Relationship between the concentration of microcystin in serum and primary liver cancer in patients attending JOOTRH, Kisumu, Kenya

Abstract

Microcystins (MCs) are toxins released by unicellular micro-organism known as cyanobacteria. These unicellular micro-organisms flourish in aquatic habitats with warm temperatures and nutrients rich water bodies. Microcystins are known to cause Liver cancer via inhibition of serine-threonine protein phosphatases (PP1 & 2A). Previous studies in China and Serbia have shown an association between MCs and occurrence of primary liver cancer (PLC). However, in Kenya, there is no data that links MCs and occurrence of PLC in humans despite there being an existence of harmful cyanobacteria within Nyanza gulf. This cross- sectional study was therefore carried out to investigate the association of serum microcystins to occurrence of PLC. The specific objectives were to determine the levels of MCs and nutrients within the Nyanza gulf; to determine the levels of serum serine-threonine protein phosphatases (PP 1 & 2A) in PLC patients and controls and to determine the correlation between mcyE and mlrA genes. A total of 40 study participants were enrolled; 20 PLC patients confirmed from JaramogiOgingaOdinga Teaching and Referral Hospital were recruited and 20 controls obtained from the source population giving rise to PLC cases. Their demographic information was obtained through questionnaire. Blood samples were collected and analyzed for total serum-serine-threonine PP1 and 2A levels using enzyme-linked immunosorbent assay. Water samples were collected from three sites along Nyanza gulf; Dunga, Homabay, Mbita; and filtration was done using 0.45 μmmembrane filter using vacuum pump to concentrate phytoplanktons. MC-toxin levels in water were measured using MC-ELISA Kit, whereas Nutrients analysis was done using photometric methods. Total RNA was extracted and quantification of mlrA and mcyE gene expression was done using RT-PCR software. MCs levels were detected using ELISA reader, Nutrients levels were quantified using spectrophotometer; whereas total serine-threonine protein phosphatase quantification were done using ELISA reader and analyzed using independent t-test, while correlation of gene expression analysis was done using Pearson correlation. RESULTS: MCs toxins were present in all samples sites, and their levels exceeded recommended WHO guidelines of 1.0µg/l for quality water safety. Highest MCs levels were detected in Homa/Bay B site (21.4 µg/L) which corresponded to high nitrogen and phosphorus levels within the same station (498.64 µg/L: 136.145 µg/L) respectively. This was followed by Mbita A (13.1 µg/L; TP = 46.14 µg/L; TN = 327.32 µg/L), Homa/Bay A (7.9 µg/L; TP = 100 µg/L; TN = 395.21 µg/L), as well as Dunga B (7.1 µg/L; TP = 84.71 µg/L; TN = 308.37 µg/L) and Mbita B (5.9µg/L; TP = 59 µg/L; TN = 330.47 µg/L). However, Dunga site A had the low level of toxin detection of about (2.2 µg/L, TP = 71.14 µg/L; TN = 247.58 µg/L) despite having high levels of nitrogen. Higher levels of serine-threonine protein phophatase activities were observed in liver cancer patients (103.9 ± 17.83 µg/ml) than in controls (25.91 ± 3.342 µg/ml). The variation was statistically significant (P < 0.05; t38 = 4.298;). Water sample analysis provided evidence of expression of MC-synthesizing gene (mcyE) and MC-biodegrading gene (mlrA). Pearson correlation revealed an insignificant moderate positive relationship between mcyE and mlrA genes, (r = 0.625, P (two-tailed) = 0.053). In conclusion, Nyanza gulf presented a high levels of MCs beyond recommended WHO values (1 µg/L) hence posing a great health risk to riparian communities. This could be attributed to variations in the levels of serine-threonine liver enzyme in PLC patients in the study, due to consumption of MC-contaminated water. Therefore, it is necessary to strengthen the protection and monitoring of drinking water source for effective control of water pollution and safeguarding of human health.