-2 (a), IFN-
IL-2 showed significant differences between the HVs and MDD patients before and during the SSRIs and SSRIs plus hDLEs treatments (
IFN-
IL-1
Variations in circulating anti-inflammatory cytokine levels are shown in Figure
Serum anti-inflammatory cytokines detected by capture ELISSA assay in HVs and MDD patients. Patients were treated with SSRIs or SSRIs plus hDLEs during 52 weeks of study. The statistical analyses were as follows. First, the patient group before antidepressant treatment (W0) was compared with the control group (HVs). Second, the values before the antidepressant treatments (W0) were compared with those during the treatment (W5, W20, W36, or W52) in patients. Third, the data of patients at W52 versus HVs were compared. IL-4 (a), IL-10(b), and IL-13 (c). HVs were not detectable. IL-4: &
The values of circulating levels of IL-4 in healthy volunteers were below the range of sensitivity of the assay (31.25–1000 pg/mL). Thus, we considered these values nondetectable (ND). Before treatments, the patients showed significant increases in IL-4 (SSRIs =
IL-10 differed significantly before and during treatments (
Before treatment (W0), patients have significantly higher IL-13 levels than healthy volunteers (SSRIs =
Hyperactivity of the HPA axis in response to increased stress is linked to dysregulation of cortisol and serotonin secretion in various psychiatric disorders, such as major depression disorder [
Hypercortisolemia is common in MDD patients—clinical assays have reported higher cortisol levels in saliva, plasma, and cerebrospinal fluid in depressed patients who have not received pharmacological treatment [
These findings could explain the hypercortisolemia in patients with MDD, a common comorbidity in this disorder that is regarded as a marker of axis hyperactivity HPA [
SSRIs, the most widely used antidepressants, upregulate extracellular serotonin concentrations by acutely blocking the serotonin transporter 5-HTT. 5-HTT regulates extracellular serotonin concentrations by removing 5-HT from the synaptic cleft [
This study examined the ability of coadministration of hDLEs and SSRI in MDD patients to restore cortisol and cytokine imbalances versus SSRIs alone. Our data show that, in depressed patients who were treated with SSRIs plus hDLE, cortisol levels, fell (54%) from W20 to the end of treatment. In contrast, SSRIs alone decreased such levels from W36 to W52. Notably, those who were given SSRIs plus hDLEs showed cortisol levels more nearby to healthy volunteers.
The underlying molecular mechanism by which SSRIs function is unknown. 5-HTT controls the reuptake of serotonin from the synapse, and its inhibition by SSRIs increases serotonin levels at the synapse. However, SSRIs may influence the endocrine and immune systems of depressed patients.
Serotonin stimulates the secretory activity of the adrenal glands through 5-HT4 receptors [
SSRIs also target cells of the immune system. A wide range of cytokine-producing cells constitutively express cortisol and the serotonin receptors 5-HT1A, 5-HT2A, 5-HT1B, and 5-HT3 [
Variations in cortisol and serotonin concentrations can directly affect cytokine-producing cells and modulate the pattern of cytokine release [
The immune system responds to stressful stimuli by secreting proinflammatory cytokines [
Previous studies are consistent with our data, in which clinical assays have shown changes in the balance of pro- and anti-inflammatory cytokines in patients with MDD without pharmacological treatment [
Antidepressants increased serotonin levels in MDD patients, inducing clinical remission at W20, as assessed by HDRS and BDI scores. At this time point, IL-2 and IFN-
These findings contrast with other reports, in which SSRIs decreased proinflammatory cytokine levels in MDD patients [
In contrast, IL-1
As discussed, SSRIs increase circulating levels of plasma serotonin [
DLEs have immunomodulatory and immunostimulatory effects in various infectious diseases, autoimmune diseases, and cancers [
In our study, MDD patients had an anti-inflammatory cytokine profile that was associated with increased cortisol levels before treatment. Healthy volunteers had undetectable levels of IL-4. SSRIs and SSRIs plus hDLEs downregulated IL-10 and IL-13, but SSRIs failed to reduce the increased levels of IL-4. Notably,
At W52, patients who were given SSRIs and hDLEs experienced a decline in IL-10 and IL-13 to comparable levels in healthy volunteers. In contrast, SSRI-treated patients showed significant variations in IL-10 and IL-13 levels versus healthy volunteers at W52.
Our report is the first study to analyze the balance between pro- and anti-inflammatory cytokines over 52 weeks of treatment, using an alternative treatment to the classical pharmacologic regimen of SSRIs. hDLEs potentiate the effects of SSRIs on HPA axis hyperactivity by decreasing cortisol levels early in the course of treatment; at the end of the study, patients who were treated with SSRIs and hDLEs consistently had a mixed pro- and anti-inflammatory cytokine pattern. Further studies with more MDD patients are necessary to determine the significance of these findings and their clinical implications for the development of alternative therapeutic approaches in the treatment of major depression.
All authors disclose that none has a commercial association that might pose a conflict of interests in connection with this paper.
Funding for this study was provided in part by the Instituto Nacional de Psiquiatria, México, Project INPRF: NC092318.0 and NC092318.1, Proyecto Factor de Transferencia-IPN: IC-10-002 and CONACYT-SALUD-2003-C01-14.