Greater Salivary Rates Linked to Lower Levels of Psoriasis Disease Severity

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A new study found greater salivary rates are associated with lower levels of disease severity in patients with psoriasis.¹

Many biomarkers have been studied to diagnose and monitor the progress of treatment in psoriasis—biomarkers in skin, serum, genetic biomarkers, transcriptomics, and proteomics—but these are not always reliable for psoriasis.² However, saliva offers a valid biological medium to detect cytokine biomarkers in patients with psoriasis.¹

“Early identification of salivation disorders or salivary gland dysfunction is very essential in the course of systemic diseases,” wrote investigators, led by Ravi Kant Sharma, from the department of Biosciences and Technology at Maharishi Markandeshwar in India

Hyposalivation, when the salivary flow rate falls under 0.2mL/min, can lead to many discomforting symptoms: dry mouth halitosis, speech difficulty, chewing, swallowing, perception of taste, and can increase the odds of oral diseases.

Investigators aimed to assess the effect of psoriasis on salivary glands by evaluating the secretion of saliva and salivary cytokine biomarkers in patients with psoriasis. Their secondary objective was to see whether the inflammatory and anti-inflammatory cytokine concentrations in the salivary glands of patients with psoriasis were linked to reduced salivary flow or the occurrence of hyposalivation.

The team recruited 120 participants, aged 21 – 68 years (mean age: 42.13 ± 12.12 years), with half having an active psoriasis clinical diagnosis (n = 60) and the other half healthy controls (n = 60), from the Dermatology department of M.M Institute of Medical Sciences and Research in India. Controls were matched to psoriasis patients by age and gender. In total, each group had 46 males and 14 females.

Patients with psoriasis had either plaque psoriasis or psoriasis vulgaris. A dermatologist assessed the severity of skin lesions with the Psoriasis Area and Severity Index (PASI) score calendar. Patients with psoriasis were only included in the study if they did not take topical or systemic medication within the last month before baseline.

Investigators collected unstimulated whole saliva through the spitting method in the morning between 9 am to 11 am to take into consideration the diurnal variations in the saliva secretion. Patients were told not to eat, drink anything but plain water, smoke, perform any oral hygiene procedures like mouth washing and tooth brushing for 2 hours, and to not take any medication for 8 hours before the saliva sample collection.

After taking the sample, the team split patients with psoriasis into 2 groups based on salivary flow rates: hyposalivation (<0.2 mL/min) and normal salivation (≥0.2 mL/min). Investigators also collected levels of tumor necrosis factor-alpha (TNF-a), interferon-gamma (IFN-y), interleukin-2 (IL-2), and IL-10, calculated through enzyme-linked immunosorbent assay.

The team observed the secretion of saliva was “considerably reduced” in psoriasis patients (salivary flow rate: 0.21±0.1604mL/min), compared to controls (salivary flow rate: 0.447 ± 0.1716) (P < .0001). Furthermore, the secretion of saliva was significantly lower in psoriasis patients with normal salivation compared to controls (P = .0417).

“It was observed that in our study, most of the patients with normal salivation showed salivary rates closer to the minimum value of normal salivary secretion (0.2 mL/min), and hence their salivary secretion, though normal, was found to be considerably reduced compared to controls,” investigators wrote.

The team theorized this could be due to the “damaging effects of the disease” and the body trying to counteract the disease’s impact on the salivary glands or other factors like stress or anxiety.

Psoriasis patients with hyposalivation had a significantly reduced salivary flow rate compared to both controls (P < .0001) and psoriasis patients with normal salivation (P < .0001).

The mean levels of TNF-α (P <0.0001), IFN-γ (P <0.0001), and IL-2 (P = 0.0004) in the unstimulated saliva of the hyposalivation group were significantly greater compared to the controls. In contrast, the mean level of salivary IL-10 (P = 0.0001) in the hyposalivation group was significantly lower than in the control group. Investigators found similar results in the normal salivation group for the levels of TNF-α (p = 0.0196) and IL-2 (p = 0.0392) in the unstimulated saliva.

A correlation analysis showed a significant negative correlation of salivary flow rates with the disease severity characterized by PASI (P < .0001).

“Inflammation may be a contributory factor to salivary gland hypofunction in psoriasis patients,” investigators concluded.

References

1. ^{Sharma RK, Sharma MR, Mahendra A, et al. Hyposalivation in patients with psoriasis: Association with severity, inflammatory, and anti-inflammatory cytokine biomarkers of the disease. Biotechnol Appl Biochem. Published online May 28, 2024. doi:10.1002/bab.2619}
2. ^{Asa’ad F, Fiore M, Alfieri A, Pigatto PDM, Franchi C, Berti E, et al. Saliva as a future field in psoriasis research. Biomed Res Int. 2018;2018:7290913. https://doi.org/10.1155/2018/7290913}