In the sample as a whole (n=11), IFN-alpha injection significantly increased the percentage of lymphocytes positive for intracellular p-p38 MAPK compared to the 9AM baseline (F=4.5, df=6,59, p<0.001), with peak increases being observed 5 hours after IFN-alpha injection (Supplementary Materials, Fig. S1
). No changes in p-p38 were observed over the diurnal cycle absent of IFN-alpha administration (data not shown). In vitro
studies of IFN-alpha-treated peripheral blood mononuclear cells revealed the majority of lymphocytes positive for p-p38 were CD4+ T cells (Supplementary Materials, Fig. S2
). Moreover, in vitro
administration of IFN-alpha was not associated with an overall increase in p38 protein as measured by Western blot (Supplementary Materials, Fig. S2
Six of 11 patients experienced significant depressive symptoms (MADRS score ≥15) at some point during the first 12 weeks of IFN-alpha treatment. No significant differences were found between patients with MADRS scores ≥15 versus those with MADRS scores <15 in age [48.0(SD=4.05) versus 46.8(SD=7.9), p=0.75], body mass index (BMI) [27.4(SD=6.0) versus 30.2(SD=5.2), p=0.44] or race, sex, history of MD, history of substance abuse, or type of IFN-alpha (Fisher Exact tests, all p>0.50).
Patients who exhibited a MADRS score ≥15 during the first 12 weeks of IFN-alpha treatment demonstrated a significantly greater percent of cells positive for intracellular p-p38 MAPK after IFN-alpha injection than did patients whose MADRS scores were consistently <15 (time by treatment interaction: F=2.4, df=6,54, p<0.05). Post hoc analyses revealed significant differences between groups at 3 and 5 hours post-IFN-alpha injection (). The mean maximal change in percent of lymphocytes positive for intracellular p-p38 MAPK (peak response minus 9AM baseline: delta max p-p38) was also significantly higher in patients with MADRS scores ≥15 versus those <15 (t=3.2, df=9, p<0.05)(). Delta max p-p38 was positively correlated with MADRS scores at week 4 (r=0.85, df=9, p=0.001)() and 12 (r=0.70, df=9, p=0.018) of IFN-alpha therapy. Similar correlations were found between delta max p-p38 and MFI scores at week 4 (r=0.72, df=9, p=0.013)() and 12 (r=0.74, df=9, p=0.009). Of note, although cut-off scores have not been established for the MFI, individuals with MFI scores above the median (>50) during the first 12 weeks of IFN-alpha treatment also exhibited a significantly higher percentage of lymphocytes positive for p-p38 at 3 hours following IFN-alpha administration (F=3.1, df=6,54, p<0.05). All correlations between delta max p-p38 and MADRS and MFI remained significant after controlling for age, sex, BMI, history of MD and type of INF-alpha.
Increased p-p38 MAPK in response to the initial IFN-alpha injection is associated with depression and fatigue during the first 12 weeks of IFN-alpha
To further understand the relationship between p38 MAPK activation and development of behavioral symptoms during IFN-alpha treatment, correlations between delta max p-p38 and baseline MADRS and HPA axis responses to the first injection of IFN-alpha were explored. Both baseline depression scores and ACTH and cortisol responses to the initial injection of IFN-alpha have been found to predict development of behavioral changes during IFN-alpha treatment (Capuron et al. 2003
; Lotrich et al. 2007
). Consistent with previous reports, MADRS at baseline significantly correlated with depressive symptoms at week 4 (r=0.88, df=9, p=0.000) and 12 (r=0.85, df=9, p=0.002), and delta max ACTH and delta max cortisol following the initial injection of IFN-alpha were positively correlated with MADRS scores at week 4 (ACTH: r=0.69, df=9, p=0.019, cortisol: r=0.81, df=9, p=0.003) but not at week 12.
Delta max p-p38 MAPK positively correlated with MADRS scores at baseline (r=0.82, df=9, p=0.002) () and delta max cortisol responses (r=0.91, df=9, p=0.000) (). Both correlations remained significant after controlling for age, sex, BMI, history of MD and type of INF-alpha. A similar relationship was observed for ACTH (r=0.75, df=9, p=0.008), however this relationship was not significant after controlling for clinical covariates noted above (r=0.73, df=4, p=0.102). No significant relationship was found between delta max p-p38 and delta max IL-6 (r=0.53, df=9, p=0.096), and as previously reported in patients receiving IFN-alpha for cancer (Capuron et al. 2003
), delta max IL-6 did not correlate with MADRS scores at week 4 (r=0.16, df=9, p=0.649) or 12 (r=−0.38, df=9, p=0.247).
The response of p-p38 MAPK to the initial IFN-alpha injection positively correlated with MADRS scores at baseline and the cortisol response to the first IFN-alpha injection
Given the relationship between baseline MADRS scores and MADRS scores at weeks 4 and 12, correlations between delta max p-p38 and development of depressive symptoms during IFN-alpha treatment were repeated using delta MADRS scores at week 4 and 12 (thus controlling for baseline). Delta max p-p38 was positively correlated with delta MADRS at week 4 (r=0.84, df=9, p=0.001) and week 12 (r=0.67, df=9, p=0.025) of IFN-alpha treatment. These relationships remained significant after controlling for clinical covariates noted above.