Copper toxicity and date palm (Phoenix dactylifera) seedling tolerance: Monitoring of related biomarkers.

Date palm (Phoenix dactylifera) seeds were exposed to different copper (Cu) solutions to examine plant stress responses. Low Cu concentrations (0.02 and 0.2 mM) caused an increase of seed germination, whereas higher Cu amounts (2 mM) significantly inhibited seed germination, delayed hypocotyl elongation, increased seedling mortality, and reduced the germination index by more than 90%. Metal-related toxicity symptoms appeared after 15 d of 2 mM of Cu exposure. Biochemical activities such as amylase activity and redox balance elements were examined to study the relationship between external Cu amount and internal plant response. The present study showed that amylolytic activity was dose- and time-dependent. Likewise, H2 O2 production increased after exposure to Cu, which was correlated with thiobarbituric acid reactive substance (TBARS) accumulation. Furthermore at low Cu concentrations, superoxide dismutase (SOD) and catalase (CAT) activities increased, suggesting that date palm seed stimulated its metal homeostasis networks. However, the highest cupric ion amounts increased cell oxidant accumulation and reduced enzyme production. Gene expression level measures of P. dactylifera phytochelatin synthase (Pdpcs) and P. dactylifera metallothionein (Pdmt) encoding genes have been carried out to investigate the implication of PdPCS and PdMT proteins in Cu homeostasis and/or its sequestration. Phoenix dactylifera metallothionein induction reached a peak after 30 d of exposure to 0.2 mM of Cu. However, it was down-regulated in plants exposed to higher Cu concentrations. In the same conditions, Pdpcs was overexpressed during 1 mo of exposure before it decreased thereafter. These observations provide a new insight into date palm cell response to Cu, a metal that can be toxic but that is also an essential element. Environ Toxicol Chem 2018;37:797-806. © 2017 SETAC.

Matrix Metalloproteinase-9 (279R/Q) Polymorphism is Associated with Clinical Severity and Airflow Limitation in Tunisian Patients with Chronic Obstructive Pulmonary Disease.

BACKGROUND: The aim of this study was to investigate the role of matrix metalloproteinase-9 (MMP-9) C-1562T and 279R/Q (836G>A) polymorphisms in the development of chronic obstructive pulmonary disease (COPD) in Tunisians and to determine their impact on disease progression and airflow obstruction. METHODS: Pulmonary functional tests were evaluated by body plethysmography. MMP-9 genotypes were determined in patients with COPD (n = 138) and healthy controls (n = 216) by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum MMP-9 and interleukin-6 (IL-6) levels were determined by enzyme-linked immunosorbent assays (ELISA) and activity of MMP-9 was evaluated by gelatin zymography. RESULTS: No significant association was found between genetic variations in MMP-9 C-1562T and 279R/Q polymorphisms and the risk of development of COPD. However, a significant correlation was retrieved between the 279 R/Q polymorphism and disease severity (P = 0.02). In addition, homozygous Q (A) genotype was associated with a poorer lung function with a fall in forced expiratory volume in 1 s (FEV1) (%) and forced vital capacity (FVC%) among COPD patients compared with both AG and GG individuals (52.06 ± 19.6 vs. 59.08 ± 17.19, P = 0.03 and 72.41 ± 21.42 vs. 82.98 ± 16.48, P = 0.002, respectively). Using ELISA, a higher level of MMP-9 was found in patients with the CT genotype (P = 0.03), while no significant impact of the 279R/Q polymorphism was observed (P = 0.48). In contrast, by using zymography gel analysis, MMP-9 activity was enhanced in individuals carrying the R(G) allele in comparison with those homozygous for the Q(A) variant (P = 0.02). CONCLUSION: Our results support a role for the 279R/Q polymorphism in physiological alterations that may affect progression and severity of COPD. These findings could be related to the decreased activity of MMP-9 among COPD patients carrying the 279Q variant.